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User Manual: FAA_InstrumentFlyingHandbook_2007

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Instrument

Flying Handbook

U.S. Department

of Transportation

FEDERAL AVIATION

ADMINISTRATION

FAA-H-8083-15A

Instrument Flying

Handbook

U.S. Department of Transportation

FEDERAL AVIATION ADMINISTRATION

Flight Standards Service

2007

iii

This Instrument Flying Handbook is designed for use by instrument ﬂ ight instructors and pilots preparing for instrument

rating tests. Instructors may ﬁ nd this handbook a valuable training aid as it includes basic reference material for knowledge

testing and instrument ﬂ ight training. Other Federal Aviation Administration (FAA) publications should be consulted for

more detailed information on related topics.

This handbook conforms to pilot training and certiﬁ cation concepts established by the FAA. There are different ways of

teaching, as well as performing, ﬂ ight procedures and maneuvers and many variations in the explanations of aerodynamic

theories and principles. This handbook adopts selected methods and concepts for instrument ﬂ ying. The discussion and

explanations reﬂ ect the most commonly used practices and principles. Occasionally the word “must” or similar language

is used where the desired action is deemed critical. The use of such language is not intended to add to, interpret, or relieve

a duty imposed by Title 14 of the Code of Federal Regulations (14 CFR).

All of the aeronautical knowledge and skills required to operate in instrument meteorological conditions (IMC) are detailed.

Chapters are dedicated to human and aerodynamic factors affecting instrument ﬂ ight, the ﬂ ight instruments, attitude instrument

ﬂ ying for airplanes, basic ﬂ ight maneuvers used in IMC, attitude instrument ﬂ ying for helicopters, navigation systems, the

National Airspace System (NAS), the air trafﬁ c control (ATC) system, instrument ﬂ ight rules (IFR) ﬂ ight procedures, and

IFR emergencies. Clearance shorthand and an integrated instrument lesson guide are also included.

This handbook supersedes FAA-H-8081-15, Instrument Flying Handbook, dated 2001.

This handbook may be purchased from the Superintendent of Documents, United States Government Printing Ofﬁ ce (GPO),

Washington, DC 20402-9325, or from GPO's web site.

http://bookstore.gpo.gov

This handbook is also available for download, in PDF format, from the Regulatory Support Division's (AFS-600) web

site.

http://www.faa.gov/about/ofﬁ ce_org/headquarters_ofﬁ ces/avs/ofﬁ ces/afs/afs600

This handbook is published by the United States Department of Transportation, Federal Aviation Administration, Airman

Testing Standards Branch, AFS-630, P.O. Box 25082, Oklahoma City, OK 73125.

Comments regarding this publication should be sent, in email form, to the following address.

AFS630comments@faa.gov

Preface

This handbook was produced as a combined Federal Aviation Administration (FAA) and industry effort. The FAA wishes

to acknowledge the following contributors:

The laboratory of Dale Purves, M.D. and Mr. Al Seckel in providing imagery (found in Chapter 1) for visual illusions

from the book, The Great Book of Optical Illusions, Fireﬂ y Books, 2004

Sikorsky Aircraft Corporation and Robinson Helicopter Company for imagery provided in Chapter 9

Garmin Ltd. for providing ﬂ ight system information and multiple display systems to include integrated ﬂ ight, GPS and

communication systems; information and hardware used with WAAS, LAAS; and information concerning encountering

emergencies with high-technology systems

Universal Avionics System Corporation for providing background information of the Flight Management System and

an overview on Vision–1 and Trafﬁ c Alert and Collision Avoidance systems (TCAS)

Meggitt/S-Tec for providing detailed autopilot information regarding installation and use

Cessna Aircraft Company in providing instrument panel layout support and information on the use of onboard systems

Kearfott Guidance and Navigation Corporation in providing background information on the Ring-LASAR gyroscope

and its history

Honeywell International Inc., for Terrain Awareness Systems (TAWS) and various communication and radio systems

sold under the Bendix-King name

Chelton Flight Systems and Century Flight Systems, Inc., for providing autopilot information relating to Highway in

the Sky (Chelton) and HSI displays (Century)

Avidyne Corporation for providing displays with alert systems developed and sold by Ryan International, L3

Communications, and Tectronics.

Additional appreciation is extended to the Aircraft Owners and Pilots Association (AOPA), the AOPA Air Safety Foundation,

and the National Business Aviation Association (NBAA) for their technical support and input.

Acknowledgements

vii

Is an Instrument Rating Necessary?

The answer to this question depends entirely upon individual

needs. Pilots may not need an instrument rating if they ﬂ y in

familiar uncongested areas, stay continually alert to weather

developments, and accept an alternative to their original plan.

However, some cross-country destinations may take a pilot

to unfamiliar airports and/or through high activity areas in

marginal visual or instrument meteorological conditions

(IMC). Under these conditions, an instrument rating may

be an alternative to rerouting, rescheduling, or canceling

a ﬂ ight. Many accidents are the result of pilots who lack

the necessary skills or equipment to ﬂ y in marginal visual

meteorological conditions (VMC) or IMC and attempt ﬂ ight

without outside references.

Pilots originally ﬂ ew aircraft strictly by sight, sound, and

feel while comparing the aircraft’s attitude to the natural

horizon. As aircraft performance increased, pilots required

more inﬂ ight information to enhance the safe operation of

their aircraft. This information has ranged from a string tied

to a wing strut, to development of sophisticated electronic

ﬂ ight information systems (EFIS) and ﬂ ight management

systems (FMS). Interpretation of the instruments and aircraft

control have advanced from the “one, two, three” or “needle,

ball, and airspeed” system to the use of “attitude instrument

ﬂ ying” techniques.

Navigation began by using ground references with dead

reckoning and has led to the development of electronic

navigation systems. These include the automatic direction

ﬁ nder (ADF), very-high frequency omnidirectional range

(VOR), distance measuring equipment (DME), tactical air

navigation (TACAN), long range navigation (LORAN),

global positioning system (GPS), instrument landing system

(ILS), microwave landing system (MLS), and inertial

navigation system (INS).

Perhaps you want an instrument rating for the same basic

reason you learned to ﬂ y in the ﬁ rst place—because you like

ﬂ ying. Maintaining and extending your proﬁ ciency, once you

have the rating, means less reliance on chance and more on

skill and knowledge. Earn the rating—not because you might

Introduction

need it sometime, but because it represents achievement and

provides training you will use continually and build upon

as long as you ﬂ y. But most importantly it means greater

safety in ﬂ ying.

Instrument Rating Requirements

A private or commercial pilot must have an instrument

rating and meet the appropriate currency requirements if

that pilot operates an aircraft using an instrument ﬂ ight

rules (IFR) ﬂ ight plan in conditions less than the minimums

prescribed for visual ﬂ ight rules (VFR), or in any ﬂ ight in

Class A airspace.

You will need to carefully review the aeronautical knowledge

and experience requirements for the instrument rating as

outlined in Title 14 of the Code of Federal Regulations

(14 CFR) part 61. After completing the Federal Aviation

Administration (FAA) Knowledge Test issued for the

instrument rating, and all the experience requirements have

been satisﬁ ed, you are eligible to take the practical test. The

regulations specify minimum total and pilot-in-command

time requirements. This minimum applies to all applicants

regardless of ability or previous aviation experience.

Training for the Instrument Rating

A person who wishes to add the instrument rating to his or

her pilot certiﬁ cate must ﬁ rst make commitments of time,

money, and quality of training. There are many combinations

of training methods available. Independent studies may be

adequate preparation to pass the required FAA Knowledge

Test for the instrument rating. Occasional periods of ground

and ﬂ ight instruction may provide the skills necessary to

pass the required test. Or, individuals may choose a training

facility that provides comprehensive aviation education and

the training necessary to ensure the pilot will pass all the

required tests and operate safely in the National Airspace

System (NAS). The aeronautical knowledge may be

administered by educational institutions, aviation-oriented

schools, correspondence courses, and appropriately rated

instructors. Each person must decide for themselves which

training program best meets his or her needs and at the same

time maintain a high quality of training. Interested persons

viii

should make inquiries regarding the available training at

nearby airports, training facilities, in aviation publications,

and through the FAA Flight Standards District Office

(FSDO).

Although the regulations specify minimum requirements,

the amount of instructional time needed is determined not

by the regulation, but by the individual’s ability to achieve

a satisfactory level of proﬁ ciency. A professional pilot with

diversiﬁ ed ﬂ ying experience may easily attain a satisfactory

level of proficiency in the minimum time required by

regulation. Your own time requirements will depend upon a

variety of factors, including previous ﬂ ying experience, rate

of learning, basic ability, frequency of ﬂ ight training, type of

aircraft ﬂ own, quality of ground school training, and quality

of ﬂ ight instruction, to name a few. The total instructional

time you will need, the scheduling of such time, is up to the

individual most qualiﬁ ed to judge your proﬁ ciency—the

instructor who supervises your progress and endorses your

record of ﬂ ight training.

You can accelerate and enrich much of your training by

informal study. An increasing number of visual aids and

programmed instrument courses is available. The best course

is one that includes a well-integrated ﬂ ight and ground school

curriculum. The sequential nature of the learning process

requires that each element of knowledge and skill be learned

and applied in the right manner at the right time.

Part of your instrument training may utilize a ﬂ ight simulator,

ﬂ ight training device, or a personal computer-based aviation

training device (PCATD). This ground-based ﬂ ight training

equipment is a valuable tool for developing your instrument

cross-check and learning procedures, such as intercepting and

tracking, holding patterns, and instrument approaches. Once

these concepts are fully understood, you can then continue

with inﬂ ight training and reﬁ ne these techniques for full

transference of your new knowledge and skills.

Holding the instrument rating does not necessarily make you a

competent all-weather pilot. The rating certiﬁ es only that you

have complied with the minimum experience requirements,

that you can plan and execute a ﬂ ight under IFR, that you

can execute basic instrument maneuvers, and that you have

shown acceptable skill and judgment in performing these

activities. Your instrument rating permits you to ﬂ y into

instrument weather conditions with no previous instrument

weather experience. Your instrument rating is issued on

the assumption that you have the good judgment to avoid

situations beyond your capabilities. The instrument training

program you undertake should help you to develop not only

essential ﬂ ying skills but also the judgment necessary to use

the skills within your own limits.

Regardless of the method of training selected, the curriculum

in Appendix B, Instrument Training Lesson Guide, provides

guidance as to the minimum training required for the addition

of an instrument rating to a private or commercial pilot

certiﬁ cate.

Maintaining the Instrument Rating

Once you hold the instrument rating, you may not act as pilot-

in-command under IFR or in weather conditions less than the

minimums prescribed for VFR, unless you meet the recent

ﬂ ight experience requirements outlined in 14 CFR part 61.

These procedures must be accomplished within the preceding

6 months and include six instrument approaches, holding

procedures, and intercepting and tracking courses through the

use of navigation systems. If you do not meet the experience

requirements during these 6 months, you have another 6

months to meet these minimums. If the requirements are

still not met, you must pass an instrument proﬁ ciency check,

which is an inﬂ ight evaluation by a qualiﬁ ed instrument

ﬂ ight instructor using tasks outlined in the instrument rating

practical test standards (PTS).

The instrument currency requirements must be accomplished

under actual or simulated instrument conditions. You may log

instrument ﬂ ight time during the time for which you control

the aircraft solely by reference to the instruments. This can

be accomplished by wearing a view-limiting device, such as

a hood, ﬂ ying an approved ﬂ ight-training device, or ﬂ ying

in actual IMC.

It takes only one harrowing experience to clarify the

distinction between minimum practical knowledge and a

thorough understanding of how to apply the procedures and

techniques used in instrument ﬂ ight. Your instrument training

is never complete; it is adequate when you have absorbed

every foreseeable detail of knowledge and skill to ensure a

solution will be available if and when you need it.

Preface ...................................................................iii

Acknowledgements ................................................ v

Introduction ...........................................................vii

Is an Instrument Rating Necessary? ............................vii

Instrument Rating Requirements .................................vii

Training for the Instrument Rating ..............................vii

Maintaining the Instrument Rating ............................viii

Table of Contents ..................................................ix

Chapter 1

Human Factors ....................................................1-1

Introduction .................................................................... 1-1

Sensory Systems for Orientation ...................................1-2

Eyes ............................................................................1-2

Vision Under Dim and Bright Illumination ............1-3

Ears ............................................................................. 1-4

Nerves .........................................................................1-5

Illusions Leading to Spatial Disorientation ....................1-5

Vestibular Illusions ....................................................1-5

The Leans ................................................................1-5

Coriolis Illusion ......................................................1-6

Graveyard Spiral .....................................................1-6

Somatogravic Illusion .............................................1-6

Inversion Illusion ....................................................1-6

Elevator Illusion ......................................................1-6

Visual Illusions ...........................................................1-7

False Horizon ..........................................................1-7

Autokinesis .............................................................1-7

Postural Considerations .................................................1-7

Demonstration of Spatial Disorientation .......................1-7

Climbing While Accelerating .....................................1-8

Climbing While Turning ............................................1-8

Diving While Turning ................................................1-8

Tilting to Right or Left ...............................................1-8

Reversal of Motion .....................................................1-8

Diving or Rolling Beyond the Vertical Plane ............1-8

Coping with Spatial Disorientation ................................1-8

Optical Illusions .............................................................1-9

Runway Width Illusion ..............................................1-9

Runway and Terrain Slopes Illusion ..........................1-9

Featureless Terrain Illusion ........................................1-9

Water Refraction ........................................................1-9

Haze ............................................................................ 1-9

Fog .............................................................................. 1-9

Ground Lighting Illusions ..........................................1-9

How To Prevent Landing Errors Due To Optical

Illusions .......................................................................... 1-9

Physiological and Psychological Factors .....................1-11

Stress ........................................................................1-11

Medical Factors ............................................................1-12

Alcohol .....................................................................1-12

Fatigue ......................................................................1-12

Acute Fatigue ........................................................1-12

Chronic Fatigue ....................................................1-13

IMSAFE Checklist ...................................................1-13

Hazard Identiﬁ cation ....................................................1-13

Situation 1 ................................................................1-13

Situation 2 ................................................................1-13

Risk Analysis ............................................................1-13

Crew Resource Management (CRM) and Single-Pilot

Resource Management (SRM) .....................................1-14

Situational Awareness ..................................................1-14

Flight Deck Resource Management .............................1-14

Human Resources .....................................................1-14

Equipment ................................................................1-14

Information Workload ..............................................1-14

Task Management ........................................................1-15

Aeronautical Decision-Making (ADM) .......................1-15

The Decision-Making Process .................................1-16

Deﬁ ning the Problem ...............................................1-16

Choosing a Course of Action ...................................1-16

Implementing the Decision and Evaluating

the Outcome .............................................................1-16

Improper Decision-Making Outcomes ....................1-16

Models for Practicing ADM ........................................1-17

Perceive, Process, Perform .......................................1-17

The DECIDE Model .................................................1-17

Hazardous Attitudes and Antidotes .............................1-18

Table of Contents

Chapter 2

Aerodynamic Factors ..........................................2-1

Introduction .................................................................... 2-1

The Wing ....................................................................2-2

Review of Basic Aerodynamics .....................................2-2

The Four Forces .........................................................2-2

Lift ..........................................................................2-2

Weight .....................................................................2-3

Thrust ...................................................................... 2-3

Drag ........................................................................2-3

Newton’s First Law, the Law of Inertia .....................2-4

Newton’s Second Law, the Law of Momentum ........2-4

Newton’s Third Law, the Law of Reaction ................2-4

Atmosphere ....................................................................2-4

Layers of the Atmosphere ..........................................2-5

International Standard Atmosphere (ISA) ..................2-5

Pressure Altitude .....................................................2-5

Density Altitude ......................................................2-5

Lift ..................................................................................2-6

Pitch/Power Relationship ...........................................2-6

Drag Curves ...................................................................2-6

Regions of Command .................................................2-7

Control Characteristics ...........................................2-7

Speed Stability ............................................................2-7

Normal Command ..................................................2-7

Reversed Command ................................................2-8

Trim ................................................................................2-8

Slow-Speed Flight ..........................................................2-8

Small Airplanes ..........................................................2-9

Large Airplanes ..........................................................2-9

Climbs ..........................................................................2-10

Acceleration in Cruise Flight ...................................2-10

Turns ............................................................................2-10

Rate of Turn .............................................................2-10

Radius of Turn ..........................................................2-11

Coordination of Rudder and Aileron Controls .........2-11

Load Factor ..................................................................2-11

Icing .............................................................................2-12

Types of Icing ..............................................................2-13

Structural Icing .........................................................2-13

Induction Icing .........................................................2-13

Clear Ice ...................................................................2-13

Rime Ice ...................................................................2-13

Mixed Ice ..................................................................2-14

General Effects of Icing on Airfoils .........................2-14

Piper PA-34-200T (Des Moines, Iowa) ................2-15

Tailplane Stall Symptoms ........................................2-16

Propeller Icing ..........................................................2-16

Effects of Icing on Critical Aircraft Systems ...........2-16

Flight Instruments .................................................2-16

Stall Warning Systems ..........................................2-16

Windshields ..........................................................2-16

Antenna Icing ...........................................................2-17

Summary ......................................................................2-17

Chapter 3

Flight Instruments ...............................................3-1

Introduction .................................................................... 3-1

Pitot/Static Systems .......................................................3-2

Static Pressure ............................................................3-2

Blockage Considerations ............................................3-2

Indications of Pitot Tube Blockage ........................3-3

Indications from Static Port Blockage ....................3-3

Effects of Flight Conditions ....................................3-3

Pitot/Static Instruments ..................................................3-3

Sensitive Altimeter .....................................................3-3

Principle of Operation .............................................3-3

Altimeter Errors ......................................................3-4

Cold Weather Altimeter Errors ...............................3-5

ICAO Cold Temperature Error Table ........................3-5

Nonstandard Pressure on an Altimeter ...................3-6

Altimeter Enhancements (Encoding) .....................3-7

Reduced Vertical Separation Minimum (RVSM) ..3-7

Vertical Speed Indicator (VSI) ...................................3-8

Dynamic Pressure Type Instruments .............................3-8

Airspeed Indicator (ASI) ............................................3-8

Types of Airspeed ...................................................3-9

Airspeed Color Codes ...........................................3-10

Magnetism ....................................................................3-10

The Basic Aviation Magnetic Compass ..................3-11

Magnetic Compass Overview ...............................3-11

Magnetic Compass Induced Errors .......................3-12

The Vertical Card Magnetic Compass .....................3-14

The Flux Gate Compass System ..............................3-14

Remote Indicating Compass .....................................3-15

Gyroscopic Systems .....................................................3-16

Power Sources .........................................................3-16

Pneumatic Systems ..............................................3-16

Vacuum Pump Systems ........................................3-17

Electrical Systems .................................................3-18

Gyroscopic Instruments ...............................................3-18

Attitude Indicators ....................................................3-18

Heading Indicators ...................................................3-19

Turn Indicators .........................................................3-20

Turn-and-Slip Indicator ........................................3-20

Turn Coordinator ..................................................3-21

Flight Support Systems ................................................3-22

Attitude and Heading Reference System (AHRS) ...3-22

Air Data Computer (ADC) .......................................3-22

Analog Pictorial Displays ............................................3-22

Horizontal Situation Indicator (HSI) .......................3-22

Attitude Direction Indicator (ADI) .........................3-23

Flight Director System (FDS) ..................................3-23

Integrated Flight Control System ............................3-24

Autopilot Systems .................................................3-24

Flight Management Systems (FMS) ............................3-25

Electronic Flight Instrument Systems ......................3-27

Primary Flight Display (PFD) ......................................3-27

Synthetic Vision .......................................................3-27

Multi-Function Display (MFD) ................................3-28

Advanced Technology Systems ...................................3-28

Automatic Dependent Surveillance—

Broadcast (ADS-B) ..................................................3-28

Safety Systems .............................................................3-30

Radio Altimeters ......................................................3-30

Trafﬁ c Advisory Systems ........................................3-31

Trafﬁ c Information System ..................................3-31

Trafﬁ c Alert Systems ...........................................3-31

Trafﬁ c Avoidance Systems ...................................3-31

Terrain Alerting Systems .....................................3-34

Required Navigation Instrument System Inspection ...3-34

Systems Preﬂ ight Procedures ...................................3-34

Before Engine Start ..................................................3-36

After Engine Start .....................................................3-37

Taxiing and Takeoff .................................................3-37

Engine Shut Down ...................................................3-37

Chapter 4, Section I

Airplane Attitude Instrument Flying

Using Analog Instrumentation ...........................4-1

Introduction .................................................................... 4-1

Learning Methods ..........................................................4-2

Attitude Instrument Flying Using the Control and

Performance Method .................................................4-2

Control Instruments ...............................................4-2

Performance Instruments .......................................4-2

Navigation Instruments ..........................................4-2

Procedural Steps in Using Control and

Performance ............................................................4-2

Aircraft Control During Instrument Flight .............4-3

Attitude Instrument Flying Using the Primary and

Supporting Method .....................................................4-4

Pitch Control ...........................................................4-4

Bank Control ...........................................................4-7

Power Control .........................................................4-8

Trim Control ...........................................................4-8

Airplane Trim .........................................................4-8

Helicopter Trim ....................................................4-10

Example of Primary and Support Instruments .........4-10

Fundamental Skills.......................................................4-10

Instrument Cross-Check ...........................................4-10

Common Cross-Check Errors ...............................4-11

Instrument Interpretation ..........................................4-13

Chapter 4, Section II

Airplane Attitude Instrument Flying

Using an Electronic Flight Display ..................4-15

Introduction .................................................................. 4-15

Learning Methods ........................................................4-16

Control and Performance Method ............................4-18

Control Instruments ..............................................4-18

Performance Instruments ......................................4-19

Navigation Instruments .........................................4-19

The Four-Step Process Used to Change Attitude .....4-20

Establish ................................................................4-20

Trim ......................................................................4-20

Cross-Check ..........................................................4-20

Adjust ....................................................................4-20

Applying the Four-Step Process ...............................4-20

Pitch Control .........................................................4-20

Bank Control .........................................................4-20

Power Control .......................................................4-21

Attitude Instrument Flying—Primary and

Supporting Method ...................................................4-21

Pitch Control .........................................................4-21

Straight-and-Level Flight ......................................4-22

Primary Pitch ........................................................4-22

Primary Bank ........................................................4-23

Primary Yaw .........................................................4-23

Primary Power ......................................................4-23

Fundamental Skills of Attitude Instrument Flying ......4-23

Instrument Cross-Check ...........................................4-24

Scanning Techniques ...................................................4-24

Selected Radial Cross-Check ...................................4-24

Starting the Scan ...................................................4-24

Trend Indicators ....................................................4-26

Common Errors ............................................................4-28

Fixation .....................................................................4-28

Omission ...................................................................4-28

Emphasis ..................................................................4-28

Chapter 5, Section I

Airplane Basic Flight Maneuvers

Using Analog Instrumentation ...........................5-1

Introduction .................................................................... 5-1

Straight-and-Level Flight ...............................................5-2

Pitch Control ..............................................................5-2

Attitude Indicator ....................................................5-2

Altimeter .................................................................5-3

Vertical Speed Indicator (VSI) ...............................5-4

xii

Airspeed Indicator (ASI) ........................................5-6

Bank Control ..............................................................5-6

Attitude Indicator ....................................................5-6

Heading Indicator ...................................................5-7

Turn Coordinator ....................................................5-7

Turn-and-Slip Indicator (Needle and Ball) .............5-8

Power Control ............................................................5-8

Power Settings ........................................................5-9

Airspeed Changes in Straight-and-Level Flight ...5-11

Trim Technique ........................................................5-12

Common Errors in Straight-and-Level Flight .........5-12

Pitch ......................................................................5-12

Heading ................................................................. 5-13

Power ....................................................................5-13

Trim ......................................................................5-13

Straight Climbs and Descents ......................................5-14

Climbs ......................................................................5-14

Entry .....................................................................5-14

Leveling Off ..........................................................5-16

Descents ...................................................................5-16

Entry .....................................................................5-17

Leveling Off ..........................................................5-17

Common Errors in Straight Climbs and Descents ...5-17

Turns ............................................................................5-19

Standard Rate Turns .................................................5-19

Turns to Predetermined Headings ............................5-20

Timed Turns .............................................................5-21

Compass Turns .........................................................5-21

Steep Turns ...............................................................5-22

Climbing and Descending Turns ..............................5-24

Change of Airspeed During Turns ...........................5-24

Common Errors in Turns ..........................................5-25

Pitch ......................................................................5-25

Bank ...................................................................... 5-25

Power ....................................................................5-26

Trim ......................................................................5-26

Errors During Compass Turns ..............................5-26

Approach to Stall .........................................................5-26

Unusual Attitudes and Recoveries ...............................5-26

Recognizing Unusual Attitudes ................................5-27

Recovery from Unusual Attitudes ............................5-27

Nose-High Attitudes .................................................5-27

Nose-Low Attitudes .................................................5-28

Common Errors in Unusual Attitudes ......................5-28

Instrument Takeoff .......................................................5-29

Common Errors in Instrument Takeoffs ..................5-29

Basic Instrument Flight Patterns ..................................5-30

Racetrack Pattern ......................................................5-30

Procedure Turn .........................................................5-30

Standard 45° Procedure Turn ...................................5-30

80/260 Procedure Turn .............................................5-31

Teardrop Patterns .....................................................5-31

Circling Approach Patterns ......................................5-32

Pattern I .................................................................5-32

Pattern II ...............................................................5-32

Chapter 5, Section II

Airplane Basic Flight Maneuvers

Using an Electronic Flight Display ..................5-33

Introduction .................................................................. 5-33

Straight-and-Level Flight .............................................5-34

Pitch Control ............................................................5-34

Attitude Indicator ..................................................5-34

Altimeter ...............................................................5-36

Partial Panel Flight ...............................................5-36

VSI Tape ...............................................................5-36

Airspeed Indicator (ASI) ......................................5-37

Bank Control ............................................................5-37

Attitude Indicator ..................................................5-37

Horizontal Situation Indicator (HSI) ....................5-38

Heading Indicator .................................................5-38

Turn Rate Indicator ...............................................5-38

Slip/Skid Indicator ................................................5-39

Power Control ..........................................................5-39

Power Settings ......................................................5-39

Airspeed Changes in Straight-and-Level Flight ...5-40

Trim Technique ........................................................5-43

Common Errors in Straight-and-Level Flight ..........5-43

Pitch ......................................................................5-43

Heading ................................................................. 5-44

Power ....................................................................5-45

Trim ......................................................................5-45

Straight Climbs and Descents ......................................5-46

Entry .........................................................................5-46

Constant Airspeed Climb From Cruise

Airspeed ................................................................ 5-46

Constant Airspeed Climb from Established

Airspeed ................................................................ 5-47

Constant Rate Climbs ...........................................5-47

Leveling Off ..........................................................5-48

Descents ...................................................................5-49

Entry .........................................................................5-49

Leveling Off ..........................................................5-50

Common Errors in Straight Climbs and Descents ...5-50

Turns ............................................................................5-51

Standard Rate Turns .................................................5-51

Establishing A Standard Rate Turn ......................5-51

Common Errors ....................................................5-51

Turns to Predetermined Headings ............................5-52

xiii

Timed Turns .............................................................5-53

Compass Turns .........................................................5-53

Steep Turns ...............................................................5-53

Unusual Attitude Recovery Protection .................5-55

Common Errors Leading to Unusual Attitudes ....5-58

Instrument Takeoff .......................................................5-60

Common Errors in Instrument Takeoffs ..................5-61

Basic Instrument Flight Patterns ..................................5-61

Chapter 6

Helicopter Attitude Instrument Flying ...............6-1

Introduction .................................................................... 6-1

Flight Instruments ..........................................................6-2

Instrument Flight ............................................................6-2

Instrument Cross-Check .............................................6-2

Instrument Interpretation ............................................6-3

Aircraft Control ..........................................................6-3

Straight-and-Level Flight ...............................................6-3

Pitch Control ..............................................................6-3

Attitude Indicator ....................................................6-3

Altimeter .................................................................6-4

Vertical Speed Indicator (VSI) ...............................6-5

Airspeed Indicator ..................................................6-5

Bank Control ..............................................................6-5

Attitude Indicator ....................................................6-5

Heading Indicator ...................................................6-6

Turn Indicator .........................................................6-7

Common Errors During Straight-and-Level Flight ....6-7

Power Control During Straight-and-Level Flight ......6-7

Common Errors During Airspeed Changes .............6-10

Straight Climbs (Constant Airspeed and

Constant Rate) ..............................................................6-10

Entry .........................................................................6-10

Level Off ..................................................................6-12

Straight Descents (Constant Airspeed and

Constant Rate) ..............................................................6-12

Entry .........................................................................6-12

Level Off ..................................................................6-13

Common Errors During Straight Climbs and

Descents ...................................................................6-13

Turns ............................................................................6-13

Turn to a Predetermined Heading ............................6-13

Timed Turns .............................................................6-13

Change of Airspeed in Turns ...................................6-14

Compass Turns .........................................................6-15

30° Bank Turn ......................................................6-15

Climbing and Descending Turns ..............................6-15

Common Errors During Turns .................................6-15

Unusual Attitudes .........................................................6-16

Common Errors During Unusual Attitude

Recoveries ................................................................6-16

Emergencies ................................................................. 6-16

Autorotations ............................................................6-17

Common Errors During Autorotations .................6-17

Servo Failure ............................................................6-17

Instrument Takeoff .......................................................6-17

Common Errors During Instrument Takeoffs ..........6-18

Changing Technology ..................................................6-18

Chapter 7

Navigation Systems ............................................7-1

Introduction .................................................................... 7-1

Basic Radio Principles ...................................................7-2

How Radio Waves Propagate .....................................7-2

Ground Wave ..........................................................7-2

Sky Wave ................................................................7-2

Space Wave ............................................................7-2

Disturbances to Radio Wave Reception .....................7-3

Traditional Navigation Systems .....................................7-3

Nondirectional Radio Beacon (NDB) ........................7-3

NDB Components ...................................................7-3

ADF Components ...................................................7-3

Function of ADF .....................................................7-4

Operational Errors of ADF .....................................7-8

Very High Frequency Omnidirectional

Range (VOR) ..............................................................7-8

VOR Components .................................................7-10

Function of VOR ..................................................7-12

VOR Operational Errors .......................................7-14

VOR Accuracy ......................................................7-16

VOR Receiver Accuracy Check ...........................7-16

VOR Test Facility (VOT) .....................................7-16

Certiﬁ ed Checkpoints ...........................................7-16

Distance Measuring Equipment (DME) ...................7-16

DME Components ................................................7-17

Function of DME ..................................................7-17

DME Arc ..............................................................7-17

Intercepting Lead Radials .....................................7-19

DME Errors ..........................................................7-19

Area Navigation (RNAV) ........................................7-19

VOR/DME RNAV ................................................7-23

VOR/DME RNAV Components ..........................7-23

Function of VOR/DME RNAV ............................7-23

VOR/DME RNAV Errors .....................................7-24

Long Range Navigation (LORAN) ..........................7-24

LORAN Components ...........................................7-25

Function of LORAN .............................................7-26

LORAN Errors ......................................................7-26

Advanced Technologies ...............................................7-26

Global Navigation Satellite System (GNSS) ...........7-26

xiv

Global Positioning System (GPS) ............................7-27

GPS Components ..................................................7-27

Function of GPS ...................................................7-28

GPS Substitution ...................................................7-28

GPS Substitution for ADF or DME .....................7-29

To Determine Aircraft Position Over a DME

Fix: ........................................................................ 7-29

To Fly a DME Arc: ...............................................7-29

To Navigate TO or FROM an NDB/Compass

Locator: ................................................................. 7-29

To Determine Aircraft Position Over an NDB/

Compass Locator: .................................................7-29

To Determine Aircraft Position Over a Fix Made

up of an NDB/Compass Locator Bearing

Crossing a VOR/LOC Course: .............................7-30

To Hold Over an NDB/Compass Locator: ...........7-30

IFR Flight Using GPS ...........................................7-30

GPS Instrument Approaches .................................7-31

Departures and Instrument Departure

Procedures (DPs) ..................................................7-33

GPS Errors ............................................................7-33

System Status ........................................................7-33

GPS Familiarization ..............................................7-34

Differential Global Positioning Systems (DGPS) ....7-34

Wide Area Augmentation System (WAAS) ............7-34

General Requirements ..........................................7-34

Instrument Approach Capabilities ........................7-36

Local Area Augmentation System (LAAS) .............7-36

Inertial Navigation System (INS) .............................7-36

INS Components ...................................................7-37

INS Errors .............................................................7-37

Instrument Approach Systems .....................................7-37

Instrument Landing Systems (ILS) ..........................7-37

ILS Components ...................................................7-39

Approach Lighting Systems (ALS) ..........................7-40

ILS Airborne Components ....................................7-42

ILS Function .............................................................7-42

ILS Errors .................................................................7-44

Marker Beacons ....................................................7-44

Operational Errors ................................................7-45

Simpliﬁ ed Directional Facility (SDF) ......................7-45

Localizer Type Directional Aid (LDA) ....................7-45

Microwave Landing System (MLS) .........................7-45

Approach Azimuth Guidance ...............................7-45

Required Navigation Performance ...............................7-46

Flight Management Systems (FMS) ............................7-48

Function of FMS ......................................................7-48

Head-Up Display (HUD) .............................................7-49

Radar Navigation (Ground Based) ...............................7-49

Functions of Radar Navigation ................................7-49

Airport Surface Detection Equipment ..................7-50

Radar Limitations .....................................................7-50

Chapter 8

The National Airspace System ...........................8-1

Introduction .................................................................... 8-1

Airspace Classiﬁ cation ...............................................8-2

Special Use Airspace ..................................................8-2

Federal Airways .........................................................8-4

Other Routing .............................................................8-5

IFR En Route Charts ......................................................8-6

Airport Information ....................................................8-6

Charted IFR Altitudes ................................................8-6

Navigation Features ....................................................8-7

Types of NAVAIDs ................................................8-7

Identifying Intersections .........................................8-7

Other Route Information .......................................8-10

Weather Information and Communication

Features ................................................................. 8-10

New Technologies .......................................................8-10

Terminal Procedures Publications ...............................8-12

Departure Procedures (DPs) .....................................8-12

Standard Terminal Arrival Routes (STARs) ............8-12

Instrument Approach Procedure (IAP) Charts ............8-12

Margin Identiﬁ cation ................................................8-12

The Pilot Brieﬁ ng .....................................................8-16

The Plan View ..........................................................8-16

Terminal Arrival Area (TAA) ......................................8-18

Course Reversal Elements in Plan View and

Proﬁ le View ..............................................................8-20

Procedure Turns ....................................................8-20

Holding in Lieu of Procedure Turn ......................8-20

Teardrop Procedure ..............................................8-21

The Proﬁ le View ...................................................8-21

Landing Minimums ..................................................8-23

Airport Sketch /Airport Diagram .............................8-27

Inoperative Components ..........................................8-27

RNAV Instrument Approach Charts ........................8-32

Chapter 9

The Air Trafﬁ c Control System ...........................9-1

Introduction .................................................................... 9-1

Communication Equipment ...........................................9-2

Navigation/Communication (NAV/COM)

Equipment ..................................................................9-2

Radar and Transponders .............................................9-3

Mode C (Altitude Reporting) ..................................9-3

Communication Procedures ...........................................9-4

Communication Facilities ..............................................9-4

Automated Flight Service Stations (AFSS) ...............9-4

ATC Towers ...............................................................9-5

Terminal Radar Approach Control (TRACON) .........9-6

Tower En Route Control (TEC) .................................9-7

Air Route Trafﬁ c Control Center (ARTCC) ..............9-7

Center Approach/Departure Control ..........................9-7

ATC Inﬂ ight Weather Avoidance Assistance ..............9-11

ATC Radar Weather Displays ..................................9-11

Weather Avoidance Assistance ................................9-11

Approach Control Facility ...........................................9-12

Approach Control Advances ........................................9-12

Precision Runway Monitor (PRM) ..........................9-12

Precision Runway Monitor (PRM) Radar ............9-12

PRM Beneﬁ ts ........................................................9-13

Control Sequence .........................................................9-13

Letters of Agreement (LOA) ....................................9-14

Chapter 10

IFR Flight ............................................................10-1

Introduction .................................................................. 10-1

Sources of Flight Planning Information .......................10-2

Aeronautical Information Manual (AIM) ................10-2

Airport/Facility Directory (A/FD) ............................10-2

Notices to Airmen Publication (NTAP) ...................10-2

POH/AFM ................................................................10-2

IFR Flight Plan .............................................................10-2

Filing in Flight ..........................................................10-2

Cancelling IFR Flight Plans .....................................10-3

Clearances ....................................................................10-3

Examples ..................................................................10-3

Clearance Separations ..............................................10-4

Departure Procedures (DPs) ........................................10-5

Obstacle Departure Procedures (ODP) ....................10-5

Standard Instrument Departures ...............................10-5

Radar Controlled Departures ....................................10-5

Departures From Airports Without an

Operating Control Tower .........................................10-7

En Route Procedures ....................................................10-7

ATC Reports ............................................................10-7

Position Reports .......................................................10-7

Additional Reports ...................................................10-7

Planning the Descent and Approach ........................10-8

Standard Terminal Arrival Routes (STARs) ............10-9

Substitutes for Inoperative or Unusable

Components .............................................................. 10-9

Holding Procedures ......................................................10-9

Standard Holding Pattern (No Wind) .......................10-9

Standard Holding Pattern (With Wind) ....................10-9

Holding Instructions .................................................10-9

Standard Entry Procedures .....................................10-11

Time Factors ...........................................................10-12

DME Holding .........................................................10-12

Approaches ................................................................10-12

Compliance With Published Standard Instrument

Approach Procedures .............................................10-12

Instrument Approaches to Civil Airports ...............10-13

Approach to Airport Without an Operating

Control Tower .....................................................10-14

Approach to Airport With an Operating

Tower, With No Approach Control ....................10-14

Approach to an Airport With an Operating

Tower, With an Approach Control .....................10-14

Radar Approaches ..................................................10-17

Radar Monitoring of Instrument Approaches ........10-18

Timed Approaches From a Holding Fix ................10-18

Approaches to Parallel Runways ............................10-20

Side-Step Maneuver ...............................................10-20

Circling Approaches ...............................................10-20

IAP Minimums .......................................................10-21

Missed Approaches ................................................10-21

Landing ...................................................................10-22

Instrument Weather Flying ........................................10-22

Flying Experience ..................................................10-22

Recency of Experience .......................................10-22

Airborne Equipment and Ground Facilities ........10-22

Weather Conditions ................................................10-22

Turbulence ..........................................................10-23

Structural Icing ...................................................10-24

Fog ......................................................................10-24

Volcanic Ash ......................................................10-24

Thunderstorms ....................................................10-25

Wind Shear .........................................................10-25

VFR-On-Top ..........................................................10-26

VFR Over-The-Top ................................................10-27

Conducting an IFR Flight ..........................................10-27

Preﬂ ight ..................................................................10-27

Departure ................................................................10-31

En Route .................................................................10-32

Arrival ....................................................................10-33

Chapter 11

Emergency Operations .....................................11-1

Introduction .................................................................. 11-1

Unforecast Adverse Weather .......................................11-2

Inadvertent Thunderstorm Encounter .......................11-2

Inadvertent Icing Encounter .....................................11-2

Precipitation Static ...................................................11-3

Aircraft System Malfunctions ......................................11-3

Electronic Flight Display Malfunction .....................11-4

Alternator/Generator Failure ....................................11-4

Techniques for Electrical Usage ..............................11-5

xvi

Master Battery Switch ..........................................11-5

Operating on the Main Battery .............................11-5

Loss of Alternator/Generator for Electronic Flight

Instrumentation .........................................................11-5

Techniques for Electrical Usage ..............................11-6

Standby Battery ....................................................11-6

Operating on the Main Battery .............................11-6

Analog Instrument Failure ...........................................11-6

Pneumatic System Failure ............................................11-7

Pitot/Static System Failure ...........................................11-7

Communication/Navigation System Malfunction .......11-8

GPS Nearest Airport Function .....................................11-9

Nearest Airports Using the PFD ...............................11-9

Additional Information for a Speciﬁ c Airport ......11-9

Nearest Airports Using the MFD ...........................11-10

Navigating the MFD Page Groups .....................11-10

Nearest Airport Page Group ...............................11-10

Nearest Airports Page Soft Keys ........................11-10

Situational Awareness ................................................11-11

Summary ............................................................. 11-12

Trafﬁ c Avoidance ...................................................11-14

Appendix A

Clearance Shorthand ......................................... A-1

Appendix B

Instrument Training Lesson Guide ................... B-1

Glossary ..............................................................G-1

Index ......................................................................I-1

1-1

Introduction

Human factors is a broad ﬁ eld that examines the interaction

between people, machines, and the environment for the

purpose of improving performance and reducing errors. As

aircraft became more reliable and less prone to mechanical

failure, the percentage of accidents related to human factors

increased. Some aspect of human factors now accounts for

over 80 percent of all accidents. Pilots who have a good

understanding of human factors are better equipped to plan

and execute a safe and uneventful ﬂ ight.

Flying in instrument meteorological conditions (IMC) can

result in sensations that are misleading to the body’s sensory

system. A safe pilot needs to understand these sensations and

effectively counteract them. Instrument ﬂ ying requires a pilot

to make decisions using all available resources.

The elements of human factors covered in this chapter

include sensory systems used for orientation, illusions in

ﬂ ight, physiological and psychological factors, medical

factors, aeronautical decision-making, and crew resource

management (CRM).

Human

Factors

Chapter 1

1-2

Figure 1-1. Rubic’s Cube Graphic.

Sensory Systems for Orientation

Orientation is the awareness of the position of the aircraft

and of oneself in relation to a speciﬁ c reference point.

Disorientation is the lack of orientation, and spatial

disorientation speciﬁ cally refers to the lack of orientation

with regard to position in space and to other objects.

Orientation is maintained through the body’s sensory organs

in three areas: visual, vestibular, and postural. The eyes

maintain visual orientation. The motion sensing system in

the inner ear maintains vestibular orientation. The nerves in

the skin, joints, and muscles of the body maintain postural

orientation. When healthy human beings are in their natural

environment, these three systems work well. When the

human body is subjected to the forces of ﬂ ight, these senses

can provide misleading information. It is this misleading

information that causes pilots to become disoriented.

Eyes

Of all the senses, vision is most important in providing

information to maintain safe flight. Even though the

human eye is optimized for day vision, it is also capable

of vision in very low light environments. During the day,

the eye uses receptors called cones, while at night, vision is

facilitated by the use of rods.

Both of these provide a level

of vision optimized for the

lighting conditions that they

were intended. That is, cones

are ineffective at night and

rods are ineffective during

the day.

Rods, which contain rhodopsin

(called visual purple), are

especially sensitive to light

and increased light washes out

the rhodopsin compromising

the night vision. Hence, when

strong light is momentarily

introduced at night, vision

may be totally ineffective as

the rods take time to become

effective again in darkness.

Smoking, alcohol, oxygen

deprivation, and age affect

vision, especially at night. It

should be noted that at night,

oxygen deprivation such as one

caused from a climb to a high

altitude causes a significant

reduction in vision. A return

back to the lower altitude will

not restore a pilot’s vision in the same transitory period used

at the climb altitude.

The eye also has two blind spots. The day blind spot is the

location on the light sensitive retina where the optic nerve

ﬁ ber bundle (which carries messages from the eye to the

brain) passes through. This location has no light receptors,

and a message cannot be created there to be sent to the brain.

The night blind spot is due to a concentration of cones in an

area surrounding the fovea on the retina. Because there are

no rods in this area, direct vision on an object at night will

disappear. As a result, off-center viewing and scanning at

night is best for both obstacle avoidance and to maximize

situational awareness. [See the Pilot’s Handbook of

Aeronautical Knowledge and the Aeronautical Information

Manual (AIM) for detailed reading.]

The brain also processes visual information based upon color,

relationship of colors, and vision from objects around us.

Figure 1-1 demonstrates the visual processing of information.

The brain assigns color based on many items to include an

object’s surroundings. In the ﬁ gure below, the orange square

on the shaded side of the cube is actually the same color

as the brown square in the center of the cube’s top face.

1-3

Figure 1-2. Shepard’s Tables.

Isolating the orange square from surrounding inﬂ uences

will reveal that it is actually brown. The application to a real

environment is evident when processing visual information

that is inﬂ uenced by surroundings. The ability to pick out an

airport in varied terrain or another aircraft in a light haze are

examples of problems with interpretation that make vigilance

all the more necessary.

Figure 1-2 illustrates problems with perception. Both tables

are the same lengths. Objects are easily misinterpreted in

size to include both length and width. Being accustomed to

a 75-foot-wide runway on ﬂ at terrain is most likely going

to influence a pilot’s perception of a wider runway on

uneven terrain simply because of the inherent processing

experience.

Vision Under Dim and Bright Illumination

Under conditions of dim illumination, aeronautical charts and

aircraft instruments can become unreadable unless adequate

ﬂ ight deck lighting is available. In darkness, vision becomes

more sensitive to light. This process is called dark adaptation.

Although exposure to total darkness for at least 30 minutes is

required for complete dark adaptation, a pilot can achieve a

moderate degree of dark adaptation within 20 minutes under

dim red ﬂ ight deck lighting.

Red light distorts colors (ﬁ lters the red spectrum), especially

on aeronautical charts, and makes it very difﬁ cult for the

eyes to focus on objects inside the aircraft. Pilots should

use it only where optimum outside night vision capability is

necessary. White ﬂ ight deck lighting (dim lighting) should

be available when needed for map and instrument reading,

especially under IMC conditions.

Since any degree of dark adaptation is lost within a few

seconds of viewing a bright light, pilots should close one eye

when using a light to preserve some degree of night vision.

During night ﬂ ights in the vicinity of lightning, ﬂ ight deck

lights should be turned up to help prevent loss of night vision

due to the bright ﬂ ashes. Dark adaptation is also impaired by

exposure to cabin pressure altitudes above 5,000 feet, carbon

monoxide inhaled through smoking, deﬁ ciency of Vitamin A

in the diet, and by prolonged exposure to bright sunlight.

During ﬂ ight in visual meteorological conditions (VMC),

the eyes are the major orientation source and usually provide

accurate and reliable information. Visual cues usually

prevail over false sensations from other sensory systems.

When these visual cues are taken away, as they are in IMC,

false sensations can cause the pilot to quickly become

disoriented.

An effective way to counter these false sensations is to

recognize the problem, disregard the false sensations, rely

on the ﬂ ight instruments, and use the eyes to determine the

aircraft attitude. The pilot must have an understanding of

the problem and the skill to control the aircraft using only

instrument indications.

1-4

Figure 1-4. Angular Acceleration and the Semicircular Tubes.

Figure 1-3. Inner Ear Orientation.

Ears

The inner ear has two major parts concerned with orientation,

the semicircular canals and the otolith organs. [Figure 1-3] The

semicircular canals detect angular acceleration of the body

while the otolith organs detect linear acceleration and gravity.

The semicircular canals consist of three tubes at right angles

to each other, each located on one of three axes: pitch, roll,

or yaw as illustrated in Figure 1-4. Each canal is ﬁ lled with

a ﬂ uid called endolymph ﬂ uid. In the center of the canal is

the cupola, a gelatinous structure that rests upon sensory

hairs located at the end of the vestibular nerves. It is the

movement of these hairs within the ﬂ uid which causes

sensations of motion.

Because of the friction between the ﬂ uid and the canal, it

may take about 15–20 seconds for the ﬂ uid in the ear canal

to reach the same speed as the canal’s motion.

To illustrate what happens during a turn, visualize the aircraft

in straight and level ﬂ ight. With no acceleration of the aircraft,

the hair cells are upright and the body senses that no turn

has occurred. Therefore, the position of the hair cells and the

actual sensation correspond.

Placing the aircraft into a turn puts the semicircular canal and

its ﬂ uid into motion, with the ﬂ uid within the semicircular

canal lagging behind the accelerated canal walls.[Figure 1-5]

This lag creates a relative movement of the ﬂ uid within the

canal. The canal wall and the cupula move in the opposite

direction from the motion of the ﬂ uid.

The brain interprets the movement of the hairs to be a turn in

the same direction as the canal wall. The body correctly senses

that a turn is being made. If the turn continues at a constant

rate for several seconds or longer, the motion of the ﬂ uid in

1-5

Figure 1-6. Linear Acceleration.

Figure 1-5. Angular Acceleration.

the canals catches up with the canal walls. The hairs are no

longer bent, and the brain receives the false impression that

turning has stopped. Thus, the position of the hair cells and the

resulting sensation during a prolonged, constant turn in either

direction will result in the false sensation of no turn.

When the aircraft returns to straight-and-level ﬂ ight, the ﬂ uid

in the canal moves brieﬂ y in the opposite direction. This sends

a signal to the brain that is falsely interpreted as movement

in the opposite direction. In an attempt to correct the falsely

perceived turn, the pilot may reenter the turn placing the

aircraft in an out of control situation.

The otolith organs detect linear acceleration and gravity in a

similar way. Instead of being ﬁ lled with a ﬂ uid, a gelatinous

membrane containing chalk-like crystals covers the sensory

hairs. When the pilot tilts his or her head, the weight of these

crystals causes this membrane to shift due to gravity and

the sensory hairs detect this shift. The brain orients this new

position to what it perceives as vertical. Acceleration and

deceleration also cause the membrane to shift in a similar

manner. Forward acceleration gives the illusion of the head

tilting backward. [Figure 1-6] As a result, during takeoff and

while accelerating, the pilot may sense a steeper than normal

climb resulting in a tendency to nose-down.

Nerves

Nerves in the body’s skin, muscles, and joints constantly

send signals to the brain, which signals the body’s relation to

gravity. These signals tell the pilot his or her current position.

Acceleration will be felt as the pilot is pushed back into the

seat. Forces created in turns can lead to false sensations of

the true direction of gravity, and may give the pilot a false

sense of which way is up.

Uncoordinated turns, especially climbing turns, can cause

misleading signals to be sent to the brain. Skids and slips

give the sensation of banking or tilting. Turbulence can create

motions that confuse the brain as well. Pilots need to be aware

that fatigue or illness can exacerbate these sensations and

ultimately lead to subtle incapacitation.

Illusions Leading to Spatial

Disorientation

The sensory system responsible for most of the illusions

leading to spatial disorientation is the vestibular system.

Visual illusions can also cause spatial disorientation.

Vestibular Illusions

The Leans

A condition called the leans can result when a banked attitude,

to the left for example, may be entered too slowly to set in

motion the ﬂ uid in the “roll” semicircular tubes. [Figure 1-5]

An abrupt correction of this attitude sets the ﬂ uid in motion,

creating the illusion of a banked attitude to the right. The

disoriented pilot may make the error of rolling the aircraft

into the original left banked attitude, or if level ﬂ ight is

maintained, will feel compelled to lean in the perceived

vertical plane until this illusion subsides.

1-6

Figure 1-7. Graveyard Spiral.

Coriolis Illusion

The coriolis illusion occurs when a pilot has been in a turn

long enough for the ﬂ uid in the ear canal to move at the same

speed as the canal. A movement of the head in a different

plane, such as looking at something in a different part of the

ﬂ ight deck, may set the ﬂ uid moving and create the illusion

of turning or accelerating on an entirely different axis.

This action causes the pilot to think the aircraft is doing a

maneuver that it is not. The disoriented pilot may maneuver

the aircraft into a dangerous attitude in an attempt to correct

the aircraft’s perceived attitude.

For this reason, it is important that pilots develop an instrument

cross-check or scan that involves minimal head movement.

Take care when retrieving charts and other objects in the ﬂ ight

deck—if something is dropped, retrieve it with minimal head

movement and be alert for the coriolis illusion.

Graveyard Spiral

As in other illusions, a pilot in a prolonged coordinated,

constant rate turn, will have the illusion of not turning.

During the recovery to level ﬂ ight, the pilot will experience

the sensation of turning in the opposite direction. The

disoriented pilot may return the aircraft to its original turn.

Because an aircraft tends to lose altitude in turns unless the

pilot compensates for the loss in lift, the pilot may notice

a loss of altitude. The absence of any sensation of turning

creates the illusion of being in a level descent. The pilot may

pull back on the controls in an attempt to climb or stop the

descent. This action tightens the spiral and increases the loss

of altitude; hence, this illusion is referred to as a graveyard

spiral. [Figure 1-7] At some point, this could lead to a loss

of control by the pilot.

Somatogravic Illusion

A rapid acceleration, such as experienced during takeoff,

stimulates the otolith organs in the same way as tilting the

head backwards. This action creates the somatogravic illusion

of being in a nose-up attitude, especially in situations without

good visual references. The disoriented pilot may push the

aircraft into a nose-low or dive attitude. A rapid deceleration

by quick reduction of the throttle(s) can have the opposite

effect, with the disoriented pilot pulling the aircraft into a

nose-up or stall attitude.

Inversion Illusion

An abrupt change from climb to straight-and-level ﬂ ight can

stimulate the otolith organs enough to create the illusion of

tumbling backwards, or inversion illusion. The disoriented

pilot may push the aircraft abruptly into a nose-low attitude,

possibly intensifying this illusion.

Elevator Illusion

An abrupt upward vertical acceleration, as can occur in

an updraft, can stimulate the otolith organs to create the

illusion of being in a climb. This is called elevator illusion.

The disoriented pilot may push the aircraft into a nose-low

attitude. An abrupt downward vertical acceleration, usually

1-7

Figure 1-8. Sensations From Centrifugal Force.

in a downdraft, has the opposite effect, with the disoriented

pilot pulling the aircraft into a nose-up attitude.

Visual Illusions

Visual illusions are especially hazardous because pilots rely

on their eyes for correct information. Two illusions that lead

to spatial disorientation, false horizon and autokinesis, are

concerned with only the visual system.

False Horizon

A sloping cloud formation, an obscured horizon, an aurora

borealis, a dark scene spread with ground lights and stars,

and certain geometric patterns of ground lights can provide

inaccurate visual information, or false horizon, for aligning

the aircraft correctly with the actual horizon. The disoriented

pilot may place the aircraft in a dangerous attitude.

Autokinesis

In the dark, a stationary light will appear to move about when

stared at for many seconds. The disoriented pilot could lose

control of the aircraft in attempting to align it with the false

movements of this light, called autokinesis.

Postural Considerations

The postural system sends signals from the skin, joints, and

muscles to the brain that are interpreted in relation to the

Earth’s gravitational pull. These signals determine posture.

Inputs from each movement update the body’s position to

the brain on a constant basis. “Seat of the pants” ﬂ ying is

largely dependent upon these signals. Used in conjunction

with visual and vestibular clues, these sensations can be

fairly reliable. However, because of the forces acting upon

the body in certain ﬂ ight situations, many false sensations

can occur due to acceleration forces overpowering gravity.

[Figure 1-8] These situations include uncoordinated turns,

climbing turns, and turbulence.

Demonstration of Spatial Disorientation

There are a number of controlled aircraft maneuvers a pilot

can perform to experiment with spatial disorientation. While

each maneuver will normally create a speciﬁ c illusion, any

false sensation is an effective demonstration of disorientation.

Thus, even if there is no sensation during any of these

maneuvers, the absence of sensation is still an effective

demonstration in that it shows the inability to detect bank

or roll. There are several objectives in demonstrating these

various maneuvers.

1. They teach pilots to understand the susceptibility of

the human system to spatial disorientation.

2. They demonstrate that judgments of aircraft attitude

based on bodily sensations are frequently false.

3. They help lessen the occurrence and degree of

disorientation through a better understanding of the

relationship between aircraft motion, head movements,

and resulting disorientation.

4. They help instill a greater conﬁ dence in relying on

ﬂ ight instruments for assessing true aircraft attitude.

1-8

A pilot should not attempt any of these maneuvers at low

altitudes, or in the absence of an instructor pilot or an

appropriate safety pilot.

Climbing While Accelerating

With the pilot’s eyes closed, the instructor pilot maintains

approach airspeed in a straight-and-level attitude for several

seconds, and then accelerates while maintaining straight-and-

level attitude. The usual illusion during this maneuver, without

visual references, will be that the aircraft is climbing.

Climbing While Turning

With the pilot’s eyes still closed and the aircraft in a straight-

and-level attitude, the instructor pilot now executes, with a

relatively slow entry, a well-coordinated turn of about 1.5

positive G (approximately 50° bank) for 90°. While in the

turn, without outside visual references and under the effect of

the slight positive G, the usual illusion produced is that of a

climb. Upon sensing the climb, the pilot should immediately

open the eyes and see that a slowly established, coordinated

turn produces the same feeling as a climb.

Diving While Turning

Repeating the previous procedure, with the exception that

the pilot’s eyes should be kept closed until recovery from

the turn is approximately one-half completed can create this

sensation. With the eyes closed, the usual illusion will be

that the aircraft is diving.

Tilting to Right or Left

While in a straight-and-level attitude, with the pilot’s eyes

closed, the instructor pilot executes a moderate or slight skid

to the left with wings level. This creates the illusion of the

body being tilted to the right.

Reversal of Motion

This illusion can be demonstrated in any of the three planes of

motion. While straight and level, with the pilot’s eyes closed,

the instructor pilot smoothly and positively rolls the aircraft to

approximately a 45° bank attitude while maintaining heading

and pitch attitude. This creates the illusion of a strong sense

of rotation in the opposite direction. After this illusion is

noted, the pilot should open his or her eyes and observe that

the aircraft is in a banked attitude.

Diving or Rolling Beyond the Vertical Plane

This maneuver may produce extreme disorientation. While

in straight-and-level ﬂ ight, the pilot should sit normally,

either with eyes closed or gaze lowered to the ﬂ oor. The

instructor pilot starts a positive, coordinated roll toward a

30° or 40° angle of bank. As this is in progress, the pilot

tilts his or her head forward, looks to the right or left, then

immediately returns his or her head to an upright position.

The instructor pilot should time the maneuver so the roll is

stopped as the pilot returns his or her head upright. An intense

disorientation is usually produced by this maneuver, and the

pilot experiences the sensation of falling downward into the

direction of the roll.

In the descriptions of these maneuvers, the instructor pilot is

doing the ﬂ ying, but having the pilot do the ﬂ ying can also

be a very effective demonstration. The pilot should close his

or her eyes and tilt the head to one side. The instructor pilot

tells the pilot what control inputs to perform. The pilot then

attempts to establish the correct attitude or control input with

eyes closed and head tilted. While it is clear the pilot has no

idea of the actual attitude, he or she will react to what the

senses are saying. After a short time, the pilot will become

disoriented and the instructor pilot then tells the pilot to

look up and recover. The beneﬁ t of this exercise is the pilot

experiences the disorientation while ﬂ ying the aircraft.

Coping with Spatial Disorientation

To prevent illusions and their potentially disastrous

consequences, pilots can:

1. Understand the causes of these illusions and remain

constantly alert for them. Take the opportunity to

understand and then experience spatial disorientation

illusions in a device such as a Barany chair, a

Vertigon, or a Virtual Reality Spatial Disorientation

Demonstrator.

2. Always obtain and understand preflight weather

brieﬁ ngs.

3. Before ﬂ ying in marginal visibility (less than 3 miles)

or where a visible horizon is not evident such as ﬂ ight

over open water during the night, obtain training and

maintain proﬁ ciency in airplane control by reference

to instruments.

4. Do not continue ﬂ ight into adverse weather conditions

or into dusk or darkness unless proﬁ cient in the use of

ﬂ ight instruments. If intending to ﬂ y at night, maintain

night-ﬂ ight currency and proﬁ ciency. Include cross-

country and local operations at various airﬁ elds.

5. Ensure that when outside visual references are used,

they are reliable, ﬁ xed points on the Earth’s surface.

6. Avoid sudden head movement, particularly during

takeoffs, turns, and approaches to landing.

7. Be physically tuned for ﬂ ight into reduced visibility.

That is, ensure proper rest, adequate diet, and, if ﬂ ying

at night, allow for night adaptation. Remember that

illness, medication, alcohol, fatigue, sleep loss, and

mild hypoxia are likely to increase susceptibility to

spatial disorientation.

1-9

Water Refraction

Rain on the windscreen can create an illusion of being at a

higher altitude due to the horizon appearing lower than it is.

This can result in the pilot ﬂ ying a lower approach.

Haze

Atmospheric haze can create an illusion of being at a greater

distance and height from the runway. As a result, the pilot

will have a tendency to be low on the approach. Conversely,

extremely clear air (clear bright conditions of a high attitude

airport) can give the pilot the illusion of being closer than he

or she actually is, resulting in a high approach, which may

result in an overshoot or go around. The diffusion of light

due to water particles on the windshield can adversely affect

depth perception. The lights and terrain features normally

used to gauge height during landing become less effective

for the pilot.

Fog

Flying into fog can create an illusion of pitching up. Pilots

who do not recognize this illusion will often steepen the

approach quite abruptly.

Ground Lighting Illusions

Lights along a straight path, such as a road or lights on moving

trains, can be mistaken for runway and approach lights. Bright

runway and approach lighting systems, especially where

few lights illuminate the surrounding terrain, may create the

illusion of less distance to the runway. The pilot who does not

recognize this illusion will often ﬂ y a higher approach.

How To Prevent Landing Errors Due to

Optical Illusions

To prevent these illusions and their potentially hazardous

consequences, pilots can:

1. Anticipate the possibility of visual illusions during

approaches to unfamiliar airports, particularly at

night or in adverse weather conditions. Consult

airport diagrams and the Airport/Facility Directory

(A/FD) for information on runway slope, terrain, and

lighting.

2. Make frequent reference to the altimeter, especially

during all approaches, day and night.

3. If possible, conduct aerial visual inspection of

unfamiliar airports before landing.

8. Most importantly, become proﬁ cient in the use of

flight instruments and rely upon them. Trust the

instruments and disregard your sensory perceptions.

The sensations that lead to illusions during instrument

ﬂ ight conditions are normal perceptions experienced by

pilots. These undesirable sensations cannot be completely

prevented, but through training and awareness, pilots can

ignore or suppress them by developing absolute reliance

on the flight instruments. As pilots gain proficiency in

instrument ﬂ ying, they become less susceptible to these

illusions and their effects.

Optical Illusions

Of the senses, vision is the most important for safe ﬂ ight.

However, various terrain features and atmospheric conditions

can create optical illusions. These illusions are primarily

associated with landing. Since pilots must transition from

reliance on instruments to visual cues outside the ﬂ ight

deck for landing at the end of an instrument approach, it is

imperative they be aware of the potential problems associated

with these illusions, and take appropriate corrective action.

The major illusions leading to landing errors are described

below.

Runway Width Illusion

A narrower-than-usual runway can create an illusion the

aircraft is at a higher altitude than it actually is, especially

when runway length-to-width relationships are comparable.

[Figure 1-9A] The pilot who does not recognize this illusion

will ﬂ y a lower approach, with the risk of striking objects

along the approach path or landing short. A wider-than-usual

runway can have the opposite effect, with the risk of leveling

out high and landing hard, or overshooting the runway.

Runway and Terrain Slopes Illusion

An upsloping runway, upsloping terrain, or both, can create

an illusion the aircraft is at a higher altitude than it actually

is. [Figure 1-9B] The pilot who does not recognize this

illusion will ﬂ y a lower approach. Downsloping runways and

downsloping approach terrain can have the opposite effect.

Featureless Terrain Illusion

An absence of surrounding ground features, as in an

overwater approach, over darkened areas, or terrain made

featureless by snow, can create an illusion the aircraft is at

a higher altitude than it actually is. This illusion, sometimes

referred to as the “black hole approach,” causes pilots to ﬂ y

a lower approach than is desired.

1-10

Figure 1-9. Runway Width and Slope Illusions.

6. Recognize that the chances of being involved in an

approach accident increase when some emergency or

other activity distracts from usual procedures.

7. Maintain optimum proﬁ ciency in landing procedures.

4. Use Visual Approach Slope Indicator (VASI) or

Precision Approach Path Indicator (PAPI) systems

for a visual reference, or an electronic glide slope,

whenever they are available.

5. Utilize the visual descent point (VDP) found on many

nonprecision instrument approach procedure charts.

1-11

Figure 1-10. Stress and Performance.

Physiological and Psychological Factors

Physiological or psychological factors can affect a pilot

and compromise the safety of a ﬂ ight. These factors are

stress, medical, alcohol, and fatigue. Any of these factors,

individually or in combination, signiﬁ cantly degrade the

pilot’s decision-making or ﬂ ying abilities.

Stress

Stress is the body’s response to demands placed upon it. These

demands can be either pleasant or unpleasant in nature. The

causes of stress for a pilot can range from unexpected weather

or mechanical problems while in ﬂ ight, to personal issues

unrelated to ﬂ ying. Stress is an inevitable and necessary part

of life; it adds motivation to life and heightens an individual’s

response to meet any challenge. The effects of stress are

cumulative and there is a limit to a person’s adaptive nature.

This limit, called the stress tolerance level (or channel

capacity), is based on the ability to cope with the situation.

At ﬁ rst, some amount of stress can be desirable and can

actually improve performance. However, higher stress levels,

particularly over long periods of time, can adversely affect

performance. Performance will generally increase with the

onset of stress, but will peak and then begin to fall off rapidly

as stress levels exceed the ability to cope. [Figure 1-10]

At this point, a pilot’s performance begins to decline and

judgment deteriorates. Complex or unfamiliar tasks require

higher levels of performance than simple or overlearned

tasks. Complex or unfamiliar tasks are also more subject to

the adverse effects of increasing stress than simple or familiar

tasks. [Figure 1-10]

The indicators of excessive stress often show as three types

of symptoms: (1) emotional, (2) physical, and (3) behavioral.

Emotional symptoms may surface as over-compensation,

denial, suspicion, paranoia, agitation, restlessness, or

defensiveness. Physical stress can result in acute fatigue

while behavioral degradation will be manifested as sensitivity

to criticism, tendency to be argumentative, arrogance, and

hostility. Pilots need to learn to recognize the symptoms of

stress as they begin to occur.

There are many techniques available that can help reduce

stress in life or help people cope with it better. Not all of the

following ideas may be a solution, but some of them should

be effective.

1. Become knowledgeable about stress.

2. Take a realistic self-assessment. (See the Pilot’s

Handbook of Aeronautical Knowledge).

3. Take a systematic approach to problem solving.

4. Develop a lifestyle that will buffer against the effects

of stress.

5. Practice behavior management techniques.

6. Establish and maintain a strong support network.

Good ﬂ ight deck stress management begins with good life

stress management. Many of the stress coping techniques

practiced for life stress management are not usually practical

in ﬂ ight. Rather, pilots must condition themselves to relax and

think rationally when stress appears. The following checklist

outlines some methods of ﬂ ight deck stress management.

1. Avoid situations that distract from ﬂ ying the aircraft.

2. Reduce ﬂ ight deck workload to reduce stress levels.

This will create a proper environment in which to make

good decisions. Typically, ﬂ ying involves higher stress

levels during takeoff and landing phases. Between the

two generally lies a period of low activity resulting

in a lower stress level. Transitioning from the cruise

phase to the landing phase is generally accompanied

by a significant workload that, if not properly

accommodated, will increase stress significantly.

Proper planning and prioritization of flight deck

duties are key to avoiding events that affect the pilot's

capacity to maintain situational awareness.

1-12

3. If a problem occurs, remain calm. If time is not a

pressing factor, follow the analytical approach to

decision-making: think for a moment, weigh the

alternatives, select and take an appropriate course of

action, and then evaluate its effects.

If an emergency situation occurs, remain calm and

use the aeronautical decision-making (ADM) process

to resolve the emergency. This process relies on the

pilot’s training and experience to accurately and

automatically respond to an emergency situation.

Constant training in handling emergency procedures

will help reduce pilot stress when an emergency

occurs.

4. Become thoroughly familiar with the aircraft, its

operation, and emergency procedures. Also, maintain

ﬂ ight proﬁ ciency to build conﬁ dence.

5. Know and respect personal limits. Studies have

suggested that highly experienced pilots have taken

more chances when flying into potential icing

conditions than low time or inexperienced pilots.

Very low time pilots without experience may analyze

and interpret the likelihood for “potential” ﬂ ight into

icing without the beneﬁ t of life experience, thereby

making decisions closely aligned with the compilation

of their training and recent academic knowledge.

Highly experienced pilots may evaluate the current

situation based upon the empirical information

(sometimes diluted with time) coupled with their

vast experience. This may lead to a level of greater

acceptability of the situation because their experience

has illustrated successful navigation of this problem

before. Therefore, the automatic decision may be in

error because not all salient facts are evaluated.

6. Do not allow small mistakes to be distractions during

ﬂ ight; rather, review and analyze them after landing.

7. If flying adds stress, either stop flying or seek

professional help to manage stress within acceptable

limits.

Medical Factors

A “go/no-go” decision based on a pilot’s medical factors is

made before each ﬂ ight. The pilot should not only preﬂ ight

check the aircraft, but also himself or herself before

every ﬂ ight. A pilot should ask, “Can I pass my medical

examination right now?” If the answer is not an absolute

“yes,” do not ﬂ y. This is especially true for pilots embarking

on ﬂ ights in IMC. Instrument ﬂ ying is much more demanding

than ﬂ ying in VMC, and peak performance is critical for the

safety of ﬂ ight.

Pilot performance can be seriously degraded by both

prescribed and over-the-counter medications, as well as

by the medical conditions for which they are taken. Many

medications, such as tranquilizers, sedatives, strong pain

relievers, and cough suppressants, have primary effects

that impair judgment, memory, alertness, coordination,

vision, and the ability to make calculations. Others, such

as antihistamines, blood pressure drugs, muscle relaxants,

and agents to control diarrhea and motion sickness, have

side effects that impair the same critical functions. Any

medication that depresses the nervous system, such as a

sedative, tranquilizer, or antihistamine, makes a pilot much

more susceptible to hypoxia.

Title 14 of the Code of Federal Regulations (14 CFR) prohibits

pilots from performing crewmember duties while using any

medication that affects the faculties in any way contrary to

safety. The safest rule is not to ﬂ y as a crewmember while

taking any medication, unless approved to do so by the

Federal Aviation Administration (FAA). If there is any doubt

regarding the effects of any medication, consult an Aviation

Medical Examiner (AME) before ﬂ ying.

Alcohol

14 CFR part 91 prohibits pilots from performing crewmember

duties within 8 hours after drinking any alcoholic beverage or

while under the inﬂ uence. Extensive research has provided a

number of facts about the hazards of alcohol consumption and

ﬂ ying. As little as one ounce of liquor, one bottle of beer, or

four ounces of wine can impair ﬂ ying skills and render a pilot

much more susceptible to disorientation and hypoxia. Even

after the body completely metabolizes a moderate amount of

alcohol, a pilot can still be impaired for many hours. There

is simply no way of increasing the metabolism of alcohol or

alleviating a hangover.

Fatigue

Fatigue is one of the most treacherous hazards to ﬂ ight safety,

as it may not be apparent to a pilot until serious errors are

made. Fatigue can be either acute (short-term) or chronic

(long-term).

Acute Fatigue

A normal occurrence of everyday living, acute fatigue is

the tiredness felt after long periods of physical and mental

strain, including strenuous muscular effort, immobility, heavy

mental workload, strong emotional pressure, monotony, and

lack of sleep. Adequate rest, regular exercise, and proper

nutrition prevent acute fatigue.

1-13

Indications of fatigue are generally subtle and hard to

recognize because the individual being assessed is generally

the person making the assessment, as in single pilot

operations. Therefore, the pilot must look at small errors

that occur to provide an indication of becoming fatigued.

These include:

• Misplacing items during the preﬂ ight;

• Leaving material (pencils, charts) in the planning

area;

• Missing radio calls;

• Answering calls improperly (read-backs); and

• Improper tuning of frequencies.

Chronic Fatigue

Chronic fatigue occurs when there is not enough time for a

full recovery from repeated episodes of acute fatigue. Chronic

fatigue’s underlying cause is generally not “rest-related” and

may have deeper points of origin. Therefore, rest alone may

not resolve chronic fatigue.

Chronic fatigue is a combination of both physiological

problems and psychological issues. Psychological problems

such as ﬁ nancial, home life, or job related stresses cause a

lack of qualiﬁ ed rest that is only resolved by mitigating the

underpinning problems. Without resolution, performance

continues to fall off, judgment becomes impaired, and

unwarranted risks are taken. Recovery from chronic fatigue

requires a prolonged and deliberate solution. In either case,

unless adequate precautions are taken, personal performance

could be impaired and adversely affect pilot judgment and

decision-making.

IMSAFE Checklist

The following checklist, IMSAFE, is intended for a pilot’s

personal preﬂ ight use. A quick check of the items on this

list will help a pilot make a good self-evaluation prior to any

ﬂ ight. If the answer to any of the checklist questions is yes,

then the pilot should consider not ﬂ ying.

Illness

Do I have any symptoms?

Medication

Have I been taking prescription or over-the-counter drugs?

Stress

Am I under psychological pressure from the job? Do I have

money, health, or family problems?

Alcohol

Have I been drinking within 8 hours? Within 24 hours?

Fatigue

Am I tired and not adequately rested?

Eating

Have I eaten enough of the proper foods to keep adequately

nourished during the entire ﬂ ight?

Hazard Identiﬁ cation

In order to identify a hazard, it would be useful to deﬁ ne what

a hazard is. The FAA System Safety course deﬁ nes a hazard

as: “a present condition, event, object, or circumstance that

could lead or contribute to an unplanned or undesired event.”

Put simply, a hazard is a source of danger. Potential hazards

may be identiﬁ ed from a number of internal and external

sources. These may be based upon several concurrent factors

that provide an indication and ultimate identiﬁ cation of a

hazard. Consider the following situations:

Situation 1

The pilot has just taken off and is entering the clouds. Suddenly,

there is an explosive sound. The sudden noise is disturbing and

occurs as the pilot is given a new heading, a climb restriction,

and the frequency for the departure control.

Situation 2

The pilot took off late in a rented aircraft (ﬁ rst time ﬂ ying

this model), and is now in night conditions due to the delay,

and ﬂ ying on an instrument ﬂ ight rules (IFR) ﬂ ight plan in

IMC conditions. The radios do not seem to work well and

develop static. They seem to be getting weaker. As the pilot

proceeds, the rotating beacon stops ﬂ ashing/rotating, and the

lights become dimmer. As the situation progresses, the pilot

is unaware of the problem because the generator warning

light, (on the lower left of the panel) is obscured by the chart

on the pilot’s lap.

Both situations above represent hazards that must be dealt

with differently and a level of risk must be associated with

each depending on various factors affecting the ﬂ ight.

Risk Analysis

Risk is deﬁ ned as the future impact of a hazard that is not

eliminated or controlled. It is the possibility of loss or injury.

Risk analysis is the process whereby hazards are characterized

by their likelihood and severity. Risk analysis evaluates

the hazards to determine the outcomes and how abrupt that

outcome will occur. The analysis applied will be qualitative

to the degree that time allows resulting in either an analytical

or automatic approach in the decision-making process.

1-14

In the ﬁ rst situation, the decision may be automatic: ﬂ y the

airplane to a safe landing. Since automatic decision-making

is based upon education and experience, an inexperienced

pilot may react improperly to the situation which results in

an inadequate action. To mitigate improper decision-making,

immediate action items from emergency procedures should

be learned. Training, education, and mentorship are all key

factors in honing automatic decision-making skills.

In the second situation, if the pilot has a ﬂ ashlight onboard, it

can be used for illumination, although its light may degrade

night vision. After changing the appropriate transponder

code, and making calls in the blind, awareness of present

location becomes imperative, especially if the pilot must

execute a controlled descent to VMC conditions. Proper

preﬂ ight planning conducted before departure and constant

awareness of location provide an element of both comfort

(reduces stress) and information from which the pilot can

draw credible information.

In both cases, the outcomes can be successful through

systems understanding, emergency procedures training, and

correctly analyzing the risks associated with each course

of action.

Crew Resource Management (CRM)

and Single-Pilot Resource Management

(SRM)

Crew resource management (CRM) and single-pilot resource

management (SRM) is the ability for the crew or pilot to

manage all resources effectively to ensure the outcome of the

ﬂ ight is successful. In general aviation, SRM will be most

often used and its focus is on the single-pilot operation. SRM

integrates the following:

• Situational Awareness

• Flight Deck Resource Management

• Task Management

• Aeronautical Decision-making (ADM) and Risk

Management

SRM recognizes the need to seek proper information from

these sources to make a valid decision. For instance, the

pilot may have to request assistance from others and be

assertive to resolve situations. Pilots should understand the

need to seek information from other sources until they have

the proper information to make the best decision. Once a

pilot has gathered all pertinent information and made the

appropriate decision, the pilot needs to perform an assessment

of the action taken.

Situational Awareness

Situational awareness is the accurate perception of

operational and environmental factors that affect the ﬂ ight. It

is a logical analysis based upon the machine, external support,

environment, and the pilot. It is knowing what is going on.

Flight Deck Resource Management

CRM is the effective use of all available resources: human,

equipment, and information. It focuses on communication

skills, teamwork, task allocation, and decision-making.

While CRM often concentrates on pilots who operate in

crew environments, the elements and concepts also apply to

single-pilot operations.

Human Resources

Human resources include everyone routinely working with the

pilot to ensure ﬂ ight safety. These people include, but are not

limited to: weather briefers, ﬂ ight line personnel, maintenance

personnel, crew members, pilots, and air trafﬁ c personnel.

Pilots need to effectively communicate with these people.

This is accomplished by using the key components of the

communication process: inquiry, advocacy, and assertion.

Pilots must recognize the need to seek enough information

from these resources to make a valid decision. After the

necessary information has been gathered, the pilot’s decision

must be passed on to those concerned, such as air trafﬁ c

controllers, crew members, and passengers. The pilot may

have to request assistance from others and be assertive to

safely resolve some situations.

Equipment

Equipment in many of today’s aircraft includes automated

ﬂ ight and navigation systems. These automatic systems, while

providing relief from many routine ﬂ ight deck tasks, present a

different set of problems for pilots. The automation intended

to reduce pilot workload essentially removes the pilot from the

process of managing the aircraft, thereby reducing situational

awareness and leading to complacency. Information from

these systems needs to be continually monitored to ensure

proper situational awareness. Pilots should be thoroughly

familiar with the operation of and information provided by

all systems used. It is essential that pilots be aware not only

of equipment capabilities, but also equipment limitations in

order to manage those systems effectively and safely.

Information Workload

Information workloads and automated systems, such as

autopilots, need to be properly managed to ensure a safe

1-15

Figure 1-11. The Margin of Safety.

ﬂ ight. The pilot ﬂ ying in IMC is faced with many tasks, each

with a different level of importance to the outcome of the

ﬂ ight. For example, a pilot preparing to execute an instrument

approach to an airport needs to review the approach chart,

prepare the aircraft for the approach and landing, complete

checklists, obtain information from Automatic Terminal

Information Service (ATIS) or air trafﬁ c control (ATC), and

set the navigation radios and equipment.

The pilot who effectively manages his or her workload

will complete as many of these tasks as early as possible

to preclude the possibility of becoming overloaded by last

minute changes and communication priorities in the later,

more critical stages of the approach. Figure 1-11 shows the

margin of safety is at the minimum level during this stage

of the approach. Routine tasks delayed until the last minute

can contribute to the pilot becoming overloaded and stressed,

resulting in erosion of performance.

By planning ahead, a pilot can effectively reduce workload

during critical phases of ﬂ ight. If a pilot enters the ﬁ nal

phases of the instrument approach unprepared, the pilot

should recognize the situation, abandon the approach, and

try it again after becoming better prepared. Effective resource

management includes recognizing hazardous situations and

attitudes, decision-making to promote good judgment and

headwork, and managing the situation to ensure the safe

outcome of the IFR ﬂ ight.

Task Management

Pilots have a limited capacity for information. Once

information ﬂ ow exceeds the pilot’s ability to mentally

process the information any additional information will

become unattended or displace other tasks and information

already being processed. This is termed channel capacity and

once reached only two alternatives exist: shed the unimportant

tasks or perform all tasks at a less than optimal level. Like an

electrical circuit being overloaded, either the consumption

must be reduced or a circuit failure is experienced.

The pilot who effectively manages the tasks and properly

prioritizes them will have a successful ﬂ ight. For example,

do not become distracted and ﬁ xate on an instrument light

failure. This unnecessary focus displaces capability and

prevents the pilot’s ability to appreciate tasks of greater

importance. By planning ahead, a pilot can effectively reduce

workload during critical phases of a ﬂ ight.

Aeronautical Decision-Making (ADM)

Flying safely requires the effective integration of three

separate sets of skills. Most obvious are the basic stick-and-

rudder skills needed to control the airplane. Next, are skills

related to proﬁ cient operation of aircraft systems, and last,

but not least, are ADM skills.

ADM is a systematic approach to the mental process used

by pilots to consistently determine the best course of action

in response to a given set of circumstances. The importance

of learning effective ADM skills cannot be overemphasized.

While progress is continually being made in the advancement

of pilot training methods, airplane equipment and systems, and

services for pilots, accidents still occur. Despite all the changes

in technology to improve ﬂ ight safety, one factor remains the

same—the human factor. While the FAA strives to eliminate

errors through training and safety programs, one fact remains:

humans make errors. It is estimated that approximately 80

percent of all aviation accidents are human factors related.

1-16

The ADM process addresses all aspects of decision making

in the ﬂ ight deck and identiﬁ es the steps involved in good

decision making. While the ADM process will not eliminate

errors, it will help the pilot recognize errors, and in turn

enable the pilot to manage the error to minimize its effects.

These steps are:

1. Identifying personal attitudes hazardous to safe

ﬂ ight;

2. Learning behavior modiﬁ cation techniques;

3. Learning how to recognize and cope with stress;

4. Developing risk assessment skills;

5. Using all resources; and

6. Evaluating the effectiveness of one’s ADM skills.

Historically, the term “pilot error” has been used to describe

the causes of these accidents. Pilot error means that an action

or decision made by the pilot was the cause, or a contributing

factor that led to the accident. This deﬁ nition also includes

the pilot’s failure to make a decision or take action. From

a broader perspective, the phrase “human factors related”

more aptly describes these accidents since it is usually not a

single decision that leads to an accident, but a chain of events

triggered by a number of factors.

The poor judgment chain, sometimes referred to as the “error

chain,” is a term used to describe this concept of contributing

factors in a human factors related accident. Breaking one link

in the chain normally is all that is necessary to change the

outcome of the sequence of events.

The Decision-Making Process

An understanding of the decision-making process provides

a pilot with a foundation for developing ADM skills.

Some situations, such as engine failures, require a pilot to

respond immediately using established procedures with a

little time for detailed analysis. This is termed automatic

decision-making and is based upon training, experience, and

recognition. Traditionally, pilots have been well trained to

react to emergencies, but are not as well prepared to make

decisions requiring a more reﬂ ective response where greater

analysis is required. Typically during a ﬂ ight, there is time

to examine any changes that occur, gather information, and

assess risk before reaching a decision. The steps leading to

this conclusion constitute the decision-making process.

Deﬁ ning the Problem

Problem deﬁ nition is the ﬁ rst step in the decision-making

process. Deﬁ ning the problem begins with recognizing that

a change has occurred or that an expected change did not

occur. A problem is perceived ﬁ rst by the senses, then is

distinguished through insight and experience. One critical

error that can be made during the decision-making process

is incorrectly deﬁ ning the problem. For example, a low oil

pressure reading could indicate that the engine is about to

fail and an emergency landing should be planned, or it could

mean that the oil pressure sensor has failed. The actions to be

taken in each of these circumstances would be signiﬁ cantly

different. One requires an immediate decision based upon

training, experience, and evaluation of the situation; whereas

the latter decision is based upon an analysis. It should be

noted that the same indication could result in two different

actions depending upon other inﬂ uences.

Choosing a Course of Action

After the problem has been identiﬁ ed, the pilot must evaluate

the need to react to it and determine the actions that may

be taken to resolve the situation in the time available.

The expected outcome of each possible action should be

considered and the risks assessed before deciding on a

response to the situation.

Implementing the Decision and Evaluating the

Outcome

Although a decision may be reached and a course of action

implemented, the decision-making process is not complete.

It is important to think ahead and determine how the decision

could affect other phases of ﬂ ight. As the ﬂ ight progresses, the

pilot must continue to evaluate the outcome of the decision

to ensure that it is producing the desired result.

Improper Decision-Making Outcomes

Pilots sometimes get in trouble not because of deﬁ cient basic

skills or system knowledge, but rather because of faulty

decision-making skills. Although aeronautical decisions

may appear to be simple or routine, each individual decision

in aviation often deﬁ nes the options available for the next

decision the pilot must make and the options, good or

bad, they provide. Therefore, a poor decision early on in

a ﬂ ight can compromise the safety of the ﬂ ight at a later

time necessitating decisions that must be more accurate and

decisive. Conversely, good decision-making early on in an

emergency provide greater latitude for options later on.

FAA Advisory Circular (AC) 60-22, deﬁ nes ADM as a

systematic approach to the mental process of evaluating a

given set of circumstances and determining the best course of

action. ADM thus builds upon the foundation of conventional

decision-making, but enhances the process to decrease

the probability of pilot error. Speciﬁ cally, ADM provides

a structure to help the pilot use all resources to develop

comprehensive situational awareness.

1-17

Figure 1-12. The 3P Model for Aeronautical Decision-Making.

Models for Practicing ADM

Two models for practicing ADM are presented below.

Perceive, Process, Perform

The Perceive–Process–Perform (3P) model for ADM offers

a simple, practical, and systematic approach that can be

used during all phases of ﬂ ight. [Figure 1-12] To use it,

the pilot will:

• Perceive the given set of circumstances for a ﬂ ight;

• Process by evaluating their impact on ﬂ ight safety;

and

• Perform by implementing the best course of action.

In the ﬁ rst step, the goal is to develop situational awareness

by perceiving hazards, which are present events, objects, or

circumstances that could contribute to an undesired future

event. In this step, the pilot will systematically identify and

list hazards associated with all aspects of the ﬂ ight: pilot,

aircraft, environment, and external pressures. It is important

to consider how individual hazards might combine. Consider,

for example, the hazard that arises when a new instrument

pilot with no experience in actual instrument conditions wants

to make a cross-country ﬂ ight to an airport with low ceilings

in order to attend an important business meeting.

In the second step, the goal is to process this information

to determine whether the identiﬁ ed hazards constitute risk,

which is deﬁ ned as the future impact of a hazard that is not

controlled or eliminated. The degree of risk posed by a given

hazard can be measured in terms of exposure (number of

people or resources affected), severity (extent of possible

loss), and probability (the likelihood that a hazard will cause

a loss). If the hazard is low ceilings, for example, the level

of risk depends on a number of other factors, such as pilot

training and experience, aircraft equipment and fuel capacity,

and others.

In the third step, the goal is to perform by taking action to

eliminate hazards or mitigate risk, and then continuously

evaluate the outcome of this action. With the example of low

ceilings at destination, for instance, the pilot can perform

good ADM by selecting a suitable alternate, knowing where

to ﬁ nd good weather, and carrying sufﬁ cient fuel to reach

it. This course of action would mitigate the risk. The pilot

also has the option to eliminate it entirely by waiting for

better weather.

Once the pilot has completed the 3P decision process and

selected a course of action, the process begins anew because

now the set of circumstances brought about by the course of

action requires analysis. The decision-making process is a

continuous loop of perceiving, processing and performing.

The DECIDE Model

Another structured approach to ADM is the DECIDE model,

which is a six-step process intended to provide a logical

way of approaching decision-making. As in the 3P model,

the elements of the DECIDE model represent a continuous

loop process to assist a pilot in the decision-making

required when faced with a situational change that requires

judgment. [Figure 1-13C] The model is primarily focused

on the intellectual component, but can have an impact on

the motivational component of judgment as well. If a pilot

continually uses the DECIDE Model in all decision-making,

it becomes natural and results in better decisions being made

under all types of situations. The steps in this approach are

listed in Figure 1-13C.

In conventional decision-making, the need for a decision is

triggered by recognition that something has changed or an

expected change did not occur. Recognition of the change,

or lack of change, is a vital step in any decision making

process. Not noticing change in a situation can lead directly

to a mishap. [Figure 1-13A] The change indicates that an

appropriate response or action is necessary in order to modify

the situation (or, at least, one of the elements that comprise it)

and bring about a desired new situation. Therefore, situational

awareness is the key to successful and safe decision making.

At this point in the process, the pilot is faced with a need to

evaluate the entire range of possible responses to the detected

change and to determine the best course of action.

Figure 1-13B illustrates how the ADM process expands

conventional decision-making, shows the interactions of the

1-18

Figure 1-13. Decision-Making.

ADM steps, and how these steps can produce a safe outcome.

Starting with the recognition of change, and following with an

assessment of alternatives, a decision to act or not act is made,

and the results are monitored. Pilots can use ADM to enhance

their conventional decision-making process because it:

1. Increases their awareness of the importance of attitude

in decision-making;

2. Teaches the ability to search for and establish relevance

of information; and

3. Increases their motivation to choose and execute actions

that ensure safety in the situational timeframe.

Hazardous Attitudes and Antidotes

Hazardous attitudes, which contribute to poor pilot judgment,

can be effectively counteracted by redirecting that hazardous

attitude so that correct action can be taken. Recognition of

hazardous thoughts is the ﬁ rst step toward neutralizing them.

After recognizing a thought as hazardous, the pilot should

label it as hazardous, then state the corresponding antidote.

Antidotes should be memorized for each of the hazardous

attitudes so they automatically come to mind when needed.

Each hazardous attitude along with its appropriate antidote

is shown in Figure 1-14.

1-19

Figure 1-14. The Five Antidotes to Hazardous Attitudes.

Research has identiﬁ ed ﬁ ve hazardous attitudes that can affect

a pilot’s judgment, as well as antidotes for each of these ﬁ ve

attitudes. ADM addresses the following:

1. Anti-authority (“Don’t tell me!”). This attitude is

found in pilots who do not like anyone telling them

what to do. They may be resentful of having someone

tell them what to do or may regard rules, regulations,

and procedures as silly or unnecessary. However, there

is always the prerogative to question authority if it is

perceived to be in error.

2. Impulsivity (“Do something quickly!”). This attitude

is found in pilots who frequently feel the need to do

something—anything—immediately. They do not

stop to think about what they are about to do, they do

not select the best course of action, and they do the

ﬁ rst thing that comes to mind.

3. Invulnerability (“It won’t happen to me!”). Many

pilots feel that accidents happen to others, but never

to them. They know accidents can happen, and they

know that anyone can be affected. They never really

feel or believe that they will be personally involved.

Pilots who think this way are more likely to take

chances and increase risk.

4. Macho (“I can do it!”). Pilots who are always trying to

prove that they are better than anyone else are thinking,

“I can do it—I’ll show them.” Pilots with this type of

attitude will try to prove themselves by taking risks in

order to impress others. This pattern is characteristic

in both men and women.

5. Resignation (“What’s the use?”). These pilots do not

see themselves as being able to make a great deal of

difference in what happens to them. When things go

well, these pilots are apt to think it is due to good luck.

When things go badly, they may feel that someone is

out to get them, or attribute it to bad luck. The pilot

will leave the action to others, for better or worse.

Sometimes, they will even go along with unreasonable

requests just to be a “nice guy.”

1-20

2-1

Introduction

Several factors affect aircraft performance including the

atmosphere, aerodynamics, and aircraft icing. Pilots need an

understanding of these factors for a sound basis for prediction

of aircraft response to control inputs, especially with regard

to instrument approaches, while holding, and when operating

at reduced airspeed in instrument meteorological conditions

(IMC). Although these factors are important to the pilot ﬂ ying

visual ﬂ ight rules (VFR), they must be even more thoroughly

understood by the pilot operating under instrument ﬂ ight

rules (IFR). Instrument pilots rely strictly on instrument

indications to precisely control the aircraft; therefore, they

must have a solid understanding of basic aerodynamic

principles in order to make accurate judgments regarding

aircraft control inputs.

Aerodynamic

Factors

Chapter 2

2-2

Figure 2-1. The Airfoil.

Figure 2-2. Angle of Attack and Relative Wind.

The Wing

To understand aerodynamic forces, a pilot needs to

understand basic terminology associated with airfoils.

Figure 2-1 illustrates a typical airfoil.

The chord line is the straight line intersecting the leading

and trailing edges of the airfoil, and the term chord refers

to the chord line longitudinal length (length as viewed from

the side).

The mean camber is a line located halfway between the

upper and lower surfaces. Viewing the wing edgewise, the

mean camber connects with the chord line at each end. The

mean camber is important because it assists in determining

aerodynamic qualities of an airfoil. The measurement of

the maximum camber; inclusive of both the displacement

of the mean camber line and its linear measurement from

the end of the chord line, provide properties useful in

evaluating airfoils.

Review of Basic Aerodynamics

The instrument pilot must understand the relationship

and differences between several factors that affect the

performance of an aircraft in ﬂ ight. Also, it is crucial to

understand how the aircraft reacts to various control and

power changes, because the environment in which instrument

pilots ﬂ y has inherent hazards not found in visual ﬂ ying. The

basis for this understanding is found in the four forces acting

on an aircraft and Newton’s Three Laws of Motion.

Relative Wind is the direction of the airﬂ ow with respect to

an airfoil.

Angle of Attack is the acute angle measured between the

relative wind, or ﬂ ight path and the chord of the airfoil.

[Figure 2-2]

Flight path is the course or track along which the aircraft is

ﬂ ying or is intended to be ﬂ own.

The Four Forces

The four basic forces [Figure 2-3] acting upon an aircraft in

ﬂ ight are lift, weight, thrust, and drag.

Lift

Lift is a component of the total aerodynamic force on an

airfoil and acts perpendicular to the relative wind. Relative

wind is the direction of the airﬂ ow with respect to an airfoil.

This force acts straight up from the average (called mean)

center of pressure (CP), which is called the center of lift. It

should be noted that it is a point along the chord line of an

airfoil through which all aerodynamic forces are considered

to act. The magnitude of lift varies proportionately with

speed, air density, shape and size of the airfoil, and angle

of attack. During straight-and-level ﬂ ight, lift and weight

are equal.

2-3

Figure 2-3. The Four Forces and Three Axes of Rotation.

Weight

Weight is the force exerted by an aircraft from the pull of

gravity. It acts on an aircraft through its center of gravity

(CG) and is straight down. This should not be confused

with the center of lift, which can be signiﬁ cantly different

from the CG. As an aircraft is descending, weight is greater

than lift.

Thrust

Thrust is a force that drives an aircraft through the air and can

be measured in thrust and/or horsepower. It is a component

that is parallel to the center of thrust and overcomes drag

providing the aircraft with its forward speed component.

Drag

Drag is the net aerodynamic force parallel to the relative

wind and is generally a sum of two components: induced

drag and parasite drag.

Induced drag

Induced drag is caused from the creation of lift and increases

with airspeed. Therefore, if the wing is not producing lift,

induced drag is zero. Conversely, induced drag increases

with airspeed.

Parasite drag

Parasite drag is all drag not caused from the production of

lift. Parasite drag is created by displacement of air by the

aircraft, turbulence generated by the airfoil, and the hindrance

of airﬂ ow as it passes over the surface of the aircraft or

components. All of these forces create drag not from the

production of lift but the movement of an object through an

air mass. Parasite drag increases with speed and includes skin

friction drag, interference drag, and form drag.

• Skin Friction Drag

Covering the entire “wetted” surface of the aircraft is a thin

layer of air called a boundary layer. The air molecules on the

surface have zero velocity in relation to the surface; however,

the layer just above moves over the stagnant molecules

below because it is pulled along by a third layer close to

the free stream of air. The velocities of the layers increase

as the distance from the surface increases until free stream

velocity is reached, but all are affected by the free stream.

The distance (total) between the skin surface and where free

stream velocity is reached is called the boundary layer. At

subsonic levels the cumulative layers are about the thickness

of a playing card, yet their motion sliding over one another

creates a drag force. This force retards motion due to the

viscosity of the air and is called skin friction drag. Because

skin friction drag is related to a large surface area its affect

on smaller aircraft is small versus large transport aircraft

where skin friction drag may be considerable.

• Interference Drag

Interference drag is generated by the collision of airstreams

creating eddy currents, turbulence, or restrictions to smooth

ﬂ ow. For instance, the airﬂ ow around a fuselage and around

the wing meet at some point, usually near the wing’s root.

These airﬂ ows interfere with each other causing a greater

2-4

Figure 2-4. Newton’s First Law of Motion: the Law of Inertia.

drag than the individual values. This is often the case when

external items are placed on an aircraft. That is, the drag of

each item individually, added to that of the aircraft, are less

than that of the two items when allowed to interfere with

one another.

• Form Drag

Form drag is the drag created because of the shape of a

component or the aircraft. If one were to place a circular

disk in an air stream, the pressure on both the top and bottom

would be equal. However, the airﬂ ow starts to break down

as the air ﬂ ows around the back of the disk. This creates

turbulence and hence a lower pressure results. Because the

total pressure is affected by this reduced pressure, it creates

a drag. Newer aircraft are generally made with consideration

to this by fairing parts along the fuselage (teardrop) so that

turbulence and form drag is reduced.

Total lift must overcome the total weight of the aircraft, which

is comprised of the actual weight and the tail-down force used

to control the aircraft’s pitch attitude. Thrust must overcome

total drag in order to provide forward speed with which to

produce lift. Understanding how the aircraft’s relationship

between these elements and the environment provide proper

interpretation of the aircraft’s instruments.

Newton’s First Law, the Law of Inertia

Newton’s First Law of Motion is the Law of Inertia. It states

that a body at rest will remain at rest, and a body in motion

will remain in motion, at the same speed and in the same

direction until affected by an outside force. The force with

which a body offers resistance to change is called the force of

inertia. Two outside forces are always present on an aircraft

in ﬂ ight: gravity and drag. The pilot uses pitch and thrust

controls to counter or change these forces to maintain the

desired ﬂ ight path. If a pilot reduces power while in straight-

and-level ﬂ ight, the aircraft will slow due to drag. However,

as the aircraft slows there is a reduction of lift, which causes

the aircraft to begin a descent due to gravity. [Figure 2-4]

Newton’s Second Law, the Law of Momentum

Newton’s Second Law of Motion is the Law of Momentum,

which states that a body will accelerate in the same direction

as the force acting upon that body, and the acceleration

will be directly proportional to the net force and inversely

proportional to the mass of the body. Acceleration refers

either to an increase or decrease in velocity, although

deceleration is commonly used to indicate a decrease. This

law governs the aircraft’s ability to change ﬂ ight path and

speed, which are controlled by attitude (both pitch and bank)

and thrust inputs. Speeding up, slowing down, entering

climbs or descents, and turning are examples of accelerations

that the pilot controls in everyday ﬂ ight. [Figure 2-5]

Newton’s Third Law, the Law of Reaction

Newton’s Third Law of Motion is the Law of Reaction,

which states that for every action there is an equal and

opposite reaction. As shown in Figure 2-6, the action of

the jet engine’s thrust or the pull of the propeller lead to the

reaction of the aircraft’s forward motion. This law is also

responsible for a portion of the lift that is produced by a wing,

from the downward deﬂ ection of the airﬂ ow around it. This

downward force of the relative wind results in an equal but

opposite (upward) lifting force created by the airﬂ ow over

the wing. [Figure 2-6]

Atmosphere

The atmosphere is the envelope of air which surrounds the

Earth. A given volume of dry air contains about 78 percent

nitrogen, 21 percent oxygen, and about 1 percent other gases

such as argon, carbon dioxide, and others to a lesser degree.

Although seemingly light, air does have weight and a one

square inch column of the atmosphere at sea level weighs

approximately 14.7 pounds. About one-half of the air by

weight is within the ﬁ rst 18,000 feet. The remainder of the air

is spread over a vertical distance in excess of 1,000 miles.

Air density is a result of the relationship between temperature

and pressure. Air density is inversely related to temperature

and directly related to pressure. For a constant pressure to be

2-5

Figure 2-6. Newton’s Third Law of Motion: the Law of Reaction.

Figure 2-5. Newton’s Second Law of Motion: the Law of

Momentum.

maintained as temperature increases, density must decrease,

and vice versa. For a constant temperature to be maintained

as pressure increases, density must increase, and vice versa.

These relationships provide a basis for understanding

instrument indications and aircraft performance.

Layers of the Atmosphere

There are several layers to the atmosphere with the

troposphere being closest to the Earth’s surface extending to

about 60,000 feet. Following is the stratosphere, mesosphere,

ionosphere, thermosphere, and ﬁ nally the exosphere. The

tropopause is the thin layer between the troposphere and

the stratosphere. It varies in both thickness and altitude but

is generally deﬁ ned where the standard lapse (generally

accepted at 2° C per 1,000 feet) decreases signiﬁ cantly

(usually down to 1° C or less).

International Standard Atmosphere (ISA)

The International Civil Aviation Organization (ICAO)

established the ICAO Standard Atmosphere as a way

of creating an international standard for reference and

performance computations. Instrument indications and

aircraft performance speciﬁ cations are derived using this

standard as a reference. Because the standard atmosphere is

a derived set of conditions that rarely exist in reality, pilots

need to understand how deviations from the standard affect

both instrument indications and aircraft performance.

In the standard atmosphere, sea level pressure is 29.92" inches

of mercury (Hg) and the temperature is 15° C (59° F). The

standard lapse rate for pressure is approximately a 1" Hg

decrease per 1,000 feet increase in altitude. The standard lapse

rate for temperature is a 2° C (3.6° F) decrease per 1,000 feet

increase, up to the top of the stratosphere. Since all aircraft

performance is compared and evaluated in the environment

of the standard atmosphere, all aircraft performance

instrumentation is calibrated for the standard atmosphere.

Because the actual operating conditions rarely, if ever, ﬁ t the

standard atmosphere, certain corrections must apply to the

instrumentation and aircraft performance. For instance, at

10,000 ISA predicts that the air pressure should be 19.92" Hg

(29.92" - 10" Hg = 19.92") and the outside temperature at -5°C

(15° C - 20° C). If the temperature or the pressure is different

than the International Standard Atmosphere (ISA) prediction

an adjustment must be made to performance predictions and

various instrument indications.

Pressure Altitude

There are two measurements of the atmosphere that affect

performance and instrument calibrations: pressure altitude

and density altitude. Pressure altitude is the height above the

standard datum pressure (SDP) (29.92" Hg, sea level under

ISA) and is used for standardizing altitudes for ﬂ ight levels

(FL). Generally, ﬂ ight levels are at or above 18,000 feet

(FL 180), providing the pressure is at or above 29.92"Hg.

For calculations involving aircraft performance when the

altimeter is set for 29.92" Hg, the altitude indicated is the

pressure altitude.

Density Altitude

Density altitude is pressure altitude corrected for nonstandard

temperatures, and is used for determining aerodynamic

performance in the nonstandard atmosphere. Density altitude

increases as the density decreases. Since density varies

directly with pressure, and inversely with temperature, a

wide range of temperatures may exist with a given pressure

altitude, which allows the density to vary. However, a

known density occurs for any one temperature and pressure

altitude combination. The density of the air has a signiﬁ cant

effect on aircraft and engine performance. Regardless of the

2-6

Figure 2-7. Relationship of Lift to Angle of Attack.

actual altitude above sea level an aircraft is operating at, its

performance will be as though it were operating at an altitude

equal to the existing density altitude.

If a chart is not available the density altitude can be estimated

by adding 120 feet for every degree Celsius above the ISA. For

example, at 3,000 feet pressure altitude (PA), the ISA prediction

is 9° C (15° C - [lapse rate of 2° C per 1,000 feet x 3 = 6° C]).

However, if the actual temperature is 20° C (11° C more than

that predicted by ISA) then the difference of 11° C is multiplied

by 120 feet equaling 1,320. Adding this ﬁ gure to the original

3,000 feet provides a density altitude of 4,320 feet (3,000 feet

+ 1,320 feet).

Lift

Lift always acts in a direction perpendicular to the relative

wind and to the lateral axis of the aircraft. The fact that lift is

referenced to the wing, not to the Earth’s surface, is the source

of many errors in learning ﬂ ight control. Lift is not always

“up.” Its direction relative to the Earth’s surface changes as

the pilot maneuvers the aircraft.

The magnitude of the force of lift is directly proportional to

the density of the air, the area of the wings, and the airspeed. It

also depends upon the type of wing and the angle of attack. Lift

increases with an increase in angle of attack up to the stalling

angle, at which point it decreases with any further increase

in angle of attack. In conventional aircraft, lift is therefore

controlled by varying the angle of attack and speed.

Pitch/Power Relationship

An examination of Figure 2-7 illustrates the relationship

between pitch and power while controlling ﬂ ight path and

airspeed. In order to maintain a constant lift, as airspeed is

reduced, pitch must be increased. The pilot controls pitch

through the elevators, which control the angle of attack.

When back pressure is applied on the elevator control, the tail

lowers and the nose rises, thus increasing the wing’s angle of

attack and lift. Under most conditions the elevator is placing

downward pressure on the tail. This pressure requires energy

that is taken from aircraft performance (speed). Therefore,

when the CG is closer to the aft portion of the aircraft the

elevator downward forces are less. This results in less energy

used for downward forces, in turn resulting in more energy

applied to aircraft performance.

Thrust is controlled by using the throttle to establish or

maintain desired airspeeds. The most precise method

of controlling flight path is to use pitch control while

simultaneously using power (thrust) to control airspeed. In

order to maintain a constant lift, a change in pitch requires a

change in power, and vice versa.

If the pilot wants the aircraft to accelerate while maintaining

altitude, thrust must be increased to overcome drag. As

the aircraft speeds up, lift is increased. To prevent gaining

altitude, the pitch angle must be lowered to reduce the

angle of attack and maintain altitude. To decelerate while

maintaining altitude, thrust must be decreased to less than the

value of drag. As the aircraft slows down, lift is reduced. To

prevent losing altitude, the pitch angle must be increased in

order to increase the angle of attack and maintain altitude.

Drag Curves

When induced drag and parasite drag are plotted on a graph,

the total drag on the aircraft appears in the form of a “drag

curve.” Graph A of Figure 2-8 shows a curve based on thrust

versus drag, which is primarily used for jet aircraft. Graph B

of Figure 2-8 is based on power versus drag, and it is used

for propeller-driven aircraft. This chapter focuses on power

versus drag charts for propeller-driven aircraft.

Understanding the drag curve can provide valuable insight

into the various performance parameters and limitations of

the aircraft. Because power must equal drag to maintain a

steady airspeed, the curve can be either a drag curve or a

power required curve. The power required curve represents

the amount of power needed to overcome drag in order to

maintain a steady speed in level ﬂ ight.

The propellers used on most reciprocating engines achieve

peak propeller efﬁ ciencies in the range of 80 to 88 percent.

As airspeed increases, the propeller efﬁ ciency increases until

it reaches its maximum. Any airspeed above this maximum

point causes a reduction in propeller efﬁ ciency. An engine

that produces 160 horsepower will have only about 80

percent of that power converted into available horsepower,

2-7

Figure 2-8. Thrust and Power Required Curves.

Figure 2-9. Regions of Command.

approximately 128 horsepower. The remainder is lost energy.

This is the reason the thrust and power available curves

change with speed.

Regions of Command

The drag curve also illustrates the two regions of command:

the region of normal command, and the region of reversed

command. The term “region of command” refers to the

relationship between speed and the power required to

maintain or change that speed. “Command” refers to the input

the pilot must give in terms of power or thrust to maintain a

new speed once reached.

The “region of normal command” occurs where power must

be added to increase speed. This region exists at speeds higher

than the minimum drag point primarily as a result of parasite

drag. The “region of reversed command” occurs where

additional power is needed to maintain a slower airspeed.

This region exists at speeds slower than the minimum drag

point (L/DMAX on the thrust required curve, Figure 2-8) and

is primarily due to induced drag. Figure 2-9 shows how one

power setting can yield two speeds, points 1 and 2. This is

because at point 1 there is high induced drag and low parasite

drag, while at point 2 there is high parasite drag and low

induced drag.

Control Characteristics

Most ﬂ ying is conducted in the region of normal command:

for example, cruise, climb, and maneuvers. The region of

reversed command may be encountered in the slow-speed

phases of ﬂ ight during takeoff and landing; however, for

most general aviation aircraft, this region is very small and

is below normal approach speeds.

Flight in the region of normal command is characterized

by a relatively strong tendency of the aircraft to maintain

the trim speed. Flight in the region of reversed command is

characterized by a relatively weak tendency of the aircraft to

maintain the trim speed. In fact, it is likely the aircraft exhibits

no inherent tendency to maintain the trim speed in this area.

For this reason, the pilot must give particular attention to

precise control of airspeed when operating in the slow-speed

phases of the region of reversed command.

Operation in the region of reversed command does not imply

that great control difﬁ culty and dangerous conditions exist.

However, it does amplify errors of basic ﬂ ying technique—

making proper ﬂ ying technique and precise control of the

aircraft very important.

Speed Stability

Normal Command

The characteristics of ﬂ ight in the region of normal command

are illustrated at point A on the curve in Figure 2-10. If the

aircraft is established in steady, level ﬂ ight at point A, lift is

equal to weight, and the power available is set equal to the

power required. If the airspeed is increased with no changes

2-8

Figure 2-10. Region of Speed Stability.

to the power setting, a power deﬁ ciency exists. The aircraft

has a natural tendency to return to the initial speed to balance

power and drag. If the airspeed is reduced with no changes

to the power setting, an excess of power exists. The aircraft

has a natural tendency to speed up to regain the balance

between power and drag. Keeping the aircraft in proper

trim enhances this natural tendency. The static longitudinal

stability of the aircraft tends to return the aircraft to the

original trimmed condition.

An aircraft ﬂ ying in steady, level ﬂ ight at point C is in

equilibrium. [Figure 2-10] If the speed were increased

or decreased slightly, the aircraft would tend to remain at

that speed. This is because the curve is relatively ﬂ at and

a slight change in speed does not produce any signiﬁ cant

excess or deﬁ ciency in power. It has the characteristic of

neutral stability, i.e., the aircraft’s tendency is to remain at

the new speed.

Reversed Command

The characteristics of ﬂ ight in the region of reversed command

are illustrated at point B on the curve in Figure 2-10. If the

aircraft is established in steady, level ﬂ ight at point B, lift is

equal to weight, and the power available is set equal to the

power required. When the airspeed is increased greater than

point B, an excess of power exists. This causes the aircraft

to accelerate to an even higher speed. When the aircraft is

slowed to some airspeed lower than point B, a deﬁ ciency

of power exists. The natural tendency of the aircraft is to

continue to slow to an even lower airspeed.

This tendency toward instability happens because the

variation of excess power to either side of point B magniﬁ es

the original change in speed. Although the static longitudinal

stability of the aircraft tries to maintain the original trimmed

condition, this instability is more of an inﬂ uence because of

the increased induced drag due to the higher angles of attack

in slow-speed ﬂ ight.

Trim

The term trim refers to employing adjustable aerodynamic

devices on the aircraft to adjust forces so the pilot does not

have to manually hold pressure on the controls. One means is

to employ trim tabs. A trim tab is a small, adjustable hinged

surface, located on the trailing edge of the elevator, aileron,

or rudder control surfaces. (Some aircraft use adjustable

stabilizers instead of trim tabs for pitch trim.) Trimming is

accomplished by deﬂ ecting the tab in the direction opposite

to that in which the primary control surface must be held.

The force of the airﬂ ow striking the tab causes the main

control surface to be deﬂ ected to a position that corrects the

unbalanced condition of the aircraft.

Because the trim tabs use airﬂ ow to function, trim is a

function of speed. Any change in speed results in the need

to re-trim the aircraft. An aircraft properly trimmed in pitch

seeks to return to the original speed before the change. It is

very important for instrument pilots to keep the aircraft in

constant trim. This reduces the pilot’s workload signiﬁ cantly,

allowing attention to other duties without compromising

aircraft control.

Slow-Speed Flight

Anytime an aircraft is ﬂ ying near the stalling speed or the

region of reversed command, such as in ﬁ nal approach for a

normal landing, the initial part of a go around, or maneuvering

in slow ﬂ ight, it is operating in what is called slow-speed

ﬂ ight. If the aircraft weighs 4,000 pounds, the lift produced

by the aircraft must be 4,000 pounds. When lift is less

than 4,000 pounds, the aircraft is no longer able to sustain

level ﬂ ight, and consequently descends. During intentional

descents, this is an important factor and is used in the total

control of the aircraft.

However, because lift is required during low speed ﬂ ight

and is characterized by high angles of attack, ﬂ aps or other

high lift devices are needed to either change the camber of

the airfoil, or delay the boundary level separation. Plain

and split ﬂ aps [Figure 2-11] are most commonly used to

change the camber of an airfoil. It should be noted that with

the application of ﬂ aps, the aircraft will stall at a lower

angle of attack. The basic wing stalls at 18° without ﬂ aps

but with the application of the ﬂ aps extended (to CL-MAX

position) the new angle of attack at which point the aircraft

will stall is 15°. However, the value of lift (ﬂ aps extended

to the CL-MAX position) produces more lift than lift at 18°

on the basic wing.

Delaying the boundary layer separation is another way to

increase CL-MAX. Several methods are employed (such as

suction and use of a blowing boundary layer control), but the

2-9

Figure 2-12. Vortex Generators.

Figure 2-11. Various Types of Flaps.

If allowed to slow several knots, the airplane could enter

the region of reversed command. At this point, the airplane

could develop an unsafe sink rate and continue to lose speed

unless the pilot takes a prompt corrective action. Proper pitch

and power coordination is critical in this region due to speed

instability and the tendency of increased divergence from

the desired speed.

Large Airplanes

Pilots of larger airplanes with higher stall speeds may ﬁ nd the

speed they maintain on the instrument approach is near 1.3

VSO, putting them near point C [Figure 2-10] the entire time

the airplane is on the ﬁ nal approach segment. In this case,

precise speed control is necessary throughout the approach. It

may be necessary to temporarily select excessive, or deﬁ cient

thrust in relation to the target thrust setting in order to quickly

correct for airspeed deviations.

most common device used on general aviation light aircraft

is the vortex generator. Small strips of metal placed along

the wing (usually in front of the control surfaces) create

turbulence. The turbulence in turn mixes high energy air from

outside the boundary layer with boundary layer air. The effect

is similar to other boundary layer devices. [Figure 2-12]

Small Airplanes

Most small airplanes maintain a speed well in excess of 1.3

times VSO on an instrument approach. An airplane with a

stall speed of 50 knots (VSO) has a normal approach speed

of 65 knots. However, this same airplane may maintain 90

knots (1.8 VSO) while on the ﬁ nal segment of an instrument

approach. The landing gear will most likely be extended at

the beginning of the descent to the minimum descent altitude,

or upon intercepting the glide slope of the instrument landing

system. The pilot may also select an intermediate ﬂ ap setting

for this phase of the approach. The airplane at this speed has

good positive speed stability, as represented by point A on

Figure 2-10. Flying in this regime permits the pilot to make

slight pitch changes without changing power settings, and

accept minor speed changes knowing that when the pitch is

returned to the initial setting, the speed returns to the original

setting. This reduces the pilot’s workload.

Aircraft are usually slowed to a normal landing speed when

on the ﬁ nal approach just prior to landing. When slowed to

65 knots, (1.3 VSO), the airplane will be close to point C.

[Figure 2-10] At this point, precise control of the pitch and

power becomes more crucial for maintaining the correct speed.

Pitch and power coordination is necessary because the speed

stability is relatively neutral since the speed tends to remain

at the new value and not return to the original setting. In

addition to the need for more precise airspeed control, the pilot

normally changes the aircraft’s conﬁ guration by extending

landing ﬂ aps. This conﬁ guration change means the pilot must

be alert to unwanted pitch changes at a low altitude.

2-10

Figure 2-13. Forces In a Turn.

Turns

Like any moving object, an aircraft requires a sideward force

to make it turn. In a normal turn, this force is supplied by

banking the aircraft in order to exert lift inward, as well as

upward. The force of lift is separated into two components

at right angles to each other. [Figure 2-13] The upward

acting lift together with the opposing weight becomes the

vertical lift component. The horizontally acting lift and its

opposing centrifugal force are the horizontal lift component,

or centripetal force. This horizontal lift component is the

sideward force that causes an aircraft to turn. The equal and

opposite reaction to this sideward force is centrifugal force,

which is merely an apparent force as a result of inertia.

The relationship between the aircraft’s speed and bank angle

to the rate and radius of turns is important for instrument

pilots to understand. The pilot can use this knowledge to

properly estimate bank angles needed for certain rates of

turn, or to determine how much to lead when intercepting

a course.

Rate of Turn

The rate of turn, normally measured in degrees per second,

is based upon a set bank angle at a set speed. If either one of

these elements changes, the rate of turn changes. If the aircraft

increases its speed without changing the bank angle, the rate

of turn decreases. Likewise, if the speed decreases without

changing the bank angle, the rate of turn increases.

Changing the bank angle without changing speed also causes

the rate of turn to change. Increasing the bank angle without

changing speed increases the rate of turn, while decreasing

the bank angle reduces the rate of turn.

For example, a pilot is on an instrument approach at 1.3

VSO, a speed near L/DMAX, and knows that a certain power

setting maintains that speed. The airplane slows several knots

below the desired speed because of a slight reduction in the

power setting. The pilot increases the power slightly, and the

airplane begins to accelerate, but at a slow rate. Because the

airplane is still in the “ﬂ at part” of the drag curve, this slight

increase in power will not cause a rapid return to the desired

speed. The pilot may need to increase the power higher

than normally needed to maintain the new speed, allow the

airplane to accelerate, then reduce the power to the setting

that maintains the desired speed.

Climbs

The ability for an aircraft to climb depends upon an excess

power or thrust over what it takes to maintain equilibrium.

Excess power is the available power over and above that

required to maintain horizontal ﬂ ight at a given speed.

Although the terms power and thrust are sometimes

used interchangeably (erroneously implying they are

synonymous), distinguishing between the two is important

when considering climb performance. Work is the product of

a force moving through a distance and is usually independent

of time. Power implies work rate or units of work per unit of

time, and as such is a function of the speed at which the force

is developed. Thrust, also a function of work, means the force

which imparts a change in the velocity of a mass.

During take off, the aircraft does not stall even though it

may be in a climb near the stall speed. The reason is that

excess power (used to produce thrust) is used during this

ﬂ ight regime. Therefore, it is important if an engine fails

after take off, to compensate the loss of thrust with pitch

and airspeed.

For a given weight of the aircraft, the angle of climb depends

on the difference between thrust and drag, or the excess

thrust. When the excess thrust is zero, the inclination of the

ﬂ ight path is zero, and the aircraft is in steady, level ﬂ ight.

When thrust is greater than drag, the excess thrust allows a

climb angle depending on the amount of excess thrust. When

thrust is less than drag, the deﬁ ciency of thrust induces an

angle of descent.

Acceleration in Cruise Flight

Aircraft accelerate in level ﬂ ight because of an excess of

power over what is required to maintain a steady speed. This

is the same excess power used to climb. Upon reaching the

desired altitude with pitch being lowered to maintain that

altitude, the excess power now accelerates the aircraft to its

cruise speed. However, reducing power too soon after level

off results in a longer period of time to accelerate.

2-11

Figure 2-14. Turns.

The standard rate of turn, 3° per second, is used as the main

reference for bank angle. Therefore, the pilot must understand

how the angle of bank varies with speed changes, such

as slowing down for holding or an instrument approach.

Figure 2-14 shows the turn relationship with reference to a

constant bank angle or a constant airspeed, and the effects on

rate of turn and radius of turn. A rule of thumb for determining

the standard rate turn is to divide the airspeed by ten and

add 7. An aircraft with an airspeed of 90 knots takes a bank

angle of 16° to maintain a standard rate turn (90 divided by

10 plus 7 equals 16°).

Radius of Turn

The radius of turn varies with changes in either speed or bank.

If the speed is increased without changing the bank angle,

the radius of turn increases, and vice versa. If the speed is

constant, increasing the bank angle reduces the radius of

turn, while decreasing the bank angle increases the radius of

turn. This means that intercepting a course at a higher speed

requires more distance, and therefore, requires a longer lead.

If the speed is slowed considerably in preparation for holding

or an approach, a shorter lead is needed than that required

for cruise ﬂ ight.

Coordination of Rudder and Aileron Controls

Any time ailerons are used, adverse yaw is produced. Adverse

yaw is caused when the ailerons are deﬂ ected as a roll motion

(as in turn) is initiated. In a right turn, the right aileron is

deﬂ ected downward while the left is deﬂ ected upward. Lift

is increased on the left side and reduced on the right, resulting

in a bank to the right. However, as a result of producing lift

on the left, induced drag is also increased on the left side.

The drag causes the left wing to slow down, in turn causing

the nose of the aircraft to initially move (left) in the direction

opposite of the turn. Correcting for this yaw with rudder, when

entering and exiting turns, is necessary for precise control of

the airplane when ﬂ ying on instruments. The pilot can tell if

the turn is coordinated by checking the ball in the turn-and-

slip indicator or the turn coordinator. [Figure 2-15]

As the aircraft banks to enter a turn, a portion of the wing’s

vertical lift becomes the horizontal component; therefore,

without an increase in back pressure, the aircraft loses altitude

during the turn. The loss of vertical lift can be offset by

increasing the pitch in one-half bar width increments. Trim

may be used to relieve the control pressures; however, if used,

it has to be removed once the turn is complete.

In a slipping turn, the aircraft is not turning at the rate

appropriate to the bank being used, and the aircraft falls to

the inside of the turn. The aircraft is banked too much for the

rate of turn, so the horizontal lift component is greater than

the centrifugal force. A skidding turn results from excess of

centrifugal force over the horizontal lift component, pulling

the aircraft toward the outside of the turn. The rate of turn

is too great for the angle of bank, so the horizontal lift

component is less than the centrifugal force.

The ball instrument indicates the quality of the turn, and

should be centered when the wings are banked. If the ball

is off of center on the side toward the turn, the aircraft is

slipping and rudder pressure should be added on that side to

increase the rate of turn or the bank angle should be reduced.

If the ball is off of center on the side away from the turn,

the aircraft is skidding and rudder pressure toward the turn

should be relaxed or the bank angle should be increased.

If the aircraft is properly rigged, the ball should be in the

center when the wings are level; use rudder and/or aileron

trim if available.

The increase in induced drag (caused by the increase in angle

of attack necessary to maintain altitude) results in a minor

loss of airspeed if the power setting is not changed.

Load Factor

Any force applied to an aircraft to deﬂ ect its ﬂ ight from a

straight line produces a stress on its structure; the amount of

this force is termed load factor. A load factor is the ratio of

2-12

Figure 2-15. Adverse Yaw.

the aerodynamic force on the aircraft to the gross weight of

the aircraft (e.g., lift/weight). For example, a load factor of 3

means the total load on an aircraft’s structure is three times

its gross weight. When designing an aircraft, it is necessary

to determine the highest load factors that can be expected in

normal operation under various operational situations. These

“highest” load factors are called “limit load factors.”

Aircraft are placed in various categories, i.e., normal, utility,

and acrobatic, depending upon the load factors they are

designed to take. For reasons of safety, the aircraft must be

designed to withstand certain maximum load factors without

any structural damage.

The speciﬁ ed load may be expected in terms of aerodynamic

forces, as in turns. In level ﬂ ight in undisturbed air, the

wings are supporting not only the weight of the aircraft, but

centrifugal force as well. As the bank steepens, the horizontal

lift component increases, centrifugal force increases, and the

load factor increases. If the load factor becomes so great that

an increase in angle of attack cannot provide enough lift to

support the load, the wing stalls. Since the stalling speed

increases directly with the square root of the load factor, the

pilot should be aware of the ﬂ ight conditions during which the

load factor can become critical. Steep turns at slow airspeed,

structural ice accumulation, and vertical gusts in turbulent

air can increase the load factor to a critical level.

Icing

One of the greatest hazards to ﬂ ight is aircraft icing. The

instrument pilot must be aware of the conditions conducive to

aircraft icing. These conditions include the types of icing, the

effects of icing on aircraft control and performance, effects

of icing on aircraft systems, and the use and limitations of

aircraft deice and anti-ice equipment. Coping with the hazards

of icing begins with preﬂ ight planning to determine where

icing may occur during a ﬂ ight and ensuring the aircraft is

2-13

Figure 2-16. Clear Ice.

free of ice and frost prior to takeoff. This attention to detail

extends to managing deice and anti-ice systems properly

during the ﬂ ight, because weather conditions may change

rapidly, and the pilot must be able to recognize when a change

of ﬂ ight plan is required.

Types of Icing

Structural Icing

Structural icing refers to the accumulation of ice on the

exterior of the aircraft. Ice forms on aircraft structures and

surfaces when super-cooled droplets impinge on them and

freeze. Small and/or narrow objects are the best collectors

of droplets and ice up most rapidly. This is why a small

protuberance within sight of the pilot can be used as an “ice

evidence probe.” It is generally one of the ﬁ rst parts of the

airplane on which an appreciable amount of ice forms. An

aircraft’s tailplane is a better collector than its wings, because

the tailplane presents a thinner surface to the airstream.

Induction Icing

Ice in the induction system can reduce the amount of air

available for combustion. The most common example of

reciprocating engine induction icing is carburetor ice. Most

pilots are familiar with this phenomenon, which occurs when

moist air passes through a carburetor venturi and is cooled. As

a result of this process, ice may form on the venturi walls and

throttle plate, restricting airﬂ ow to the engine. This may occur

at temperatures between 20° F (-7° C) and 70° F (21° C). The

problem is remedied by applying carburetor heat, which uses

the engine’s own exhaust as a heat source to melt the ice or

prevent its formation. On the other hand, fuel-injected aircraft

engines usually are less vulnerable to icing but still can be

affected if the engine’s air source becomes blocked with ice.

Manufacturers provide an alternate air source that may be

selected in case the normal system malfunctions.

In turbojet aircraft, air that is drawn into the engines creates

an area of reduced pressure at the inlet, which lowers the

temperature below that of the surrounding air. In marginal

icing conditions (i.e., conditions where icing is possible),

this reduction in temperature may be sufﬁ cient to cause ice

to form on the engine inlet, disrupting the airﬂ ow into the

engine. Another hazard occurs when ice breaks off and is

ingested into a running engine, which can cause damage to

fan blades, engine compressor stall, or combustor ﬂ ameout.

When anti-icing systems are used, runback water also can

refreeze on unprotected surfaces of the inlet and, if excessive,

reduce airﬂ ow into the engine or distort the airﬂ ow pattern

in such a manner as to cause compressor or fan blades to

vibrate, possibly damaging the engine. Another problem

in turbine engines is the icing of engine probes used to set

power levels (for example, engine inlet temperature or engine

pressure ratio (EPR) probes), which can lead to erroneous

readings of engine instrumentation operational difﬁ culties

or total power loss.

The type of ice that forms can be classiﬁ ed as clear, rime, or

mixed, based on the structure and appearance of the ice. The

type of ice that forms varies depending on the atmospheric

and ﬂ ight conditions in which it forms. Signiﬁ cant structural

icing on an aircraft can cause serious aircraft control and

performance problems.

Clear Ice

A glossy, transparent ice formed by the relatively slow

freezing of super cooled water is referred to as clear ice.

[Figure 2-16] The terms “clear” and “glaze” have been used

for essentially the same type of ice accretion. This type of

ice is denser, harder, and sometimes more transparent than

rime ice. With larger accretions, clear ice may form “horns.”

[Figure 2-17] Temperatures close to the freezing point, large

amounts of liquid water, high aircraft velocities, and large

droplets are conducive to the formation of clear ice.

Rime Ice

A rough, milky, opaque ice formed by the instantaneous or

very rapid freezing of super cooled droplets as they strike

the aircraft is known as rime ice. [Figure 2-18] The rapid

freezing results in the formation of air pockets in the ice,

giving it an opaque appearance and making it porous and

brittle. For larger accretions, rime ice may form a streamlined

extension of the wing. Low temperatures, lesser amounts of

liquid water, low velocities, and small droplets are conducive

to the formation of rime ice.

2-14

Figure 2-19. Aerodynamic Effects of Icing.

Figure 2-18. Rime Ice.

Figure 2-17. Clear Ice Buildup.

Mixed Ice

Mixed ice is a combination of clear and rime ice formed on

the same surface. It is the shape and roughness of the ice that

is most important from an aerodynamic point of view.

General Effects of Icing on Airfoils

The most hazardous aspect of structural icing is its aerodynamic

effects. [Figure 2-19] Ice alters the shape of an airfoil, reducing

the maximum coefﬁ cient of lift and angle of attack at which

the aircraft stalls. Note that at very low angles of attack, there

may be little or no effect of the ice on the coefﬁ cient of lift.

Therefore, when cruising at a low angle of attack, ice on the

wing may have little effect on the lift. However, note that the

ice signiﬁ cantly reduces the CL-MAX, and the angle of attack

at which it occurs (the stall angle) is much lower. Thus, when

slowing down and increasing the angle of attack for approach,

the pilot may ﬁ nd that ice on the wing, which had little effect

on lift in cruise now, causes stall to occur at a lower angle of

attack and higher speed. Even a thin layer of ice at the leading

edge of a wing, especially if it is rough, can have a signiﬁ cant

effect in increasing stall speed. For large ice shapes, especially

those with horns, the lift may also be reduced at a lower angle

of attack. The accumulation of ice affects the coefﬁ cient

of drag of the airfoil. [Figure 2-19] Note that the effect is

signiﬁ cant even at very small angles of attack.

A signiﬁ cant reduction in CL-MAX and a reduction in the angle

of attack where stall occurs can result from a relatively small

ice accretion. A reduction of CL-MAX by 30 percent is not

unusual, and a large horn ice accretion can result in reductions

of 40 percent to 50 percent. Drag tends to increase steadily

as ice accretes. An airfoil drag increase of 100 percent is not

unusual, and for large horn ice accretions, the increase can

be 200 percent or even higher.

2-15

Figure 2-20. Effect of Ice and Frost on Lift.

Figure 2-21. Downward Force on the Tailplane.

Figure 2-22. Ice on the Tailplane.

Ice on an airfoil can have other effects not depicted in these

curves. Even before airfoil stall, there can be changes in the

pressure over the airfoil that may affect a control surface at

the trailing edge. Furthermore, on takeoff, approach, and

landing, the wings of many aircraft are multi-element airfoils

with three or more elements. Ice may affect the different

elements in different ways. Ice may also affect the way in

which the air streams interact over the elements.

Ice can partially block or limit control surfaces, which

limits or makes control movements ineffective. Also, if the

extra weight caused by ice accumulation is too great, the

aircraft may not be able to become airborne and, if in ﬂ ight,

the aircraft may not be able to maintain altitude. Therefore

any accumulation of ice or frost should be removed before

attempting ﬂ ight.

Another hazard of structural icing is the possible uncommanded

and uncontrolled roll phenomenon, referred to as roll upset,

associated with severe in-ﬂ ight icing. Pilots ﬂ ying aircraft

certiﬁ cated for ﬂ ight in known icing conditions should be

aware that severe icing is a condition outside of the aircraft’s

certiﬁ cation icing envelope. Roll upset may be caused by

airﬂ ow separation (aerodynamic stall), which induces self-

deﬂ ection of the ailerons and loss of or degraded roll handling

characteristics [Figure 2-20]. These phenomena can result

from severe icing conditions without the usual symptoms of

ice accumulation or a perceived aerodynamic stall.

Most aircraft have a nose-down pitching moment from the

wings because the CG is ahead of the CP. It is the role of the

tailplane to counteract this moment by providing a downward

force. [Figure 2-21] The result of this conﬁ guration is

that actions which move the wing away from stall, such

as deployment of ﬂ aps or increasing speed, may increase

the negative angle of attack of the tail. With ice on the

tailplane, it may stall after full or partial deployment of ﬂ aps.

[Figure 2-22]

Since the tailplane is ordinarily thinner than the wing, it is a

more efﬁ cient collector of ice. On most aircraft the tailplane

is not visible to the pilot, who therefore cannot observe how

well it has been cleared of ice by any deicing system. Thus, it

is important that the pilot be alert to the possibility of tailplane

stall, particularly on approach and landing.

Piper PA-34-200T (Des Moines, Iowa)

The pilot of this ﬂ ight, which took place on January 9,

1996, said that upon crossing the runway threshold and

lowering the ﬂ aps 25°, “the airplane pitched down.” The

pilot “immediately released the ﬂ aps and added power, but

the airplane was basically uncontrollable at this point.” The

pilot reduced power and lowered the ﬂ aps before striking

the runway on its centerline and sliding 1,000 feet before

2-16

coming to a stop. The accident resulted in serious injury to

the pilot, the sole occupant.

Examination of the wreckage revealed heavy impact

damage to the airplane’s forward fuselage, engines, and

wings. Approximately one-half inch of rime ice was

observed adhering to the leading edges of the left and right

horizontal stabilizers and along the leading edge of the

vertical stabilizer.

The National Transportation Safety Board (NTSB)

determined the probable cause of the accident was the pilot’s

failure to use the airplane’s deicing system, which resulted

in an accumulation of empennage ice and a tailplane stall.

Factors relating to this accident were the icing conditions and

the pilot’s intentional ﬂ ight into those known conditions.

Tailplane Stall Symptoms

Any of the following symptoms, occurring singly or in

combination, may be a warning of tailplane icing:

• Elevator control pulsing, oscillations, or vibrations;

• Abnormal nose-down trim change;

• Any other unusual or abnormal pitch anomalies

(possibly resulting in pilot induced oscillations);

• Reduction or loss of elevator effectiveness;

• Sudden change in elevator force (control would move

nose-down if unrestrained); and

• Sudden uncommanded nose-down pitch.

If any of the above symptoms occur, the pilot should:

• Immediately retract the ﬂ aps to the previous setting

and apply appropriate nose-up elevator pressure;

• Increase airspeed appropriately for the reduced ﬂ ap

extension setting;

• Apply sufficient power for aircraft configuration

and conditions. (High engine power settings may

adversely impact response to tailplane stall conditions

at high airspeed in some aircraft designs. Observe the

manufacturer’s recommendations regarding power

settings.);

• Make nose-down pitch changes slowly, even in

gusting conditions, if circumstances allow; and

• If a pneumatic deicing system is used, operate the

system several times in an attempt to clear the tailplane

of ice.

Once a tailplane stall is encountered, the stall condition

tends to worsen with increased airspeed and possibly may

worsen with increased power settings at the same flap

setting. Airspeed, at any ﬂ ap setting, in excess of the airplane

manufacturer’s recommendations, accompanied by uncleared

ice contaminating the tailplane, may result in a tailplane stall

and uncommanded pitch down from which recovery may not

be possible. A tailplane stall may occur at speeds less than

the maximum ﬂ ap extended speed (VFE).

Propeller Icing

Ice buildup on propeller blades reduces thrust for the same

aerodynamic reasons that wings tend to lose lift and increase

drag when ice accumulates on them. The greatest quantity

of ice normally collects on the spinner and inner radius of

the propeller. Propeller areas on which ice may accumulate

and be ingested into the engine normally are anti-iced rather

than deiced to reduce the probability of ice being shed into

the engine.

Effects of Icing on Critical Aircraft Systems

In addition to the hazards of structural and induction icing,

the pilot must be aware of other aircraft systems susceptible

to icing. The effects of icing do not produce the performance

loss of structural icing or the power loss of induction icing

but can present serious problems to the instrument pilot.

Examples of such systems are flight instruments, stall

warning systems, and windshields.

Flight Instruments

Various aircraft instruments including the airspeed indicator,

altimeter, and rate-of-climb indicator utilize pressures

sensed by pitot tubes and static ports for normal operation.

When covered by ice these instruments display incorrect

information thereby presenting serious hazard to instrument

flight. Detailed information on the operation of these

instruments and the speciﬁ c effects of icing is presented in

Chapter 3, Flight Instruments.

Stall Warning Systems

Stall warning systems provide essential information to pilots.

These systems range from a sophisticated stall warning vane

to a simple stall warning switch. Icing affects these systems

in several ways resulting in possible loss of stall warning to

the pilot. The loss of these systems can exacerbate an already

hazardous situation. Even when an aircraft’s stall warning

system remains operational during icing conditions, it may

be ineffective because the wing stalls at a lower angle of

attack due to ice on the airfoil.

Windshields

Accumulation of ice on ﬂ ight deck windows can severely

restrict the pilot’s visibility outside of the aircraft. Aircraft

equipped for ﬂ ight into known icing conditions typically have

some form of windshield anti-icing to enable the pilot to see

2-17

outside the aircraft in case icing is encountered in ﬂ ight. One

system consists of an electrically heated plate installed onto

the airplane’s windshield to give the pilot a narrow band of

clear visibility. Another system uses a bar at the lower end

of the windshield to spray deicing ﬂ uid onto it and prevent

ice from forming. On high performance aircraft that require

complex windshields to protect against bird strikes and

withstand pressurization loads, the heating element often is

a layer of conductive ﬁ lm or thin wire strands through which

electric current is run to heat the windshield and prevent ice

from forming.

Antenna Icing

Because of their small size and shape, antennas that do not lay

ﬂ ush with the aircraft’s skin tend to accumulate ice rapidly.

Furthermore, they often are devoid of internal anti-icing

or deicing capability for protection. During ﬂ ight in icing

conditions, ice accumulations on an antenna may cause it to

begin to vibrate or cause radio signals to become distorted

and it may cause damage to the antenna. If a frozen antenna

breaks off, it can damage other areas of the aircraft in addition

to causing a communication or navigation system failure.

Summary

Ice-contaminated aircraft have been involved in many

accidents. Takeoff accidents have usually been due to failure

to deice or anti-ice critical surfaces properly on the ground.

Proper deicing and anti-icing procedures are addressed in

two other pilot guides, Advisory Circular (AC) 120-58, Pilot

Guide: Large Aircraft Ground Deicing and AC 135-17, Pilot

Guide: Small Aircraft Ground Deicing.

The pilot of an aircraft, which is not certiﬁ cated or equipped

for ﬂ ight in icing conditions, should avoid all icing conditions.

The aforementioned guides provide direction on how to do

this, and on how to exit icing conditions promptly and safely

should they be inadvertently encountered.

The pilot of an aircraft, which is certiﬁ cated for ﬂ ight in

icing conditions can safely operate in the conditions for

which the aircraft was evaluated during the certiﬁ cation

process but should never become complacent about icing.

Even short encounters with small amounts of rough icing

can be very hazardous. The pilot should be familiar with all

information in the Aircraft Flight Manual (AFM) or Pilot’s

Operating Handbook (POH) concerning flight in icing

conditions and follow it carefully. Of particular importance

are proper operation of ice protection systems and any

airspeed minimums to be observed during or after ﬂ ight

in icing conditions. There are some icing conditions for

which no aircraft is evaluated in the certiﬁ cation process,

such as super-cooled large drops (SLD). These subfreezing

water droplets, with diameters greater than 50 microns,

occur within or below clouds and sustained ﬂ ight in these

conditions can be very hazardous. The pilot should be familiar

with any information in the AFM or POH relating to these

conditions, including aircraft-speciﬁ c cues for recognizing

these hazardous conditions within clouds.

The information in this chapter is an overview of the hazards

of aircraft icing. For more detailed information refer to AC

91-74, Pilot Guide: Flight in Icing Conditions, AC 91-51A,

Effect of Icing on Aircraft Control and Airplane Deice and

Anti-Ice Systems, AC 20-73A, Aircraft Ice Protection and

AC 23.143-1, Ice Contaminated Tailplane Stall (ICTS).

2-18

3-1

Introduction

Aircraft became a practical means of transportation when

accurate ﬂ ight instruments freed the pilot from the necessity

of maintaining visual contact with the ground. Flight

instruments are crucial to conducting safe ﬂ ight operations

and it is important that the pilot have a basic understanding

of their operation. The basic ﬂ ight instruments required

for operation under visual ﬂ ight rules (VFR) are airspeed

indicator (ASI), altimeter, and magnetic direction indicator.

In addition to these, operation under instrument ﬂ ight rules

(IFR) requires a gyroscopic rate-of-turn indicator, slip-skid

indicator, sensitive altimeter adjustable for barometric

pressure, clock displaying hours, minutes, and seconds with

a sweep-second pointer or digital presentation, gyroscopic

pitch-and-bank indicator (artiﬁ cial horizon), and gyroscopic

direction indicator (directional gyro or equivalent).

Flight Instruments

Chapter 3

3-2

Figure 3-1. A Typical Electrically Heated Pitot-Static Head.

Aircraft that are ﬂ own in instrument meteorological conditions

(IMC) are equipped with instruments that provide attitude

and direction reference, as well as navigation instruments that

allow precision ﬂ ight from takeoff to landing with limited or

no outside visual reference.

The instruments discussed in this chapter are those required

by Title 14 of the Code of Federal Regulations (14 CFR)

part 91, and are organized into three groups: pitot-static

instruments, compass systems, and gyroscopic instruments.

The chapter concludes with a discussion of how to preﬂ ight

these systems for IFR ﬂ ight. This chapter addresses additional

avionics systems such as Electronic Flight Information

Systems (EFIS), Ground Proximity Warning System

(GPWS), Terrain Awareness and Warning System (TAWS),

Trafﬁ c Alert and Collision Avoidance System (TCAS),

Head Up Display (HUD), etc., that are increasingly being

incorporated into general aviation aircraft.

Pitot/Static Systems

Pitot pressure, or impact air pressure, is sensed through an

open-end tube pointed directly into the relative wind ﬂ owing

around the aircraft. The pitot tube connects to pressure

operated ﬂ ight instruments such as the ASI.

Static Pressure

Other instruments depend upon accurate sampling of the

ambient still air atmospheric pressure to determine the

height and speed of movement of the aircraft through the

air, both horizontally and vertically. This pressure, called

static pressure, is sampled at one or more locations outside

the aircraft. The pressure of the static air is sensed at a ﬂ ush

port where the air is not disturbed. On some aircraft, air is

sampled by static ports on the side of the electrically heated

pitot-static head. [Figure 3-1] Other aircraft pick up the static

pressure through ﬂ ush ports on the side of the fuselage or

the vertical ﬁ n. These ports are in locations proven by ﬂ ight

tests to be in undisturbed air, and they are normally paired,

one on either side of the aircraft. This dual location prevents

lateral movement of the aircraft from giving erroneous static

pressure indications. The areas around the static ports may be

heated with electric heater elements to prevent ice forming

over the port and blocking the entry of the static air.

Three basic pressure-operated instruments are found in most

aircraft instrument panels. These are the sensitive altimeter,

ASI, and vertical speed indicator (VSI). All three receive

pressures sensed by the aircraft pitot-static system. The static

ports supply pressure to the ASI, altimeter, and VSI.

Blockage Considerations

The pitot tube is particularly sensitive to blockage especially

by icing. Even light icing can block the entry hole of the pitot

tube where ram air enters the system. This affects the ASI

and is the reason most airplanes are equipped with a pitot

heating system.

3-3

Figure 3-2. A Typical Pitot-Static System.

Indications of Pitot Tube Blockage

If the pitot tube becomes blocked, the ASI displays inaccurate

speeds. At the altitude where the pitot tube becomes blocked,

the ASI remains at the existing airspeed and doesn’t reﬂ ect

actual changes in speed.

• At altitudes above where the pitot tube became

blocked, the ASI displays a higher-than-actual

airspeed increasing steadily as altitude increases.

• At lower altitudes, the ASI displays a lower-than-actual

airspeed decreasing steadily as altitude decreases.

Indications from Static Port Blockage

Many aircraft also have a heating system to protect the

static ports to ensure the entire pitot-static system is clear

of ice. If the static ports become blocked, the ASI would

still function but could produce inaccurate indications. At

the altitude where the blockage occurs, airspeed indications

would be normal.

• At altitudes above which the static ports became

blocked, the ASI displays a lower-than-actual airspeed

continually decreasing as altitude is increased.

• At lower altitudes, the ASI displays a higher-than-actual

airspeed increasing steadily as altitude decreases.

The trapped pressure in the static system causes the altimeter

to remain at the altitude where the blockage occurred. The

VSI remains at zero. On some aircraft, an alternate static

air source valve is used for emergencies. [Figure 3-2] If

the alternate source is vented inside the airplane, where

static pressure is usually lower than outside static pressure,

selection of the alternate source may result in the following

erroneous instrument indications:

1. Altimeter reads higher than normal,

2. Indicated airspeed (IAS) reads greater than normal,

and

3. VSI momentarily shows a climb. Consult the Pilot’s

Operating Handbook/Airplane Flight Manual (POH/

AFM) to determine the amount of error.

Effects of Flight Conditions

The static ports are located in a position where the air at

their surface is as undisturbed as possible. But under some

ﬂ ight conditions, particularly at a high angle of attack with

the landing gear and ﬂ aps down, the air around the static

port may be disturbed to the extent that it can cause an error

in the indication of the altimeter and ASI. Because of the

importance of accuracy in these instruments, part of the

certiﬁ cation tests for an aircraft is a check of position error

in the static system.

The POH/AFM contains any corrections that must be applied

to the airspeed for the various conﬁ gurations of ﬂ aps and

landing gear.

Pitot/Static Instruments

Sensitive Altimeter

A sensitive altimeter is an aneroid barometer that measures

the absolute pressure of the ambient air and displays it in

terms of feet or meters above a selected pressure level.

Principle of Operation

The sensitive element in a sensitive altimeter is a stack of

evacuated, corrugated bronze aneroid capsules. [Figure 3-3]

The air pressure acting on these aneroids tries to compress

them against their natural springiness, which tries to expand

them. The result is that their thickness changes as the air

pressure changes. Stacking several aneroids increases the

dimension change as the pressure varies over the usable

range of the instrument.

Below 10,000 feet, a striped segment is visible. Above this

altitude, a mask begins to cover it, and above 15,000 feet,

all of the stripes are covered. [Figure 3-4]

Another conﬁ guration of the altimeter is the drum-type.

[Figure 3-5] These instruments have only one pointer that

makes one revolution for every 1,000 feet. Each number

represents 100 feet and each mark represents 20 feet. A drum,

marked in thousands of feet, is geared to the mechanism that

drives the pointer. To read this type of altimeter, ﬁ rst look at

3-4

Figure 3-3. Sensitive Altimeter Components.

Figure 3-4. Three-Pointer Altimeter. Figure 3-5. Drum-Type Altimeter.

the drum to get the thousands of feet, and then at the pointer

to get the feet and hundreds of feet.

A sensitive altimeter is one with an adjustable barometric scale

allowing the pilot to set the reference pressure from which the

altitude is measured. This scale is visible in a small window

called the Kollsman window. A knob on the instrument adjusts

the scale. The range of the scale is from 28.00" to 31.00"

inches of mercury (Hg), or 948 to 1,050 millibars.

Rotating the knob changes both the barometric scale and

the altimeter pointers in such a way that a change in the

barometric scale of 1" Hg changes the pointer indication

by 1,000 feet. This is the standard pressure lapse rate

below 5,000 feet. When the barometric scale is adjusted

to 29.92" Hg or 1,013.2 millibars, the pointers indicate the

pressure altitude. The pilot displays indicate altitude by

adjusting the barometric scale to the local altimeter setting.

The altimeter then indicates the height above the existing

sea level pressure.

Altimeter Errors

A sensitive altimeter is designed to indicate standard changes

from standard conditions, but most ﬂ ying involves errors

caused by nonstandard conditions and the pilot must be able

to modify the indications to correct for these errors. There

are two types of errors: mechanical and inherent.

Mechanical

A preﬂ ight check to determine the condition of an altimeter

consists of setting the barometric scale to the local altimeter

setting. The altimeter should indicate the surveyed elevation

3-5

Figure 3-6. The loss of altitude experienced when ﬂ ying into an area where the air is warmer (less dense) than standard.

of the airport. If the indication is off by more than 75 feet from

the surveyed elevation, the instrument should be referred

to a certiﬁ cated instrument repair station for recalibration.

Differences between ambient temperature and/or pressure

causes an erroneous indication on the altimeter.

Inherent Altimeter Error

Figure 3-6 shows how nonstandard temperature affects an

altimeter. When the aircraft is ﬂ ying in air that is warmer

than standard, the air is less dense and the pressure levels

are farther apart. When the aircraft is ﬂ ying at an indicated

altitude of 5,000 feet, the pressure level for that altitude is

higher than it would be in air at standard temperature, and

the aircraft is higher than it would be if the air were cooler.

If the air is colder than standard, it is denser and the pressure

levels are closer together. When the aircraft is ﬂ ying at an

indicated altitude of 5,000 feet, its true altitude is lower than

it would be if the air were warmer.

Cold Weather Altimeter Errors

A correctly calibrated pressure altimeter indicates true

altitude above mean sea level (MSL) when operating within

the International Standard Atmosphere (ISA) parameters of

pressure and temperature. Nonstandard pressure conditions are

corrected by applying the correct local area altimeter setting.

Temperature errors from ISA result in true altitude being

higher than indicated altitude whenever the temperature is

warmer than ISA and true altitude being lower than indicated

altitude whenever the temperature is colder than ISA.

True altitude variance under conditions of colder than ISA

temperatures poses the risk of inadequate obstacle clearance.

Under extremely cold conditions, pilots may need to add an

appropriate temperature correction determined from the chart

in Figure 3-7 to charted IFR altitudes to ensure terrain and

obstacle clearance with the following restrictions:

• Altitudes speciﬁ cally assigned by Air Trafﬁ c Control

(ATC), such as “maintain 5,000 feet” shall not be

corrected. Assigned altitudes may be rejected if the

pilot decides that low temperatures pose a risk of

inadequate terrain or obstacle clearance.

• If temperature corrections are applied to charted

IFR altitudes (such as procedure turn altitudes, ﬁ nal

approach ﬁ x crossing altitudes, etc.), the pilot must

advise ATC of the applied correction.

ICAO Cold Temperature Error Table

The cold temperature induced altimeter error may be

significant when considering obstacle clearances when

temperatures are well below standard. Pilots may wish to

increase their minimum terrain clearance altitudes with a

corresponding increase in ceiling from the normal minimum

when ﬂ ying in extreme cold temperature conditions. Higher

altitudes may need to be selected when ﬂ ying at low terrain

clearances. Most ﬂ ight management systems (FMS) with

air data computers implement a capability to compensate

for cold temperature errors. Pilots ﬂ ying with these systems

should ensure they are aware of the conditions under which

the system will automatically compensate. If compensation

is applied by the FMS or manually, ATC must be informed

that the aircraft is not ﬂ ying the assigned altitude. Otherwise,

vertical separation from other aircraft may be reduced

creating a potentially hazardous situation. The table in

Figure 3-7, derived from International Civil Aviation

3-6

Figure 3-7. ICAO Cold Temperature Error Table.

Organization (ICAO) standard formulas, shows how much

error can exist when the temperature is extremely cold. To

use the table, ﬁ nd the reported temperature in the left column,

and then read across the top row to the height above the

airport/reporting station. Subtract the airport elevation from

the altitude of the ﬁ nal approach ﬁ x (FAF). The intersection

of the column and row is the amount of possible error.

Example: The reported temperature is -10° Celsius and the

FAF is 500 feet above the airport elevation. The reported

current altimeter setting may place the aircraft as much as 50

feet below the altitude indicated by the altimeter.

When using the cold temperature error table, the altitude

error is proportional to both the height above the reporting

station elevation and the temperature at the reporting

station. For IFR approach procedures, the reporting station

elevation is assumed to be airport elevation. It is important

to understand that corrections are based upon the temperature

at the reporting station, not the temperature observed at the

aircraft’s current altitude and height above the reporting

station and not the charted IFR altitude.

To see how corrections are applied, note the following

example:

Airport Elevation 496 feet

Airport Temperature - 50° C

A charted IFR approach to the airport provides the following

data:

Minimum Procedure Turn Altitude 1,800 feet

Minimum FAF Crossing Altitude 1,200 feet

Straight-in Minimum Descent Altitude 800 feet

Circling MDA 1,000 feet

The Minimum Procedure Turn Altitude of 1,800 feet will

be used as an example to demonstrate determination of

the appropriate temperature correction. Typically, altitude

values are rounded up to the nearest 100-foot level. The

charted procedure turn altitude of 1,800 feet minus the airport

elevation of 500 feet equals 1,300 feet. The altitude difference

of 1,300 feet falls between the correction chart elevations of

1,000 feet and 1,500 feet. At the station temperature of -50°C,

the correction falls between 300 feet and 450 feet. Dividing

the difference in compensation values by the difference in

altitude above the airport gives the error value per foot.

In this case, 150 feet divided by 500 feet = 0.33 feet for each

additional foot of altitude above 1,000 feet. This provides a

correction of 300 feet for the ﬁ rst 1,000 feet and an additional

value of 0.33 times 300 feet, or 99 feet, which is rounded to

100 feet. 300 feet + 100 feet = total temperature correction

of 400 feet. For the given conditions, correcting the charted

value of 1,800 feet above MSL (equal to a height above the

reporting station of 1,300 feet) requires the addition of 400

feet. Thus, when ﬂ ying at an indicated altitude of 2,200 feet,

the aircraft is actually ﬂ ying a true altitude of 1,800 feet.

Minimum Procedure Turn Altitude

1,800 feet charted = 2,200 feet corrected

Minimum FAF Crossing Altitude

1,200 feet charted = 1,500 feet corrected

Straight-in MDA

800 feet charted = 900 feet corrected

Circling MDA

1,000 feet charted = 1,200 feet corrected

Nonstandard Pressure on an Altimeter

Maintaining a current altimeter setting is critical because the

atmosphere pressure is not constant. That is, in one location

the pressure might be higher than the pressure just a short

distance away. Take an aircraft whose altimeter setting is set

to 29.92" of local pressure. As the aircraft moves to an area

of lower pressure (Point A to B in Figure 3-8) and the pilot

fails to readjust the altimeter setting (essentially calibrating

it to local pressure), then as the pressure decreases, the

indicated altitude will be lower. Adjusting the altimeter

3-7

Figure 3-8. Effects of Nonstandard Pressure on an Altimeter of an

Aircraft Flown into Air of Lower Than Standard Pressure (Air is

Less Dense).

settings compensates for this. When the altimeter shows an

indicated altitude of 5,000 feet, the true altitude at Point A

(the height above mean sea level) is only 3,500 feet at Point

B. The fact that the altitude indication is not always true lends

itself to the memory aid, “When ﬂ ying from hot to cold or

from a high to a low, look out below.” [Figure 3-8]

Altimeter Enhancements (Encoding)

It is not sufﬁ cient in the airspace system for only the pilot

to have an indication of the aircraft’s altitude; the air trafﬁ c

controller on the ground must also know the altitude of the

aircraft. To provide this information, the aircraft is typically

equipped with an encoding altimeter.

When the ATC transponder is set to Mode C, the encoding

altimeter supplies the transponder with a series of pulses

identifying the ﬂ ight level (in increments of 100 feet) at

which the aircraft is ﬂ ying. This series of pulses is transmitted

to the ground radar where they appear on the controller’s

scope as an alphanumeric display around the return for the

aircraft. The transponder allows the ground controller to

identify the aircraft and determine the pressure altitude at

which it is ﬂ ying.

A computer inside the encoding altimeter measures the

pressure referenced from 29.92" Hg and delivers this data to

the transponder. When the pilot adjusts the barometric scale

to the local altimeter setting, the data sent to the transponder

is not affected. This is to ensure that all Mode C aircraft are

transmitting data referenced to a common pressure level. ATC

equipment adjusts the displayed altitudes to compensate for

local pressure differences allowing display of targets at correct

altitudes. 14 CFR part 91 requires the altitude transmitted by

the transponder to be within 125 feet of the altitude indicated

on the instrument used to maintain ﬂ ight altitude.

Reduced Vertical Separation Minimum (RVSM)

Below 31,000 feet, a 1,000 foot separation is the minimum

required between usable ﬂ ight levels. Flight levels (FLs)

generally start at 18,000 feet where the local pressure is

29.92" Hg or greater. All aircraft 18,000 feet and above use

a standard altimeter setting of 29.92" Hg, and the altitudes

are in reference to a standard hence termed FL. Between FL

180 and FL 290, the minimum altitude separation is 1,000

feet between aircraft. However, for ﬂ ight above FL 290

(primarily due to aircraft equipage and reporting capability;

potential error) ATC applied the requirement of 2,000 feet of

separation. FL 290, an altitude appropriate for an eastbound

aircraft, would be followed by FL 310 for a westbound

aircraft, and so on to FL 410, or seven FLs available for ﬂ ight.

With 1,000-foot separation, or a reduction of the vertical

separation between FL 290 and FL 410, an additional six

FLs become available. This results in normal ﬂ ight level and

direction management being maintained from FL 180 through

FL 410. Hence the name is Reduced Vertical Separation

Minimum (RVSM). Because it is applied domestically, it is

called United States Domestic Reduced Vertical Separation

Minimum, or DRVSM.

However, there is a cost to participate in the DRVSM program

which relates to both aircraft equipage and pilot training. For

example, altimetry error must be reduced signiﬁ cantly and

operators using RVSM must receive authorization from the

appropriate civil aviation authority. RVSM aircraft must

meet required altitude-keeping performance standards.

Additionally, operators must operate in accordance with

RVSM policies/procedures applicable to the airspace where

they are ﬂ ying.

The aircraft must be equipped with at least one automatic

altitude control—

• Within a tolerance band of ±65 feet about an acquired

altitude when the aircraft is operated in straight-and-

level ﬂ ight.

• Within a tolerance band of ±130 feet under no

turbulent, conditions for aircraft for which application

for type certiﬁ cation occurred on or before April 9,

1997 that are equipped with an automatic altitude

control system with ﬂ ight management/performance

system inputs.

3-8

Figure 3-9. Increase in Aircraft Permitted Between FL 180 and

FL 410.

Figure 3-10. Rate of Climb or Descent in Thousands of Feet Per

Minute.

That aircraft must be equipped with an altitude alert system

that signals an alert when the altitude displayed to the ﬂ ight

crew deviates from the selected altitude by more than (in most

cases) 200 feet. For each condition in the full RVSM ﬂ ight

envelope, the largest combined absolute value for residual

static source error plus the avionics error may not exceed 200

feet. Aircraft with TCAS must have compatibility with RVSM

Operations. Figure 3-9 illustrates the increase in aircraft

permitted between FL 180 and FL 410. Most noteworthy,

however, is the economization that aircraft can take advantage

of by the higher FLs being available to more aircraft.

Vertical Speed Indicator (VSI)

The VSI in Figure 3-10 is also called a vertical velocity

indicator (VVI), and was formerly known as a rate-of-

climb indicator. It is a rate-of-pressure change instrument

that gives an indication of any deviation from a constant

pressure level.

Inside the instrument case is an aneroid very much like the

one in an ASI. Both the inside of this aneroid and the inside

of the instrument case are vented to the static system, but

the case is vented through a calibrated oriﬁ ce that causes

the pressure inside the case to change more slowly than

the pressure inside the aneroid. As the aircraft ascends, the

static pressure becomes lower. The pressure inside the case

compresses the aneroid, moving the pointer upward, showing

a climb and indicating the rate of ascent in number of feet

per minute (fpm).

When the aircraft levels off, the pressure no longer changes.

The pressure inside the case becomes equal to that inside

the aneroid, and the pointer returns to its horizontal, or

zero, position. When the aircraft descends, the static

pressure increases. The aneroid expands, moving the pointer

downward, indicating a descent.

The pointer indication in a VSI lags a few seconds behind

the actual change in pressure. However, it is more sensitive

than an altimeter and is useful in alerting the pilot of an

upward or downward trend, thereby helping maintain a

constant altitude.

Some of the more complex VSIs, called instantaneous vertical

speed indicators (IVSI), have two accelerometer-actuated air

pumps that sense an upward or downward pitch of the aircraft

and instantaneously create a pressure differential. By the time

the pressure caused by the pitch acceleration dissipates, the

altitude pressure change is effective.

Dynamic Pressure Type Instruments

Airspeed Indicator (ASI)

An ASI is a differential pressure gauge that measures the

dynamic pressure of the air through which the aircraft is

ﬂ ying. Dynamic pressure is the difference in the ambient

static air pressure and the total, or ram, pressure caused by

the motion of the aircraft through the air. These two pressures

are taken from the pitot-static system.

3-9

Figure 3-11. Mechanism of an Airspeed Indicator.

Equivalent Airspeed (EAS)

EAS is CAS corrected for compression of the air inside the

pitot tube. EAS is the same as CAS in standard atmosphere

at sea level. As the airspeed and pressure altitude increase,

the CAS becomes higher than it should be, and a correction

for compression must be subtracted from the CAS.

True Airspeed (TAS)

TAS is CAS corrected for nonstandard pressure and

temperature. TAS and CAS are the same in standard

atmosphere at sea level. Under nonstandard conditions, TAS

is found by applying a correction for pressure altitude and

temperature to the CAS.

Some aircraft are equipped with true ASIs that have a

temperature-compensated aneroid bellows inside the

instrument case. This bellows modiﬁ es the movement of

the rocking shaft inside the instrument case so the pointer

shows the actual TAS.

The TAS indicator provides both true and IAS. These

instruments have the conventional airspeed mechanism,

with an added subdial visible through cutouts in the regular

dial. A knob on the instrument allows the pilot to rotate the

subdial and align an indication of the outside air temperature

with the pressure altitude being ﬂ own. This alignment causes

the instrument pointer to indicate the TAS on the subdial.

[Figure 3-12]

The mechanism of the ASI in Figure 3-11 consists of a thin,

corrugated phosphor bronze aneroid, or diaphragm, that

receives its pressure from the pitot tube. The instrument

case is sealed and connected to the static ports. As the

pitot pressure increases or the static pressure decreases, the

diaphragm expands. This dimensional change is measured by

a rocking shaft and a set of gears that drives a pointer across

the instrument dial. Most ASIs are calibrated in knots, or

nautical miles per hour; some instruments show statute miles

per hour, and some instruments show both.

Types of Airspeed

Just as there are several types of altitude, there are multiple

types of airspeed: Indicated Airspeed (IAS), Calibrated

Airspeed (CAS), Equivalent Airspeed (EAS), and True

Airspeed (TAS).

Indicated Airspeed (IAS)

IAS is shown on the dial of the instrument, uncorrected for

instrument or system errors.

Calibrated Airspeed (CAS)

CAS is the speed at which the aircraft is moving through

the air, which is found by correcting IAS for instrument

and position errors. The POH/AFM has a chart or graph to

correct IAS for these errors and provide the correct CAS for

the various ﬂ ap and landing gear conﬁ gurations.

3-10

Figure 3-12. A true airspeed indicator allows the pilot to correct

IAS for nonstandard temperature and pressure.

Figure 3-13. A Machmeter shows the ratio of the speed of sound to

the TAS the aircraft is ﬂ ying.

Figure 3-14. A maximum allowable airspeed indicator has a movable

pointer that indicates the never-exceed speed, which changes with

altitude to avoid the onset of transonic shock waves.

Most high-speed aircraft are limited to a maximum Mach

number at which they can ﬂ y. This is shown on a Machmeter

as a decimal fraction. [Figure 3-13] For example, if the

Machmeter indicates .83 and the aircraft is ﬂ ying at 30,000

feet where the speed of sound under standard conditions is

589.5 knots, the airspeed is 489.3 knots. The speed of sound

varies with the air temperature. If the aircraft were ﬂ ying at

Mach .83 at 10,000 feet where the air is much warmer, its

airspeed would be 530 knots.

Maximum Allowable Airspeed

Some aircraft that ﬂ y at high subsonic speeds are equipped

with maximum allowable ASIs like the one in Figure 3-14.

This instrument looks much like a standard air-speed indicator,

calibrated in knots, but has an additional pointer colored red,

checkered, or striped. The maximum airspeed pointer is

actuated by an aneroid, or altimeter mechanism, that moves

it to a lower value as air density decreases. By keeping the

airspeed pointer at a lower value than the maximum pointer,

the pilot avoids the onset of transonic shock waves.

Airspeed Color Codes

The dial of an ASI is color coded to alert the pilot, at a

glance, of the signiﬁ cance of the speed at which the aircraft

is ﬂ ying. These colors and their associated airspeeds are

shown in Figure 3-15.

Magnetism

The Earth is a huge magnet, spinning in space, surrounded

by a magnetic ﬁ eld made up of invisible lines of ﬂ ux. These

lines leave the surface at the magnetic north pole and reenter

at the magnetic South Pole.

Lines of magnetic ﬂ ux have two important characteristics:

any magnet that is free to rotate will align with them, and

Mach Number

As an aircraft approaches the speed of sound, the air ﬂ owing

over certain areas of its surface speeds up until it reaches the

speed of sound, and shock waves form. The IAS at which

these conditions occur changes with temperature. Therefore,

in this case, airspeed is not entirely adequate to warn the

pilot of the impending problems. Mach number is more

useful. Mach number is the ratio of the TAS of the aircraft

to the speed of sound in the same atmospheric conditions.

An aircraft ﬂ ying at the speed of sound is ﬂ ying at Mach

1.0. Some older mechanical Machmeters not driven from

an air data computer use an altitude aneroid inside the

instrument that converts pitot-static pressure into Mach

number. These systems assume that the temperature at any

altitude is standard; therefore, the indicated Mach number is

inaccurate whenever the temperature deviates from standard.

These systems are called indicated Machmeters. Modern

electronic Machmeters use information from an air data

computer system to correct for temperature errors. These

systems display true Mach number.

3-11

Figure 3-15. Color Codes for an Airspeed Indicator.

Figure 3-16. A Magnetic Compass. The vertical line is called the

lubber line.

an electrical current is induced into any conductor that cuts

across them. Most direction indicators installed in aircraft

make use of one of these two characteristics.

The Basic Aviation Magnetic Compass

One of the oldest and simplest instruments for indicating

direction is the magnetic compass. It is also one of the basic

instruments required by 14 CFR part 91 for both VFR and

IFR ﬂ ight.

Magnetic Compass Overview

A magnet is a piece of material, usually a metal containing

iron, which attracts and holds lines of magnetic flux.

Regardless of size, every magnet has two poles: a north

pole and a south pole. When one magnet is placed in the

ﬁ eld of another, the unlike poles attract each other and like

poles repel.

An aircraft magnetic compass, such as the one in Figure 3-16,

has two small magnets attached to a metal ﬂ oat sealed inside a

bowl of clear compass ﬂ uid similar to kerosene. A graduated

scale, called a card, is wrapped around the ﬂ oat and viewed

through a glass window with a lubber line across it. The card

is marked with letters representing the cardinal directions,

north, east, south, and west, and a number for each 30°

between these letters. The ﬁ nal “0” is omitted from these

directions; for example, 3 = 30°, 6 = 60°, and 33 = 330°.

There are long and short graduation marks between the letters

and numbers, with each long mark representing 10° and each

short mark representing 5°.

Magnetic Compass Construction

The ﬂ oat and card assembly has a hardened steel pivot in its

center that rides inside a special, spring-loaded, hard-glass

jewel cup. The buoyancy of the ﬂ oat takes most of the weight

off the pivot, and the ﬂ uid damps the oscillation of the ﬂ oat

and card. This jewel-and-pivot type mounting allows the ﬂ oat

freedom to rotate and tilt up to approximately 18° angle of

bank. At steeper bank angles, the compass indications are

erratic and unpredictable.

The compass housing is entirely full of compass ﬂ uid. To

prevent damage or leakage when the ﬂ uid expands and

contracts with temperature changes, the rear of the compass

case is sealed with a ﬂ exible diaphragm, or with a metal

bellows in some compasses.

Magnetic Compass Theory of Operations

The magnets align with the Earth’s magnetic ﬁ eld and the

pilot reads the direction on the scale opposite the lubber line.

Note that in Figure 3-16, the pilot sees the compass card from

its backside. When the pilot is ﬂ ying north as the compass

shows, east is to the pilot’s right, but on the card “33”, which

represents 330° (west of north), is to the right of north. The

reason for this apparent backward graduation is that the card

remains stationary, and the compass housing and the pilot turn

around it, always viewing the card from its backside.

3-12

Figure 3-17. Isogonic lines are lines of equal variation.

Figure 3-18. Utilization of a Compass Rose Aids Compensation

for Deviation Errors.

A compensator assembly mounted on the top or bottom of the

compass allows an aviation maintenance technician (AMT)

to create a magnetic ﬁ eld inside the compass housing that

cancels the inﬂ uence of local outside magnetic ﬁ elds. This is

done to correct for deviation error. The compensator assembly

has two shafts whose ends have screwdriver slots accessible

from the front of the compass. Each shaft rotates one or two

small compensating magnets. The end of one shaft is marked

E-W, and its magnets affect the compass when the aircraft is

pointed east or west. The other shaft is marked N-S and its

magnets affect the compass when the aircraft is pointed north

or south.

Magnetic Compass Induced Errors

The magnetic compass is the simplest instrument in the

panel, but it is subject to a number of errors that must be

considered.

Variation

The Earth rotates about its geographic axis; maps and charts

are drawn using meridians of longitude that pass through the

geographic poles. Directions measured from the geographic

poles are called true directions. The north magnetic pole to

which the magnetic compass points is not collocated with

the geographic north pole, but is some 1,300 miles away;

directions measured from the magnetic poles are called

magnetic directions. In aerial navigation, the difference

between true and magnetic directions is called variation. This

same angular difference in surveying and land navigation is

called declination.

Figure 3-17 shows the isogonic lines that identify the number

of degrees of variation in their area. The line that passes near

Chicago is called the agonic line. Anywhere along this line

the two poles are aligned, and there is no variation. East of

this line, the magnetic pole is to the west of the geographic

pole and a correction must be applied to a compass indication

to get a true direction.

Flying in the Washington, D.C. area, for example, the variation

is 10° west. If the pilot wants to ﬂ y a true course of south (180°),

the variation must be added to this resulting in a magnetic course

to ﬂ y of 190°. Flying in the Los Angeles, CA area, the variation

is 14° east. To ﬂ y a true course of 180° there, the pilot would

have to subtract the variation and ﬂ y a magnetic course of 166°.

The variation error does not change with the heading of the

aircraft; it is the same anywhere along the isogonic line.

Deviation

The magnets in a compass align with any magnetic ﬁ eld.

Local magnetic ﬁ elds in an aircraft caused by electrical current

ﬂ owing in the structure, in nearby wiring or any magnetized

part of the structure, conﬂ ict with the Earth’s magnetic ﬁ eld

and cause a compass error called deviation.

Deviation, unlike variation, is different on each heading, but it is

not affected by the geographic location. Variation error cannot

be reduced or changed, but deviation error can be minimized

when a pilot or AMT performs the maintenance task known

as “swinging the compass.”

Most airports have a compass rose, which is a series of lines

marked out on a taxiway or ramp at some location where there

is no magnetic interference. Lines, oriented to magnetic north,

are painted every 30°, as shown in Figure 3-18.

The pilot or AMT aligns the aircraft on each magnetic

heading and adjusts the compensating magnets to minimize

the difference between the compass indication and the actual

magnetic heading of the aircraft. Any error that cannot be

removed is recorded on a compass correction card, like the one

in Figure 3-19, and placed in a cardholder near the compass.

If the pilot wants to ﬂ y a magnetic heading of 120° and the

3-13

Figure 3-19. A compass correction card shows the deviation

correction for any heading.

Figure 3-20. Northerly Turning Error.

aircraft is operating with the radios on, the pilot should ﬂ y a

compass heading of 123°.

The corrections for variation and deviation must be applied

in the correct sequence and is shown below starting from the

true course desired.

Step 1: Determine the Magnetic Course

True Course (180°) ± Variation (+10°) = Magnetic Course (190°)

The Magnetic Course (190°) is steered if there is no deviation

error to be applied. The compass card must now be considered

for the compass course of 190°.

Step 2: Determine the Compass Course

Magnetic Course (190°, from step 1) ± Deviation (-2°, from

correction card) = Compass Course (188°)

NOTE: Intermediate magnetic courses between those listed on

the compass card need to be interpreted. Therefore, to steer a true

course of 180°, the pilot would follow a compass course of 188°.

To ﬁ nd the true course that is being ﬂ own when the compass

course is known:

Compass Course ± Deviation = Magnetic Course ± Variation

= True Course

Dip Errors

The lines of magnetic ﬂ ux are considered to leave the Earth at

the magnetic north pole and enter at the magnetic South Pole. At

both locations the lines are perpendicular to the Earth’s surface.

At the magnetic equator, which is halfway between the poles,

the lines are parallel with the surface. The magnets in a compass

align with this ﬁ eld, and near the poles they dip, or tilt, the ﬂ oat

and card. The ﬂ oat is balanced with a small dip-compensating

weight, so it stays relatively level when operating in the middle

latitudes of the northern hemisphere. This dip along with this

weight causes two very noticeable errors: northerly turning error

and acceleration error.

The pull of the vertical component of the Earth’s magnetic ﬁ eld

causes northerly turning error, which is apparent on a heading

of north or south. When an aircraft ﬂ ying on a heading of north

makes a turn toward east, the aircraft banks to the right, and the

compass card tilts to the right. The vertical component of the

Earth’s magnetic ﬁ eld pulls the north-seeking end of the magnet

to the right, and the ﬂ oat rotates, causing the card to rotate toward

west, the direction opposite the direction the turn is being made.

[Figure 3-20]

If the turn is made from north to west, the aircraft banks to the left

and the compass card tilts down on the left side. The magnetic

ﬁ eld pulls on the end of the magnet that causes the card to rotate

toward east. This indication is again opposite to the direction

the turn is being made. The rule for this error is: when starting

3-14

Figure 3-21. The Effects of Acceleration Error.

a turn from a northerly heading, the compass indication lags

behind the turn.

When an aircraft is ﬂ ying on a heading of south and begins

a turn toward east, the Earth’s magnetic ﬁ eld pulls on the

end of the magnet that rotates the card toward east, the same

direction the turn is being made. If the turn is made from south

toward west, the magnetic pull starts the card rotating toward

west—again, in the same direction the turn is being made. The

rule for this error is: When starting a turn from a southerly

heading, the compass indication leads the turn.

In acceleration error, the dip-correction weight causes the end

of the ﬂ oat and card marked N (the south-seeking end) to be

heavier than the opposite end. When the aircraft is ﬂ ying at

a constant speed on a heading of east or west, the ﬂ oat and

card is level. The effects of magnetic dip and the weight are

approximately equal. If the aircraft accelerates on a heading

of east [Figure 3-21], the inertia of the weight holds its end of

the ﬂ oat back and the card rotates toward north. As soon as the

speed of the aircraft stabilizes, the card swings back to its east

indication. If, while ﬂ ying on this easterly heading, the aircraft

decelerates, the inertia causes the weight to move ahead and the

card rotates toward south until the speed again stabilizes.

When ﬂ ying on a heading of west, the same things happen.

Inertia from acceleration causes the weight to lag, and the

card rotates toward north. When the aircraft decelerates on a

heading of west, inertia causes the weight to move ahead and

the card rotates toward south.

Oscillation Error

Oscillation is a combination of all of the other errors, and it

results in the compass card swinging back and forth around

the heading being flown. When setting the gyroscopic

heading indicator to agree with the magnetic compass, use

the average indication between the swings.

The Vertical Card Magnetic Compass

The ﬂ oating magnet type of compass not only has all the

errors just described, but also lends itself to confused reading.

It is easy to begin a turn in the wrong direction because its card

appears backward. East is on what the pilot would expect to be

the west side. The vertical card magnetic compass eliminates

some of the errors and confusion. The dial of this compass

is graduated with letters representing the cardinal directions,

numbers every 30°, and marks every 5°. The dial is rotated by

a set of gears from the shaft-mounted magnet, and the nose

of the symbolic airplane on the instrument glass represents

the lubber line for reading the heading of the aircraft from

the dial. Eddy currents induced into an aluminum-damping

cup damp oscillation of the magnet. [Figure 3-22]

The Flux Gate Compass System

As mentioned earlier, the lines of ﬂ ux in the Earth’s magnetic

ﬁ eld have two basic characteristics: a magnet aligns with

these lines, and an electrical current is induced, or generated,

in any wire crossed by them.

3-15

Figure 3-22. Vertical Card Magnetic Compass.

Figure 3-23. The soft iron frame of the ﬂ ux valve accepts the ﬂ ux

from the Earth’s magnetic ﬁ eld each time the current in the center

coil reverses. This ﬂ ux causes current to ﬂ ow in the three pickup

coils.

Figure 3-24. The current in each of the three pickup coils changes

with the heading of the aircraft.

Figure 3-25. Pictorial Navigation Indicator (HSI Top), Slaving

Control and Compensator Unit.

The ﬂ ux gate compass that drives slaved gyros uses the

characteristic of current induction. The ﬂ ux valve is a small,

segmented ring, like the one in Figure 3-23, made of soft

iron that readily accepts lines of magnetic ﬂ ux. An electrical

coil is wound around each of the three legs to accept the

current induced in this ring by the Earth’s magnetic ﬁ eld. A

coil wound around the iron spacer in the center of the frame

has 400-Hz alternating current (A.C.) ﬂ owing through it.

During the times when this current reaches its peak, twice

during each cycle, there is so much magnetism produced by

this coil that the frame cannot accept the lines of ﬂ ux from

the Earth’s ﬁ eld.

But as the current reverses between the peaks, it demagnetizes

the frame so it can accept the ﬂ ux from the Earth’s ﬁ eld. As

this ﬂ ux cuts across the windings in the three coils, it causes

current to ﬂ ow in them. These three coils are connected in

such a way that the current ﬂ owing in them changes as the

heading of the aircraft changes. [Figure 3-24]

The three coils are connected to three similar but smaller coils

in a synchro inside the instrument case. The synchro rotates

the dial of a radio magnetic indicator (RMI) or a horizontal

situation indicator (HSI).

Remote Indicating Compass

Remote indicating compasses were developed to compensate

for the errors and limitations of the older type of heading

indicators. The two panel-mounted components of a typical

system are the pictorial navigation indicator and the slaving

control and compensator unit. [Figure 3-25] The pictorial

navigation indicator is commonly referred to as a HSI.

3-16

Figure 3-26. Driven by signals from a ﬂ ux valve, the compass card

in this RMI indicates the heading of the aircraft opposite the upper

center index mark. The green pointer is driven by the ADF.

The slaving control and compensator unit has a pushbutton

that provides a means of selecting either the “slaved gyro”

or “free gyro” mode. This unit also has a slaving meter

and two manual heading-drive buttons. The slaving meter

indicates the difference between the displayed heading and

the magnetic heading. A right deﬂ ection indicates a clockwise

error of the compass card; a left deflection indicates a

counterclockwise error. Whenever the aircraft is in a turn

and the card rotates, the slaving meter shows a full deﬂ ection

to one side or the other. When the system is in “free gyro”

mode, the compass card may be adjusted by depressing the

appropriate heading-drive button.

A separate unit, the magnetic slaving transmitter is mounted

remotely; usually in a wingtip to eliminate the possibility of

magnetic interference. It contains the ﬂ ux valve, which is

the direction-sensing device of the system. A concentration

of lines of magnetic force, after being ampliﬁ ed, becomes

a signal relayed to the heading indicator unit, which is also

remotely mounted. This signal operates a torque motor in

the heading indicator unit that processes the gyro unit until

it is aligned with the transmitter signal. The magnetic slaving

transmitter is connected electrically to the HSI.

There are a number of designs of the remote indicating

compass; therefore, only the basic features of the system are

covered here. Instrument pilots must become familiar with

the characteristics of the equipment in their aircraft.

As instrument panels become more crowded and the pilot’s

available scan time is reduced by a heavier ﬂ ight deck

workload, instrument manufacturers have worked toward

combining instruments. One good example of this is the

RMI in Figure 3-26. The compass card is driven by signals

from the ﬂ ux valve, and the two pointers are driven by an

automatic direction ﬁ nder (ADF) and a very high frequency

omnidirectional range (VOR).

Gyroscopic Systems

Flight without reference to a visible horizon can be safely

accomplished by the use of gyroscopic instrument systems

and the two characteristics of gyroscopes, which are rigidity

and precession. These systems include attitude, heading,

and rate instruments, along with their power sources. These

instruments include a gyroscope (or gyro) that is a small wheel

with its weight concentrated around its periphery. When this

wheel is spun at high speed, it becomes rigid and resists tilting

or turning in any direction other than around its spin axis.

Attitude and heading instruments operate on the principle

of rigidity. For these instruments, the gyro remains rigid

in its case and the aircraft rotates about it. Rate indicators,

such as turn indicators and turn coordinators, operate on the

principle of precession. In this case, the gyro processes (or

rolls over) proportionate to the rate the aircraft rotates about

one or more of its axes.

Power Sources

Aircraft and instrument manufacturers have designed

redundancy in the ﬂ ight instruments so that any single failure

will not deprive the pilot of the ability to safely conclude

the ﬂ ight. Gyroscopic instruments are crucial for instrument

ﬂ ight; therefore, they are powered by separate electrical or

pneumatic sources.

Pneumatic Systems

Pneumatic gyros are driven by a jet of air impinging on

buckets cut into the periphery of the wheel. On many aircraft

this stream of air is obtained by evacuating the instrument

case with a vacuum source and allowing ﬁ ltered air to ﬂ ow

into the case through a nozzle to spin the wheel.

Venturi Tube Systems

Aircraft that do not have a pneumatic pump to evacuate the

instrument case can use venturi tubes mounted on the outside

of the aircraft, similar to the system shown in Figure 3-27. Air

ﬂ owing through the venturi tube speeds up in the narrowest

part and, according to Bernoulli’s principle, the pressure

drops. This location is connected to the instrument case by

a piece of tubing. The two attitude instruments operate on

approximately 4" Hg of suction; the turn-and-slip indicator

needs only 2" Hg, so a pressure-reducing needle valve is

used to decrease the suction. Air ﬂ ows into the instruments

through ﬁ lters built into the instrument cases. In this system,

ice can clog the venturi tube and stop the instruments when

they are most needed.

3-17

Figure 3-27. A venturi tube system that provides necessary vacuum

to operate key instruments.

Figure 3-28. Single-engine instrument vacuum system using a steel-vane wet-type vacuum pump.

Vacuum Pump Systems

Wet-Type Vacuum Pump

Steel-vane air pumps have been used for many years to

evacuate the instrument cases. The vanes in these pumps

are lubricated by a small amount of engine oil metered into

the pump and discharged with the air. In some aircraft the

discharge air is used to inﬂ ate rubber deicer boots on the

wing and empennage leading edges. To keep the oil from

deteriorating the rubber boots, it must be removed with an

oil separator like the one in Figure 3-28.

The vacuum pump moves a greater volume of air than is

needed to supply the instruments with the suction needed,

so a suction-relief valve is installed in the inlet side of the

pump. This spring-loaded valve draws in just enough air to

maintain the required low pressure inside the instruments,

as is shown on the suction gauge in the instrument panel.

Filtered air enters the instrument cases from a central air

ﬁ lter. As long as aircraft ﬂ y at relatively low altitudes, enough

air is drawn into the instrument cases to spin the gyros at a

sufﬁ ciently high speed.

Dry Air Vacuum Pump

As ﬂ ight altitudes increase, the air is less dense and more air

must be forced through the instruments. Air pumps that do not

mix oil with the discharge air are used in high ﬂ ying aircraft.

3-18

Figure 3-29. Twin-Engine Instrument Pressure System Using a Carbon-Vane Dry-Type Air Pump.

Steel vanes sliding in a steel housing need to be lubricated,

but vanes made of a special formulation of carbon sliding

inside carbon housing provide their own lubrication in a

microscopic amount as they wear.

Pressure Indicating Systems

Figure 3-29 is a diagram of the instrument pneumatic

system of a twin-engine general aviation airplane. Two dry

air pumps are used with ﬁ lters in their inlet to ﬁ lter out any

contaminants that could damage the fragile carbon vanes in

the pump. The discharge air from the pump ﬂ ows through

a regulator, where excess air is bled off to maintain the

pressure in the system at the desired level. The regulated air

then ﬂ ows through inline ﬁ lters to remove any contamination

that could have been picked up from the pump, and from

there into a manifold check valve. If either engine should

become inoperative or either pump should fail, the check

valve isolates the inoperative system and the instruments are

driven by air from the operating system. After the air passes

through the instruments and drives the gyros, it is exhausted

from the case. The gyro pressure gauge measures the pressure

drop across the instruments.

Electrical Systems

Many general aviation aircraft that use pneumatic attitude

indicators use electric rate indicators and/or the reverse. Some

instruments identify their power source on their dial, but it

is extremely important that pilots consult the POH/AFM to

determine the power source of all instruments to know what

action to take in the event of an instrument failure. Direct

current (D.C.) electrical instruments are available in 14- or

28-volt models, depending upon the electrical system in

the aircraft. A.C. is used to operate some attitude gyros and

autopilots. Aircraft with only D.C. electrical systems can use

A.C. instruments via installation of a solid-state D.C. to A.C.

inverter, which changes 14 or 28 volts D.C. into three-phase

115-volt, 400-Hz A.C.

Gyroscopic Instruments

Attitude Indicators

The ﬁ rst attitude instrument (AI) was originally referred to as

an artiﬁ cial horizon, later as a gyro horizon; now it is more

properly called an attitude indicator. Its operating mechanism

is a small brass wheel with a vertical spin axis, spun at a high

speed by either a stream of air impinging on buckets cut into

its periphery, or by an electric motor. The gyro is mounted in

a double gimbal, which allows the aircraft to pitch and roll

about the gyro as it remains ﬁ xed in space.

A horizon disk is attached to the gimbals so it remains in

the same plane as the gyro, and the aircraft pitches and

rolls about it. On early instruments, this was just a bar that

3-19

Figure 3-30. The dial of this attitude indicator has reference lines

to show pitch and roll.

represented the horizon, but now it is a disc with a line

representing the horizon and both pitch marks and bank-angle

lines. The top half of the instrument dial and horizon disc

is blue, representing the sky; and the bottom half is brown,

representing the ground. A bank index at the top of the

instrument shows the angle of bank marked on the banking

scale with lines that represent 10°, 20°, 30°, 45°, and 60°.

[Figure 3-30]

A small symbolic aircraft is mounted in the instrument case so it

appears to be ﬂ ying relative to the horizon. A knob at the bottom

center of the instrument case raises or lowers the aircraft to

compensate for pitch trim changes as the airspeed changes. The

width of the wings of the symbolic aircraft and the dot in the center

of the wings represent a pitch change of approximately 2°.

For an AI to function properly, the gyro must remain

vertically upright while the aircraft rolls and pitches around

it. The bearings in these instruments have a minimum of

friction; however, even this small amount places a restraint

on the gyro producing precession and causing the gyro to tilt.

To minimize this tilting, an erection mechanism inside the

instrument case applies a force any time the gyro tilts from

its vertical position. This force acts in such a way to return

the spinning wheel to its upright position.

The older artiﬁ cial horizons were limited in the amount of

pitch or roll they could tolerate, normally about 60° in pitch

and 100° in roll. After either of these limits was exceeded,

the gyro housing contacted the gimbals, applying such a

precessing force that the gyro tumbled. Because of this

limitation, these instruments had a caging mechanism that

locked the gyro in its vertical position during any maneuvers

that exceeded the instrument limits. Newer instruments do

not have these restrictive tumble limits; therefore, they do

not have a caging mechanism.

When an aircraft engine is ﬁ rst started and pneumatic or

electric power is supplied to the instruments, the gyro is

not erect. A self-erecting mechanism inside the instrument

actuated by the force of gravity applies a precessing force,

causing the gyro to rise to its vertical position. This erection

can take as long as 5 minutes, but is normally done within

2 to 3 minutes.

Attitude indicators are free from most errors, but depending

upon the speed with which the erection system functions,

there may be a slight nose-up indication during a rapid

acceleration and a nose-down indication during a rapid

deceleration. There is also a possibility of a small bank angle

and pitch error after a 180° turn. These inherent errors are

small and correct themselves within a minute or so after

returning to straight-and-level ﬂ ight.

Heading Indicators

A magnetic compass is a dependable instrument used as a

backup instrument. Although very reliable, it has so many

inherent errors that it has been supplemented with gyroscopic

heading indicators.

The gyro in a heading indicator is mounted in a double gimbal,

as in an attitude indicator, but its spin axis is horizontal

permitting sensing of rotation about the vertical axis of the

aircraft. Gyro heading indicators, with the exception of slaved

gyro indicators, are not north seeking, therefore they must

be manually set to the appropriate heading by referring to

a magnetic compass. Rigidity causes them to maintain this

heading indication, without the oscillation and other errors

inherent in a magnetic compass.

Older directional gyros use a drum-like card marked in the

same way as the magnetic compass card. The gyro and the

card remain rigid inside the case with the pilot viewing the

card from the back. This creates the possibility the pilot might

start a turn in the wrong direction similar to using a magnetic

compass. A knob on the front of the instrument, below the

dial, can be pushed in to engage the gimbals. This locks the

gimbals allowing the pilot to rotate the gyro and card until

the number opposite the lubber line agrees with the magnetic

compass. When the knob is pulled out, the gyro remains rigid

and the aircraft is free to turn around the card.

Directional gyros are almost all air-driven by evacuating

the case and allowing ﬁ ltered air to ﬂ ow into the case and

out through a nozzle, blowing against buckets cut in the

3-20

Figure 3-31. The heading indicator is not north seeking, but must

be set periodically (about every 15 minutes) to agree with the

magnetic compass.

Figure 3-32. Precession causes a force applied to a spinning

wheel to be felt 90° from the point of application in the direction

of rotation.

Figure 3-33. Turn-and-Slip Indicator.

periphery of the wheel. The Earth constantly rotates at 15°

per hour while the gyro is maintaining a position relative

to space, thus causing an apparent drift in the displayed

heading of 15° per hour. When using these instruments, it

is standard practice to compare the heading indicated on the

directional gyro with the magnetic compass at least every 15

minutes and to reset the heading as necessary to agree with

the magnetic compass.

Heading indicators like the one in Figure 3-31 work on the

same principle as the older horizontal card indicators, except

that the gyro drives a vertical dial that looks much like the

dial of a vertical card magnetic compass. The heading of the

aircraft is shown against the nose of the symbolic aircraft on

the instrument glass, which serves as the lubber line. A knob

in the front of the instrument may be pushed in and turned

to rotate the gyro and dial. The knob is spring loaded so it

disengages from the gimbals as soon as it is released. This

instrument should be checked about every 15 minutes to see

if it agrees with the magnetic compass.

Turn Indicators

Attitude and heading indicators function on the principle

of rigidity, but rate instruments such as the turn-and-

slip indicator operate on precession. Precession is the

characteristic of a gyroscope that causes an applied force to

produce a movement, not at the point of application, but at

a point 90° from the point of application in the direction of

rotation. [Figure 3-32]

Turn-and-Slip Indicator

The ﬁ rst gyroscopic aircraft instrument was the turn indicator

in the needle and ball, or turn-and-bank indicator, which

has more recently been called a turn-and-slip indicator.

[Figure 3-33]

The inclinometer in the instrument is a black glass ball sealed

inside a curved glass tube that is partially ﬁ lled with a liquid

for damping. This ball measures the relative strength of the

force of gravity and the force of inertia caused by a turn.

When the aircraft is ﬂ ying straight-and-level, there is no

inertia acting on the ball, and it remains in the center of the

tube between two wires. In a turn made with a bank angle

that is too steep, the force of gravity is greater than the inertia

and the ball rolls down to the inside of the turn. If the turn is

made with too shallow a bank angle, the inertia is greater than

gravity and the ball rolls upward to the outside of the turn.

The inclinometer does not indicate the amount of bank, nor

does it indicate slip; it only indicates the relationship between

the angle of bank and the rate of yaw.

3-21

Figure 3-34. The rate gyro in both turn-and-slip indicator and turn

coordinator. Figure 3-35. A turn coordinator senses rotation about both roll

and yaw axes.

The turn indicator is a small gyro spun either by air or by

an electric motor. The gyro is mounted in a single gimbal

with its spin axis parallel to the lateral axis of the aircraft

and the axis of the gimbal parallel with the longitudinal axis.

[Figure 3-34]

When the aircraft yaws, or rotates about its vertical axis, it

produces a force in the horizontal plane that, due to precession,

causes the gyro and its gimbal to rotate about the gimbal’s

axis. It is restrained in this rotation plane by a calibration

spring; it rolls over just enough to cause the pointer to deﬂ ect

until it aligns with one of the doghouse-shaped marks on the

dial, when the aircraft is making a standard rate turn.

The dial of these instruments is marked “2 MIN TURN.” Some

turn-and-slip indicators used in faster aircraft are marked “4

MIN TURN.” In either instrument, a standard rate turn is being

made whenever the needle aligns with a doghouse.

Turn Coordinator

The major limitation of the older turn-and-slip indicator is that

it senses rotation only about the vertical axis of the aircraft. It

tells nothing of the rotation around the longitudinal axis, which

in normal ﬂ ight occurs before the aircraft begins to turn.

A turn coordinator operates on precession, the same as the

turn indicator, but its gimbals frame is angled upward about

30° from the longitudinal axis of the aircraft. [Figure 3-34]

This allows it to sense both roll and yaw. Therefore during

a turn, the indicator ﬁ rst shows the rate of banking and once

stabilized, the turn rate. Some turn coordinator gyros are dual-

powered and can be driven by either air or electricity.

Rather than using a needle as an indicator, the gimbal moves

a dial that is the rear view of a symbolic aircraft. The bezel

of the instrument is marked to show wings-level ﬂ ight and

bank angles for a standard rate turn. [Figure 3-35]

The inclinometer, similar to the one in a turn-and-slip

indicator, is called a coordination ball, which shows the

relationship between the bank angle and the rate of yaw. The

turn is coordinated when the ball is in the center, between the

marks. The aircraft is skidding when the ball rolls toward the

outside of the turn and is slipping when it moves toward the

inside of the turn. A turn coordinator does not sense pitch.

This is indicated on some instruments by placing the words

“NO PITCH INFORMATION” on the dial.

3-22

Figure 3-36. The Kearfott Attitude Heading Reference System (AHRS) on the left incorporates a Monolithic Ring Laser Gyro (MRLG)

(center), which is housed in an Inertial Sensor Assembly (ISA) on the right.

Flight Support Systems

Attitude and Heading Reference System (AHRS)

As aircraft displays have transitioned to new technology,

the sensors that feed them have also undergone signiﬁ cant

change. Traditional gyroscopic flight instruments have

been replaced by Attitude and Heading Reference Systems

(AHRS) improving reliability and thereby reducing cost and

maintenance.

The function of an AHRS is the same as gyroscopic systems;

that is, to determine which way is level and which way is north.

By knowing the initial heading the AHRS can determine both

the attitude and magnetic heading of the aircraft.

The genesis of this system was initiated by the development

of the ring-LASAR gyroscope developed by Kearfott located

in Little Falls, New Jersey. [Figure 3-36] Their development

of the Ring-LASAR gyroscope in the 1960s/1970s was

in support of Department of Defense (DOD) programs to

include cruise missile technology. With the precision of

these gyroscopes, it became readily apparent that they could

be leveraged for multiple tasks and functions. Gyroscopic

miniaturization has become so common that solid-state

gyroscopes are found in products from robotics to toys.

Because the AHRS system replaces separate gyroscopes,

such as those associated with an attitude indicator, magnetic

heading indicator and turn indicator these individual systems

are no longer needed. As with many systems today, AHRS

itself had matured with time. Early AHRS systems used

expensive inertial sensors and ﬂ ux valves. However, today the

AHRS for aviation and general aviation in particular are small

solid-state systems integrating a variety of technology such

as low cost inertial sensors, rate gyros, and magnetometers,

and have capability for satellite signal reception.

Air Data Computer (ADC)

An Air Data Computer (ADC) [Figure 3-37] is an aircraft

computer that receives and processes pitot pressure, static

pressure, and temperature to calculate very precise altitude,

IAS, TAS, and air temperature. The ADC outputs this

information in a digital format that can be used by a variety

of aircraft systems including an EFIS. Modern ADCs

are small solid-state units. Increasingly, aircraft systems

such as autopilots, pressurization, and FMS utilize ADC

information for normal operations. NOTE: In most modern

general aviation systems, both the AHRS and ADC are

integrated within the electronic displays themselves thereby

reducing the number of units, reducing weight, and providing

simpliﬁ cation for installation resulting in reduced costs.

Analog Pictorial Displays

Horizontal Situation Indicator (HSI)

The HSI is a direction indicator that uses the output from

a ﬂ ux valve to drive the dial, which acts as the compass

card. This instrument, shown in Figure 3-37, combines the

magnetic compass with navigation signals and a glide slope.

This gives the pilot an indication of the location of the aircraft

with relationship to the chosen course.

3-23

Figure 3-38. Horizontal Situation Indicator (HSI).

Figure 3-37. Air Data Computer (Collins).

In Figure 3-38, the aircraft heading displayed on the rotating

azimuth card under the upper lubber line is North or 360°.

The course-indicating arrowhead shown is set to 020; the

tail indicates the reciprocal, 200°. The course deviation bar

operates with a VOR/Localizer (VOR/LOC) navigation

receiver to indicate left or right deviations from the course

selected with the course-indicating arrow, operating in the

same manner that the angular movement of a conventional

VOR/LOC needle indicates deviation from course.

The desired course is selected by rotating the course-

indicating arrow in relation to the azimuth card by means

of the course select knob. This gives the pilot a pictorial

presentation: the ﬁ xed aircraft symbol and course deviation

bar display the aircraft relative to the selected course, as

though the pilot were above the aircraft looking down.

The TO/FROM indicator is a triangular pointer. When the

indicator points to the head of the course arrow, it shows

that the course selected, if properly intercepted and ﬂ own,

takes the aircraft to the selected facility. When the indicator

points to the tail of the course arrow, it shows that the course

selected, if properly intercepted and ﬂ own, takes the aircraft

directly away from the selected facility.

The glide slope deviation pointer indicates the relation of

the aircraft to the glide slope. When the pointer is below the

center position, the aircraft is above the glide slope, and an

increased rate of descent is required. In most installations,

the azimuth card is a remote indicating compass driven by

a ﬂ uxgate; however, in few installations where a ﬂ uxgate is

not installed, or in emergency operation, the heading must

be checked against the magnetic compass occasionally and

reset with the course select knob.

Attitude Direction Indicator (ADI)

Advances in attitude instrumentation combine the gyro

horizon with other instruments such as the HSI, thereby

reducing the number of separate instruments to which the

pilot must devote attention. The attitude direction indicator

(ADI) is an example of such technological advancement.

A ﬂ ight director incorporates the ADI within its system,

which is further explained below (Flight Director System).

However, an ADI need not have command cues; however,

it is normally equipped with this feature.

Flight Director System (FDS)

A Flight Director System (FDS) combines many instruments

into one display that provides an easily interpreted

understanding of the aircraft’s ﬂ ight path. The computed

solution furnishes the steering commands necessary to obtain

and hold a desired path.

Major components of an FDS include an ADI, also called

a Flight Director Indicator (FDI), an HSI, a mode selector,

and a ﬂ ight director computer. It should be noted that a

ﬂ ight director in use does not infer the aircraft is being

manipulated by the autopilot (coupled), but is providing

steering commands that the pilot (or the autopilot, if coupled)

follows.

Typical ﬂ ight directors use one of two display systems for

steerage. The ﬁ rst is a set of command bars, one horizontal

and one vertical. The command bars in this conﬁ guration

are maintained in a centered position (much like a centered

glide slope). The second uses a miniature aircraft aligned to

a command cue.

A ﬂ ight director displays steerage commands to the pilot on

the ADI. As previously mentioned, the ﬂ ight director receives

its signals from one of various sources and provides that to the

ADI for steerage commands. The mode controller provides

signals through the ADI to drive the steering bars, e.g., the

3-24

Figure 3-39. A Typical Cue That a Pilot Would Follow.

Figure 3-40. Components of a Typical Flight Director System.

pilot ﬂ ies the aircraft to place the delta symbol in the V of the

steering bars. “Command” indicators tell the pilot in which

direction and how much to change aircraft attitude to achieve

the desired result.

The computed command indications relieve the pilot of

many of the mental calculations required for instrument

ﬂ ight. The yellow cue in the ADI [Figure 3-39] provides all

steering commands to the pilot. It is driven by a computer that

receives information from the navigation systems, the ADC,

AHRS, and other sources of data. The computer processes this

information, providing the pilot with a single cue to follow.

Following the cue provides the pilot with the necessary three-

dimensional ﬂ ight trajectory to maintain the desired path.

One of the ﬁ rst widely used ﬂ ight directors was developed

by Sperry and was called the Sperry Three Axis Attitude

Reference System (STARS). Developed in the 1960s, it was

commonly found on both commercial and business aircraft

alike. STARS (with a modiﬁ cation) and successive ﬂ ight

directors were integrated with the autopilots and aircraft

providing a fully integrated ﬂ ight system.

The flight director/autopilot system described below is

typical of installations in many general aviation aircraft.

The components of a typical ﬂ ight director include the mode

controller, ADI, HSI, and annunciator panel. These units are

illustrated in Figure 3-40.

The pilot may choose from among many modes including

the HDG (heading) mode, the VOR/LOC (localizer tracking)

mode, or the AUTO Approach (APP) or G/S (automatic

capture and tracking of instrument landing system (ILS)

localizers and glide path) mode. The auto mode has a fully

automatic pitch selection computer that takes into account

aircraft performance and wind conditions, and operates once

the pilot has reached the ILS glide slope. More sophisticated

systems allow more ﬂ ight director modes.

Integrated Flight Control System

The integrated ﬂ ight control system integrates and merges

various systems into a system operated and controlled by one

principal component. Figure 3-41 illustrates key components

of the ﬂ ight control system that was developed from the

onset as a fully integrated system comprised of the airframe,

autopilot, and ﬂ ight director system. This trend of complete

integration, once seen only in large commercial aircraft, are

now becoming common in the general aviation ﬁ eld.

Autopilot Systems

An autopilot is a mechanical means to control an aircraft

using electrical, hydraulic, or digital systems. Autopilots can

control three axes of the aircraft: roll, pitch, and yaw. Most

autopilots in general aviation control roll and pitch.

Autopilots also function using different methods. The ﬁ rst

is position based. That is, the attitude gyro senses the degree

of difference from a position such as wings level, a change

in pitch, or a heading change.

3-25

Figure 3-41. The S-TEC/Meggit Corporation Integrated Autopilot Installed in the Cirrus.

Figure 3-42. An Autopilot by Century.

Determining whether a design is position based and/or rate

based lies primarily within the type of sensors used. In order

for an autopilot to possess the capability of controlling an

aircraft’s attitude (i.e., roll and pitch), that system must be

provided with constant information on the actual attitude

of that aircraft. This is accomplished by the use of several

different types of gyroscopic sensors. Some sensors are

designed to indicate the aircraft’s attitude in the form of

position in relation to the horizon, while others indicate rate

(position change over time).

Rate-based systems use the turn-and-bank sensor for the

autopilot system. The autopilot uses rate information on

two of the aircraft’s three axes: movement about the vertical

axis (heading change or yaw) and about the longitudinal

axis (roll). This combined information from a single sensor

is made possible by the 30° offset in the gyro’s axis to the

longitudinal axis.

Other systems use a combination of both position and rate-

based information to beneﬁ t from the attributes of both systems

while newer autopilots are digital. Figure 3-42 illustrates an

autopilot by Century.

Figure 3-43 is a diagram layout of a rate-based autopilot by

S-Tec, which permits the purchaser to add modular capability

form basic wing leveling to increased capability.

Flight Management Systems (FMS)

In the mid-1970s, visionaries in the avionics industry such

as Hubert Naimer of Universal, and followed by others such

as Ed King, Jr., were looking to advance the technology of

aircraft navigation. As early as 1976, Naimer had a vision

of a “Master Navigation System” that would accept inputs

from a variety of different types of sensors on an aircraft

and automatically provide guidance throughout all phases

of ﬂ ight.

At that time aircraft navigated over relatively short distances

with radio systems, principally VOR or ADF. For long-range

ﬂ ight inertial navigation systems (INS), Omega, Doppler,

and Loran were in common use. Short-range radio systems

usually did not provide area navigation capability. Long-

range systems were only capable of en route point-to-point

navigation between manually entered waypoints described

as longitude and latitude coordinates, with typical systems

containing a limited number of waypoints.

3-26

Figure 3-43. A Diagram Layout of an Autopilot by S-Tec.

Figure 3-44. A Control Display Unit (CDU) Used to Control the

Flight Management System.

The laborious process of manually entering cryptic latitude

and longitude data for each ﬂ ight waypoint created high

crew workloads and frequently resulted in incorrect data

entry. The requirement of a separate control panel for each

long-range system consumed precious ﬂ ight deck space and

increased the complexity of interfacing the systems with

display instruments, ﬂ ight directors, and autopilots.

The concept employed a master computer interfaced with all

of the navigation sensors on the aircraft. A common control

display unit (CDU) interfaced with the master computer would

provide the pilot with a single control point for all navigation

systems, thereby reducing the number of required ﬂ ight deck

panels. Management of the various individual sensors would

be transferred from the pilot to the new computer.

Since navigation sensors rarely agree exactly about position,

Naimer believed that blending all available sensor position

data through a highly sophisticated, mathematical ﬁ ltering

system would produce a more accurate aircraft position. He

called the process output the “Best Computed Position.” By

using all available sensors to keep track of position, the system

could readily provide area navigation capability. The master

computer, not the individual sensors, would be integrated into

the airplane, greatly reducing wiring complexity.

To solve the problems of manual waypoint entry, a pre-

loaded database of global navigation information would

be readily accessible by the pilot through the CDU. Using

such a system a pilot could quickly and accurately construct

a ﬂ ight plan consisting of dozens of waypoints, avoiding

the tedious typing of data and the error potential of latitude/

longitude coordinates. Rather than simply navigating point-

to-point, the master system would be able to maneuver the

aircraft, permitting use of the system for terminal procedures

including departures, arrivals, and approaches. The system

would be able to automate any aspect of manual pilot

navigation of the aircraft. When the ﬁ rst system, called the

UNS-1, was released by Universal in 1982, it was called a

ﬂ ight management system (FMS). [Figure 3-44]

3-27

An FMS uses an electronic database of worldwide

navigational data including navigation aids, airways and

intersections, Standard Instrument Departures (SIDs),

Standard Terminal Arrival Routes (STARs), and Instrument

Approach Procedures (IAPs) together with pilot input through

a CDU to create a ﬂ ight plan. The FMS provides outputs to

several aircraft systems including desired track, bearing and

distance to the active waypoint, lateral course deviation and

related data to the ﬂ ight guidance system for the HSI displays,

and roll steering command for the autopilot/ﬂ ight director

system. This allows outputs from the FMS to command

the airplane where to go and when and how to turn. To

support adaptation to numerous aircraft types, an FMS is

usually capable of receiving and outputting both analog and

digital data and discrete information. Currently, electronic

navigation databases are updated every 28 days.

The introduction of the Global Positioning System (GPS) has

provided extremely precise position at low cost, making GPS

the dominant FMS navigation sensor today. Currently, typical

FMS installations require that air data and heading information

be available electronically from the aircraft. This limits FMS

usage in smaller aircraft, but emerging technologies allow this

data from increasingly smaller and less costly systems.

Some systems interface with a dedicated Distance Measuring

Equipment (DME) receiver channel under the control of the

FMS to provide an additional sensor. In these systems, the

FMS determines which DME sites should be interrogated

for distance information using aircraft position and the

navigation database to locate appropriate DME sites. The

FMS then compensates aircraft altitude and station altitude

with the aid of the database to determine the precise distance

to the station. With the distances from a number of sites the

FMS can compute a position nearly as accurately as GPS.

Aimer visualized three-dimensional aircraft control with

an FMS. Modern systems provide Vertical Navigation

(VNAV) as well as Lateral Navigation (LNAV) allowing

the pilot to create a vertical ﬂ ight proﬁ le synchronous with

the lateral ﬂ ight plan. Unlike early systems, such as Inertial

Reference Systems (IRS) that were only suitable for en route

navigation, the modern FMS can guide an aircraft during

instrument approaches.

Today, an FMS provides not only real-time navigation

capability but typically interfaces with other aircraft systems

providing fuel management, control of cabin brieﬁ ng and

display systems, display of uplinked text and graphic weather

data and air/ground data link communications.

Electronic Flight Instrument Systems

Modern technology has introduced into aviation a new

method of displaying ﬂ ight instruments, such as electronic

ﬂ ight instrument systems, integrated ﬂ ight deck displays, and

others. For the purpose of the practical test standards, any

ﬂ ight instrument display that utilizes LCD or picture tube like

displays is referred to as “electronic ﬂ ight instrument display”

and/or a glass ﬂ ight deck. In general aviation there is typically

a primary ﬂ ight display (PFD) and a multi-function display

(MFD). Although both displays are in many cases identical,

the PFD provides the pilot instrumentation necessary for

ﬂ ight to include altitude, airspeed, vertical velocity, attitude,

heading and trim and trend information.

Glass ﬂ ight decks (a term coined to describe electronic ﬂ ight

instrument systems) are becoming more widespread as cost

falls and dependability continually increases. These systems

provide many advantages such as being lighter, more reliable,

no moving parts to wear out, consuming less power, and

replacing numerous mechanical indicators with a single glass

display. Because the versatility offered by glass displays is

much greater than that offered by analog displays, the use

of such systems will only increase with time until analog

systems are eclipsed.

Primary Flight Display (PFD)

PFDs provide increased situational awareness to the pilot by

replacing the traditional six instruments used for instrument

ﬂ ight with an easy-to-scan display that provides the horizon,

airspeed, altitude, vertical speed, trend, trim, rate of turn

among other key relevant indications. Examples of PFDs

are illustrated in Figure 3-45.

Synthetic Vision

Synthetic vision provides a realistic depiction of the aircraft

in relation to terrain and ﬂ ight path. Systems such as those

produced by Chelton Flight Systems, Universal Flight

Systems, and others provide for depictions of terrain and

course. Figure 3-46 is an example of the Chelton Flight

System providing both 3-dimensional situational awareness

and a synthetic highway in the sky, representing the desired

ﬂ ight path. Synthetic vision is used as a PFD, but provides

guidance in a more normal, outside reference format.

3-28

Figure 3-45. Two Primary Flight Displays (Avidyne on the Left and Garmin on the Right).

Figure 3-46. The beneﬁ ts of realistic visualization imagery, as

illustrated by Synthetic Vision manufactured by Chelton Flight

Systems. The system provides the pilot a realistic, real-time, three-

dimensional depiction of the aircraft and its relation to terrain

around it.

Multi-Function Display (MFD)

In addition to a PFD directly in front of the pilot, an MFD

that provides the display of information in addition to primary

ﬂ ight information is used within the ﬂ ight deck. [Figure 3-47]

Information such as a moving map, approach charts, Terrain

Awareness Warning System, and weather depiction can all

be illustrated on the MFD. For additional redundancy both

the PFD and MFD can display all critical information that

the other normally presents thereby providing redundancy

(using a reversionary mode) not normally found in general

aviation ﬂ ight decks.

Advanced Technology Systems

Automatic Dependent Surveillance—Broadcast

(ADS-B)

Although standards for Automatic Dependent Surveillance

(Broadcast) (ADS-B) are still under continuing development,

the concept is simple: aircraft broadcast a message on

a regular basis, which includes their position (such as

latitude, longitude and altitude), velocity, and possibly

other information. Other aircraft or systems can receive this

information for use in a wide variety of applications. The

key to ADS-B is GPS, which provides three-dimensional

position of the aircraft.

As an simpliﬁ ed example, consider air-trafﬁ c radar. The radar

measures the range and bearing of an aircraft. The bearing is

measured by the position of the rotating radar antenna when it

receives a reply to its interrogation from the aircraft, and the

range by the time it takes for the radar to receive the reply.

An ADS-B based system, on the other hand, would listen

for position reports broadcast by the aircraft. [Figure 3-48]

These position reports are based on satellite navigation

systems. These transmissions include the transmitting

aircraft’s position, which the receiving aircraft processes into

usable pilot information. The accuracy of the system is now

determined by the accuracy of the navigation system, not

measurement errors. Furthermore the accuracy is unaffected

by the range to the aircraft as in the case of radar. With radar,

detecting aircraft speed changes require tracking the data and

changes can only be detected over a period of several position

updates. With ADS-B, speed changes are broadcast almost

instantaneously and received by properly equipped aircraft.

3-29

Figure 3-47. Example of a Multi-Function Display (MFD).

Figure 3-48. Aircraft equipped with Automatic Dependent Surveillance—Broadcast (ADS-B) continuously broadcast their identiﬁ cation,

altitude, direction, and vertical trend. The transmitted signal carries signiﬁ cant information for other aircraft and ground stations alike.

Other ADS-equipped aircraft receive this information and process it in a variety of ways. It is possible that in a saturated environment

(assuming all aircraft are ADS equipped), the systems can project tracks for their respective aircraft and retransmit to other aircraft

their projected tracks, thereby enhancing collision avoidance. At one time, there was an Automatic Dependent Surveillance—Addressed

(ADS-A) and that is explained in the Pilot’s Handbook of Aeronautical Knowledge.

3-30

Figure 3-49. An aircraft equipped with ADS will receive identiﬁ cation, altitude in hundreds of feet (above or below using + or -), direction

of the trafﬁ c, and aircraft descent or climb using an up or down arrow. The yellow target is an illustration of how a non-ADS equipped

aircraft would appear on an ADS-equipped aircraft’s display.

Figure 3-50. An aircraft equipped with ADS has the ability to upload and display weather.

Additionally, other information can be obtained by properly

equipped aircraft to include notices to airmen (NOTAM),

weather, etc. [Figures 3-49 and 3-50] At the present time,

ADS-B is predominantly available along the east coast of

the United States where it is matured.

Safety Systems

Radio Altimeters

A radio altimeter, commonly referred to as a radar altimeter,

is a system used for accurately measuring and displaying the

height above the terrain directly beneath the aircraft. It sends

a signal to the ground and processes the timed information.

3-31

Figure 3-51. Components of a Radar Altimeter.

Figure 3-52. Coverage Provided by a Trafﬁ c Information System.

Its primary application is to provide accurate absolute altitude

information to the pilot during approach and landing. In

advanced aircraft today, the radar altimeter also provides its

information to other onboard systems such as the autopilot

and ﬂ ight directors while they are in the glide slope capture

mode below 200-300 feet above ground level (AGL).

A typical system consists of a receiver-transmitter (RT)

unit, antenna(s) for receiving and transmitting the signal,

and an indicator. [Figure 3-51] Category II and III precision

approach procedures require the use of a radar altimeter and

specify the exact minimum height above the terrain as a

decision height (DH) or radio altitude (RA).

Trafﬁ c Advisory Systems

Trafﬁ c Information System

The Trafﬁ c Information Service (TIS) is a ground-based

service providing information to the ﬂ ight deck via data

link using the S-mode transponder and altitude encoder. TIS

improves the safety and efﬁ ciency of “see and avoid” ﬂ ight

through an automatic display that informs the pilot of nearby

trafﬁ c. The display can show location, direction, altitude

and the climb/descent trend of other transponder-equipped

aircraft. TIS provides estimated position, altitude, altitude

trend, and ground track information for up to several aircraft

simultaneously within about 7 NM horizontally, 3,500 feet

above and 3,500 feet below the aircraft. [Figure 3-52] This

data can be displayed on a variety of MFDs. [Figure 3-53]

Figure 3-54 displays the pictorial concept of the trafﬁ c

information system. Noteworthy is the requirement to have

Mode S and that the ground air trafﬁ c station processes the

Mode S signal.

Trafﬁ c Alert Systems

Trafﬁ c alert systems receive transponder information from

nearby aircraft to help determine their relative position to the

equipped aircraft. They provide three-dimensional location

of other aircraft [Figures 3-55, 3-56, and 3-57] and are cost

effective alternatives to TCAS equipage for smaller aircraft.

Trafﬁ c Avoidance Systems

Trafﬁ c Alert and Collision Avoidance System (TCAS)

The TCAS is an airborne system developed by the FAA that

operates independently from the ground-based ATC system.

TCAS was designed to increase ﬂ ight deck awareness of

proximate aircraft and to serve as a “last line of defense” for

the prevention of mid-air collisions.

There are two levels of TCAS systems. TCAS I was developed

to accommodate the general aviation (GA) community and

the regional airlines. This system issues trafﬁ c advisories

(TAs) to assist pilots in visual acquisition of intruder aircraft.

TCAS I provides approximate bearing and relative altitude

of aircraft with a selectable range. It provides the pilot

with trafﬁ c advisory (TA) alerting him or her to potentially

conﬂ icting trafﬁ c. The pilot then visually acquires the trafﬁ c

and takes appropriate action for collision avoidance.

TCAS II is a more sophisticated system which provides the

same information of TCAS I. It also analyzes the projected

ﬂ ight path of approaching aircraft and issues resolution

advisories (RAs) to the pilot to resolve potential mid-air

collisions. Additionally, if communicating with another

TCAS II equipped aircraft, the two systems coordinate the

resolution alerts provided to their respective ﬂ ight crews.

[Figure 3-58]

3-32

Figure 3-53. Multi-Function Display (MFD).

Figure 3-54. Concept of the Trafﬁ c Information System.

3-33

Figure 3-55. Theory of a Typical Alert System.

Figure 3-56. A Skywatch System.

Figure 3-57. Alert System by Avidyne (Ryan).

3-34

Figure 3-58. An example of a resolution advisory being provided

the pilot. In this case, the pilot is requested to climb, with 1,200

feet being the appropriate rate of ascent to avoid trafﬁ c conﬂ ict.

This visual indication plus the aural warning provide the pilot

with excellent trafﬁ c awareness that augments see and avoid

practices.

Terrain Alerting Systems

Ground Proximity Warning System (GPWS)

An early application of technology to reduce CFIT was the

GPWS. In airline use since the early 1970s, GPWS uses the

radio altimeter, speed, and barometric altitude to determine the

aircraft’s position relative to the ground. The system uses this

information in determining aircraft clearance above the Earth

and provides limited predictability about aircraft position

relative to rising terrain. It does this based upon algorithms

within the system and developed by the manufacturer for

different airplanes or helicopters. However, in mountainous

areas the system is unable to provide predictive information

due to the unusual slope encountered.

This inability to provide predictive information was evidenced

in 1999 when a DH-7 crashed in South America. The crew

had a GPWS onboard, but the sudden rise of the terrain

rendered it ineffective; the crew continued unintentionally

into a mountain with steep terrain. Another incident involved

Secretary of Commerce Brown who, along with all on board,

was lost when the crew ﬂ ew over rapidly rising terrain where

the GPWS capability is offset by terrain gradient. However,

the GPWS is tied into and considers landing gear status, ﬂ ap

position, and ILS glide slope deviation to detect unsafe aircraft

operation with respect to terrain, excessive descent rate,

excessive closure rate to terrain, unsafe terrain clearance while

not in a landing conﬁ guration, excessive deviation below an

ILS glide slope. It also provides advisory callouts.

Generally, the GPWS is tied into the hot bus bar of the electrical

system to prevent inadvertent switch off. This was demonstrated

in an accident involving a large four-engine turboprop airplane.

While on ﬁ nal for landing with the landing gear inadvertently

up, the crew failed to heed the GPWS warning as the aircraft

crossed a large berm close to the threshold. In fact, the crew

attempted without success to shut the system down and attributed

the signal to a malfunction. Only after the mishap did the crew

realize the importance of the GPWS warning.

Terrain Awareness and Warning System (TAWS)

A TAWS uses GPS positioning and a database of terrain and

obstructions to provide true predictability of the upcoming

terrain and obstacles. The warnings it provides pilots are

both aural and visual, instructing the pilot to take speciﬁ c

action. Because TAWS relies on GPS and a database of

terrain/obstacle information, predictability is based upon

aircraft location and projected location. The system is time

based and therefore compensates for the performance of the

aircraft and its speed. [Figure 3-59]

Head-Up Display (HUD)

The HUD is a display system that provides a projection of

navigation and air data (airspeed in relation to approach

reference speed, altitude, left/right and up/down glide slope)

on a transparent screen between the pilot and the windshield.

The concept of a HUD is to diminish the shift between

looking at the instrument panel and outside. Virtually any

information desired can be displayed on the HUD if it is

available in the aircraft’s ﬂ ight computer. The display for

the HUD can be projected on a separate panel near the

windscreen or as shown in Figure 3-60 on an eye piece. Other

information may be displayed, including a runway target in

relation to the nose of the aircraft, which allows the pilot to

see the information necessary to make the approach while

also being able to see out the windshield.

Required Navigation Instrument System

Inspection

Systems Preﬂ ight Procedures

Inspecting the instrument system requires a relatively small

part of the total time required for preﬂ ight activities, but its

importance cannot be overemphasized. Before any ﬂ ight

involving aircraft control by instrument reference, the pilot

should check all instruments and their sources of power

for proper operation. NOTE: The following procedures are

appropriate for conventional aircraft instrument systems.

Aircraft equipped with electronic instrument systems utilize

different procedures.

3-35

Figure 3-59. A six-frame sequence illustrating the manner in which TAWS operates. A TAWS installation is aircraft speciﬁ c and provides

warnings and cautions based upon time to potential impact with terrain rather than distance. The TAWS is illustrated in an upper left

window while aircrew view is provided out of the windscreen. illustrates the aircraft in relation to the outside terrain while and

illustrate the manner in which the TAWS system displays the terrain. is providing a caution of terrain to be traversed, while

provides an illustration of a warning with an aural and textural advisory (red) to pull up. also illustrates a pilot taking appropriate

action (climb in this case) while illustrates that a hazard is no longer a factor.

3-36

Figure 3-60. A Head-Up Display.

Before Engine Start

1. Walk-around inspection: Check the condition of all

antennas and check the pitot tube for the presence

of any obstructions and remove the cover. Check

the static ports to be sure they are free from dirt

and obstructions, and ensure there is nothing on the

structure near the ports that would disturb the air

ﬂ owing over them.

2. Aircraft records: Conﬁ rm that the altimeter and static

system have been checked and found within approved

limits within the past 24 calendar months. Check the

replacement date for the emergency locator transmitter

(ELT) batteries noted in the maintenance record, and

be sure they have been replaced within this time

interval.

3. Preflight paperwork: Check the Airport/Facility

Directory (A/FD) and all Notices to Airmen

(NOTAMs) for the condition and frequencies of all the

navigation aid (NAVAIDs) that are used on the ﬂ ight.

Handbooks, en route charts, approach charts, computer

and ﬂ ight log should be appropriate for the departure,

en route, destination, and alternate airports.

4. Radio equipment: Switches off.

5. Suction gauge: Proper markings as applicable if

electronic ﬂ ight instrumentation is installed.

6. ASI: Proper reading, as applicable. If electronic

ﬂ ight instrumentation is installed, check emergency

instrument.

7. Attitude indicator: Uncaged, if applicable. If electronic

ﬂ ight instrumentation is installed, check emergency

system to include its battery as appropriate.

8. Altimeter: Set the current altimeter setting and ensure

that the pointers indicate the elevation of the airport.

9. VSI: Zero indication, as applicable (if electronic ﬂ ight

instrumentation is installed).

10. Heading indicator: Uncaged, if applicable.

11. Turn coordinator: If applicable, miniature aircraft

level, ball approximately centered (level terrain).

12. Magnetic compass: Full of ﬂ uid and the correction

card is in place and current.

13. Clock: Set to the correct time and running.

14. Engine instruments: Proper markings and readings,

as applicable if electronic ﬂ ight instrumentation is

installed.

15. Deicing and anti-icing equipment: Check availability

and ﬂ uid quantity.

16. Alternate static-source valve: Be sure it can be opened

if needed, and that it is fully closed.

3-37

17. Pitot tube heater: Check by watching the ammeter

when it is turned on, or by using the method speciﬁ ed

in the POH/AFM.

After Engine Start

1. When the master switch is turned on, listen to the

gyros as they spin up. Any hesitation or unusual noises

should be investigated before ﬂ ight.

2. Suction gauge or electrical indicators: Check the

source of power for the gyro instruments. The suction

developed should be appropriate for the instruments

in that particular aircraft. If the gyros are electrically

driven, check the generators and inverters for proper

operation.

3. Magnetic compass: Check the card for freedom of

movement and confirm the bowl is full of fluid.

Determine compass accuracy by comparing the

indicated heading against a known heading (runway

heading) while the airplane is stopped or taxiing

straight. Remote indicating compasses should also be

checked against known headings. Note the compass

card correction for the takeoff runway heading.

4. Heading indicator: Allow 5 minutes after starting

engines for the gyro to spin up. Before taxiing, or

while taxiing straight, set the heading indicator to

correspond with the magnetic compass heading. A

slaved gyrocompass should be checked for slaving

action and its indications compared with those of the

magnetic compass. If an electronic ﬂ ight instrument

system is installed, consult the ﬂ ight manual for proper

procedures.

5. Attitude indicator: Allow the same time as noted

above for gyros to spin up. If the horizon bar erects

to the horizontal position and remains at the correct

position for the attitude of the airplane, or if it begins

to vibrate after this attitude is reached and then slowly

stops vibrating altogether, the instrument is operating

properly. If an electronic ﬂ ight instrument system

is installed, consult the flight manual for proper

procedures.

6. Altimeter: With the altimeter set to the current reported

altimeter setting, note any variation between the

known ﬁ eld elevation and the altimeter indication. If

the indication is not within 75 feet of ﬁ eld elevation,

the accuracy of the altimeter is questionable and

the problem should be referred to a repair station

for evaluation and possible correction. Because the

elevation of the ramp or hangar area might differ

signiﬁ cantly from ﬁ eld elevation, recheck when in

the run-up area if the error exceeds 75 feet. When

no altimeter setting is available, set the altimeter

to the published ﬁ eld elevation during the preﬂ ight

instrument check.

7. VSI: The instrument should read zero. If it does not,

tap the panel gently. If an electronic ﬂ ight instrument

system is installed, consult the ﬂ ight manual for proper

procedures.

8. Engine instruments: Check for proper readings.

9. Radio equipment: Check for proper operation and set

as desired.

10. Deicing and anti-icing equipment: Check operation.

Taxiing and Takeoff

1. Turn coordinator: During taxi turns, check the

miniature aircraft for proper turn indications. The ball

or slip/skid should move freely. The ball or slip/skid

indicator should move opposite to the direction of

turns. The turn instrument should indicate the direction

of the turn. While taxiing straight, the miniature

aircraft (as appropriate) should be level.

2. Heading indicator: Before takeoff, recheck the heading

indicator. If the magnetic compass and deviation card

are accurate, the heading indicator should show the

known taxiway or runway direction when the airplane

is aligned with them (within 5°).

3. Attitude indicator: If the horizon bar fails to remain

in the horizontal position during straight taxiing, or

tips in excess of 5° during taxi turns, the instrument is

unreliable. Adjust the miniature aircraft with reference

to the horizon bar for the particular airplane while on

the ground. For some tricycle-gear airplanes, a slightly

nose-low attitude on the ground gives a level ﬂ ight

attitude at normal cruising speed.

Engine Shut Down

When shutting down the engine, note any abnormal

instrument indications.

3-38

4-1

Introduction

Attitude instrument ﬂ ying is deﬁ ned as the control of an

aircraft’s spatial position by using instruments rather than

outside visual references. Today’s aircraft come equipped

with analog and/or digital instruments. Analog instrument

systems are mechanical and operate with numbers

representing directly measurable quantities, such as a watch

with a sweep second hand. In contrast, digital instrument

systems are electronic and operate with numbers expressed

in digits. Although more manufacturers are providing aircraft

with digital instrumentation, analog instruments remain more

prevalent. This section acquaints the pilot with the use of

analog ﬂ ight instruments.

Airplane Attitude

Instrument Flying

Chapter 4, Section I

Using Analog Instrumentation

4-2

Figure 4-1. Control Instruments.

Any ﬂ ight, regardless of the aircraft used or route ﬂ own,

consists of basic maneuvers. In visual ﬂ ight, aircraft attitude

is controlled by using certain reference points on the aircraft

with relation to the natural horizon. In instrument ﬂ ight,

the aircraft attitude is controlled by reference to the ﬂ ight

instruments. Proper interpretation of the ﬂ ight instruments

provides essentially the same information that outside

references do in visual ﬂ ight. Once the role of each instrument

in establishing and maintaining a desired aircraft attitude is

learned, a pilot is better equipped to control the aircraft in

emergency situations involving failure of one or more key

instruments.

Learning Methods

The two basic methods used for learning attitude instrument

ﬂ ying are “control and performance” and “primary and

supporting.” Both methods utilize the same instruments

and responses for attitude control. They differ in their

reliance on the attitude indicator and interpretation of other

instruments.

Attitude Instrument Flying Using the Control and

Performance Method

Aircraft performance is achieved by controlling the aircraft

attitude and power. Aircraft attitude is the relationship

of both the aircraft’s pitch and roll axes in relation to the

Earth’s horizon. An aircraft is ﬂ own in instrument ﬂ ight by

controlling the attitude and power, as necessary, to produce

both controlled and stabilized ﬂ ight without reference to a

visible horizon. This overall process is known as the control

and performance method of attitude instrument flying.

Starting with basic instrument maneuvers, this process can

be applied through the use of control, performance, and

navigation instruments, resulting in a smooth ﬂ ight, from

takeoff to landing.

Control Instruments

The control instruments display immediate attitude and power

indications and are calibrated to permit those respective

adjustments in precise increments. In this discussion, the

term “power” is used in place of the more technically correct

term “thrust or drag relationship.” Control is determined

by reference to the attitude and power indicators. Power

indicators vary with aircraft and may include manifold

pressure, tachometers, fuel ﬂ ow, etc. [Figure 4-1]

Performance Instruments

The performance instruments indicate the aircraft’s actual

performance. Performance is determined by reference to the

altimeter, airspeed or vertical speed indicator (VSI), heading

indicator, and turn-and-slip indicator. [Figure 4-2]

Navigation Instruments

The navigation instruments indicate the position of the aircraft

in relation to a selected navigation facility or ﬁ x. This group

of instruments includes various types of course indicators,

range indicators, glide-slope indicators, and bearing pointers.

[Figure 4-3] Newer aircraft with more technologically

advanced instrumentation provide blended information,

giving the pilot more accurate positional information.

Procedural Steps in Using Control and

Performance

1. Establish an attitude and power setting on the

control instruments that results in the desired

performance. Known or computed attitude changes

and approximated power settings helps to reduce the

pilot’s workload.

2. Trim (fine tune the control forces) until control

pressures are neutralized. Trimming for hands-off

ﬂ ight is essential for smooth, precise aircraft control.

4-3

Figure 4-2. Performance Instruments.

Figure 4-3. Flight Panel Instrumentation.

It allows a pilot to attend to other ﬂ ight deck duties

with minimum deviation from the desired attitude.

3. Cross-check the performance instruments to determine

if the established attitude or power setting is providing

the desired performance. The cross-check involves

both seeing and interpreting. If a deviation is noted,

determine the magnitude and direction of adjustment

required to achieve the desired performance.

4. Adjust the attitude and/or power setting on the control

instruments as necessary.

Aircraft Control During Instrument Flight

Attitude Control

Proper control of aircraft attitude is the result of proper use

of the attitude indicator, knowledge of when to change the

4-4

Figure 4-4. Pitch Instruments.

attitude, and then smoothly changing the attitude a precise

amount. The attitude reference provides an immediate, direct,

and corresponding indication of any change in aircraft pitch

or bank attitude.

Pitch Control

Changing the “pitch attitude” of the miniature aircraft or

fuselage dot by precise amounts in relation to the horizon

makes pitch changes. These changes are measured in degrees

or fractions thereof, or bar widths depending upon the type of

attitude reference. The amount of deviation from the desired

performance determines the magnitude of the correction.

Bank Control

Bank changes are made by changing the “bank attitude” or

bank pointers by precise amounts in relation to the bank scale.

The bank scale is normally graduated at 0°, 10°, 20°, 30°,

60°, and 90° and is located at the top or bottom of the attitude

reference. Normally, use a bank angle that approximates the

degrees to turn, not to exceed 30°.

Power Control

Proper power control results from the ability to smoothly

establish or maintain desired airspeeds in coordination

with attitude changes. Power changes are made by throttle

adjustments and reference to the power indicators. Power

indicators are not affected by such factors as turbulence,

improper trim, or inadvertent control pressures. Therefore,

in most aircraft little attention is required to ensure the power

setting remains constant.

Experience in an aircraft teaches a pilot approximately how

far to move the throttle to change the power a given amount.

Power changes are made primarily by throttle movement,

followed by an indicator cross-check to establish a more

precise setting. The key is to avoid ﬁ xating on the indicators

while setting the power. Knowledge of approximate power

settings for various ﬂ ight conﬁ gurations helps the pilot avoid

overcontrolling power.

Attitude Instrument Flying Using the Primary and

Supporting Method

Another basic method for teaching attitude instrument ﬂ ying

classiﬁ es the instruments as they relate to control function as

well as aircraft performance. All maneuvers involve some

degree of motion about the lateral (pitch), longitudinal (bank/

roll), and vertical (yaw) axes. Attitude control is stressed in

this handbook in terms of pitch control, bank control, power

control, and trim control. Instruments are grouped as they

relate to control function and aircraft performance as pitch

control, bank control, power control, and trim.

Pitch Control

Pitch control is controlling the rotation of the aircraft about the

lateral axis by movement of the elevators. After interpreting

the pitch attitude from the proper ﬂ ight instruments, exert

control pressures to effect the desired pitch attitude with

reference to the horizon. These instruments include the

attitude indicator, altimeter, VSI, and airspeed indicator.

[Figure 4-4] The attitude indicator displays a direct indication

of the aircraft’s pitch attitude while the other pitch attitude

control instruments indirectly indicate the pitch attitude of

the aircraft.

Attitude Indicator

The pitch attitude control of an aircraft controls the angular

relationship between the longitudinal axis of the aircraft and

the actual horizon. The attitude indicator gives a direct and

immediate indication of the pitch attitude of the aircraft. The

aircraft controls are used to position the miniature aircraft

in relation to the horizon bar or horizon line for any pitch

attitude required. [Figure 4-5]

4-5

Figure 4-5. Attitude Indicator.

Figure 4-6. Pitch Correction Using the Attitude Indicator.

Figure 4-7. Pitch Correction Using the Altimeter.

Altimeter

If the aircraft is maintaining level ﬂ ight, the altimeter needles

maintain a constant indication of altitude. If the altimeter

indicates a loss of altitude, the pitch attitude must be adjusted

upward to stop the descent. If the altimeter indicates a gain

in altitude, the pitch attitude must be adjusted downward to

stop the climb. [Figure 4-7] The altimeter can also indicate

the pitch attitude in a climb or descent by how rapidly the

needles move. A minor adjustment in pitch attitude may be

made to control the rate at which altitude is gained or lost.

Pitch attitude is used only to correct small altitude changes

caused by external forces, such as turbulence or up and

down drafts.

Vertical Speed Indicator (VSI)

In ﬂ ight at a constant altitude, the VSI (sometimes referred

to as vertical velocity indicator or rate-of-climb indicator)

remains at zero. If the needle moves above zero, the pitch

attitude must be adjusted downward to stop the climb and

return to level ﬂ ight. Prompt adjustments to the changes in

the indications of the VSI can prevent any signiﬁ cant change

in altitude. [Figure 4-8] Turbulent air causes the needle to

ﬂ uctuate near zero. In such conditions, the average of the

The miniature aircraft should be placed in the proper position

in relation to the horizon bar or horizon line before takeoff.

The aircraft operator’s manual explains this position. As soon

as practicable in level ﬂ ight and at desired cruise airspeed,

the miniature aircraft should be moved to a position that

aligns its wings in front of the horizon bar or horizon line.

This adjustment can be made anytime varying loads or other

conditions indicate a need. Otherwise, the position of the

miniature aircraft should not be changed for ﬂ ight at other than

cruise speed. This is to make sure that the attitude indicator

displays a true picture of pitch attitude in all maneuvers.

When using the attitude indicator in applying pitch attitude

corrections, control pressure should be extremely light.

Movement of the horizon bar above or below the miniature

aircraft of the attitude indicator in an airplane should not

exceed one-half the bar width. [Figure 4-6] If further change

is required, an additional correction of not more than one-half

horizon bar wide normally counteracts any deviation from

normal ﬂ ight.

4-6

Figure 4-8. Vertical Speed Indicator.

ﬂ uctuations should be considered as the correct reading.

Reference to the altimeter helps in turbulent air because it is

not as sensitive as the VSI.

Vertical speed is represented in feet per minute (fpm).

[Figure 4-8] The face of the instrument is graduated with

numbers such as 1, 2, 3, etc. These represent thousands of

feet up or down in a minute. For instance, if the pointer is

aligned with .5 (1/2 of a thousand, or 500 fpm) the aircraft

will climb 500 feet in one minute. The instrument is

divided into two regions, one for climbing (up) and one for

descending (down).

During turbulence, it is not uncommon to see large

ﬂ uctuations on the VSI. It is important to remember that small

corrections should be employed to avoid further exacerbating

a potentially divergent situation.

Overcorrecting causes the aircraft to overshoot the desired

altitude; however, corrections should not be so small that

the return to altitude is unnecessarily prolonged. As a guide,

the pitch attitude should produce a rate of change on the VSI

about twice the size of the altitude deviation. For example,

if the aircraft is 100 feet off the desired altitude, a 200 fpm

rate of correction would be used.

During climbs or descents, the VSI is used to change the

altitude at a desired rate. Pitch attitude and power adjustments

are made to maintain the desired rate of climb or descent on

the VSI.

When pressure is applied to the controls and the VSI shows

an excess of 200 fpm from that desired, overcontrolling is

indicated. For example, if attempting to regain lost altitude

at the rate of 500 fpm, a reading of more than 700 fpm

would indicate overcontrolling. Initial movement of the

needle indicates the trend of vertical movement. The time

for the VSI to reach its maximum point of deﬂ ection after a

correction is called lag. The lag is proportional to speed and

magnitude of pitch change. In an airplane, overcontrolling

may be reduced by relaxing pressure on the controls, allowing

the pitch attitude to neutralize. In some helicopters with

servo-assisted controls, no control pressures are apparent.

In this case, overcontrolling can be reduced by reference to

the attitude indicator.

Some aircraft are equipped with an instantaneous vertical

speed indicator (IVSI). The letters “IVSI” appear on the face

of the indicator. This instrument assists in interpretation by

instantaneously indicating the rate of climb or descent at a

given moment with little or no lag as displayed in a VSI.

Occasionally, the VSI is slightly out of calibration and

indicates a gradual climb or descent when the aircraft is in

level ﬂ ight. If readjustments cannot be accomplished, the error

in the indicator should be considered when the instrument is

used for pitch control. For example, an improperly set VSI

may indicate a descent of 100 fpm when the aircraft is in

level ﬂ ight. Any deviation from this reading would indicate

a change in pitch attitude.

Airspeed Indicator

The airspeed indicator gives an indirect reading of the pitch

attitude. With a constant power setting and a constant altitude,

the aircraft is in level ﬂ ight and airspeed remains constant. If the

airspeed increases, the pitch attitude has lowered and should be

raised. [Figure 4-9] If the airspeed decreases, the pitch attitude

has moved higher and should be lowered. [Figure 4-10] A

rapid change in airspeed indicates a large change in pitch; a

slow change in airspeed indicates a small change in pitch.

Although the airspeed indicator is used as a pitch instrument,

it may be used in level ﬁ ght for power control. Changes in

pitch are reﬂ ected immediately by a change in airspeed. There

is very little lag in the airspeed indicator.

Pitch Attitude Instrument Cross-Check

The altimeter is an important instrument for indicating pitch

attitude in level ﬂ ight except when used in conditions of

exceptionally strong vertical currents, such as thunderstorms.

With proper power settings, any of the pitch attitude

instruments can be used to hold reasonably level ﬂ ight

attitude. However, only the altimeter gives the exact altitude

information. Regardless of which pitch attitude control

instrument indicates a need for a pitch attitude adjustment,

the attitude indicator, if available, should be used to make the

4-7

Figure 4-9. Pitch attitude has lowered. Figure 4-10. Pitch attitude has moved higher.

Figure 4-11. Bank Instruments.

adjustment. Common errors in pitch attitude control are:

• Overcontrolling,

• Improperly using power, and

• Failing to adequately cross-check the pitch attitude

instruments and take corrective action when pitch

attitude change is needed

Bank Control

Bank control is controlling the angle made by the wing and

the horizon. After interpreting the bank attitude from the

appropriate instruments, exert the necessary pressures to move

the ailerons and roll the aircraft about the longitudinal axis.

As illustrated in Figure 4-11, these instruments include:

Attitude Indicator

As previously discussed, the attitude indicator is the only

instrument that portrays both instantly and directly the actual

ﬂ ight attitude and is the basic attitude reference.

Heading Indicator

The heading indicator supplies the pertinent bank and

heading information and is considered a primary instrument

for bank.

Magnetic Compass

The magnetic compass provides heading information and is

considered a bank instrument when used with the heading

indicator. Care should be exercised when using the magnetic

compass as it is affected by acceleration, deceleration in ﬂ ight

caused by turbulence, climbing, descending, power changes,

and airspeed adjustments. Additionally, the magnetic compass

indication will lead and lag in its reading depending upon

the direction of turn. As a result, acceptance of its indication

should be considered with other instruments that indicate turn

information. These include the already mentioned attitude

and heading indicators as well as the turn-and-slip indicator

and turn coordinator.

4-8

Figure 4-12. Turn Coordinator and Turn-and-Slip Indicator.

Figure 4-13. An Increase in Power Inscreasing Airpseed Accordingly in Level Flight.

Turn Coordinator/Turn-and-Slip Indicator

Both of these instruments provide turn information.

[Figure 4-12] The turn coordinator provides both bank rate

and then turn rate once stabilized. The turn-and-slip indicator

provides only turn rate.

Power Control

A power change to adjust airspeed may cause movement

around some or all of the aircraft axes. The amount and

direction of movement depends on how much or how rapidly

the power is changed, whether single-engine or multiengine

airplane or helicopter. The effect on pitch attitude and

airspeed caused by power changes during level ﬂ ight is

illustrated in Figures 4-13 and 4-14. During or immediately

after adjusting the power control(s), the power instruments

should be cross-checked to see if the power adjustment is as

desired. Whether or not the need for a power adjustment is

indicated by another instrument(s), adjustment is made by

cross-checking the power instruments. Aircraft are powered

by a variety of power plants, each power plant having

certain instruments that indicate the amount of power being

applied to operate the aircraft. During instrument ﬂ ight,

these instruments must be used to make the required power

adjustments.

As illustrated in Figure 4-15, power indicator instruments

include:

Airspeed Indicator

The airspeed indicator provides an indication of power

best observed initially in level ﬂ ight where the aircraft

is in balance and trim. If in level ﬂ ight the airspeed is

increasing, it can generally be assumed that the power has

increased, necessitating the need to adjust power or re-trim

the aircraft.

Engine Instruments

Engine instruments, such as the manifold pressure (MP)

indicator, provide an indication of aircraft performance for a

given setting under stable conditions. If the power conditions

are changed, as reﬂ ected in the respective engine instrument

readings, there is an affect upon the aircraft performance,

either an increase or decrease of airspeed. When the propeller

rotational speed (revolutions per minute (RPM) as viewed

on a tachometer) is increased or decreased on ﬁ xed-pitch

propellers, the performance of the aircraft reﬂ ects a gain or

loss of airspeed as well.

Trim Control

Proper trim technique is essential for smooth and accurate

instrument ﬂ ying and utilizes instrumentation illustrated in

Figure 4-16. The aircraft should be properly trimmed while

executing a maneuver. The degree of ﬂ ying skill, which

ultimately develops, depends largely upon how well the

aviator learns to keep the aircraft trimmed.

Airplane Trim

An airplane is correctly trimmed when it is maintaining a

desired attitude with all control pressures neutralized. By

relieving all control pressures, it is much easier to maintain

the aircraft at a certain attitude. This allows more time to

devote to the navigation instruments and additional ﬂ ight

deck duties.

4-9

Figure 4-14. Pitch Control and Power Adjustment Required To Bring Aircraft to Level Flight.

Figure 4-15. Power Instruments.

Figure 4-16. Trim Instruments.

4-10

• Airspeed Indicator—supplies the most pertinent

information concerning performance in level ﬂ ight

in terms of power output and is primary for power.

Although the attitude indicator is the basic attitude reference,

the concept of primary and supporting instruments does not

devalue any particular ﬂ ight instrument, when available, in

establishing and maintaining pitch-and-bank attitudes. It is the

only instrument that instantly and directly portrays the actual

ﬂ ight attitude. It should always be used, when available, in

establishing and maintaining pitch-and-bank attitudes. The

speciﬁ c use of primary and supporting instruments during

basic instrument maneuvers is presented in more detail in

Chapter 5, Airplane Basic Flight Maneuvers.

Fundamental Skills

During attitude instrument training, two fundamental ﬂ ight

skills must be developed. They are instrument cross-check

and instrument interpretation, both resulting in positive

aircraft control. Although these skills are learned separately

and in deliberate sequence, a measure of proﬁ ciency in

precision ﬂ ying is the ability to integrate these skills into

uniﬁ ed, smooth, positive control responses to maintain any

prescribed ﬂ ight path.

Instrument Cross-Check

The ﬁ rst fundamental skill is cross-checking (also called

“scanning” or “instrument coverage”). Cross-checking is the

continuous and logical observation of instruments for attitude

and performance information. In attitude instrument ﬂ ying,

the pilot maintains an attitude by reference to instruments,

producing the desired result in performance. Observing and

interpreting two or more instruments to determine attitude and

performance of an aircraft is called cross-checking. Although

no speciﬁ c method of cross-checking is recommended, those

instruments that give the best information for controlling the

aircraft in any given maneuver should be used. The important

instruments are the ones that give the most pertinent

information for any particular phase of the maneuver. These

are usually the instruments that should be held at a constant

indication. The remaining instruments should help maintain

the important instruments at the desired indications, which

is also true in using the emergency panel.

Cross-checking is mandatory in instrument flying. In

visual ﬂ ight, a level attitude can be maintained by outside

references. However, even then the altimeter must be checked

to determine if altitude is being maintained. Due to human

error, instrument error, and airplane performance differences

in various atmospheric and loading conditions, it is impossible

to establish an attitude and have performance remain constant

for a long period of time. These variables make it necessary

An aircraft is placed in trim by:

• Applying control pressure(s) to establish a desired

attitude. Then, the trim is adjusted so that the aircraft

maintains that attitude when flight controls are

released. The aircraft is trimmed for coordinated ﬂ ight

by centering the ball of the turn-and-slip indicator.

• Moving the rudder trim in the direction where the

ball is displaced from center. Aileron trim may then

be adjusted to maintain a wings-level attitude.

• Using balanced power or thrust when possible to aid

in maintaining coordinated ﬂ ight. Changes in attitude,

power, or conﬁ guration may require trim adjustments.

Use of trim alone to establish a change in aircraft

attitude usually results in erratic aircraft control.

Smooth and precise attitude changes are best attained

by a combination of control pressures and subsequent

trim adjustments. The trim controls are aids to smooth

aircraft control.

Helicopter Trim

A helicopter is placed in trim by continually cross-checking

the instruments and performing the following:

• Using the cyclic centering button. If the helicopter is so

equipped, this relieves all possible cyclic pressures.

• Using the pedal adjustment to center the ball of the

turn indicator. Pedal trim is required during all power

changes and is used to relieve all control pressures

held after a desired attitude has been attained.

An improperly trimmed helicopter requires constant control

pressures, produces tension, distracts attention from cross-

checking, and contributes to abrupt and erratic attitude

control. The pressures felt on the controls should be only

those applied while controlling the helicopter.

Adjust the pitch attitude, as airspeed changes, to maintain

desired attitude for the maneuver being executed. The bank

must be adjusted to maintain a desired rate of turn, and the

pedals must be used to maintain coordinated ﬂ ight. Trim must

be adjusted as control pressures indicate a change is needed.

Example of Primary and Support Instruments

Straight-and-level ﬂ ight at a constant airspeed means that an

exact altitude is to be maintained with zero bank (constant

heading). The primary pitch, bank, and power instruments

used to maintain this ﬂ ight condition are:

• Altimeter—supplies the most pertinent altitude

information and is primary for pitch.

• Heading Indicator—supplies the most pertinent bank

or heading information and is primary for bank.

4-11

Figure 4-17. Radial Cross-Check.

for the pilot to constantly check the instruments and make

appropriate changes in airplane attitude using cross-checking

of instruments. Examples of cross-checking are explained in

the following paragraphs.

Selected Radial Cross-Check

When the selected radial cross-check is used, a pilot spends

80 to 90 percent of ﬂ ight time looking at the attitude indicator,

taking only quick glances at the other ﬂ ight instruments (for

this discussion, the ﬁ ve instruments surrounding the attitude

indicator are called the ﬂ ight instruments). With this method,

the pilot’s eyes never travel directly between the ﬂ ight

instruments but move by way of the attitude indicator. The

maneuver being performed determines which instruments to

look at in the pattern. [Figure 4-17]

Inverted-V Cross-Check

In the inverted-V cross-check, the pilot scans from the

attitude indicator down to the turn coordinator, up to the

attitude indicator, down to the VSI, and back up to the attitude

indicator. [Figure 4-18]

Rectangular Cross-Check

In the rectangular cross-check, the pilot scans across

the top three instruments (airspeed indicator, attitude

indicator, and altimeter) and then drops down to scan the

bottom three instruments (VSI, heading indicator, and

turn instrument). This scan follows a rectangular path

(clockwise or counterclockwise rotation is a personal choice).

[Figure 4-19]

This cross-checking method gives equal weight to the

information from each instrument, regardless of its

importance to the maneuver being performed. However, this

method lengthens the time it takes to return to an instrument

critical to the successful completion of the maneuver.

Common Cross-Check Errors

A beginner might cross-check rapidly, looking at the

instruments without knowing exactly what to look for. With

increasing experience in basic instrument maneuvers and

familiarity with the instrument indications associated with

them, a pilot learns what to look for, when to look for it,

and what response to make. As proﬁ ciency increases, a pilot

cross-checks primarily from habit, suiting scanning rate and

sequence to the demands of the ﬂ ight situation. Failure to

maintain basic instrument proﬁ ciency through practice can

result in many of the following common scanning errors,

both during training and at any subsequent time.

Fixation, or staring at a single instrument, usually occurs for

a reason, but has poor results. For example, a pilot may stare

at the altimeter reading 200 feet below the assigned altitude,

and wonder how the needle got there. While ﬁ xated on the

4-12

Figure 4-18. Inverted-V Cross-Check.

Figure 4-19. Rectangular Cross-Check.

4-13

Figure 4-20. Power and Attitude Equal Performance.

instrument, increasing tension may be unconsciously exerted

on the controls, which leads to an unnoticed heading change

that leads to more errors. Another common ﬁ xation is likely

when initiating an attitude change. For example, a shallow

bank is established for a 90° turn and, instead of maintaining

a cross-check of other pertinent instruments, the pilot stares at

the heading indicator throughout the turn. Since the aircraft is

turning, there is no need to recheck the heading indicator for

approximately 25 seconds after turn entry. The problem here

may not be entirely due to cross-check error. It may be related

to difﬁ culties with instrument interpretation. Uncertainty

about reading the heading indicator (interpretation) or

uncertainty because of inconsistency in rolling out of turns

(control) may cause the ﬁ xation.

Omission of an instrument from a cross-check is another

likely fault. It may be caused by failure to anticipate

significant instrument indications following attitude

changes. For example, in a roll-out from a 180° steep turn,

straight-and-level ﬂ ight is established with reference only

to the attitude indicator, and the pilot neglects to check the

heading indicator for constant heading information. Because

of precession error, the attitude indicator temporarily shows

a slight error, correctable by quick reference to the other

ﬂ ight instruments.

Emphasis on a single instrument, instead of on the combination

of instruments necessary for attitude information, is an

understandable fault during the initial stages of training. It

is a natural tendency to rely on the instrument that is most

readily understood, even when it provides erroneous or

inadequate information. Reliance on a single instrument is

poor technique. For example, a pilot can maintain reasonably

close altitude control with the attitude indicator, but cannot

hold altitude with precision without including the altimeter

in the cross-check.

Instrument Interpretation

The second fundamental skill, instrument interpretation, requires

more thorough study and analysis. It begins by understanding

each instrument’s construction and operating principles. Then,

this knowledge must be applied to the performance of the

aircraft being ﬂ own, the particular maneuvers to be executed,

the cross-check and control techniques applicable to that

aircraft, and the ﬂ ight conditions.

For example, a pilot uses full power in a small airplane for a

5-minute climb from near sea level, and the attitude indicator

shows the miniature aircraft two bar widths (twice the

thickness of the miniature aircraft wings) above the artiﬁ cial

horizon. [Figure 4-20] The airplane is climbing at 500 fpm

as shown on the VSI, and at airspeed of 90 knots, as shown

on the airspeed indicator. With the power available in this

particular airplane and the attitude selected by the pilot, the

performance is shown on the instruments. Now, set up the

identical picture on the attitude indicator in a jet airplane.

With the same airplane attitude as shown in the ﬁ rst example,

the VSI in the jet reads 2,000 fpm and the airspeed indicator

reads 300 knots.

As the performance capabilities of the aircraft are learned,

a pilot interprets the instrument indications appropriately

4-14

in terms of the attitude of the aircraft. If the pitch attitude

is to be determined, the airspeed indicator, altimeter, VSI,

and attitude indicator provide the necessary information. If

the bank attitude is to be determined, the heading indicator,

turn coordinator, and attitude indicator must be interpreted.

For each maneuver, learn what performance to expect and

the combination of instruments to be interpreted in order

to control aircraft attitude during the maneuver. It is the

two fundamental ﬂ ight skills, instrument cross-check and

instrument interpretation, that provide the smooth and

seamless control necessary for basic instrument ﬂ ight as

discussed at the beginning of the chapter.

4-15

Introduction

Attitude instrument ﬂ ying is deﬁ ned as the control of an

aircraft’s spatial position by using instruments rather than

outside visual references. As noted in Section I, today’s

aircraft come equipped with analog and/or digital instruments.

Section II acquaints the pilot with the use of digital instruments

known as an electronic ﬂ ight display (EFD).

The improvements in avionics coupled with the introduction

of EFDs to general aviation aircraft offer today’s pilot an

unprecedented array of accurate instrumentation to use in

the support of instrument ﬂ ying.

Airplane Attitude

Instrument Flying

Chapter 4, Section II

Using an Electronic Flight Display

4-16

Figure 4-21. Primary Flight Display (PFD) and Analog Counterparts.

Until recently, most general aviation aircraft were equipped

with individual instruments utilized collectively to safely

maneuver the aircraft by instrument reference alone. With

the release of the electronic flight display system, the

conventional instruments have been replaced by multiple

liquid crystal display (LCD) screens. The ﬁ rst screen is

installed in front of the left seat pilot position and is referred

to as the primary ﬂ ight display (PFD). [Figure 4-21] The

second screen is positioned in approximately the center of

the instrument panel and is referred to as the multi-function

display (MFD). [Figure 4-22] The pilot can use the MFD

to display navigation information (moving maps), aircraft

systems information (engine monitoring), or should the need

arise, a PFD. [Figure 4-23] With just these two screens,

aircraft designers have been able to de-clutter instrument

panels while increasing safety. This has been accomplished

through the utilization of solid-state instruments which have

a failure rate far lower than those of conventional analog

instrumentation.

However, in the event of electrical failure, the pilot still

has emergency instruments as a backup. These instruments

either do not require electrical power, or as in the case

of many attitude indicators, they are battery equipped.

[Figure 4-24]

Pilots ﬂ ying under visual ﬂ ight rules (VFR) maneuver their

aircraft by reference to the natural horizon, utilizing speciﬁ c

reference points on the aircraft. In order to operate the aircraft

in other than VFR weather, with no visual reference to the

natural horizon, pilots need to develop additional skills.

These skills come from the ability to maneuver the aircraft by

reference to ﬂ ight instruments alone. These ﬂ ight instruments

replicate all the same key elements that a VFR pilot utilizes

during a normal ﬂ ight. The natural horizon is replicated on

the attitude indicator by the artiﬁ cial horizon.

Understanding how each ﬂ ight instrument operates and

what role it plays in controlling the attitude of the aircraft

is fundamental in learning attitude instrument ﬂ ying. When

the pilot understands how all the instruments are used in

establishing and maintaining a desired aircraft attitude, the

pilot is better prepared to control the aircraft should one

or more key instruments fail or if the pilot should enter

instrument ﬂ ight conditions.

Learning Methods

There are two basic methods utilized for learning attitude

instrument ﬂ ying. They are “control and performance” and

“primary and supporting.” These methods rely on the same

ﬂ ight instruments and require the pilot to make the same

adjustments to the ﬂ ight and power controls to control aircraft

attitude. The main difference between the two methods is the

importance that is placed on the attitude indicator and the

interpretation of the other ﬂ ight instruments.

4-17

Figure 4-22. Multifunction Display (MFD).

Figure 4-23. Reversionary Displays.

4-18

Figure 4-24. Emergency Back-up of the Airspeed Indicator, Attitude Indicator, and Altitude Indicator.

Figure 4-25. Control Instruments.

Control and Performance Method

Aircraft performance is accomplished by controlling the

aircraft attitude and power output. Aircraft attitude is the

relationship of its longitudinal and lateral axes to the Earth’s

horizon. When ﬂ ying in instrument ﬂ ight conditions, the

pilot controls the attitude of the aircraft by referencing the

ﬂ ight instruments and manipulating the power output of the

engine to achieve the performance desired. This method can

be used to achieve a speciﬁ c performance level enabling a

pilot to perform any basic instrument maneuver.

The instrumentation can be broken up into three different

categories: control, performance, and navigation.

Control Instruments

The control instruments depict immediate attitude and power

changes. The instrument for attitude display is the attitude

indicator. Power changes are directly reﬂ ected on the manifold

pressure gauge and the tachometer. [Figure 4-25] All three

of these instruments can reﬂ ect small adjustments, allowing

for precise control of aircraft attitude.

4-19

Figure 4-26. Performance Instruments.

Figure 4-27. Navigation Instruments.

In addition, the conﬁ guration of the power indicators installed

in each aircraft may vary to include the following types of

power indicators: tachometers, manifold pressure indicator,

engine pressure ratio indicator, fuel ﬂ ow gauges, etc.

The control instruments do not indicate how fast the aircraft

is ﬂ ying or at what altitude it is ﬂ ying. In order to determine

these variables and others, a pilot needs to refer to the

performance instruments.

Performance Instruments

The performance instruments directly reﬂ ect the performance

the aircraft is achieving. The speed of the aircraft can be

referenced on the airspeed indicator. The altitude can be

referenced on the altimeter. The aircraft’s climb performance

can be determined by referencing the vertical speed indicator

(VSI). [Figure 4-26] Other performance instruments

available are the heading indicator, angle of attack indicator,

and the slip/skid indicator.

The performance instruments will most directly reﬂ ect a

change in acceleration, which is deﬁ ned as change in velocity

or direction. Therefore, these instruments indicate if the

aircraft is changing airspeed, altitude, or heading, which are

horizontal, vertical, or lateral vectors.

Navigation Instruments

The navigation instruments are comprised of global

positioning system (GPS) displays and indicators, very high

frequency omnidirectional range/nondirectional radio beacon

(VOR/NDB) indicators, moving map displays, localizer, and

glide slope (GS) indicators. [Figure 4-27] The instruments

indicate the position of the aircraft relative to a selected

navigation facility or ﬁ x. Navigation instruments allow

the pilot to maneuver the aircraft along a predetermined

path of ground-based or spaced-based navigation signals

without reference to any external visual cues. The navigation

instruments can support both lateral and visual inputs.

4-20

Figure 4-28. The chevron’s relationship to the horizon line

indicates the pitch of the aircraft.

The Four-Step Process Used to Change Attitude

In order to change the attitude of the aircraft, the pilot must

make the proper changes to the pitch, bank, or power settings

of the aircraft. Four steps (establish, trim, cross-check, and

adjust) have been developed in order to aid in the process.

Establish

Any time the attitude of the aircraft requires changing, the

pilot must adjust the pitch and/or bank in conjunction with

power to establish the desired performance. The changes

in pitch and bank require the pilot to reference the attitude

indicator in order to make precise changes. Power changes

should be veriﬁ ed on the tachometer, manifold pressure

gauge, etc. To ease the workload, the pilot should become

familiar with the approximate pitch and power changes

necessary to establish a speciﬁ ed attitude.

Trim

Another important step in attitude instrument flying is

trimming the aircraft. Trim is utilized to eliminate the need

to apply force to the control yoke in order to maintain the

desired attitude. When the aircraft is trimmed appropriately,

the pilot is able to relax pressure on the control yoke and

momentarily divert attention to another task at hand without

deviating from the desired attitude. Trimming the aircraft is

very important, and poor trim is one of the most common

errors instructors note in instrument students.

Cross-Check

Once the initial attitude changes have been made, the pilot

should verify the performance of the aircraft. Cross-checking

the control and performance instruments requires the pilot

to visually scan the instruments as well as interpret the

indications. All the instruments must be utilized collectively

in order to develop a full understanding of the aircraft attitude.

During the cross-check, the pilot needs to determine the

magnitude of any deviations and determine how much of a

change is required. All changes are then made based on the

control instrument indications.

Adjust

The ﬁ nal step in the process is adjusting for any deviations

that have been noted during the cross-check. Adjustments

should be made in small increments. The attitude indicator

and the power instruments are graduated in small increments

to allow for precise changes to be made. The pitch should be

made in reference to bar widths on the miniature airplane.

The bank angle can be changed in reference to the roll scale

and the power can be adjusted in reference to the tachometer,

manifold pressure gauge, etc.

By utilizing these four steps, pilots can better manage the

attitude of their aircraft. One common error associated with

this process is making a larger than necessary change when

a deviation is noted. Pilots need to become familiar with the

aircraft and learn how great a change in attitude is needed to

produce the desired performance.

Applying the Four-Step Process

In attitude instrument ﬂ ight, the four-step process is used to

control pitch attitude, bank attitude, and power application of

the aircraft. The EFD displays indications precisely enough

that a pilot can apply control more accurately.

Pitch Control

The pitch control is indicated on the attitude indicator which

spans the full width of the PFD. Due to the increased size of

the display, minute changes in pitch can be made and corrected

for. The pitch scale on the attitude indicator is graduated in

5-degree increments which allow the pilot to make correction

with precision to approximately 1/2 degree. The miniature

airplane utilized to represent the aircraft in conventional

attitude indicators is replaced in glass panel displays by a

yellow chevron. [Figure 4-28] Representing the nose of the

aircraft, the point of the chevron affords the pilot a much

more precise indication of the degree of pitch and allows

the pilot to make small, precise changes should the desired

aircraft performance change. When the desired performance

is not being achieved, precise pitch changes should be made

by referencing the point of the yellow chevron.

Bank Control

Precise bank control can be developed utilizing the roll

pointer in conjunction with the roll index displayed on the

4-21

Figure 4-29. Bank Control Index Lines.

attitude indicator. The roll index is sectioned by hash marks at

0°, 10°, 20°, 30°, 45°, 60° and the horizon line which depicts

90° of bank. [Figure 4-29] The addition of the 45° hash mark

is an improvement over conventional attitude indicators.

In addition to the roll index, the instrument pilot utilizes

the turn rate indicator to maintain the aircraft in a standard

rate turn (3° per second). Most instrument maneuvers can

be done comfortably, safely, and efﬁ ciently by utilizing a

standard rate turn.

Power Control

The power instruments indicate how much power is being

generated by the engine. They are not affected by turbulence,

improper trim, or control pressures. All changes in power

should be made with reference to power instruments and

cross-checked on performance instruments.

Power control needs to be learned from the beginning of

ﬂ ight training. Attitude instrument ﬂ ying demands increased

precision when it comes to power control. As experience

increases, pilots begin to know approximately how much

change in throttle position is required to produce the desired

change in airspeed. Different aircraft demand differing

amounts of throttle change to produce speciﬁ c performance.

It is imperative that the pilot make the speciﬁ c changes on

the power instruments and allow the performance to stabilize.

Avoid the tendency to overcontrol.

One common error encountered with glass panel displays

is associated with the precision of the digital readouts.

This precision causes pilots to focus too much attention on

establishing the exact power setting.

Control and power instruments are the foundation for precise

attitude instrument ﬂ ying. The keys to attitude instrument

ﬂ ying are establishing the desired aircraft attitude on the

attitude indicator and selecting the desired engine output on

the power instruments. Cross-checking is the vital ingredient

in maintaining precise attitude instrument ﬂ ight.

Attitude Instrument Flying—Primary and

Supporting Method

The second method for performing attitude instrument

ﬂ ight is a direct extension of the control/power method.

By utilizing the primary and supporting ﬂ ight instruments

in conjunction with the control and power instruments, the

pilot can precisely maintain aircraft attitude. This method

utilizes the same instruments as the control/power method;

however, it focuses more on the instruments that depict the

most accurate indication for the aspect of the aircraft attitude

being controlled. The four key elements (pitch, bank, roll,

and trim) are discussed in detail.

Similar to the control/power method, all changes to aircraft

attitude need to be made using the attitude indicator and the

power instruments (tachometer, manifold pressure gauge,

etc.). The following explains how each component of the

aircraft attitude is monitored for performance.

Pitch Control

The pitch of the aircraft refers to the angle between the

longitudinal axis of the aircraft and the natural horizon. When

ﬂ ying in instrument meteorological conditions, the natural

horizon is unavailable for reference, and an artiﬁ cial horizon

is utilized in its place. [Figure 4-30] The only instrument

capable of depicting the aircraft attitude is the attitude

indicator displayed on the PFD. The attitude and heading

reference system (AHRS) is the engine that drives the attitude

display. The AHRS unit is capable of precisely tracking

minute changes in the pitch, bank, and yaw axes, thereby

making the PFD very accurate and reliable. The AHRS unit

determines the angle between the aircraft’s longitudinal

axis and the horizon line on initialization. There is no need

4-22

Figure 4-30. Pitch of the Aircraft.

Figure 4-31. Supporting Instruments.

or means for the pilot to adjust the position of the yellow

chevron which represents the nose of the aircraft.

Straight-and-Level Flight

In straight-and-level ﬂ ight, the pilot maintains a constant

altitude, airspeed and, for the most part, heading for

extended periods of time. To achieve this, three primary

instruments need to be referenced in order to maintain these

three variables.

Primary Pitch

When the pilot is maintaining a constant altitude, the primary

instrument for pitch is the altimeter. As long as the aircraft

maintains a constant airspeed and pitch attitude, the altitude

should remain constant.

Two factors that cause the altitude to deviate are turbulence

and momentary distractions. When a deviation occurs,

a change in the pitch needs to be made on the attitude

indicator. Small deviations require small corrections while

large deviations require larger corrections. Pilots should

avoid making large corrections that result in rapid attitude

changes, for this may lead to spatial disorientation. Smooth,

timely corrections should be made to bring the aircraft back

to the desired attitude.

Pay close attention to indications on the PFD. An increase in

pitch of 2.5° produces a climb rate of 450 feet per minute (fpm).

Small deviations do not require large attitude changes.

A rule of thumb for correcting altitude deviations is to establish

a change rate of twice the altitude deviation, not to exceed 500

fpm. For example, if the aircraft is off altitude by 40 feet, 2 x

40 = 80 feet, so a descent of approximately 100 fpm allows

the aircraft to return to the desired altitude in a controlled,

timely fashion.

In addition to the primary instrument, there are also

supporting instruments that assist the pilot in cross-checking

the pitch attitude. The supporting instruments indicate trend,

but they do not indicate precise attitude indications. Three

instruments (vertical speed, airspeed, and altitude trend

tape) indicate when the pitch attitude has changed and that

the altitude is changing. [Figure 4-31] When the altitude is

constant, the VSI and altitude trend tape are not shown on

the PFD. When these two trend indicators are displayed, the

pilot is made aware that the pitch attitude of the aircraft has

changed and may need adjustment.

The instrument cross-check necessitates utilizing these

supporting instruments to better manage altitude control.

The VSI and trend tape provide the pilot with information

regarding the direction and rate of altitude deviations. The

pilot is thus able to make correction to the pitch attitude

4-23

Figure 4-32. Primary Bank.

moving through the air with the longitudinal axis of the

aircraft aligned with the relative wind.

Primary Power

The primary power instrument for straight-and-level ﬂ ight is

the airspeed indicator. The main focus of power is to maintain

a desired airspeed during level ﬂ ight. No other instrument

delivers instantaneous indication.

Learning the primary and supporting instruments for

each variable is the key to successfully mastering attitude

instrument ﬂ ying. At no point does the primary and supporting

method devalue the importance of the attitude indicator or the

power instruments. All instruments (control, performance,

primary, and supporting) must be utilized collectively.

Fundamental Skills of Attitude Instrument

Flying

When ﬁ rst learning attitude instrument ﬂ ying, it is very

important that two major skills be mastered. Instrument cross-

check and instrument interpretation comprise the foundation

for safely maneuvering the aircraft by reference to instruments

alone. Without mastering both skills, the pilot will not be able

to maintain precise control of aircraft attitude.

before a large deviation in altitude occurs. The airspeed

indicator depicts an increase if the pitch attitude is lowered.

Conversely, when the pitch attitude increases, the pilot should

note a decrease in the airspeed.

Primary Bank

When ﬂ ying in instrument meteorological conditions, pilots

maintain preplanned or assigned headings. With this in

mind, the primary instrument for bank angle is the heading

indicator. Heading changes are displayed instantaneously.

The heading indicator is the only instrument that displays the

current magnetic heading, provided that it is matched to the

magnetic compass with all deviation adjustments accounted

for. [Figure 4-32]

There are supporting instruments associated with bank as

well. The turn rate trend indicator shows the pilot when the

aircraft is changing heading. The magnetic compass is also

useful for maintaining a heading; however, it is inﬂ uenced

by several errors in various phases of ﬂ ight.

Primary Yaw

The slip/skid indicator is the primary instrument for yaw.

It is the only instrument that can indicate if the aircraft is

4-24

Figure 4-33. Note that the altitude and vertical speed tapes are slightly to the right of the pilot’s direct forward line of sight.

to include the stand-by ﬂ ight instruments as well as the

engine indications in the scan. Due to the size of the

attitude instrument display, scanning techniques have been

simpliﬁ ed because the attitude indicator is never out of

peripheral view.

Selected Radial Cross-Check

The radial scan is designed so that your eyes remain on the

attitude indicator 80–90 percent of the time. The remainder

of the time is spent transitioning from the attitude indicator

to the various other ﬂ ight instruments. [Figure 4-34]

The radial scan pattern works well for scanning the PFD. The

close proximity of the instrument tape displays necessitates

very little eye movement in order to focus in on the desired

instrument. While the eyes move in any direction, the

extended artiﬁ cial horizon line allows the pilot to keep the

pitch attitude in his or her peripheral vision. This extended

horizon line greatly reduces the tendency to ﬁ xate on one

instrument and completely ignore all others. Because of

the size of the attitude display, some portion of the attitude

indicator is always visible while viewing another instrument

display on the PFD.

Starting the Scan

Start the scan in the center of the PFD on the yellow chevron.

Note the pitch attitude and then transition the eyes upward to

the slip/skid indicator. Ensure that the aircraft is coordinated

Instrument Cross-Check

The first fundamental skill is cross-checking (also call

“scanning”). Cross-checking is the continuous observation of

the indications on the control and performance instruments.

It is imperative that the new instrument pilot learn to observe

and interpret the various indications in order to control

the attitude and performance of the aircraft. Due to the

conﬁ guration of some glass panel displays such as the Garmin

G1000, one or more of the performance instruments may be

located on an MFD installed to the right of the pilot’s direct

forward line of sight. [Figure 4-33]

How a pilot gathers the necessary information to control the

aircraft varies by individual pilot. No speciﬁ c method of

cross-checking (scanning) is recommended; the pilot must

learn to determine which instruments give the most pertinent

information for any particular phase of a maneuver. With

practice, the pilot is able to observe the primary instruments

quickly and cross-check with the supporting instruments

in order to maintain the desired attitude. At no time during

instrument ﬂ ying should the pilot stop cross-checking the

instrumentation.

Scanning Techniques

Since most of the primary and supporting aircraft attitude

information is displayed on the PFD, standard scanning

techniques can be utilized. It is important to remember

4-25

Figure 4-34. Selected Radial Cross-Check.

Figure 4-35. Roll Pointer and Slip/Skid Indicator.

by aligning the split triangle symbol. The top of the split

triangle is referred to as the roll pointer. The lower portion of

the split triangle is the slip/skid indicator. If the lower portion

of the triangle is off to one side, step on the rudder pedal on

the same side to offset it. [Figure 4-35 NOTE: The aircraft

is not changing heading. There is no trend vector on the turn

rate indicator.]

While scanning that region, check the roll pointer and assure

that the desired degree of roll is being indicated on the bank

scale. The roll index and the bank scale remain stationary at

the top of the attitude indicator. The index is marked with

angles of 10°, 20°, 30°, 45° and 60° in both directions. If the

desired bank angle is not indicated, make the appropriate

4-26

Figure 4-36. Airspeed Trend Indicators.

Figure 4-37. Airspeed Indicators With No Trend Present.

Figure 4-38. Altimeter Trend Indicators.

aileron corrections. Verify the bank angle is correct and

continue scanning back to the yellow chevron.

Scan left to the airspeed tape and verify that the airspeed is

as desired, then return back to the center of the display. Scan

right to the altimeter tape. Verify that the desired altitude is

being maintained. If it is not, make the appropriate pitch

change and verify the result. Once the desired altitude has

been veriﬁ ed, return to the center of the display. Transition

down to the heading indicator to verify the desired heading.

When the heading has been conﬁ rmed, scan to the center of

the display.

It is also important to include the engine indications in the

scan. Individualized scan methods may require adjustment

if engine indications are presented on a separate MFD. A

modiﬁ ed radial scan can be performed to incorporate these

instruments into the scan pattern. Another critical component

to include in the scan is the moving map display located on

the MFD. To aid in situational awareness and facilitate a more

centralized scan, a smaller inset map can be displayed in the

lower left corner of the PFD screen.

Trend Indicators

One improvement the glass panel displays brought to the

general aviation industry is the trend vector. Trend vectors

are magenta lines that appear on the airspeed and altitude

tapes as well as on the turn rate indicator. These magenta

lines indicate what the associated airspeed, altitude, or

heading will be in 6 seconds [Figure 4-36] if the current

rate is maintained. The trend vector is not displayed if there

is no change to the associated tape and the value remains

constant [Figure 4-37] or if there is a failure in some portion

of the system that would preclude the vector from being

determined.

Trend vectors are a very good source of information for the

new instrument ﬂ ight rules (IFR) pilot. Pilots who utilize

good scanning techniques can pick up subtle deviations

from desired parameters and make small correction to the

desired attitude. As soon as a trend is indicated on the PFD,

a conscientious pilot can adjust to regain the desired attitude.

[Figure 4-38]

Another advancement in attitude instrument ﬂ ying is the turn

rate trend indicator. As in the cases of airspeed, altitude, and

vertical speed trend indicators, the turn rate trend indicator

depicts what the aircraft’s heading will be in 6 seconds. While

examining the top of the heading indicator, notice two white

lines on the exterior of the compass rose. [Figure 4-39] These

4-27

Figure 4-39. Horizontal Situation Indicator (HSI) Trend Indicator Elongates Proportionally With the Rate of Turn.

Figure 4-40. HSI Indicator (enlargement).

two tick marks located on both sides of the top of the heading

indicator show half-standard rate turns as well as standard

rate turns.

In Figure 4-40, when the aircraft begins its turn to the left,

the magenta trend indicator elongates proportionally with the

rate of turn. To initiate a half-standard rate turn, position the

indicator on the ﬁ rst tick mark. A standard rate turn would

be indicated by the trend indicator extending to the second

tick mark. A turn rate in excess of standard rate would be

indicated by the trend indicator extending past the second tick

mark. This trend indicator shows what the aircraft’s heading

will be in 6 seconds, but is limited to indicate no more than

24° in front of the aircraft, or 4° per second. When the aircraft

exceeds a turning rate of 25° in 6 seconds, the trend indicator

has an arrowhead attached to it.

Trend indicators are very useful when leveling off at a speciﬁ c

altitude, when rolling out on a heading, or when stabilizing

airspeed. One method of determining when to start to level

off from a climb or descent is to start leveling at 10 percent

of the vertical speed rate prior to the desired altitude.

As the aircraft approaches the desired altitude, adjust the

pitch attitude to keep the trend indicator aligned with the

target altitude. As the target approaches, the trend indicator

gradually shrinks until altitude stabilizes. Trend indicators

should be used as a supplement, not as a primary means of

determining pitch change.

4-28

Common Errors

Fixation

Fixation, or staring at one instrument, is a common error

observed in pilots ﬁ rst learning to utilize trend indicators.

The pilot may initially ﬁ xate on the trend indicator and make

adjustments with reference to that alone. Trend indicators are

not the only tools to aid the pilot in maintaining the desired

power or attitude; they should be used in conjunction with the

primary and supporting instruments in order to better manage

the ﬂ ight. With the introduction of airspeed tapes, the pilot

can monitor airspeed to within one knot. Fixation can lead

to attempting to keep the airspeed to an unnecessarily tight

tolerance. There is no need to hold airspeed to within one

knot; the Instrument Rating Practical Test Standards (PTS)

allows greater latitude.

Omission

Another common error associated with attitude instrument

ﬂ ying is omission of an instrument from the cross-check. Due

to the high reliability of the PFD and associated components,

pilots tend to omit the stand-by instruments as well as the

magnetic compass from their scans. An additional reason

for the omission is the position of the stand-by instruments.

Pilots should continue to monitor the stand-by instruments

in order to detect failures within those systems. One of the

most commonly omitted instruments from the scan is the

slip/skid indicator.

Emphasis

In initial training, placing emphasis on a single instrument

is very common and can become a habit if not corrected.

When the importance of a single instrument is elevated above

another, the pilot begins to rely solely on that instrument

for guidance. When rolling out of a 180° turn, the attitude

indicator, heading indicator, slip/skid indicator, and altimeter

need to be referenced. If a pilot omits the slip/skid indicator,

coordination is sacriﬁ ced.

5-1

Introduction

Instrument ﬂ ying techniques differ according to aircraft

type, class, performance capability, and instrumentation.

Therefore, the procedures and techniques that follow need

to be modiﬁ ed to suit individual aircraft. Recommended

procedures, performance data, operating limitations, and

ﬂ ight characteristics of a particular aircraft are available in the

Pilot’s Operating Handbook/Airplane Flight Manual (POH/

AFM) for study before practicing the ﬂ ight maneuvers.

The ﬂ ight maneuvers discussed here in Chapter 5-I assume

the use of a single-engine, propeller-driven small airplane

with retractable gear and ﬂ aps and a panel with instruments

representative of those discussed earlier in Chapter 3, Flight

Instruments. With the exception of the instrument takeoff, all

of the maneuvers can be performed on “partial panel,” with the

attitude gyro and heading indicator covered or inoperative.

Airplane Basic

Flight Maneuvers

Chapter 5, Section I

Using Analog Instrumentation

5-2

Figure 5-2. Pitch Attitude and Airspeed in Level Flight, Fast Cruise

Speed.

Figure 5-1. Pitch Attitude and Airspeed in Level Flight, Slow

Cruise Speed.

Figure 5-3. Pitch Attitude and Airspeed in Level Flight, Normal

Cruise Speed.

Straight-and-Level Flight

Pitch Control

The pitch attitude of an airplane is the angle between the

longitudinal axis of the airplane and the actual horizon. In

level ﬂ ight, the pitch attitude varies with airspeed and load.

For training purposes, the latter factor can normally be

disregarded in small airplanes. At a constant airspeed, there is

only one speciﬁ c pitch attitude for level ﬂ ight. At slow cruise

speeds, the level ﬂ ight attitude is nose high with indications

as in Figure 5-1; at fast cruise speeds, the level-ﬂ ight attitude

is nose low. [Figure 5-2] Figure 5-3 shows the indications

for the attitude at normal cruise speeds. The instruments used

to determine the pitch attitude of the aircraft are the attitude

indicator, the altimeter, the vertical speed indicator (VSI),

and the airspeed indicator (ASI).

Attitude Indicator

The attitude indicator gives the direct indication of pitch

attitude. The desired pitch attitude is gained by using the

elevator control to raise or lower the miniature aircraft in

relation to the horizon bar. This corresponds to the way pitch

attitude is adjusted in visual ﬂ ight by raising or lowering

the nose of the airplane in relation to the natural horizon.

However, unless the airspeed is constant, and until the

level ﬂ ight attitude for that airspeed has been identiﬁ ed and

established, there is no way to know whether level ﬂ ight as

5-3

Figure 5-4. Pitch Correction for Level Flight, One-Half Bar

Width.

Figure 5-5. Pitch Correction for Level Flight, One Bar Width.

Figure 5-6. Pitch Correction for Level Flight, One-and-One-Half

Bar Width.

indicated on the attitude indicator is resulting in level ﬂ ight

as shown on the altimeter, VSI, and ASI. If the miniature

aircraft of the attitude indicator is properly adjusted on the

ground before takeoff, it shows approximately level ﬂ ight at

normal cruise speed when the pilot completes the level off

from a climb. If further adjustment of the miniature aircraft

is necessary, the other pitch instruments must be used to

maintain level ﬂ ight while the adjustment is made.

To practice pitch control for level ﬂ ight using only the

attitude indicator, use the following exercise. Restrict the

displacement of the horizon bar to a one-half bar width, a

bar width up or down, then a one-and-one-half bar width.

One-half, one, and one-and-one-half bar width nose-high

attitudes are shown in Figures 5-4, 5-5, and 5-6.

An instructor pilot can demonstrate these normal pitch

corrections and compare the indications on the attitude

indicator with the airplane’s position to the natural horizon.

Pitch attitude changes for corrections to level ﬂ ight by reference

to instruments are much smaller than those commonly used

for visual ﬂ ight. With the airplane correctly trimmed for level

ﬂ ight, the elevator displacement and the control pressures

necessary to effect these standard pitch changes are usually

very slight. The following are a few helpful hints to help

determine how much elevator control pressure is required.

First, a tight grip on the controls makes it difﬁ cult to feel

control pressure changes. Relaxing and learning to control

the aircraft usually takes considerable conscious effort during

the early stages of instrument training.

Second, make smooth and small pitch changes with positive

pressure. With practice, a pilot can make these small pitch

corrections up or down, “freezing” (holding constant) the

one-half, full, and one-and-one-half bar widths on the

attitude indicator.

Third, with the airplane properly trimmed for level ﬂ ight,

momentarily release all pressure on the elevator control

when becoming aware of tenseness. This is a reminder that

the airplane is stable; except under turbulent conditions, it

will maintain level ﬂ ight if left alone. Even when no control

change is called for, it will be difﬁ cult to resist the impulse

to move the controls. This may be one of the most difﬁ cult

initial training problems in instrument ﬂ ight.

Altimeter

At constant power, any deviation from level ﬂ ight (except

in turbulent air) is the result of a pitch change. Therefore,

the altimeter gives an indirect indication of the pitch attitude

in level ﬂ ight, assuming constant power. Since the altitude

5-4

Figure 5-7. Using the Altimeter for Pitch Interpretation, a High

Altitude Means a Nose-High Pitch Attitude.

Figure 5-8. Pitch Correction Following Altitude Increase—Lower

Nose to Correct Altitude Error.

should remain constant when the airplane is in level ﬂ ight,

any deviation from the desired altitude signals the need for a

pitch change. If the aircraft is gaining altitude, the nose must

be lowered. [Figures 5-7 and 5-8]

The rate of movement of the altimeter needle is as important

as its direction of movement in maintaining level ﬂ ight

without the use of the attitude indicator. An excessive pitch

deviation from level ﬂ ight results in a relatively rapid change

of altitude; a slight pitch deviation causes a slow change.

Thus, if the altimeter needle moves rapidly clockwise, assume

a considerable nose-high deviation from level ﬂ ight attitude.

Conversely, if the needle moves slowly counterclockwise to

indicate a slightly nose-low attitude, assume that the pitch

correction necessary to regain the desired altitude is small.

As the altimeter is added to the attitude indicator in a cross-

check, a pilot will learn to recognize the rate of movement

of the altimeter needle for a given pitch change as shown on

the attitude indicator.

To practice precision control of pitch in an airplane without

an attitude indicator, make small pitch changes by visual

reference to the natural horizon, and note the rate of

movement of the altimeter. Note what amount of pitch change

gives the slowest steady rate of change on the altimeter. Then

practice small pitch corrections by accurately interpreting

and controlling the rate of needle movement.

An instructor pilot can demonstrate an excessive nose-down

deviation (indicated by rapid movement of the altimeter

needle) and then, as an example, show the result of improper

corrective technique. The normal impulse is to make a

large pitch correction in a hurry, but this inevitably leads

to overcontrolling. The needle slows down, then reverses

direction, and finally indicates an excessive nose-high

deviation. The result is tension on the controls, erratic control

response, and increasingly extreme control movements. The

correct technique, which is slower and smoother, will return

the airplane to the desired attitude more quickly, with positive

control and no confusion.

When a pitch error is detected, corrective action should be

taken promptly, but with light control pressures and two

distinct changes of attitude: (1) a change of attitude to stop

the needle movement and (2) a change of attitude to return

to the desired altitude.

When the altimeter indicates an altitude deviation, apply

just enough elevator pressure to decrease the rate of needle

movement. If it slows down abruptly, ease off some of the

pressure until the needle continues to move, but ease off

slowly. Slow needle movement means the airplane attitude

is close to level ﬂ ight. Add slightly more corrective pressure

to stop the direction of needle movement. At this point level

ﬂ ight is achieved; a reversal of needle movement means

the aircraft has passed through it. Relax control pressures

carefully, continuing to cross-check since changing airspeed

will cause changes in the effectiveness of a given control

pressure. Next, adjust the pitch attitude with elevator pressure

for the rate of change of altimeter needle movement that is

correlated with normal pitch corrections, and return to the

desired altitude.

As a rule of thumb, for errors of less than 100 feet, use a half

bar width correction. [Figures 5-9 and 5-10] For errors in

excess of 100 feet, use an initial full bar width correction.

[Figures 5-11 and 5-12] Practice predetermined altitude

changes using the altimeter alone, then in combination with

the attitude indicator.

Vertical Speed Indicator (VSI)

The VSI, like the altimeter, gives an indirect indication of

pitch attitude and is both a trend and a rate instrument. As

a trend instrument, it shows immediately the initial vertical

movement of the airplane, which disregarding turbulence

can be considered a reﬂ ection of pitch change. To maintain

level ﬂ ight, use the VSI in conjunction with the altimeter and

attitude indicator. Note any positive or negative trend of the

needle from zero and apply a very light corrective elevator

5-5

Figure 5-9. Altitude Error, Less Than 100 Feet.

Figure 5-10. Pitch Correction, Less Than 100 Feet—One-Half Bar

Low to Correct Altitude Error.

Figure 5-11. Altitude Error, Greater Than 100 Feet.

Figure 5-12. Pitch Correction, Greater Than 100 Feet—One Bar

Correction Initially.

pressure. As the needle returns to zero, relax the corrective

pressure. If control pressures have been smooth and light, the

needle reacts immediately and slowly, and the altimeter shows

little or no change of altitude. As a rate instrument, the VSI

requires consideration of lag characteristics.

Lag refers to the delay involved before the needle attains a

stable indication following a pitch change. Lag is directly

proportional to the speed and magnitude of a pitch change.

If a slow, smooth pitch change is initiated, the needle moves

with minimum lag to a point of deﬂ ection corresponding

to the extent of the pitch change, and then stabilizes as the

aerodynamic forces are balanced in the climb or descent.

A large and abrupt pitch change produces erratic needle

movement, a reverse indication, and introduces greater time

delay (lag) before the needle stabilizes. Pilots are cautioned

not to chase the needle when flight through turbulent

conditions produces erratic needle movements. The apparent

lag in airspeed indications with pitch changes varies greatly

among different airplanes and is due to the time required for

the airplane to accelerate or decelerate when the pitch attitude

is changed. There is no appreciable lag due to the construction

or operation of the instrument. Small pitch changes, smoothly

executed, result in an immediate change of airspeed.

When using the VSI as a rate instrument and combining it

with the altimeter and attitude indicator to maintain level

ﬂ ight, a pilot should know that the amount the altimeter

needle moves from the desired altitude governs the rate which

should be used to return to that altitude. A rule of thumb is

to make an attitude change that will result in a vertical-speed

rate approximately double the error in altitude. For example,

if altitude is off by 100 feet, the rate of return to the desired

altitude should be approximately 200 feet per minute (fpm).

If it is off by more than 100 feet, the correction should

be correspondingly greater, but should never exceed the

optimum rate of climb or descent for the airplane at a given

airspeed and conﬁ guration.

A deviation of more than 200 fpm from the desired rate

of return is considered overcontrolling. For example, if

attempting to change altitude by 200 feet, a rate in excess of

400 fpm indicates overcontrolling.

When returning to an altitude, the VSI is the primary pitch

instrument. Occasionally, the VSI is slightly out of calibration

and may indicate a climb or descent when the airplane is in

level ﬂ ight. If the instrument cannot be adjusted, take the

error into consideration when using it for pitch control. For

5-6

Figure 5-13. Constant Power Plus Constant Pitch Equals Constant

Speed.

Figure 5-14. Constant Power Plus Decreased Pitch Equals

Increased Airspeed.

Figure 5-15. Constant Power Plus Increased Pitch Equals

Decreased Airspeed.

Constant Airspeed Constant Pitch

Increased Airspeed Decreased Pitch

Decreased Airspeed Increased Pitch

example, if the needle indicates a descent of 200 fpm while

in level ﬂ ight, use this indication as the zero position.

Airspeed Indicator (ASI)

The ASI presents an indirect indication of the pitch attitude.

In non-turbulent conditions with a constant power setting and

pitch attitude, airspeed remains constant. [Figure 5-13] As the

pitch attitude lowers, airspeed increases, and the nose should

be raised. [Figure 5-14] As the pitch attitude rises, airspeed

decreases, and the nose should be lowered. [Figure 5-15] A

rapid change in airspeed indicates a large pitch change, and

a slow change of airspeed indicates a small pitch change.

Pitch control in level ﬂ ight is a question of cross-check and

interpretation of the instrument panel for the instrument

information that enables a pilot to visualize and control pitch

attitude. Regardless of individual differences in cross-check

technique, all pilots should use the instruments that give the

best information for controlling the airplane in any given

maneuver. Pilots should also check the other instruments

to aid in maintaining the primary instruments at the desired

indication.

As noted previously, the primary instrument is the one

that gives the most pertinent information for a particular

maneuver. It is usually the one that should be held at a

constant indication. Which instrument is primary for pitch

control in level ﬂ ight, for example? This question should

be considered in the context of speciﬁ c airplane, weather

conditions, pilot experience, operational conditions, and other

factors. Attitude changes must be detected and interpreted

instantly for immediate control action in high-performance

airplanes. On the other hand, a reasonably proficient

instrument pilot in a slower airplane may rely more on the

altimeter for primary pitch information, especially if it is

determined that too much reliance on the attitude indicator

fails to provide the necessary precise attitude information.

Whether the pilot decides to regard the altimeter or the

attitude indicator as primary depends on which approach will

best help control the attitude. In this handbook, the altimeter

is normally considered as the primary pitch instrument during

level ﬂ ight.

Bank Control

The bank attitude of an airplane is the angle between the

airplane’s wings and the natural horizon. To maintain a

straight-and-level ﬂ ight path, the wings of the airplane are

kept level with the horizon (assuming the airplane is in

coordinated ﬂ ight). The instruments used for bank control

are the attitude indicator, the heading indicator, and the

turn coordinator. Figure 5-16 illustrates coordinated ﬂ ight.

The aircraft is banked left with the attitude indicator and

turn coordinator indicating the bank. The heading indicator

indicates a left turn by apparent clockwise rotation of the

compass card behind the airplane silhouette.

Attitude Indicator

The attitude indicator shows any change in bank attitude

directly and instantly and is, therefore, a direct indicator. On

the standard attitude indicator, the angle of bank is shown

pictorially by the relationship of the miniature aircraft to the

artiﬁ cial horizon bar, and by the alignment of the pointer with

the banking scale at the top of the instrument. On the face of

the standard three-inch instrument, small angles of bank can

be difﬁ cult to detect by reference to the miniature aircraft,

especially if leaning to one side or changing a seating position

5-7

Figure 5-16. Instruments Used for Bank Control.

Figure 5-17. Bank Interpretation with the Attitude Indicator.

slightly. The position of the scale pointer is a good check

against the apparent miniature aircraft position. Disregarding

precession error, small deviations from straight coordinated

ﬂ ight can be readily detected on the scale pointer. The

banking index may be graduated as shown in Figure 5-17,

or it may be graduated in 30° increments.

The instrument depicted in Figure 5-17 has a scale pointer

that moves in the same direction of bank shown by the

miniature aircraft. In this case, the aircraft is in a left 15°

bank. Precession errors in this instrument are common

and predictable, but the obvious advantage of the attitude

indicator is an immediate indication of both pitch attitude

and bank attitude in a single glance. Even with the precession

errors associated with many attitude indicators, the quick

attitude presentation requires less visual effort and time for

positive control than other ﬂ ight instruments.

Heading Indicator

The bank attitude of an aircraft in coordinated ﬂ ight is shown

indirectly on the heading indicator, since banking results in

a turn and change in heading. Assuming the same airspeed

in both instances, a rapid movement of the heading indicator

(azimuth card in a directional gyro) indicates a large angle

of bank, whereas slow movement reﬂ ects a small angle of

bank. Note the rate of movement of the heading indicator

and compare it to the attitude indicator’s degrees of bank.

The attitude indicator’s precession error makes a precise

check of heading information necessary in order to maintain

straight ﬂ ight.

When deviations from straight ﬂ ight are noted on the heading

indicator, correct to the desired heading using a bank angle no

greater than the number of degrees to be turned. In any case,

limit bank corrections to a bank angle no greater than that

required for a standard rate turn. Use of larger bank angles

requires a very high level of proﬁ ciency, and normally results

in overcontrolling and erratic bank control.

Turn Coordinator

The miniature aircraft of the turn coordinator gives an indirect

indication of the bank attitude of the airplane. When the

miniature aircraft is level, the airplane is in straight ﬂ ight.

When the miniature airplane is aligned with one of the

alignment marks and the aircraft is rolling to the left or right

the indication represents the roll rate, with the alignment

marks indicating a roll of 3° per second in the direction of

the miniature aircraft. This can be seen in level ﬂ ight when

a bank is introduced either to the left or the right. The turn

coordinator’s indicator will indicate the rolling motion

although there is no turn being made. Conversely, a pedal

input to the right or left causes the aircraft to turn momentarily

about its vertical axis (with no rolling motion) with an

indication of turn on the turn coordinator. After the turn

becomes stabilized and the aircraft is no longer rolling, the

turn coordinator displays the rate of turn with the alignment

marks equaling a turn of 3° per second. The turn coordinator

is able to display both roll and turn parameters because its

electrically powered gyroscope is canted at an angle. As a

result, the turn-and-slip indicator provides both roll and turn

indications. Autopilots in general aviation today use this

instrument in determining both roll and turn information.

After the completion of a turn, return to straight ﬂ ight is

accomplished by coordinated aileron and rudder pressure to

5-8

Figure 5-18. Skid Indication.

Figure 5-19. Slip Indication.

level the miniature aircraft. Include the miniature aircraft in

the cross-check and correct for even the smallest deviations

from the desired position. When this instrument is used to

maintain straight ﬂ ight, control pressures must be applied

very lightly and smoothly.

The ball of the turn coordinator is actually a separate

instrument, conveniently located under the miniature aircraft

because the two instruments are used together. The ball

instrument indicates the quality of the turn. If the ball is off

center, the airplane is slipping or skidding. That is, if the

coordinator’s miniature airplane is tilted right and the ball is

displaced to the right, the aircraft is in a skid. [Figure 5-18] If

however, the miniature airplane is tilted to the right with the

ball off-center to the left, the aircraft is in a slip. [Figure 5-19]

If the wings are level and the airplane is properly trimmed,

the ball will remain in the center, and the airplane will be

in straight ﬂ ight. If the ball is not centered, the airplane is

improperly trimmed.

To maintain straight-and-level ﬂ ight with proper trim, note

the direction of ball displacement. If the ball is to the left of

center and the left wing is low, apply left rudder pressure

to center the ball and correct the slip. At the same time

apply right aileron pressure as necessary to level the wings,

cross-checking the heading indicator and attitude indicator

while centering the ball. If the wings are level and the ball is

displaced from the center, the airplane is skidding. Note the

direction of ball displacement, and use the same corrective

technique as for an indicated slip. Center the ball (left ball/left

rudder, right ball/right rudder), use aileron as necessary for

bank control, and retrim.

To trim the airplane using only the turn coordinator, use

aileron pressure to level the miniature aircraft and rudder

pressure to center the ball. Hold these indications with control

pressures, gradually releasing them while applying rudder

trim sufﬁ cient to relieve all rudder pressure. Apply aileron

trim, if available, to relieve aileron pressure. With a full

instrument panel, maintain a wings level attitude by reference

to all available instruments while trimming the airplane.

Turn-and-Slip Indicator (Needle and Ball)

Unlike the turn coordinator that provides three indications

(roll, turn, and trim), the turn-and-slip indicator provides

two: turn-rate and trim. Although the turn-and-slip indicator

needle provides an indication of turn only, it provides an

indirect indication of aircraft attitude when used with roll

indicators such as a heading indicator or magnetic compass.

As with the turn coordinator (after stabilizing from a roll),

when the turn-and-slip indicator’s needle is aligned with the

alignment marks the aircraft is in a standard turn of 3° per

second or 360° in 2 minutes.

The ball of the turn-and-bank indicator provides important

trim in the same manner that the ball in the turn coordinator

does. Figures 5-18 and 5-19 provide a comparison of the

two instruments.

Power Control

Power produces thrust which, with the appropriate angle of

attack of the wing, overcomes the forces of gravity, drag,

and inertia to determine airplane performance.

Power control must be related to its effect on altitude and

airspeed, since any change in power setting results in a change

in the airspeed or the altitude of the airplane. At any given

airspeed, the power setting determines whether the airplane

is in level ﬂ ight, in a climb, or in a descent. If the power is

increased in straight-and-level ﬂ ight and the airspeed held

constant, the airplane climbs. If power is decreased while

the airspeed is held constant, the airplane descends. On the

other hand, if altitude is held constant, the power applied will

determine the airspeed.

The relationship between altitude and airspeed determines the

need for a change in pitch or power. If the airspeed is not the

desired value, always check the altimeter before deciding that

a power change is necessary. Think of altitude and airspeed

as interchangeable; altitude can be traded for airspeed by

lowering the nose, or convert airspeed to altitude by raising

the nose. If altitude is higher than desired and airspeed is

5-9

Figure 5-20. Airspeed Low and Altitude High—Lower Pitch.

Figure 5-21. Airspeed and Altitude High—Lower Pitch and Reduce Power.

low, or vice versa, a change in pitch alone may return the

airplane to the desired altitude and airspeed. [Figure 5-20] If

both airspeed and altitude are high or if both are low, then a

change in both pitch and power is necessary in order to return

to the desired airspeed and altitude. [Figure 5-21]

For changes in airspeed in straight-and-level ﬂ ight, pitch,

bank, and power must be coordinated in order to maintain

constant altitude and heading. When power is changed to

vary airspeed in straight-and-level ﬂ ight, a single-engine,

propeller-driven airplane tends to change attitude around all

axes of movement. Therefore, to maintain constant altitude

and heading, apply various control pressures in proportion

to the change in power. When power is added to increase

airspeed, the pitch instruments indicate a climb unless

forward elevator control pressure is applied as the airspeed

changes. With an increase in power, the airplane tends to

yaw and roll to the left unless counteracting aileron and

rudder pressures are applied. Keeping ahead of these changes

requires increasing cross-check speed, which varies with the

type of airplane and its torque characteristics, the extent of

power and speed change involved.

Power Settings

Power control and airspeed changes are much easier when

approximate power settings necessary to maintain various

airspeeds in straight-and-level ﬂ ight are known in advance.

However, to change airspeed by any appreciable amount, the

common procedure is to underpower or overpower on initial

power changes to accelerate the rate of airspeed change.

(For small speed changes, or in airplanes that decelerate or

accelerate rapidly, overpowering or underpowering is not

necessary.)

Consider the example of an airplane that requires 23"

mercury (Hg) of manifold pressure to maintain a normal

cruising airspeed of 120 knots, and 18" Hg of manifold

pressure to maintain an airspeed of 100 knots. The reduction

in airspeed from 120 knots to 100 knots while maintaining

straight-and-level ﬂ ight is discussed below and illustrated in

Figures 5-22, 5-23, and 5-24.

Instrument indications, prior to the power reduction, are

shown in Figure 5-22. The basic attitude is established and

maintained on the attitude indicator. The speciﬁ c pitch,

bank, and power control requirements are detected on these

primary instruments:

Altimeter—Primary Pitch

Heading Indicator—Primary Bank

Airspeed Indicator—Primary Power

Supporting pitch-and-bank instruments are shown in

Figure 5-23. Note that the supporting power instrument is

the manifold pressure gauge (or tachometer if the propeller

is ﬁ xed pitch). However, when a smooth power reduction to

approximately 15" Hg (underpower) is made, the manifold

pressure gauge becomes the primary power instrument.

[Figure 5-23] With practice, power setting can be changed

with only a brief glance at the power instrument, by sensing

5-10

Figure 5-22. Straight-and-Level Flight (Normal Cruising Speed).

Figure 5-23. Straight-and-Level Flight (Airspeed Decreasing).

5-11

Figure 5-24. Straight-and-Level Flight (Reduced Airspeed Stabilized).

the movement of the throttle, the change in sound, and the

changes in the feel of control pressures.

As thrust decreases, increase the speed of the cross-check

and be ready to apply left rudder, back-elevator, and aileron

control pressure the instant the pitch-and-bank instruments

show a deviation from altitude and heading. As proﬁ ciency

is obtained, a pilot learns to cross-check, interpret, and

control the changes with no deviation of heading and altitude.

Assuming smooth air and ideal control technique, as airspeed

decreases, a proportionate increase in airplane pitch attitude

is required to maintain altitude. Similarly, effective torque

control means counteracting yaw with rudder pressure.

As the power is reduced, the altimeter is primary for pitch,

the heading indicator is primary for bank, and the manifold

pressure gauge is momentarily primary for power (at 15"

Hg in this example). Control pressures should be trimmed

off as the airplane decelerates. As the airspeed approaches

the desired airspeed of 100 knots, the manifold pressure

is adjusted to approximately 18" Hg and becomes the

supporting power instrument. The ASI again becomes

primary for power. [Figure 5-24]

Airspeed Changes in Straight-and-Level Flight

Practice of airspeed changes in straight-and-level ﬂ ight provides

an excellent means of developing increased proﬁ ciency in all

three basic instrument skills, and brings out some common

errors to be expected during training in straight-and-level ﬂ ight.

Having learned to control the airplane in a clean conﬁ guration

(minimum drag conditions), increase proﬁ ciency in cross-

check and control by practicing speed changes while extending

or retracting the ﬂ aps and landing gear. While practicing, be

sure to comply with the airspeed limitations speciﬁ ed in the

POH/AFM for gear and ﬂ ap operation.

Sudden and exaggerated attitude changes may be necessary

in order to maintain straight-and-level ﬂ ight as the landing

gear is extended and the ﬂ aps are lowered in some airplanes.

The nose tends to pitch down with gear extension, and when

ﬂ aps are lowered, lift increases momentarily (at partial ﬂ ap

settings) followed by a marked increase in drag as the ﬂ aps

near maximum extension.

Control technique varies according to the lift and drag

characteristics of each airplane. Accordingly, knowledge of

the power settings and trim changes associated with different

combinations of airspeed, gear and ﬂ ap conﬁ gurations will

reduce instrument cross-check and interpretation problems.

For example, assume that in straight-and-level flight

instruments indicate 120 knots with power at 23" Hg/2,300

revolutions per minute (rpm), gear and flaps up. After

reduction in airspeed, with gear and ﬂ aps fully extended,

straight-and-level ﬂ ight at the same altitude requires 25"

Hg manifold pressure/2,500 rpm. Maximum gear extension

speed is 115 knots; maximum ﬂ ap extension speed is 105

5-12

knots. Airspeed reduction to 95 knots, gear and ﬂ aps down,

can be made in the following manner:

1. Maintain rpm at 2,500, since a high power setting will

be used in full drag conﬁ guration.

2. Reduce manifold pressure to 10" Hg. As the airspeed

decreases, increase cross-check speed.

3. Make trim adjustments for an increased angle of attack

and decrease in torque.

4. Lower the gear at 115 knots. The nose may tend to

pitch down and the rate of deceleration increases.

Increase pitch attitude to maintain constant altitude,

and trim off some of the back-elevator pressures.

If full ﬂ aps are lowered at 105 knots, cross-check,

interpretation, and control must be very rapid. A

simpler technique is to stabilize attitude with gear

down before lowering the ﬂ aps.

5. Since 18" Hg manifold pressure will hold level

flight at 100 knots with the gear down, increase

power smoothly to that setting until the ASI shows

approximately 105 knots, and retrim. The attitude

indicator now shows approximately two-and-a-half

bar width nose-high in straight-and-level ﬂ ight.

6. Actuate the ﬂ ap control and simultaneously increase

power to the predetermined setting (25" Hg) for the

desired airspeed, and trim off the pressures necessary

to hold constant altitude and heading. The attitude

indicator now shows a bar width nose-low in straight-

and-level ﬂ ight at 95 knots.

Proﬁ ciency in straight-and-level ﬂ ight is attained when a

pilot can consistently maintain constant altitude and heading

with smooth pitch, bank, power, and trim control during the

pronounced changes in aircraft attitude.

Trim Technique

Proper trim technique is essential for smooth and precise

aircraft control during all phases of ﬂ ight. By relieving all

control pressures, it is much easier to hold a given attitude

constant, and devote more attention to other ﬂ ight deck

duties.

An aircraft is trimmed by applying control pressures to

establish a desired attitude, then adjusting the trim so the

aircraft will maintain that attitude when the ﬂ ight controls are

released. Trim the aircraft for coordinated ﬂ ight by centering

the ball of the turn-and-slip indicator, by using rudder trim in

the direction the ball is displaced from the center. Differential

power control on multiengine aircraft is an additional factor

affecting coordinated ﬂ ight. Use balanced power or thrust,

when possible, to aid in maintaining coordinated ﬂ ight.

Changes in attitude, power, or conﬁ guration will require a

trim adjustment in most cases. Using trim alone to establish

a change in aircraft attitude invariably leads to erratic aircraft

control. Smooth and precise attitude changes are best attained

by a combination of control pressures and trim adjustments.

Therefore, when used correctly, trim adjustment is an aid to

smooth aircraft control.

Common Errors in Straight-and-Level Flight

Pitch

Pitch errors usually result from the following faults:

1. Improper adjustment of the attitude indicator’s

miniature aircraft to the wings level attitude.

Following the initial level off from a climb, check the

attitude indicator and make any necessary adjustment

in the miniature aircraft for level ﬂ ight indication at

normal cruise airspeed.

2. Insufﬁ cient cross-check and interpretation of pitch

instruments. For example, the airspeed indication is

low. The pilot, believing a nose-high attitude exists,

applies forward pressure without noting that a low

power setting is the cause of the airspeed discrepancy.

Increase cross-check speed to include all relevant

instrument indications before making a control input.

3. Uncaging the attitude indicator (if caging feature is

present) when the airplane is not in level ﬂ ight. The

altimeter and heading indicator must be stabilized with

airspeed indication at normal cruise before pulling

out the caging knob, to obtain correct indications in

straight-and-level ﬂ ight at normal cruise airspeed.

4. Failure to interpret the attitude indicator in terms of

the existing airspeed.

5. Late pitch corrections. Pilots commonly like to leave

well enough alone. When the altimeter indicates a 20

foot error, there is a reluctance to correct it, perhaps

because of fear of overcontrolling. If overcontrolling

is the anticipated error, practice small corrections and

ﬁ nd the cause of overcontrolling. If any deviation is

tolerated, errors will increase.

6. Chasing the vertical speed indications. This tendency

can be corrected by proper cross-check of other

pitch instruments, as well as by increasing overall

understanding of instrument characteristics.

7. Using excessive pitch corrections for the altimeter

evaluation. Rushing a pitch correction by making a

large pitch change usually aggravates the existing

error, saving neither time nor effort.

5-13

8. Failure to maintain established pitch corrections, a

common error associated with cross-check and trim

errors. For example, having established a pitch change

to correct an altitude error, there is a tendency to

slow down the cross-check, waiting for the airplane

to stabilize in the new pitch attitude. To maintain

the attitude, continue to cross-check and trim off the

pressures.

9. Fixations during cross-check. After initiating a

heading correction, for example, there is a tendency

to become preoccupied with bank control and miss

errors in pitch attitude. Likewise, during an airspeed

change, unnecessary gazing at the power instrument

is common. A small error in power setting is of less

consequence than large altitude and heading errors.

The airplane will not decelerate any faster by staring

at the manifold pressure gauge.

Heading

Heading errors usually result from the following faults:

1. Failure to cross-check the heading indicator, especially

during changes in power or pitch attitude.

2. Misinterpretation of changes in heading, with resulting

corrections in the wrong direction.

3. Failure to note and remember a preselected heading.

4. Failure to observe the rate of heading change and its

relation to bank attitude.

5. Overcontrolling in response to heading changes,

especially during changes in power settings.

6. Anticipating heading changes with premature

application of rudder control.

7. Failure to correct small heading deviations. Unless

zero error in heading is the goal, a pilot will tolerate

larger and larger deviations. Correction of a 1° error

takes a lot less time and concentration than correction

of a 20° error.

8. Correcting with improper bank attitude. If correcting

a 10° heading error with 20° of bank, the airplane

will roll past the desired heading before the bank

is established, requiring another correction in the

opposite direction. Do not multiply existing errors

with errors in corrective technique.

9. Failure to note the cause of a previous heading error

and thus repeating the same error. For example, the

airplane is out of trim, with a left wing low tendency.

Repeated corrections for a slight left turn are made,

yet trim is ignored.

10. Failure to set the heading indicator properly or failure

to uncage it.

Power

Power errors usually result from the following faults:

1. Failure to know the power settings and pitch attitudes

appropriate to various airspeeds and airplane

conﬁ gurations.

2. Abrupt use of throttle.

3. Failure to lead the airspeed when making power

changes. For example, during airspeed reduction in

level ﬂ ight, especially with gear and ﬂ aps extended,

adjust the throttle to maintain the slower speed before

the airspeed actually reaches the desired speed.

Otherwise, the airplane will decelerate to a speed

lower than that desired, resulting in additional power

adjustments. The amount of lead depends upon how

fast the airplane responds to power changes.

4. Fixation on airspeed or manifold pressure instruments

during airspeed changes, resulting in erratic control

of both airspeed and power.

Trim

Trim errors usually result from the following faults:

1. Improper adjustment of seat or rudder pedals for

comfortable position of legs and feet. Tension in the

ankles makes it difﬁ cult to relax rudder pressures.

2. Confusion about the operation of trim devices, which

differ among various airplane types. Some trim wheels

are aligned appropriately with the airplane’s axes;

others are not. Some rotate in a direction contrary to

what is expected.

3. Faulty sequence in trim technique. Trim should be

used not as a substitute for control with the wheel

(stick) and rudders, but to relieve pressures already

held to stabilize attitude. As proﬁ ciency is gained,

little conscious effort will be required to trim off the

pressures as they occur.

4. Excessive trim control. This induces control pressures

that must be held until the airplane is trimmed

properly. Use trim frequently and in small amounts.

5. Failure to understand the cause of trim changes. Lack

of understanding the basic aerodynamics related to

basic instrument skills will cause a pilot to continually

lag behind the airplane.

5-14

Figure 5-25. Climb Entry for Constant Airspeed Climb.

Straight Climbs and Descents

Climbs

For a given power setting and load condition, there is only

one attitude that will give the most efﬁ cient rate of climb.

The airspeed and climb power setting that will determine this

climb attitude are given in the performance data found in the

POH/AFM. Details of the technique for entering a climb vary

according to airspeed on entry and the type of climb (constant

airspeed or constant rate) desired. (Heading and trim control

are maintained as discussed in Straight-and-Level Flight.)

Entry

To enter a constant-airspeed climb from cruising airspeed,

raise the miniature aircraft to the approximate nose-high

indication for the predetermined climb speed. The attitude

will vary according to the type of airplane. Apply light back-

elevator pressure to initiate and maintain the climb attitude.

The pressures will vary as the airplane decelerates. Power

may be advanced to the climb power setting simultaneously

with the pitch change, or after the pitch change is established

and the airspeed approaches climb speed. If the transition

from level ﬂ ight to climb is smooth, the VSI will show an

immediate trend upward, continue to move slowly, and

then stop at a rate appropriate to the stabilized airspeed and

attitude. (Primary and supporting instruments for the climb

entry are shown in Figure 5-25.)

Once the airplane stabilizes at a constant airspeed and attitude,

the ASI is primary for pitch and the heading indicator remains

primary for bank. [Figure 5-26] Monitor the tachometer or

manifold pressure gauge as the primary power instrument to

ensure the proper climb power setting is being maintained. If

the climb attitude is correct for the power setting selected, the

airspeed will stabilize at the desired speed. If the airspeed is

low or high, make an appropriately small pitch correction.

To enter a constant airspeed climb, ﬁ rst complete the airspeed

reduction from cruise airspeed to climb speed in straight-

and-level ﬂ ight. The climb entry is then identical to entry

from cruising airspeed, except that power must be increased

simultaneously to the climb setting as the pitch attitude is

increased. Climb entries on partial panel are more easily

and accurately controlled if entering the maneuver from

climbing speed.

The technique for entering a constant rate climb is very

similar to that used for entry to a constant-airspeed climb

from climb airspeed. As the power is increased to the

approximate setting for the desired rate, simultaneously

raise the miniature aircraft to the climbing attitude for the

desired airspeed and rate of climb. As the power is increased,

the ASI is primary for pitch control until the vertical speed

approaches the desired value. As the vertical speed needle

stabilizes, it becomes primary for pitch control and the ASI

becomes primary for power control. [Figure 5-27]

5-15

Figure 5-26. Stabilized Climb at Constant Airspeed.

Figure 5-27. Stabilized Climb at Constant Rate.

5-16

Figure 5-28. Airspeed Low and Vertical Speed High—Reduce Pitch.

Pitch and power corrections must be promptly and closely

coordinated. For example, if the vertical speed is correct, but

the airspeed is low, add power. As the power is increased,

the miniature aircraft must be lowered slightly to maintain

constant vertical speed. If the vertical speed is high and the

airspeed is low, lower the miniature aircraft slightly and note

the increase in airspeed to determine whether or not a power

change is also necessary. [Figure 5-28] Familiarity with the

approximate power settings helps to keep pitch and power

corrections at a minimum.

Leveling Off

To level off from a climb and maintain an altitude, it is

necessary to start the level off before reaching the desired

altitude. The amount of lead varies with rate of climb and

pilot technique. If the airplane is climbing at 1,000 fpm, it will

continue to climb at a decreasing rate throughout the transition

to level ﬂ ight. An effective practice is to lead the altitude by

10 percent of the vertical speed shown (500 fpm/ 50-foot lead,

1,000 fpm/100-foot lead).

To level off at cruising airspeed, apply smooth, steady

forward-elevator pressure toward level ﬂ ight attitude for the

speed desired. As the attitude indicator shows the pitch change,

the vertical speed needle will move slowly toward zero, the

altimeter needle will move more slowly, and the airspeed will

show acceleration. [Figure 5-29] When the altimeter, attitude

indicator, and VSI show level ﬂ ight, constant changes in

pitch and torque control will have to be made as the airspeed

increases. As the airspeed approaches cruising speed, reduce

power to the cruise setting. The amount of lead depends upon

the rate of acceleration of the airplane.

To level off at climbing airspeed, lower the nose to the pitch

attitude appropriate to that airspeed in level ﬂ ight. Power

is simultaneously reduced to the setting for that airspeed

as the pitch attitude is lowered. If power reduction is at a

rate proportionate to the pitch change, airspeed will remain

constant.

Descents

A descent can be made at a variety of airspeeds and attitudes

by reducing power, adding drag, and lowering the nose

to a predetermined attitude. The airspeed will eventually

stabilize at a constant value. Meanwhile, the only ﬂ ight

instrument providing a positive attitude reference, is the

attitude indicator. Without the attitude indicator (such as

during a partial panel descent), the ASI, the altimeter, and

the VSI will show varying rates of change until the airplane

decelerates to a constant airspeed at a constant attitude.

During the transition, changes in control pressure and trim,

as well as cross-check and interpretation, must be accurate

to maintain positive control.

5-17

Figure 5-29. Level Off at Cruising Speed.

Entry

The following method for entering descents is effective

with or without an attitude indicator. First, reduce airspeed

to a selected descent airspeed while maintaining straight-

and-level ﬂ ight, then make a further reduction in power

(to a predetermined setting). As the power is adjusted,

simultaneously lower the nose to maintain constant airspeed,

and trim off control pressures.

During a constant airspeed descent, any deviation from the

desired airspeed calls for a pitch adjustment. For a constant

rate descent, the entry is the same, but the VSI is primary for

pitch control (after it stabilizes near the desired rate), and the

ASI is primary for power control. Pitch and power must be

closely coordinated when corrections are made, as they are

in climbs. [Figure 5-30]

Leveling Off

The level off from a descent must be started before reaching

the desired altitude. The amount of lead depends upon the

rate of descent and control technique. With too little lead, the

airplane will tend to overshoot the selected altitude unless

technique is rapid. Assuming a 500 fpm rate of descent, lead

the altitude by 100–150 feet for a level off at an airspeed

higher than descending speed. At the lead point, add power to

the appropriate level ﬂ ight cruise setting. [Figure 5-31] Since

the nose will tend to rise as the airspeed increases, hold

forward elevator pressure to maintain the vertical speed at

the descending rate until approximately 50 feet above the

altitude, and then smoothly adjust the pitch attitude to the

level ﬂ ight attitude for the airspeed selected.

To level off from a descent at descent airspeed, lead the desired

altitude by approximately 50 feet, simultaneously adjusting

the pitch attitude to level ﬂ ight and adding power to a setting

that will hold the airspeed constant. [Figure 5-32] Trim off

the control pressures and continue with the normal straight-

and-level ﬂ ight cross-check.

Common Errors in Straight Climbs and Descents

Common errors result from the following faults:

1. Overcontrolling pitch on climb entry. Until the pitch

attitudes related to speciﬁ c power settings used in

climbs and descents are known, larger than necessary

pitch adjustments are made. One of the most difﬁ cult

habits to acquire during instrument training is to

restrain the impulse to disturb a ﬂ ight attitude until

the result is known. Overcome the inclination to

make a large control movement for a pitch change,

and learn to apply small control pressures smoothly,

cross-checking rapidly for the results of the change,

and continuing with the pressures as instruments show

the desired results. Small pitch changes can be easily

controlled, stopped, and corrected; large changes are

more difﬁ cult to control.

5-18

Figure 5-31. Level Off Airspeed Higher Than Descent Airspeed.

Figure 5-30. Constant Airspeed Descent, Airspeed High—Reduce Power.

5-19

Figure 5-32. Level Off at Descent Airspeed.

2. Failure to vary the rate of cross-check during speed,

power, or attitude changes or climb or descent

entries.

3. Failure to maintain a new pitch attitude. For example,

raising the nose to the correct climb attitude, and as

the airspeed decreases, either overcontrol and further

increase the pitch attitude, or allow the nose to lower. As

control pressures change with airspeed changes, cross-

check must be increased and pressures readjusted.

4. Failure to trim off pressures. Unless the airplane is

trimmed, there will be difﬁ culty in determining whether

control pressure changes are induced by aerodynamic

changes or by the pilot’s own movements.

5. Failure to learn and use proper power settings.

6. Failure to cross-check both airspeed and vertical speed

before making pitch or power adjustments.

7. Improper pitch and power coordination on slow-speed

level offs, due to slow cross-check of airspeed and

altimeter indications.

8. Failure to cross-check the VSI against the other pitch

control instruments, resulting in chasing the vertical

speed.

9. Failure to note the rate of climb or descent to determine

the lead for level offs, resulting in overshooting or

undershooting the desired altitude.

10. Ballooning (allowing the nose to pitch up) on level

offs from descents, resulting from failure to maintain

descending attitude with forward-elevator pressure as

power is increased to the level ﬂ ight cruise setting.

11. Failure to recognize the approaching straight-and-level

ﬂ ight indications as level off is completed. Maintain

an accelerated cross-check until positively established

in straight-and-level ﬂ ight.

Turns

Standard Rate Turns

A standard rate turn is one in which the pilot will do a

complete 360° circle in two minutes, or 3° per second. A

standard rate turn, although always 3° per second, will

require higher angles of bank as airspeed increases. To enter a

standard rate level turn, apply coordinated aileron and rudder

pressures in the desired direction of turn. Pilots commonly

roll into turns at a much too rapid rate. During initial training

in turns, base control pressures on the rate of cross-check

and interpretation. Maneuvering an airplane faster than

the capability to keep up with the changes in instrument

indications only creates the need to make corrections.

A rule of thumb to determine the approximate angle of bank

required for a standard rate turn is to use 15 percent of the

true airspeed. A simple way to determine this amount is to

5-20

Figure 5-33. Standard Rate Turn, Constant Airspeed.

divide the airspeed by 10 and add one-half the result. For

example, at 100 knots, approximately 15° of bank is required

(100 ÷ 10 = 10 + 5 = 15); at 120 knots, approximately 18°

of bank is needed for a standard rate turn.

On the roll-in, use the attitude indicator to establish

the approximate angle of bank, and then check the turn

coordinator’s miniature aircraft for a standard rate turn

indication or the aircraft’s turn-and-bank indicator. Maintain

the bank for this rate of turn, using the turn coordinator’s

miniature aircraft as the primary bank reference and the

attitude indicator as the supporting bank instrument.

[Figure 5-33] Note the exact angle of bank shown on

the banking scale of the attitude indicator when the turn

coordinator indicates a standard rate turn.

During the roll-in, check the altimeter, VSI, and attitude

indicator for the necessary pitch adjustments as the vertical

lift component decreases with an increase in bank. If constant

airspeed is to be maintained, the ASI becomes primary for

power, and the throttle must be adjusted as drag increases. As

the bank is established, trim off the pressures applied during

pitch and power changes.

To recover to straight-and-level ﬂ ight, apply coordinated

aileron and rudder pressures opposite to the direction of the

turn. Strive for the same rate of roll-out used to roll into the

turn; fewer problems will be encountered in estimating the

lead necessary for roll-out on exact headings, especially on

partial panel maneuvers. Upon initiation of the turn recovery,

the attitude indicator becomes the primary bank instrument.

When the airplane is approximately level, the heading

indicator is the primary bank instrument as in straight-and-

level ﬂ ight. Pitch, power, and trim adjustments are made as

changes in vertical lift component and airspeed occur. The

ball should be checked throughout the turn, especially if

control pressures are held rather than trimmed off.

Some airplanes are very stable during turns, requiring only

slight trim adjustments that permit hands-off ﬂ ight while the

airplane remains in the established attitude. Other airplanes

require constant, rapid cross-check and control during turns to

correct overbanking tendencies. Due to the interrelationship

of pitch, bank, and airspeed deviations during turns, cross-

check must be fast in order to prevent an accumulation of

errors.

Turns to Predetermined Headings

As long as an airplane is in a coordinated bank, it continues

to turn. Thus, the roll-out to a desired heading must be started

before the heading is reached. The amount of lead varies with

the relationship between the rate of turn, angle of bank, and

rate of recovery. For small heading changes, use a bank angle

that does not exceed the number of degrees to be turned.

Lead the desired heading by one-half the number of degrees

of bank used. For example, if a 10° bank is used during a

change in heading, start the roll-out 5° before reaching the

desired heading. For larger changes in heading, the amount

5-21

Figure 5-34. Turn Coordinator Calibration.

of lead varies since the angle of bank for a standard rate turn

varies with the true airspeed.

Practice with a lead of one-half the angle of bank until the

precise lead a given technique requires is determined. If

rates of roll-in and roll-out are consistent, the precise amount

of lead suitable to a particular roll-out technique can be

determined.

Timed Turns

A timed turn is a turn in which the clock and the turn

coordinator are used to change heading by a speciﬁ c number

of degrees in a given time. For example, in a standard rate turn

(3° per second), an airplane turns 45° in 15 seconds; in a half

standard rate turn, the airplane turns 45° in 30 seconds.

Prior to performing timed turns, the turn coordinator should

be calibrated to determine the accuracy of its indications.

[Figure 5-34] Establish a standard rate turn as indicated by

the turn coordinator, and as the sweep-second hand of the

clock passes a cardinal point (12, 3, 6, 9), check the heading

on the heading indicator. While holding the indicated rate

of turn constant, note the indicated heading changes at 10

second intervals. If the airplane turns more than or less than

30° in that interval, a respectively larger or smaller deﬂ ection

of the miniature aircraft of the turn coordinator is necessary

to produce a standard rate turn. After calibrating the turn

coordinator during turns in each direction, note the corrected

deﬂ ections, if any, and apply them during all timed turns.

The same cross-check and control technique is used in making

a timed turn that is used to execute turns to predetermined

headings, except the clock is substituted for the heading

indicator. The miniature aircraft of the turn coordinator is

primary for bank control, the altimeter is primary for pitch

control, and the ASI is primary for power control. Start the

roll-in when the clock’s second hand passes a cardinal point,

hold the turn at the calibrated standard rate indication (or

half-standard rate for small heading changes), and begin the

roll-out when the computed number of seconds has elapsed.

If the rates of roll-in and roll-out are the same, the time taken

during entry and recovery does not need to be considered in

the time computation.

Practice timed turns with a full instrument panel and check

the heading indicator for the accuracy of turns. If the turns are

executed without the gyro heading indicator, use the magnetic

compass at the completion of the turn to check turn accuracy,

taking compass deviation errors into consideration.

Compass Turns

In most small airplanes, the magnetic compass is the only

direction-indicating instrument independent of other airplane

instruments and power sources. Because of its operating

characteristics, called compass errors, pilots are prone to

use it only as a reference for setting the heading indicator,

but knowledge of magnetic compass characteristics permits

full use of the instrument to turn the airplane to correct and

maintain headings.

5-22

Figure 5-35. North and South Turn Error.

Remember the following points when making turns to

magnetic compass headings or when using the magnetic

compass as a reference for setting the heading indicator:

1. If on a north heading and a turn is started to the east

or west, the compass indication lags, or indicates a

turn in the opposite direction.

2. If on a south heading and a turn is started toward the

east or west, the compass indication precedes the turn,

indicating a greater amount of turn than is actually

occurring.

3. When on an east or west heading, the compass

indicates correctly when starting a turn in either

direction.

4. If on an east or west heading, acceleration results in

a north turn indication; deceleration results in a south

turn indication.

5. When maintaining a north or south heading, no error

results from diving, climbing, or changing airspeed.

With an angle of bank between 15° and 18°, the amount of

lead or lag to be used when turning to northerly or southerly

headings varies with, and is approximately equal to, the

latitude of the locality over which the turn is being made.

When turning to a heading of north, the lead for roll-out must

include the number of degrees of change of latitude, plus the

lead normally used in recovery from turns. During a turn to

a south heading, maintain the turn until the compass passes

south the number of degrees of latitude, minus normal roll-

out lead. [Figure 5-35]

For example, when turning from an easterly direction to

north, where the latitude is 30°, start the roll-out when the

compass reads 37° (30° plus one-half the 15° angle of bank,

or whatever amount is appropriate for the rate of roll-out).

When turning from an easterly direction to south, start the

roll-out when the magnetic compass reads 203° (180° plus

30° minus one-half the angle of bank). When making similar

turns from a westerly direction, the appropriate points at

which to begin the roll-out would be 323° for a turn to north,

and 157° for a turn to south.

When turning to a heading of east or west from a northerly

direction, start the roll-out approximately 10° to 12° before

the east or west indication is reached. When turning to an

east or west heading from a southerly direction, start the

rollout approximately 5° before the east or west indication

is reached. When turning to other headings, the lead or lag

must be interpolated.

Abrupt changes in attitude or airspeed and the resulting erratic

movements of the compass card make accurate interpretations

of the instrument very difﬁ cult. Proﬁ ciency in compass turns

depends on knowledge of compass characteristics, smooth

control technique, and accurate bank-and-pitch control.

Steep Turns

For purposes of instrument ﬂ ight training in conventional

airplanes, any turn greater than a standard rate is considered

steep. [Figure 5-36] The exact angle of bank at which a

normal turn becomes steep is unimportant. What is important

is learning to control the airplane with bank attitudes in

excess of those normally used on instruments. Practicing

steep turns will not only increase proﬁ ciency in the basic

instrument ﬂ ying skills, but also enable smooth, quick, and

conﬁ dent reactions to unexpected abnormal ﬂ ight attitudes

under instrument ﬂ ight conditions.

Pronounced changes occur in the effects of aerodynamic

forces on aircraft control at progressively greater bank

attitudes. Skill in cross-check, interpretation, and control is

increasingly necessary in proportion to the amount of these

changes, though the techniques for entering, maintaining, and

recovering from the turn are the same in principle for steep

turns as for shallower turns.

Enter a steep turn in the same way as a shallower turn, but

prepare to cross-check rapidly as the turn steepens. Because

of the greatly reduced vertical lift component, pitch control

is usually the most difﬁ cult aspect of this maneuver. Unless

5-23

Figure 5-36. Steep Left Turn.

Figure 5-37. Diving Spiral.

for pitch changes, smooth, steady back elevator pressure

will maintain constant altitude. However, overbanking

to excessively steep angles without adjusting pitch as the

bank changes occur, requires increasingly stronger elevator

pressure. The loss of vertical lift and increase in wing loading

ﬁ nally reach a point at which further application of back-

elevator pressure tightens the turn without raising the nose.

How does a pilot recognize overbanking and low pitch

attitude? What should a pilot do to correct them? If a rapid

downward movement of the altimeter needle or vertical speed

needle, together with an increase in airspeed, is observed

despite application of back elevator pressure, the airplane is in

a diving spiral. [Figure 5-37] Immediately shallow the bank

with smooth and coordinated aileron and rudder pressures,

hold or slightly relax elevator pressure, and increase the cross-

check of the attitude indicator, altimeter, and VSI. Reduce

power if the airspeed increase is rapid. When the vertical

speed trends upward, the altimeter needle will move slower

as the vertical lift increases. When the elevator is effective in

raising the nose, hold the bank attitude shown on the attitude

indicator and adjust elevator control pressures smoothly for

the nose-high attitude appropriate to the bank maintained.

If pitch control is consistently late on entries to steep turns,

rollout immediately to straight-and-level ﬂ ight and analyze

possible errors. Practice shallower turns initially and learn the

attitude changes and control responses required, then increase

the banks as a quicker and more accurate cross-check and

control techniques are developed.

The power necessary to maintain constant airspeed increases

as the bank and drag increase. With practice, the power

immediately noted and corrected with a pitch increase, the

loss of vertical lift results in rapid movement of the altimeter,

vertical speed, and airspeed needles. The faster the rate of

bank change, the more suddenly the lift changes occur. If

a cross-check is fast enough to note the immediate need

5-24

Figure 5-38. Change of Airspeed During Turn.

settings appropriate to speciﬁ c bank attitudes are learned, and

adjustments can be made without undue attention to airspeed

and power instruments. During training in steep turns, as in

any other maneuver, attend to the most important tasks ﬁ rst.

Keep the pitch attitude relatively constant, and more time can

be devoted to cross-check and instrument interpretation.

During recovery from steep turns to straight-and-level

ﬂ ight, elevator and power control must be coordinated with

bank control in proportion to the changes in aerodynamic

forces. Back elevator pressures must be released and power

decreased. The common errors associated with steep turns are

the same as those discussed later in this section. Remember,

errors are more exaggerated, more difﬁ cult to correct, and

more difﬁ cult to analyze unless rates of entry and recovery

are consistent with the level of proﬁ ciency in the three basic

instrument ﬂ ying skills.

Climbing and Descending Turns

To execute climbing and descending turns, combine the

technique used in straight climbs and descents with the various

turn techniques. The aerodynamic factors affecting lift and

power control must be considered in determining power

settings, and the rate of cross-check and interpretation must be

increased to enable control of bank as well as pitch changes.

Change of Airspeed During Turns

Changing airspeed during turns is an effective maneuver

for increasing proficiency in all three basic instrument

skills. Since the maneuver involves simultaneous changes

in all components of control, proper execution requires

rapid cross-check and interpretation as well as smooth

control. Proﬁ ciency in the maneuver will also contribute

to conﬁ dence in the instruments during attitude and power

changes involved in more complex maneuvers. Pitch and

power control techniques are the same as those used during

changes in airspeed in straight-and-level ﬂ ight.

The angle of bank necessary for a given rate of turn is

proportional to the true airspeed. Since the turns are executed

at a standard rate, the angle of bank must be varied in direct

proportion to the airspeed change in order to maintain a

constant rate of turn. During a reduction of airspeed, decrease

the angle of bank and increase the pitch attitude to maintain

altitude and a standard rate turn.

The altimeter and turn coordinator indications should remain

constant throughout the turn. The altimeter is primary for

pitch control and the miniature aircraft of the turn coordinator

is primary for bank control. The manifold pressure gauge (or

tachometer) is primary for power control while the airspeed

is changing. As the airspeed approaches the new indication,

the ASI becomes primary for power control.

Two methods of changing airspeed in turns may be used. In the

ﬁ rst method, airspeed is changed after the turn is established.

[Figure 5-38] In the second method, the airspeed change is

initiated simultaneously with the turn entry. The ﬁ rst method

is easier, but regardless of the method used, the rate of cross-

check must be increased as power is reduced. As the airplane

decelerates, check the altimeter and VSI for necessary pitch

changes and the bank instruments for required bank changes.

If the miniature aircraft of the turn coordinator indicates a

deviation from the desired deﬂ ection, adjust the bank. Adjust

5-25

pitch attitude to maintain altitude. When approaching the

desired airspeed, pitch attitude becomes primary for power

control and the manifold pressure gauge (or tachometer) is

adjusted to maintain the desired airspeed. Trim is important

throughout the maneuver to relieve control pressures.

Until control technique is very smooth, frequent cross-check

of the attitude indicator is essential to prevent overcontrolling

and to provide approximate bank angles appropriate to the

changing airspeeds.

Common Errors in Turns

Pitch

Pitch errors result from the following faults:

1. Preoccupation with bank control during turn entry

and recovery. If 5 seconds are required to roll into a

turn, check the pitch instruments as bank pressures

are initiated. If bank control pressure and rate of bank

change are consistent, a sense of the time required

for an attitude change will be developed. During the

interval, check pitch, power, and trim—as well as

bank—controlling the total attitude instead of one

factor at a time.

2. Failure to understand or remember the need for

changing the pitch attitude as the vertical lift

component changes, resulting in consistent loss of

altitude during entries.

3. Changing the pitch attitude before it is necessary. This

fault is very likely if a cross-check is slow and rate

of entry too rapid. The error occurs during the turn

entry due to a mechanical and premature application

of back-elevator control pressure.

4. Overcontrolling the pitch changes. This fault

commonly occurs with the previous error.

5. Failure to properly adjust the pitch attitude as the

vertical lift component increases during the roll-out,

resulting in consistent gain in altitude on recovery to

headings.

6. Failure to trim during turn entry and following turn

recovery (if turn is prolonged).

7. Failure to maintain straight-and-level cross-check

after roll-out. This error commonly follows a perfectly

executed turn.

8. Erratic rates of bank change on entry and recovery,

resulting from failure to cross-check the pitch

instruments with a consistent technique appropriate

to the changes in lift.

Bank

Bank and heading errors result from the following faults:

1. Overcontrolling, resulting in overbanking upon turn

entry, overshooting and undershooting headings, as

well as aggravated pitch, airspeed, and trim errors.

2. Fixation on a single bank instrument. On a 90° change

of heading, for example, leave the heading indicator

out of the cross-check for approximately 20 seconds

after establishing a standard rate turn, since at 3°

per second the turn will not approach the lead point

until that time has elapsed. Make the cross-check

selective, checking only what needs to be checked at

the appropriate time.

3. Failure to check for precession of the horizon bar

following recovery from a turn. If the heading

indicator shows a change in heading when the attitude

indicator shows level ﬂ ight, the airplane is turning. If

the ball is centered, the attitude gyro has precessed;

if the ball is not centered, the airplane may be in a

slipping or skidding turn. Center the ball with rudder

pressure, check the attitude indicator and heading

indicator, stop the heading change if it continues, and

retrim.

4. Failure to use the proper degree of bank for the amount

of heading change desired. Rolling into a 20° bank

for a heading change of 10° will normally overshoot

the heading. Use the bank attitude appropriate to the

amount of heading change desired.

5. Failure to remember the heading to which the aircraft

is being turned. This fault is likely when rushing the

maneuver.

6. Turning in the wrong direction, due to misreading or

misinterpreting the heading indicator, or to confusion

regarding the location of points on the compass. Turn

in the shortest direction to reach a given heading,

unless there is a speciﬁ c reason to turn the long way

around. Study the compass rose and visualize at least

the positions of the eight major points around the

azimuth. A number of methods can be used to make

quick computations for heading changes. For example,

to turn from a heading of 305° to a heading of 110°,

would a pilot turn right or left for the shortest way

around? Subtracting 200 from 305 and adding 20,

gives 125° as the reciprocal of 305°; therefore, execute

the turn to the right. Likewise, to ﬁ gure the reciprocal

of a heading less than 180°, add 200 and subtract 20.

Computations are done more quickly using multiples

of 100s and 10s than by adding or subtracting 180°

from the actual heading; therefore, the method

suggested above may save time and confusion.

5-26

7. Failure to check the ball of the turn coordinator when

interpreting the instrument for bank information. If the

roll rate is reduced to zero, the miniature aircraft of

the turn coordinator indicates only direction and rate

of turn. Unless the ball is centered, do not assume the

turn is resulting from a banked attitude.

Power

Power and airspeed errors result from the following faults:

1. Failure to cross-check the ASI as pitch changes are

made.

2. Erratic use of power control. This may be due to

improper throttle friction control, inaccurate throttle

settings, chasing the airspeed readings, abrupt or

overcontrolled pitch-and-bank changes, or failure

to recheck the airspeed to note the effect of a power

adjustment.

3. Poor coordination of throttle control with pitch-and-

bank changes, associated with slow cross-check or

failure to understand the aerodynamic factors related

to turns.

Trim

Trim errors result from the following faults:

1. Failure to recognize the need for a trim change due

to slow cross-check and interpretation. For example,

a turn entry at a rate too rapid for a cross-check leads

to confusion in cross-check and interpretation, with

resulting tension on the controls.

2. Failure to understand the relationship between trim

and attitude/power changes.

3. Chasing the vertical speed needle. Overcontrolling

leads to tension and prevents sensing the pressures to

be trimmed off.

4. Failure to trim following power changes.

Errors During Compass Turns

In addition to the faults discussed above, the following errors

connected with compass turns should be noted:

1. Faulty understanding or computation of lead and

lag.

2. Fixation on the compass during the roll-out. Until

the airplane is in straight-and-level unaccelerated

ﬂ ight, it is unnecessary to read the indicated heading.

Accordingly, after the roll-out, cross-check for

straight-and-level ﬂ ight before checking the accuracy

of the turn.

Approach to Stall

Practicing approach to stall recoveries in various airplane

conﬁ gurations should build conﬁ dence in a pilot’s ability to

control the airplane in unexpected situations. Approach to

stall should be practiced from straight ﬂ ight and from shallow

banks. The objective is to practice recognition and recovery

from the approach to a stall.

Prior to stall recovery practice, select a safe altitude above

the terrain, an area free of conﬂ icting air trafﬁ c, appropriate

weather, and the availability of radar traffic advisory

service.

Approaches to stalls are accomplished in the following

conﬁ gurations:

1. Takeoff conﬁ guration—should begin from level ﬂ ight

near liftoff speed. Power should be applied while

simultaneously increasing the angle of attack to induce

an indication of a stall.

2. Clean conﬁ guration—should begin from a reduced

airspeed, such as pattern airspeed, in level ﬂ ight.

Power should be applied while simultaneously

increasing the angle of attack to induce an indication

of a stall.

3. Approach or landing configuration—should be

initiated at the appropriate approach or landing

airspeed. The angle of attack should be smoothly

increased to induce an indication of a stall.

Recoveries should be prompt in response to a stall warning

device or an aerodynamic indication by smoothly reducing

the angle of attack and applying maximum power, or as

recommended by the POH/AFM. The recovery should be

completed without an excessive loss of altitude, and on a

predetermined heading, altitude, and airspeed.

Unusual Attitudes and Recoveries

An unusual attitude is an airplane attitude not normally

required for instrument flight. Unusual attitudes may

result from a number of conditions, such as turbulence,

disorientation, instrument failure, confusion, preoccupation

with flight deck duties, carelessness in cross-checking,

errors in instrument interpretation, or lack of proﬁ ciency in

aircraft control. Since unusual attitudes are not intentional

maneuvers during instrument ﬂ ight, except in training, they

are often unexpected, and the reaction of an inexperienced

or inadequately trained pilot to an unexpected abnormal

ﬂ ight attitude is usually instinctive rather than intelligent

5-27

Figure 5-39. Unusual Attitude—Nose-High.

and deliberate. This individual reacts with abrupt muscular

effort, which is purposeless and even hazardous in turbulent

conditions, at excessive speeds, or at low altitudes. However,

with practice, the techniques for rapid and safe recovery from

unusual attitudes can be mastered.

When an unusual attitude is noted during the cross-check,

the immediate problem is not how the airplane got there, but

what it is doing and how to get it back to straight-and-level

ﬂ ight as quickly as possible.

Recognizing Unusual Attitudes

As a general rule, any time an instrument rate of movement

or indication other than those associated with the basic

instrument ﬂ ight maneuvers is noted, assume an unusual

attitude and increase the speed of cross-check to conﬁ rm the

attitude, instrument error, or instrument malfunction.

Nose-high attitudes are shown by the rate and direction of

movement of the altimeter needle, vertical speed needle, and

airspeed needle, as well as the immediately recognizable

indication of the attitude indicator (except in extreme

attitudes). [Figure 5-39] Nose-low attitudes are shown

by the same instruments, but in the opposite direction.

[Figure 5-40]

Recovery from Unusual Attitudes

In moderate unusual attitudes, the pilot can normally

reorient by establishing a level ﬂ ight indication on the

attitude indicator. However, the pilot should not depend on

this instrument if the attitude indicator is the spillable type,

because its upset limits may have been exceeded or it may

have become inoperative due to mechanical malfunction.

If it is the nonspillable-type instrument and is operating

properly, errors up to 5° of pitch-and-bank may result and its

indications are very difﬁ cult to interpret in extreme attitudes.

As soon as the unusual attitude is detected, the recommended

recovery procedures stated in the POH/AFM should be

initiated. If there are no recommended procedures stated in

the POH/AFM, the recovery should be initiated by reference

to the ASI, altimeter, VSI, and turn coordinator.

Nose-High Attitudes

If the airspeed is decreasing, or below the desired airspeed,

increase power (as necessary in proportion to the observed

deceleration), apply forward elevator pressure to lower the

nose and prevent a stall, and correct the bank by applying

coordinated aileron and rudder pressure to level the

miniature aircraft and center the ball of the turn coordinator.

The corrective control applications are made almost

simultaneously, but in the sequence given above. A level

pitch attitude is indicated by the reversal and stabilization

5-28

Figure 5-40. Unusual Attitude—Nose-Low.

of the ASI and altimeter needles. Straight coordinated ﬂ ight

is indicated by the level miniature aircraft and centered ball

of the turn coordinator.

Nose-Low Attitudes

If the airspeed is increasing, or is above the desired airspeed,

reduce power to prevent excessive airspeed and loss of

altitude. Correct the bank attitude with coordinated aileron

and rudder pressure to straight ﬂ ight by referring to the turn

coordinator. Raise the nose to level ﬂ ight attitude by applying

smooth back elevator pressure. All components of control

should be changed simultaneously for a smooth, proﬁ cient

recovery. However, during initial training a positive,

conﬁ dent recovery should be made by the numbers, in the

sequence given above. A very important point to remember

is that the instinctive reaction to a nose-down attitude is to

pull back on the elevator control.

After initial control has been applied, continue with a

fast cross-check for possible overcontrolling, since the

necessary initial control pressures may be large. As the rate

of movement of altimeter and ASI needles decreases, the

attitude is approaching level ﬂ ight. When the needles stop

and reverse direction, the aircraft is passing through level

ﬂ ight. As the indications of the ASI, altimeter, and turn

coordinator stabilize, incorporate the attitude indicator into

the cross-check.

The attitude indicator and turn coordinator should be checked

to determine bank attitude and then corrective aileron

and rudder pressures should be applied. The ball should

be centered. If it is not, skidding and slipping sensations

can easily aggravate disorientation and retard recovery. If

entering the unusual attitude from an assigned altitude (either

by an instructor or by air trafﬁ c control (ATC) if operating

under instrument ﬂ ight rules (IFR)), return to the original

altitude after stabilizing in straight-and-level ﬂ ight.

Common Errors in Unusual Attitudes

Common errors associated with unusual attitudes include

the following faults:

1. Failure to keep the airplane properly trimmed. A ﬂ ight

deck interruption when holding pressures can easily

lead to inadvertent entry into unusual attitudes.

2 Disorganized ﬂ ight deck. Hunting for charts, logs,

computers, etc., can seriously distract attention from

the instruments.

3. Slow cross-check and ﬁ xations. The impulse is to

stop and stare when noting an instrument discrepancy

unless a pilot has trained enough to develop the skill

required for immediate recognition.

5-29

4. Attempting to recover by sensory sensations other than

sight. The discussion of disorientation in Chapter 1,

Human Factors, indicates the importance of trusting

the instruments.

5. Failure to practice basic instrument skills. All of the

errors noted in connection with basic instrument skills

are aggravated during unusual attitude recoveries until

the elementary skills have been mastered.

Instrument Takeoff

Competency in instrument takeoffs will provide the

proficiency and confidence necessary for use of flight

instruments during departures under conditions of low

visibility, rain, low ceilings, or disorientation at night. A

sudden rapid transition from “visual” to “instrument” ﬂ ight

can result in serious disorientation and control problems.

Instrument takeoff techniques vary with different types of

airplanes, but the method described below is applicable

whether the airplane is single- or multiengine; tricycle gear

or conventional gear.

Align the airplane with the centerline of the runway with

the nosewheel or tailwheel straight. Lock the tailwheel, if so

equipped, and hold the brakes ﬁ rmly to avoid creeping while

preparing for takeoff. Set the heading indicator with the nose

index on the 5° mark nearest the published runway heading

to allow instant detection of slight changes in heading during

the takeoff. Make certain that the instrument is uncaged (if it

has a caging feature) by rotating the knob after uncaging and

checking for constant heading indication. If using an electric

heading indicator with a rotatable needle, rotate the needle

so that it points to the nose position, under the top index.

Advance the throttle to an rpm that will provide partial rudder

control. Release the brakes, advancing the power smoothly

to takeoff setting.

During the takeoff roll, hold the heading constant on the

heading indicator by using the rudder. In multiengine,

propeller-driven airplanes, also use differential throttle to

maintain direction. The use of brakes should be avoided,

except as a last resort, as it usually results in overcontrolling

and extending the takeoff roll. Once the brakes are released,

any deviation in heading must be corrected instantly.

As the airplane accelerates, cross-check both heading

indicator and ASI rapidly. The attitude indicator may precess

to a slight nose-up attitude. As ﬂ ying speed is approached

(approximately 15–25 knots below takeoff speed), smoothly

apply elevator control for the desired takeoff attitude on the

attitude indicator. This is approximately a two bar width

climb indication for most small airplanes.

Continue with a rapid cross-check of heading indicator and

attitude indicator as the airplane leaves the ground. Do not

pull it off; let it ﬂ y off while holding the selected attitude

constant. Maintain pitch-and-bank control by referencing

the attitude indicator, and make coordinated corrections in

heading when indicated on the heading indicator. Cross-

check the altimeter and VSI for a positive rate of climb

(steady clockwise rotation of the altimeter needle, and the VSI

showing a stable rate of climb appropriate to the airplane).

When the altimeter shows a safe altitude (approximately 100

feet), raise the landing gear and ﬂ aps, maintaining attitude by

referencing the attitude indicator. Because of control pressure

changes during gear and ﬂ ap operation, overcontrolling is

likely unless the pilot notes pitch indications accurately and

quickly. Trim off control pressures necessary to hold the

stable climb attitude. Check the altimeter, VSI, and airspeed

for a smooth acceleration to the predetermined climb speed

(altimeter and airspeed increasing, vertical speed stable). At

climb speed, reduce power to climb setting (unless full power

is recommended for climb by the POH/AFM and trim).

Throughout the instrument takeoff, cross-check and

interpretation must be rapid, and control positive and smooth.

During liftoff, gear and ﬂ ap retraction, power reduction, and

the changing control reactions demand rapid cross-check,

adjustment of control pressures, and accurate trim changes.

Common Errors in Instrument Takeoffs

Common errors during the instrument takeoff include the

following:

1. Failure to perform an adequate ﬂ ight deck check

before the takeoff. Pilots have attempted instrument

takeoffs with inoperative airspeed indicators (pitot

tube obstructed), gyros caged, controls locked,

and numerous other oversights due to haste or

carelessness.

2. Improper alignment on the runway. This may result

from improper brake application, allowing the airplane

to creep after alignment, or from alignment with the

nosewheel or tailwheel cocked. In any case, the result

is a built-in directional control problem as the takeoff

starts.

3. Improper application of power. Abrupt application

of power complicates directional control. Add power

with a smooth, uninterrupted motion.

4. Improper use of brakes. Incorrect seat or rudder pedal

adjustment, with feet in an uncomfortable position,

frequently cause inadvertent application of brakes and

excessive heading changes.

5-30

Figure 5-41. Racetrack Pattern (Entire Pattern in Level Flight).

5. Overcontrolling rudder pedals. This fault may be

caused by late recognition of heading changes, tension

on the controls, misinterpretation of the heading

indicator (and correcting in the wrong direction),

failure to appreciate changing effectiveness of rudder

control as the aircraft accelerates, and other factors. If

heading changes are observed and corrected instantly

with small movement of the rudder pedals, swerving

tendencies can be reduced.

6. Failure to maintain attitude after becoming airborne.

If the pilot reacts to seat-of-the-pants sensations when

the airplane lifts off, pitch control is guesswork.

The pilot may either allow excessive pitch or apply

excessive forward elevator pressure, depending on the

reaction to trim changes.

7. Inadequate cross-check. Fixations are likely during trim

changes, attitude changes, gear and ﬂ ap retractions,

and power changes. Once an instrument or a control

input is applied, continue the cross-check and note the

effect during the next cross-check sequence.

8. Inadequate interpretation of instruments. Failure to

understand instrument indications immediately indicates

that further study of the maneuver is necessary.

Basic Instrument Flight Patterns

Flight patterns are basic maneuvers, ﬂ own by sole reference

to the instruments rather than outside visual clues, for the

purpose of practicing basic attitude ﬂ ying. The patterns

simulate maneuvers encountered on instrument flights

such as holding patterns, procedure turns, and approaches.

After attaining a reasonable degree of proﬁ ciency in basic

maneuvers, apply these skills to the various combinations of

individual maneuvers. The following practice ﬂ ight patterns

are directly applicable to operational instrument ﬂ ying.

Racetrack Pattern

1. Time 3 minutes straight-and-level ﬂ ight from A to B.

[Figure 5-41] During this interval, reduce airspeed to

the holding speed appropriate for the aircraft.

2. Start a 180° standard rate turn to the right at B. Roll-out

at C on the reciprocal of the heading originally used

at A.

3. Time a 1 minute straight-and-level ﬂ ight from C to D.

4. Start a 180° standard rate turn to the right at D, rolling-

out on the original heading.

5. Fly 1 minute on the original heading, adjusting

the outbound leg so that the inbound segment is 1

minute.

NOTE: This pattern is an exercise combining use of the clock

with basic maneuvers.

Procedure Turn

A procedure turn is a maneuver that facilitates:

• A reversal in ﬂ ight direction.

• A descent from an initial approach ﬁ x or assigned

altitude to a permissible altitude (usually the procedure

turn altitude).

• An interception of the inbound course at a sufﬁ cient

distance allowing the aircraft to become aligned with

the ﬁ nal approach.

Procedure turn types include the 45° turn, the 80/260 turn, and

the teardrop turn. All of these turns are normally conducted no

more than 10 nautical miles (NM) from the primary airport.

The procedure turn altitude generally provides a minimum

of 1,000' obstacle clearance in the procedure turn area (not

necessarily within the 10 NM arc around the primary airport).

Turns may have to be increased or decreased but should not

exceed 30° of a bank angle.

Standard 45° Procedure Turn

1. Start timing at point A (usually identiﬁ ed on approach

procedures by a ﬁ x). For example, ﬂ y outbound on a

heading of 360° for a given time (2 minutes, in this

example). [Figure 5-42]

2. After ﬂ ying outbound for 2 minutes (point B), turn left

45° to a heading of 315° using a standard rate turn.

After roll-out and stabilizing, ﬂ y this new heading

of 315° for 40 seconds and the aircraft will be at the

approximate position of C.

5-31

Figure 5-42. Standard Procedure Turn (Entire Pattern in Level

Flight).

Figure 5-43. 80/260 Procedure Turn (Entire Pattern in Level

Flight). Figure 5-44. Teardrop Pattern (Entire Pattern in Level Flight).

3. At point C, turn 225° right (using a standard rate turn)

which will provide a heading of 180°. The timing is

such that in a no wind environment, the pilot will be

aligned with the ﬁ nal approach course of 180° at D.

Wind conditions, however must be considered during

the execution of the procedure turn. Compensating

for wind may result in changes to outbound time,

procedure turn heading and/or time and minor changes

in the inbound turn.

80/260 Procedure Turn

1. Start timing at point A (usually identiﬁ ed on approach

procedures by a ﬁ x). For example, ﬂ y outbound on a

heading of 360° for 2 minutes. [Figure 5-43]

2. At B, enter a left standard rate turn of 80° to a heading

of 280°.

3. At the completion of the 80° turn to 280° (Point C),

immediately turn right 260°, rolling-out on a heading

of 180° (Point D) and also the reciprocal of the entry

heading.

Teardrop Patterns

There are three typical teardrop procedure turns. A 30°, 20°,

and a 10° teardrop pattern. The below steps indicate actions

for all three starting on a heading of 360°. [Figure 5-44]

1. At point B (after stabilizing on the outbound course)

turn left:

• 30° to a heading of 330° and time for 1 minute

• 20° to a heading of 340° and time for 2 minutes

• 10° to a heading of 350° and time for 3 minutes

2. After the appropriate time above (Point C), make a

standard rate turn to the right for:

• 30° teardrop—210° to the ﬁ nal course heading

of 180° (Point D)

• 20° teardrop—200° to the ﬁ nal course heading

of 180° (Point D)

• 10° teardrop—190° to the ﬁ nal course heading

of 180° (Point D)

By using the different teardrop patterns, a pilot is afforded the

ability to manage time more efﬁ ciently. For instance, a 10°

pattern for 3 minutes provides about three times the distance

5-32

Figure 5-45. Circling Approach Pattern I (Imaginary Runway).

Figure 5-46. Circling Approach Pattern II (Imaginary Runway).

(and time) than a 30° pattern. Pattern selection should be

based upon an individual assessment of the procedure turn

requirements to include wind, complexity, the individual

preparedness, etc.

Circling Approach Patterns

Pattern I

1. At A, start timing for 2 minutes from A to B; reduce

airspeed to approach speed. [Figure 5-45]

2. At B, make a standard rate turn to the left for 45°.

3. At the completion of the turn, time for 45 seconds to

4. At C, turn to the original heading; ﬂ y 1 minute to D,

lowering the landing gear and ﬂ aps.

5. At D, turn right 180°, rolling-out at E on the reciprocal

of the entry heading.

6. At E, enter a 500 fpm rate descent. At the end of a 500

foot descent, enter a straight constant-airspeed climb,

retracting gear and ﬂ aps.

Pattern II

Steps:

1. At A, start timing for 2 minutes from A to B; reduce

airspeed to approach speed. [Figure 5-46]

2. At B, make a standard rate turn to the left for 45°.

3. At the completion of the turn, time for 1 minute to

4. At C, turn right for 180° to D; ﬂ y for 1-1/2 minutes

to E, lowering the landing gear and ﬂ aps.

5. At E, turn right for 180°, rolling-out at F.

6. At F, enter a 500 fpm rate descent. At the end of a 500

foot descent, enter a straight constant-airspeed climb,

retracting gear and ﬂ aps.

5-33

Introduction

The previous chapters have laid the foundation for instrument

ﬂ ying. The pilot’s ability to use and interpret the information

displayed and apply corrective action is required to maneuver

the aircraft and maintain safe ﬂ ight. A pilot must recognize

that each aircraft make and model ﬂ own may require a

different technique. Aircraft weight, speed, and conﬁ guration

changes require the pilot to vary his or her technique in order

to perform successful attitude instrument ﬂ ying. A pilot must

become familiar with all sections of the Pilot’s Operating

Handbook/Airplane Flight Manual (POH/AFM) prior to

performing any ﬂ ight maneuver.

Chapter 5–II describes basic attitude instrument flight

maneuvers and explains how to perform each one by

interpreting the indications presented on the electronic

ﬂ ight display (EFD). In addition to normal ﬂ ight maneuvers,

“partial panel” ﬂ ight will be addressed. With the exception of

the instrument takeoff, all ﬂ ight maneuvers can be performed

on “partial panel” with the Attitude Heading Reference

System (AHRS) unit simulated or rendered inoperative.

Airplane Basic

Flight Maneuvers

Chapter 5, Section II

Using an Electronic Flight Display

5-34

Figure 5-47. Pitch Attitude and Airspeed in Level Flight, Slow

Cruise Speed.

Figure 5-48. Pitch Attitude Decreasing and Airspeed Increasing—Indicates Need to Increase Pitch.

Straight-and-Level Flight

Pitch Control

The pitch attitude of an airplane is the angle between the

longitudinal axis of the airplane and the actual horizon.

In level ﬂ ight, the pitch attitude varies with airspeed and

load. For training purposes, the latter factor can normally

be disregarded in small airplanes. At a constant airspeed,

there is only one speciﬁ c pitch attitude for level ﬂ ight. At

slow cruise speeds, the level ﬂ ight attitude is nose-high with

indications as in Figure 5-47; at fast cruise speeds, the level

ﬂ ight attitude is nose-low. [Figure 5-48] Figure 5-49 shows

the indications for the attitude at normal cruise speeds.

The instruments that directly or indirectly indicate pitch on

the Primary Flight Display (PFD) are the attitude indicator,

altimeter, vertical speed indicator (VSI), airspeed indicator

(ASI), and both airspeed and altitude trend indicators.

Attitude Indicator

The attitude indicator gives the pilot a direct indication of

the pitch attitude. The increased size of the attitude display

on the EFD system greatly increases situational awareness

for the pilot. Most attitude indicators span the entire width

of the PFD screen.

The aircraft pitch attitude is controlled by changing the

deﬂ ection of the elevator. As the pilot pulls back on the

control yoke causing the elevator to rise, the yellow chevron

will begin to show a displacement up from the artiﬁ cial

horizon line. This is caused by the AHRS unit sensing the

changing angle between the longitudinal plane of the earth

and the longitudinal axis of the aircraft.

The attitude indicator displayed on the PFD screen is a

representation of outside visual cues. Rather than rely on

the natural horizon visible during visual ﬂ ight rules (VFR)

ﬂ ight, the pilot must rely on the artiﬁ cial horizon of the

PFD screen.

During normal cruise airspeed, the point of the yellow

chevron (aircraft symbol) will be positioned on the artiﬁ cial

horizon. Unlike conventional attitude indicators, the EFD

attitude indicator does not allow for manipulating the position

of the chevron in relationship to the artiﬁ cial horizon. The

position is ﬁ xed and therefore will always display the pitch

angle as calculated by the AHRS unit.

5-35

Figure 5-49. Various Pitch Attitudes (Right), Aircraft Shown in

Level Flight.

Figure 5-50. Pitch Indications for Various Attitudes (1° through 5°). Figure 5-51. Pitch Illustrated at 10°.

The attitude indicator only shows pitch attitude and does

not indicate altitude. A pilot should not attempt to maintain

level ﬂ ight using the attitude indicator alone. It is important

for the pilot to understand how small displacements both up

and down can affect the altitude of the aircraft. To achieve

this, the pilot should practice increasing the pitch attitude

incrementally to become familiar with how each degree of

pitch changes the altitude. [Figures 5-50 and 5-51] In both

cases, the aircraft will slow and gain altitude.

The full height of the chevron is approximately 5° and

provides an accurate reference for pitch adjustment. It is

imperative that the pilot make the desired changes to pitch

by referencing the attitude indicator and then trimming off

any excess control pressures. Relieving these pressures will

allow for a more stabilized ﬂ ight and will reduce pilot work

load. Once the aircraft is trimmed for level ﬂ ight, the pilot

must smoothly and precisely manipulate the elevator control

forces in order to change the pitch attitude.

To master the ability to smoothly control the elevator, a pilot

must develop a very light touch on the control yoke. The

thumb and two ﬁ ngers are normally sufﬁ cient to move the

control yoke. The pilot should avoid griping the yoke with

a full ﬁ st. When a pilot grips the yoke with a full ﬁ st, there

is a tendency to apply excess pressures, thus changing the

aircraft attitude.

Practice making smooth, small pitch changes both up and

down until precise corrections can be made. With practice

a pilot will be able to make pitch changes in 1° increments,

smoothly controlling the attitude of the aircraft.

The last step in mastering elevator control is trim. Trimming

the aircraft to relieve any control pressures is essential

for smooth attitude instrument ﬂ ight. To accomplish this,

momentarily release the control yoke. Note which way the

aircraft pitch attitude wants to move. Grasp the control yoke

again and then reapply the pressure to return the attitude

to the previous position. Apply trim in the direction of the

control pressure. Small applications of trim will make large

changes in the pitch attitude. Be patient and make multiple

changes to trim, if necessary.

Once the aircraft is in trim, relax on the control yoke as

much as practicable. When pressure is held on the yoke,

unconscious pressures are applied to the elevator and ailerons

which displaces the aircraft from its desired ﬂ ight path. If the

aircraft is in trim, in calm, non-turbulent air, a pilot should be

able to release the control yoke and maintain level ﬂ ight for

extended periods of time. This is one of the hardest skills to

learn prior to successfully ﬂ ying in instrument meteorological

conditions (IMC).

5-36

Altimeter

At constant power, any deviation from level ﬂ ight (except

in turbulent air) must be the result of a pitch change. If the

power is constant, the altimeter gives an indirect indication

of the pitch attitude in level ﬂ ight. Since the altitude should

remain constant when the airplane is in level ﬂ ight, any

deviation from the desired altitude signals the need for a

pitch change. For example, if the aircraft is gaining altitude,

the nose must be lowered.

In the PFD, as the pitch starts to change, the altitude trend

indicator on the altitude tape will begin to show a change

in the direction of displacement. The rate at which the trend

indicator grows and the altimeter numbers change aids the

pilot in determining how much of a pitch change is necessary

to stop the trend.

As a pilot becomes familiar with a specific aircraft’s

instruments, he or she learns to correlate pitch changes,

altimeter tapes, and altitude trend indicators. By adding the

altitude tape display and the altitude trend indicator into the

scan along with the attitude indicator, a pilot starts to develop

the instrument cross-check.

Partial Panel Flight

One important skill to practice is partial panel ﬂ ight by

referencing the altimeter as the primary pitch indicator.

Practice controlling the pitch by referencing the altitude

tape and trend indicator alone without the use of the attitude

indicator. Pilots need to learn to make corrections to altitude

deviations by referencing the rate of change of the altitude

tape and trend indicator. When operating in IMC and in a

partial panel conﬁ guration, the pilot should avoid abrupt

changes to the control yoke. Reacting abruptly to altitude

changes can lead to large pitch changes and thus a larger

divergence from the initial altitude.

When a pilot is controlling pitch by the altitude tape and

altitude trend indicators alone, it is possible to overcontrol the

aircraft by making a larger than necessary pitch correction.

Overcontrolling will cause the pilot to move from a nose-

high attitude to a nose-low attitude and vice versa. Small

changes to pitch are required to insure prompt corrective

actions are taken to return the aircraft to its original altitude

with less confusion.

When an altitude deviation occurs, two actions need to be

accomplished. First, make a smooth control input to stop

the needle movement. Once the altitude tape has stopped

moving, make a change to the pitch attitude to start back to

the entry altitude.

During instrument ﬂ ight with limited instrumentation, it is

imperative that only small and precise control inputs are

made. Once a needle movement is indicated denoting a

deviation in altitude, the pilot needs to make small control

inputs to stop the deviation. Rapid control movements will

only compound the deviation by causing an oscillation effect.

This type of oscillation can quickly cause the pilot to become

disoriented and begin to ﬁ xate on the altitude. Fixation on

the altimeter can lead to a loss of directional control as well

as airspeed control.

As a general rule of thumb, for altitude deviations less than

100 feet, utilize a pitch change of 1°, which equates to 1/5 of

the thickness of the chevron. Small incremental pitch changes

will allow the performance to be evaluated and will eliminate

overcontrolling of the aircraft.

Instrumentation needs to be utilized collectively, but

failures will occur which leave the pilot with only limited

instrumentation. That is why partial panel ﬂ ying training

is important. If the pilot understands how to utilize each

instrument independently, no signiﬁ cant change is encountered

in carrying out the ﬂ ight when other instruments fail.

VSI Tape

The VSI tape provides for an indirect indication of pitch

attitude and gives the pilot a more immediate indication of a

pending altitude deviation. In addition to trend information,

the vertical speed also gives a rate indication. By using the

VSI tape in conjunction with the altitude trend tape, a pilot

will have a better understanding of how much of a correction

needs to be made. With practice, the pilot will learn the

performance of a particular aircraft and know how much

pitch change is required in order to correct for a speciﬁ c

rate indication.

Unlike older analog VSIs, new glass panel displays have

instantaneous VSIs. Older units had a lag designed into the

system that was utilized to indicate rate information. The

new glass panel displays utilize a digital air data computer

that does not indicate a lag. Altitude changes are shown

immediately and can be corrected for quickly.

The VSI tape should be used to assist in determining what

pitch changes are necessary to return to the desired altitude.

A good rule of thumb is to use a vertical speed rate of change

that is double the altitude deviation. However, at no time

should the rate of change be more than the optimum rate of

climb or descent for the speciﬁ c aircraft being ﬂ own. For

example, if the altitude is off by 200 feet from the desired

altitude, then a 400 feet per minute (fpm) rate of change

5-37

would be sufﬁ cient to get the aircraft back to the original

altitude. If the altitude has changed by 700 feet, then doubling

that would necessitate a 1,400 fpm change. Most aircraft

are not capable of that, so restrict changes to no more than

optimum climb and descent. An optimum rate of change

would vary between 500 and 1,000 fpm.

One error the instrument pilot encounters is overcontrolling.

Overcontrolling occurs when a deviation of more than

200 fpm is indicated over the optimum rate of change. For

example, an altitude deviation of 200 feet is indicated on the

altimeter, a vertical speed rate of 400 feet should be indicated

on the gauge. If the vertical speed rate showed 600 fpm (200

more than optimum), the pilot would be overcontrolling the

aircraft.

When returning to altitude, the primary pitch instrument

is the VSI tape. If any deviation from the desired vertical

speed is indicated, make the appropriate pitch change using

the attitude indicator.

As the aircraft approaches the target altitude, the vertical

speed rate can be slowed in order to capture the altitude in a

more stabilized fashion. Normally within 10 percent of the

rate of climb or descent from the target altitude, begin to

slow the vertical speed rate in order to level off at the target

altitude. This will allow the pilot to level at the desired altitude

without rapid control inputs or experiencing discomfort due

to G-load.

Airspeed Indicator (ASI)

The ASI presents an indirect indication of the pitch attitude.

At a constant power setting and pitch attitude, airspeed

remains constant. As the pitch attitude lowers, airspeed

increases, and the nose should be raised.

As the pitch attitude is increased, the nose of the aircraft will

raise, which will result in an increase in the angle of attack

as well as an increase in induced drag. The increased drag

will begin to slow the momentum of the aircraft which will

be indicated on the ASI. The airspeed trend indicator will

show a trend as to where the airspeed will be in 6 seconds.

Conversely, if the nose of the aircraft should begin to fall, the

angle of attack as well as induced drag will decrease.

There is a lag associated with the ASI when using it as a pitch

instrument. It is not a lag associated with the construction

of the ASI, but a lag associated with momentum change.

Depending on the rate of momentum change, the ASI may not

indicate a pitch change in a timely fashion. If the ASI is being

used as the sole reference for pitch change, it may not allow

for a prompt correction. However, if smooth pitch changes

are executed, modern glass panel displays are capable of

indicating 1 knot changes in airspeed and also capable of

projecting airspeed trends.

When ﬂ ying by reference to ﬂ ight instruments alone, it

is imperative that all of the ﬂ ight instruments be cross-

checked for pitch control. By cross-checking all pitch related

instruments, the pilot can better visualize the aircraft attitude

at all times.

As previously stated, the primary instrument for pitch is the

instrument that gives the pilot the most pertinent information

for a speciﬁ c parameter. When in level ﬂ ight and maintaining

a constant altitude, what instrument shows a direct indication

of altitude? The only instrument that is capable of showing

altitude is the altimeter. The other instruments are supporting

instruments that are capable of showing a trend away from

altitude, but do not directly indicate an altitude.

The supporting instruments forewarn of an impending

altitude deviation. With an efﬁ cient cross-check, a proﬁ cient

pilot will be better able to maintain altitude.

Bank Control

This discussion assumes the aircraft is being flown in

coordinated ﬂ ight which means the longitudinal axis of the

aircraft is aligned with the relative wind. On the PFD, the

attitude indicator shows if the wings are level. The turn rate

indicator, slip/skid indicator, and the heading indicator also

indicate whether or not the aircraft is maintaining a straight

(zero bank) ﬂ ight path.

Attitude Indicator

The attitude indicator is the only instrument on the PFD that

has the capability of displaying the precise bank angle of the

aircraft. This is made possible by the display of the roll scale

depicted as part of the attitude indicator.

Figure 5-52 identiﬁ es the components that make up the

attitude indicator display. Note that the top of the display

is blue, representing sky, the bottom is brown, depicting

dirt, and the white line separating them is the horizon. The

lines parallel to the horizon line are the pitch scale which is

marked in 5° increments and labeled every 10°. The pitch

scale always remains parallel to the horizon.

The curved line in the blue area is the roll scale. The triangle

on the top of the scale is the zero index. The hash marks on

the scale represent the degree of bank. [Figure 5-53] The

roll scale always remains in the same position relative to

the horizon line.

5-38

Figure 5-53. Attitude Indicator Showing a 15° left bank.

Figure 5-54. Slip/Skid and Turn Rate Indicator.

Figure 5-52. Attitude Indicator.

The roll pointer indicates the direction and degree of bank.

[Figure 5-53] The roll pointer is aligned with the aircraft

symbol. The roll pointer indicates the angle of the lateral axis

of the aircraft compared to the natural horizon. The slip/skid

indicator will show if the longitudinal axis of the aircraft is

aligned with the relative wind, which is coordinated ﬂ ight. With

the roll index and the slip/skid indicator aligned, any deﬂ ection,

either right or left of the roll index will cause the aircraft to turn

in that direction. With the small graduations on the roll scale, it

is easy to determine the bank angle within approximately 1°. In

coordinated ﬂ ight, if the roll index is aligned with the roll pointer,

the aircraft is achieving straight ﬂ ight.

An advantage of EFDs is the elimination of the precession

error. Precession error in analog gauges is caused by forces

being applied to a spinning gyro. With the new solid state

instruments, precession error has been eliminated.

Since the attitude indicator is capable of showing precise

pitch and bank angles, the only time that the attitude indicator

will be a primary instrument is when attempting to ﬂ y at a

speciﬁ c bank angle or pitch angle. Other times, the attitude

instrument can be thought of as a control instrument.

Horizontal Situation Indicator (HSI)

The HSI is a rotating 360° compass card that indicates

magnetic heading. The HSI is the only instrument that is

capable of showing exact headings. The magnetic compass

can be used as a backup instrument in case of an HSI failure;

however, due to erratic, unstable movements, it is more likely

to be used a supporting instrument.

In order for the pilot to achieve the desired rate of change,

it is important for him or her to understand the relationship

between the rate at which the HSI changes heading displays

and the amount of bank angle required to meet that rate of

change. A very small rate of heading change means the bank

angle is small, and it will take more time to deviate from the

desired straight ﬂ ight path. A larger rate of heading change

means a greater bank angle will happen at a faster rate.

Heading Indicator

The heading indicator is the large black box with a white

number that indicates the magnetic heading of the aircraft.

[Figure 5-54] The aircraft heading is displayed to the nearest

degree. When this number begins to change, the pilot should

be aware that straight ﬂ ight is no longer being achieved.

Turn Rate Indicator

The turn rate indicator gives an indirect indication of bank. It is

a magenta trend indicator capable of displaying half-standard

as well as standard rate turns to both the left and right. The

turn indicator is capable of indicating turns up to 4° per second

by extending the magenta line outward from the standard

rate mark. If the rate of turn has exceeded 4° per second, the

5-39

Figure 5-55. An aircraft decreasing in airspeed while gaining

altitude. In this case, the pilot has decreased pitch.

Figure 5-56. Figure shows both an increase in speed and altitude

where pitch adjustment alone is insufﬁ cient. In this situation, a

reduction of power is also necessary.

magenta line can not precisely indicate where the heading

will be in the next 6 seconds, the magenta line freezes and an

arrowhead will be displayed. This alerts the pilot to the fact

that the normal range of operation has been exceeded.

Slip/Skid Indicator

The slip/skid indicator is the small portion of the lower

segmented triangle displayed on the attitude indicator. This

instrument depicts whether the aircraft’s longitudinal axis is

aligned with the relative wind. [Figure 5-54]

The pilot must always remember to cross-check the roll index

to the roll pointer when attempting to maintain straight ﬂ ight.

Any time the heading remains constant and the roll pointer and

the roll index are not aligned, the aircraft is in uncoordinated

ﬂ ight. To make a correction, the pilot should apply rudder

pressure to bring the aircraft back to coordinated ﬂ ight.

Power Control

Power produces thrust which, with the appropriate angle of

attack of the wing, overcomes the forces of gravity, drag,

and inertia to determine airplane performance.

Power control must be related to its effect on altitude and

airspeed, since any change in power setting results in a change

in the airspeed or the altitude of the airplane. At any given

airspeed, the power setting determines whether the airplane

is in level ﬂ ight, in a climb, or in a descent. If the power is

increased in straight-and-level ﬂ ight and the airspeed held

constant, the airplane will climb; if power is decreased while

the airspeed is held constant, the airplane will descend. On

the other hand, if altitude is held constant, the power applied

will determine the airspeed.

The relationship between altitude and airspeed determines the

need for a change in pitch or power. If the airspeed is off the

desired value, always check the altimeter before deciding that

a power change is necessary. Think of altitude and airspeed

as interchangeable; altitude can be traded for airspeed by

lowering the nose, or convert airspeed to altitude by raising

the nose. If altitude is higher than desired and airspeed is

low, or vice versa, a change in pitch alone may return the

airplane to the desired altitude and airspeed. [Figure 5-55] If

both airspeed and altitude are high or if both are low, then a

change in both pitch and power is necessary in order to return

to the desired airspeed and altitude. [Figure 5-56]

For changes in airspeed in straight-and-level ﬂ ight, pitch,

bank, and power must be coordinated in order to maintain

constant altitude and heading. When power is changed to

vary airspeed in straight-and-level ﬂ ight, a single-engine,

propeller-driven airplane tends to change attitude around all

axes of movement. Therefore, to maintain constant altitude

and heading, apply various control pressures in proportion

to the change in power. When power is added to increase

airspeed, the pitch instruments indicate a climb unless

forward-elevator control pressure is applied as the airspeed

changes. With an increase in power, the airplane tends to

yaw and roll to the left unless counteracting aileron and

rudder pressures are applied. Keeping ahead of these changes

requires increasing cross-check speed, which varies with the

type of airplane and its torque characteristics, the extent of

power and speed change involved.

Power Settings

Power control and airspeed changes are much easier when

approximate power settings necessary to maintain various

airspeeds in straight-and-level ﬂ ight are known in advance.

However, to change airspeed by any appreciable amount, the

common procedure is to underpower or overpower on initial

power changes to accelerate the rate of airspeed change. (For

small speed changes, or in airplanes that decelerate or accelerate

rapidly, overpowering or underpowering is not necessary.)

5-40

Figure 5-57. Straight-and-Level Flight (Normal Cruising Speed).

Consider the example of an airplane that requires 23" of

manifold pressure (Hg) to maintain a normal cruising airspeed

of 120 knots, and 18" Hg to maintain an airspeed of 100 knots.

The reduction in airspeed from 120 knots to 100 knots while

maintaining straight-and-level ﬂ ight is discussed below and

illustrated in Figures 5-57, 5-58, and 5-59.

Instrument indications, prior to the power reduction, are

shown in Figure 5-57. The basic attitude is established and

maintained on the attitude indicator. The speciﬁ c pitch,

bank, and power control requirements are detected on these

primary instruments:

Altimeter—Primary Pitch

Heading Indicator—Primary Bank

Airspeed Indicator—Primary Power

Supporting pitch and bank instruments are shown in

Figure 5-57. Note that the supporting power instrument is

the manifold pressure gauge (or tachometer if the propeller

is ﬁ xed pitch). However, when a smooth power reduction to

approximately 15" Hg (underpower) is made, the manifold

pressure gauge becomes the primary power instrument.

[Figure 5-58] With practice, power setting can be changed

with only a brief glance at the power instrument, by sensing

the movement of the throttle, the change in sound, and the

changes in the feel of control pressures.

As the thrust decreases, increase the speed of the cross-check

and be ready to apply left rudder, back-elevator, and aileron

control pressure the instant the pitch-and-bank instruments

show a deviation from altitude and heading. As proﬁ ciency

is obtained, a pilot will learn to cross-check, interpret, and

control the changes with no deviation of heading and altitude.

Assuming smooth air and ideal control technique, as airspeed

decreases, a proportionate increase in airplane pitch attitude

is required to maintain altitude. Similarly, effective torque

control means counteracting yaw with rudder pressure.

As the power is reduced, the altimeter is primary for pitch,

the heading indicator is primary for bank, and the manifold

pressure gauge is momentarily primary for power (at 15"

Hg in Figure 5-58). Control pressures should be trimmed

off as the airplane decelerates. As the airspeed approaches

the desired airspeed of 100 knots, the manifold pressure

is adjusted to approximately 18" Hg and becomes the

supporting power instrument. The ASI again becomes

primary for power. [Figure 5-58]

Airspeed Changes in Straight-and-Level Flight

Practice of airspeed changes in straight-and-level ﬂ ight

provides an excellent means of developing increased

proﬁ ciency in all three basic instrument skills, and brings

out some common errors to be expected during training

in straight-and-level ﬂ ight. Having learned to control the

airplane in a clean conﬁ guration (minimum drag conditions),

increase proﬁ ciency in cross-check and control by practicing

speed changes while extending or retracting the ﬂ aps and

landing gear. While practicing, be sure to comply with the

airspeed limitations speciﬁ ed in the POH/AFM for gear and

ﬂ ap operation.

5-41

Figure 5-58. Straight-and-Level Flight (Airspeed Decreasing).

Figure 5-59. Straight-and-Level Flight (Reduced Airspeed Stabilized).

5-42

Figure 5-60. Cross-check Supporting Instruments.

2. Reduce manifold pressure to 10" Hg. As the airspeed

decreases, increase cross-check speed.

3. Make trim adjustments for an increased angle of attack

and decrease in torque.

4. Lower the gear at 115 knots. The nose may tend to

pitch down and the rate of deceleration increases.

Increase pitch attitude to maintain constant altitude,

and trim off some of the back-elevator pressures.

If full ﬂ aps are lowered at 105 knots, cross-check,

interpretation, and control must be very rapid. A

simpler technique is to stabilize attitude with gear

down before lowering the ﬂ aps.

5. Since 18" Hg manifold pressure will hold level

flight at 100 knots with the gear down, increase

power smoothly to that setting as the ASI shows

approximately 105 knots, and retrim. The attitude

indicator now shows approximately two-and-a-half

bar width nose-high in straight-and-level ﬂ ight.

6. Actuate the ﬂ ap control and simultaneously increase

power to the predetermined setting (25" Hg) for the

desired airspeed, and trim off the pressures necessary

to hold constant altitude and heading. The attitude

indicator now shows a bar width nose-low in straight-

and-level ﬂ ight at 95 knots.

Sudden and exaggerated attitude changes may be necessary

in order to maintain straight-and-level ﬂ ight as the landing

gear is extended and the ﬂ aps are lowered in some airplanes.

The nose tends to pitch down with gear extension, and when

ﬂ aps are lowered, lift increases momentarily (at partial ﬂ ap

settings) followed by a marked increase in drag as the ﬂ aps

near maximum extension.

Control technique varies according to the lift and drag

characteristics of each airplane. Accordingly, knowledge of

the power settings and trim changes associated with different

combinations of airspeed, gear, and ﬂ ap conﬁ gurations will

reduce instrument cross-check and interpretation problems.

[Figure 5-60]

For example, assume that in straight-and-level flight

instruments indicate 120 knots with power at 23" Hg

manifold pressure/2,300 revolutions per minute (rpm), gear

and ﬂ aps up. After reduction in airspeed, with gear and ﬂ aps

fully extended, straight-and-level ﬂ ight at the same altitude

requires 25" Hg manifold pressure/2,500 rpm. Maximum

gear extension speed is 115 knots; maximum ﬂ ap extension

speed is 105 knots. Airspeed reduction to 95 knots, gear and

ﬂ aps down, can be made in the following manner:

1. Maintain rpm at 2,500, since a high power setting will

be used in full drag conﬁ guration.

5-43

Figure 5-61. Insufﬁ cient cross-check. The problem is power and not nose-high. In this case, the pilot decreased pitch inappropriately.

Trim Technique

Trim control is one of the most important ﬂ ight habits to

cultivate. Trimming refers to relieving any control pressures

that need to be applied by the pilot to the control surfaces to

maintain a desired ﬂ ight attitude. The desired result is for the

pilot to be able to take his or her hands off the control surfaces

and have the aircraft remain in the current attitude. Once the

aircraft is trimmed for hands-off ﬂ ight, the pilot is able to

devote more time to monitoring the ﬂ ight instruments and

other aircraft systems.

In order to trim the aircraft, apply pressure to the control surface

that needs trimming and roll the trim wheel in the direction

pressure is being held. Relax the pressure that is being applied to

the control surface and monitor the primary instrument for that

attitude. If the desired performance is achieved, ﬂ y hands off. If

additional trimming is required, redo the trimming steps.

An aircraft is trimmed for a speciﬁ c airspeed, not pitch attitude

or altitude. Any time an aircraft changes airspeed there is a

need to re-trim. For example, an aircraft is ﬂ ying at 100 knots

straight-and-level. An increase of 50 rpm will cause the airspeed

to increase. As the airspeed increases, additional lift will be

generated and the aircraft will climb. Once the additional thrust

has stabilized at some higher altitude, the airspeed will again

stabilize at 100 knots.

This demonstrates how trim is associated with airspeed and

not altitude. If the initial altitude is to be maintained, forward

pressure would need to be applied to the control wheel while

the trim wheel needs to be rolled forward to eliminate any

control pressures. Rolling forward on the trim wheel is equal

to increasing for a trimmed airspeed. Any time the airspeed

is changed, re-trimming will be required. Trimming can be

accomplished during any transitional period; however, prior

to ﬁ nal trimming, the airspeed must be held constant. If the

airspeed is allowed to change, the trim will not be adjusted

properly and the altitude will vary until the airspeed for which

the aircraft is trimmed is achieved.

Common Errors in Straight-and-Level Flight

Pitch

Pitch errors usually result from the following errors:

1. Improper adjustment of the yellow chevron (aircraft

symbol) on the attitude indicator.

Corrective Action: Once the aircraft has leveled off and

the airspeed has stabilized, make small corrections to

the pitch attitude to achieve the desired performance.

Cross-check the supporting instruments for validation.

2. Insufﬁ cient cross-check and interpretation of pitch

instruments. [Figure 5-61]

5-44

Example: The airspeed indication is low. The pilot,

believing a nose-high pitch attitude exists, applies

forward pressure without noting that a low power setting

is the cause of the airspeed discrepancy.

Corrective Action: Increase the rate of cross-check of all

the supporting ﬂ ight instruments. Airspeed and altitude

should be stabilized before making a control input.

3. Acceptance of deviations.

Example: A pilot has an altitude range of ±100 feet

according to the practical test standards for straight-and

level-ﬂ ight. When the pilot notices that the altitude has

deviated by 60 feet, no correction is made because the

altitude is holding steady and is within the standards.

Corrective Action: The pilot should cross-check the

instruments and, when a deviation is noted, prompt

corrective actions should be taken in order to bring the

aircraft back to the desired altitude. Deviations from

altitude should be expected but not accepted.

4. Overcontrolling—Excessive Pitch Changes.

Example: A pilot notices a deviation in altitude. In an

attempt to quickly return to altitude, the pilot makes a

large pitch change. The large pitch change destabilizes

the attitude and compounds the error.

Corrective Action: Small, smooth corrections should

be made in order to recover to the desired altitude

(0.5° to 2° depending on the severity of the deviation).

Instrument ﬂ ying is comprised of small corrections to

maintain the aircraft attitude. When ﬂ ying in IMC,

a pilot should avoid making large attitude changes

in order to avoid loss of aircraft control and spatial

disorientation.

5. Failure to Maintain Pitch Corrections.

Pitch changes need to be made promptly and held for

validation. Many times pilots will make corrections

and allow the pitch attitude to change due to not

trimming the aircraft. It is imperative that any time a

pitch change is made; the trim is readjusted in order to

eliminate any control pressures that are being held. A

rapid cross-check will aid in avoiding any deviations

from the desired pitch attitude.

Example: A pilot notices a deviation in altitude. A

change in the pitch attitude is accomplished but no

adjustment to the trim is made. Distractions cause

the pilot to slow the cross-check and an inadvertent

reduction in the pressure to the control column

commences. The pitch attitude then changes, thus

complicating recovery to the desired altitude.

Corrective Action: The pilot should initiate a pitch

change and then immediately trim the aircraft to

relieve any control pressures. A rapid cross-check

should be established in order to validate the desired

performance is being achieved.

6. Fixation During Cross-Check.

Devoting an unequal amount of time to one instrument

either for interpretation or assigning too much

importance to an instrument. Equal amounts of time

should be spent during the cross-check to avoid an

unnoticed deviation in one of the aircraft attitudes.

Example: A pilot makes a correction to the pitch

attitude and then devotes all of the attention to the

altimeter to determine if the pitch correction is

valid. During this time, no attention is paid to the

heading indicator which shows a turn to the left.

[Figure 5-62]

Corrective Action: The pilot should monitor all

instrumentation during the cross-check. Do not ﬁ xate

on one instrument waiting for validation. Continue to

scan all instruments to avoid allowing the aircraft to

begin a deviation in another attitude.

Heading

Heading errors usually result from but are not limited to the

following errors:

1. Failure to cross-check the heading indicator, especially

during changes in power or pitch attitude.

2. Misinterpretation of changes in heading, with resulting

corrections in the wrong direction.

3. Failure to note and remember a preselected heading.

4. Failure to observe the rate of heading change and its

relation to bank attitude.

5. Overcontrolling in response to heading changes,

especially during changes in power settings.

6. Anticipating heading changes with premature

application of rudder pressure.

7. Failure to correct small heading deviations. Unless

zero error in heading is the goal, a pilot will tolerate

larger and larger deviations. Correction of a 1° error

takes far less time and concentration than correction

of a 20° error.

8. Correcting with improper bank attitude. If correcting

a 10° heading error with a 20° bank correction, the

aircraft will roll past the desired heading before the

bank is established, requiring another correction in

the opposite direction. Do not multiply existing errors

with errors in corrective technique.

5-45

Figure 5-62. The pilot has ﬁ xated on pitch and altitude, leaving bank indications unattended. Note the trend line to the left.

9. Failure to note the cause of a previous heading error

and thus repeating the same error. For example, the

airplane is out of trim, with a left wing low tendency.

Repeated corrections for a slight left turn are made,

yet trim is ignored.

Power

Power errors usually result from but are not limited to the

following errors:

1. Failure to become familiar with the aircraft’s speciﬁ c

power settings and pitch attitudes.

2. Abrupt use of throttle.

3. Failure to lead the airspeed when making power

changes, climbs or descents.

Example: When leveling off from a descent, increase

the power in order to avoid the airspeed from bleeding

off due to the decrease in momentum of the aircraft.

If the pilot waits to bring in the power until after the

aircraft is established in the level pitch attitude, the

aircraft will have already decreased below the speed

desired which will require additional adjustment in

the power setting.

4. Fixation on airspeed tape or manifold pressure

indications during airspeed changes, resulting in

erratic control of airspeed, power, as well as pitch and

bank attitudes.

Trim

Trim errors usually result from the following faults:

1. Improper adjustment of seat or rudder pedals for

comfortable position of legs and feet. Tension in the

ankles makes it difﬁ cult to relax rudder pressures.

2. Confusion about the operation of trim devices, which

differ among various airplane types. Some trim wheels

are aligned appropriately with the airplane’s axes;

others are not. Some rotate in a direction contrary to

expectations.

3. Failure to understand the principles of trim and that

the aircraft is being trimmed for airspeed, not a pitch

attitude.

4. Faulty sequence in trim techniques. Trim should be

utilized to relieve control pressures, not to change

pitch attitudes. The proper trim technique has the pilot

holding the control wheel ﬁ rst and then trimming to

relieve any control pressures. Continuous trim changes

will be required as the power setting is changed.

Utilize the trim continuously, but in small amounts.

5-46

Figure 5-63. Constant Airspeed Climb From Cruise Airspeed.

Straight Climbs and Descents

Each aircraft will have a speciﬁ c pitch attitude and airspeed

that corresponds to the most efﬁ cient climb rate for a speciﬁ ed

weight. The POH/AFM contains the speeds that will produce

the desired climb. These numbers are based on maximum

gross weight. Pilots must be familiar with how the speeds will

vary with weight so they can compensate during ﬂ ight.

Entry

Constant Airspeed Climb From Cruise Airspeed

To enter a constant airspeed climb from cruise airspeed,

slowly and smoothly apply aft elevator pressure in order

to raise the yellow chevron (aircraft symbol) until the tip

points to the desired degree of pitch. [Figure 5-63] Hold

the aft control pressure and smoothly increase the power

to the climb power setting. This increase in power may be

initiated either prior to initiating the pitch change or after

having established the desired pitch setting. Consult the

POH/AFM for speciﬁ c climb power settings if anything other

than a full power climb is desired. Pitch attitudes will vary

depending on the type of aircraft being ﬂ own. As airspeed

decreases, control forces will need to be increased in order

to compensate for the additional elevator deﬂ ection required

to maintain attitude. Utilize trim to eliminate any control

pressures. By effectively using trim, the pilot will be better

able to maintain the desired pitch without constant attention.

The pilot is thus able to devote more time to maintaining an

effective scan of all instrumentation.

The VSI should be utilized to monitor the performance of the

aircraft. With a smooth pitch transition, the VSI tape should

begin to show an immediate trend upward and stabilize on a

5-47

Figure 5-64. Constant-Airspeed Climb From Established Airspeed.

rate of climb equivalent to the pitch and power setting being

utilized. Depending on current weight and atmospheric

conditions, this rate will be different. This will require the

pilot to be knowledgeable of how weight and atmospheric

conditions affect aircraft performance.

Once the aircraft is stabilized at a constant airspeed and pitch

attitude, the primary ﬂ ight instrument for pitch will be the ASI

and the primary bank instrument will be the heading indicator.

The primary power instrument will be the tachometer or the

manifold pressure gauge depending on the aircraft type. If the

pitch attitude is correct, the airspeed should slowly decrease

to the desired speed. If there is any variation in airspeed,

make small pitch changes until the aircraft is stabilized at

the desired speed. Any change in airspeed will require a trim

adjustment.

Constant Airspeed Climb from Established Airspeed

In order to enter a constant airspeed climb, ﬁ rst complete the

airspeed reduction from cruise airspeed to climb airspeed.

Maintain straight-and-level ﬂ ight as the airspeed is reduced.

The entry to the climb is similar to the entry from cruise

airspeed with the exception that the power must be increased

when the pitch attitude is raised. [Figure 5-64] Power added

after the pitch change will show a decrease in airspeed due

to the increased drag encountered. Power added prior to a

pitch change will cause the airspeed to increase due to the

excess thrust.

Constant Rate Climbs

Constant rate climbs are very similar to the constant airspeed

climbs in the way the entry is made. As power is added,

5-48

Figure 5-65. Constant Rate Climbs.

smoothly apply elevator pressure to raise the yellow chevron

to the desired pitch attitude that equates to the desired vertical

speed rate. The primary instrument for pitch during the initial

portion of the maneuver is the ASI until the vertical speed

rate stabilizes and then the VSI tape becomes primary. The

ASI then becomes the primary instrument for power. If any

deviation from the desired vertical speed is noted, small

pitch changes will be required in order to achieve the desired

vertical speed. [Figure 5-65]

When making changes to compensate for deviations in

performance, pitch, and power, pilot inputs need to be

coordinated to maintain a stable ﬂ ight attitude. For instance,

if the vertical speed is lower than desired but the airspeed is

correct, an increase in pitch will momentarily increase the

vertical speed. However, the increased drag will quickly

start to degrade the airspeed if no increase in power is made.

A change to any one variable will mandate a coordinated

change in the other.

Conversely, if the airspeed is low and the pitch is high, a

reduction in the pitch attitude alone may solve the problem.

Lower the nose of the aircraft very slightly to see if a power

reduction is necessary. Being familiar with the pitch and

power settings for the aircraft aids in achieving precise

attitude instrument ﬂ ying.

Leveling Off

Leveling off from a climb requires a reduction in the pitch

prior to reaching the desired altitude. If no change in pitch

is made until reaching the desired altitude, the momentum

of the aircraft causes the aircraft to continue past the desired

altitude throughout the transition to a level pitch attitude. The

amount of lead to be applied depends on the vertical speed

rate. A higher vertical speed requires a larger lead for level

off. A good rule of thumb to utilize is to lead the level off

by 10 percent of the vertical speed rate (1,000 fpm ÷ 10 =

100 feet lead).

To level off at the desired altitude, refer to the attitude display

and apply smooth forward elevator pressure toward the desired

level pitch attitude while monitoring the VSI and altimeter

tapes. The rates should start to slow and airspeed should

begin to increase. Maintain the climb power setting until the

airspeed approaches the desired cruise airspeed. Continue to

monitor the altimeter to maintain the desired altitude as the

airspeed increases. Prior to reaching the cruise airspeed, the

power must be reduced to avoid overshooting the desired

speed. The amount of lead time that is required depends on

the speed at which the aircraft accelerates. Utilization of the

airspeed trend indicator can assist by showing how quickly

the aircraft will arrive at the desired speed.

5-49

Figure 5-66. The top image illustrates a reduction of power and descending at 500 fpm to an altitude of 5,000 feet. The bottom image

illustrates an increase in power and the initiation of leveling off.

To level off at climbing airspeed, lower the nose to the

appropriate pitch attitude for level ﬂ ight with a simultaneous

reduction in power to a setting that will maintain the desired

speed. With a coordinated reduction in pitch and power there

should be no change in the airspeed.

Descents

Descending ﬂ ight can be accomplished at various airspeeds

and pitch attitudes by reducing power, lowering the nose to

a pitch attitude lower than the level ﬂ ight attitude, or adding

drag. Once any of these changes have been made, the airspeed

will eventually stabilize. During this transitional phase, the

only instrument that will display an accurate indication of

pitch is the attitude indicator. Without the use of the attitude

indicator (such as in partial panel ﬂ ight), the ASI tape, the VSI

tape, and the altimeter tape will show changing values until

the aircraft stabilizes at a constant airspeed and constant rate

of descent. The altimeter tape continues to show a descent.

Hold pitch constant and allow the aircraft to stabilize. During

any change in attitude or airspeed, continuous application of

trim is required to eliminate any control pressures that need

to be applied to the control yoke. An increase in the scan rate

during the transition is important since changes are being

made to the aircraft ﬂ ight path and speed. [Figure 5-66]

Entry

Descents can be accomplished with a constant rate, constant

airspeed or a combination. The following method can

accomplish any of these with or without an attitude indicator.

Reduce the power to allow the aircraft to decelerate to the

desired airspeed while maintaining straight-and-level ﬂ ight.

As the aircraft approaches the desired airspeed, reduce the

5-50

power to a predetermined value. The airspeed continues to

decrease below the desired airspeed unless a simultaneous

reduction in pitch is performed. The primary instrument

for pitch is the ASI tape. If any deviation from the desired

speed is noted, make small pitch corrections by referencing

the attitude indicator and validate the changes made with the

airspeed tape. Utilize the airspeed trend indicator to judge if

the airspeed will be increasing and at what rate. Remember

to trim off any control pressures.

The entry procedure for a constant rate descent is the same

except the primary instrument for pitch is the VSI tape.

The primary instrument for power will be the ASI. When

performing a constant rate descent while maintaining

a speciﬁ c airspeed, coordinated use of pitch and power

will be required. Any change in pitch directly affects the

airspeed. Conversely, any change in airspeed will have a

direct impact on vertical speed as long as the pitch is being

held constant.

Leveling Off

When leveling off from a descent with the intention of

returning to cruise airspeed, ﬁ rst start by increasing the

power to cruise prior to increasing the pitch back toward

the level ﬂ ight attitude. A technique used to determine

how soon to start the level off is to lead the level off by an

altitude corresponding to 10 percent of the rate of descent.

For example, if the aircraft is descending at 1,000 fpm, start

the level off 100 feet above the level off altitude. If the pitch

attitude change is started late, there is a tendency to overshoot

the desired altitude unless the pitch change is made with

a rapid movement. Avoid making any rapid changes that

could lead to control issues or spatial disorientation. Once

in level pitch attitude, allow the aircraft to accelerate to the

desired speed. Monitor the performance on the airspeed and

altitude tapes. Make adjustments to the power in order to

correct any deviations in the airspeed. Verify that the aircraft

is maintaining level ﬂ ight by cross-checking the altimeter

tape. If deviations are noticed, make an appropriate smooth

pitch change in order to arrive back at desired altitude. Any

change in pitch requires a smooth coordinated change to the

power setting. Monitor the airspeed in order to maintain the

desired cruise airspeed.

To level off at a constant airspeed, the pilot must again

determine when to start to increase the pitch attitude toward

the level attitude. If pitch is the only item that is changing,

airspeed varies due to the increase in drag as the aircraft’s

pitch increases. A smooth coordinated increase in power will

need to be made to a predetermined value in order to maintain

speed. Trim the aircraft to relieve any control pressure that

may have to be applied.

Common Errors in Straight Climbs and Descents

Climbing and descending errors usually result from but are

not limited to the following errors:

1. Overcontrolling pitch on beginning the climb.

Aircraft familiarization is the key to achieving precise

attitude instrument ﬂ ying. Until the pilot becomes

familiar with the pitch attitudes associated with

speciﬁ c airspeeds, the pilot must make corrections

to the initial pitch settings. Changes do not produce

instantaneous and stabilized results; patience must be

maintained while the new speeds and vertical speed

rates stabilize. Avoid the temptations to make a change

and then rush into making another change until the

ﬁ rst one is validated. Small changes will produce more

expeditious results and allow for a more stabilized

ﬂ ight path. Large changes to pitch and power are

more difﬁ cult to control and can further complicate

the recovery process.

2. Failure to increase the rate of instrument cross-check.

Any time a pitch or power change is made, an increase

in the rate a pilot cross-checks the instrument is

required. A slow cross-check can lead to deviations

in other ﬂ ight attitudes.

3. Failure to maintain new pitch attitudes. Once a

pitch change is made to correct for a deviation, that

pitch attitude must be maintained until the change

is validated. Utilize trim to assist in maintaining the

new pitch attitude. If the pitch is allowed to change,

it is impossible to validate whether the initial pitch

change was sufﬁ cient to correct the deviation. The

continuous changing of the pitch attitude delays the

recovery process.

4. Failure to utilize effective trim techniques. If control

pressures have to be held by the pilot, validation of

the initial correction will be impossible if the pitch

is allowed to vary. Pilots have the tendency to either

apply or relax additional control pressures when

manually holding pitch attitudes. Trim allows the

pilot to ﬂ y without holding pressure on the control

yoke.

5. Failure to learn and utilize proper power settings. Any

time a pilot is not familiar with an aircraft’s speciﬁ c

pitch and power settings, or does not utilize them, a

change in ﬂ ight paths will take longer. Learn pitch

and power settings in order to expedite changing the

ﬂ ight path.

6. Failure to cross-check both airspeed and vertical speed

prior to making adjustments to pitch and or power. It is

possible that a change in one may correct a deviation

in the other.

5-51

7. Uncoordinated use of pitch and power during level

offs. During level offs, both pitch and power settings

need to be made in unison in order to achieve the

desired results. If pitch is increased before adding

power, additional drag will be generated thereby

reducing airspeed below the desired value.

8. Failure to utilize supporting pitch instruments which

will lead to chasing the VSI. Always utilize the attitude

indicator as the control instrument on which to change

the pitch.

9. Failure to determine a proper lead time for level off

from a climb or descent. Waiting too long can lead to

overshooting the altitude.

10. Ballooning—Failure to maintain forward control

pressure during level off as power is increased.

Additional lift is generated causing the nose of the

aircraft to pitch up.

Turns

Standard Rate Turns

The previous sections have addressed ﬂ ying straight-and-

level as well as climbs and descents. However, attitude

instrument ﬂ ying is not accomplished solely by ﬂ ying in

a straight line. At some point, the aircraft will need to be

turned to maneuver along victor airways, global positioning

system (GPS) courses, and instrument approaches. The

key to instrument ﬂ ying is smooth, controlled changes to

pitch and bank. Instrument ﬂ ying should be a slow but

deliberate process that takes the pilot from departure airport

to destination airport without any radical ﬂ ight maneuvers.

A turn to speciﬁ c heading should be made at standard rate.

Standard rate is deﬁ ned as a turning rate of 3° per second

which will yield a complete 360° turn in 2 minutes. A

turning rate of 3° per second will allow for a timely heading

change, as well as allowing the pilot sufﬁ cient time to cross-

check the ﬂ ight instruments and avoid drastic changes to

the aerodynamic forces being exerted on the aircraft. At no

time should the aircraft be maneuvered faster than the pilot

is comfortable cross-checking the ﬂ ight instruments. Most

autopilots are programmed to turn at standard rate.

Establishing A Standard Rate Turn

In order to initiate a standard rate turn, approximate the

bank angle and then establish that bank angle on the attitude

indicator. A rule of thumb to determine the approximate angle

of bank is to use 15 percent of the true airspeed. A simple

way to determine this amount is to divide the airspeed by

10 and add one-half the result. For example, at 100 knots,

approximately 15° of bank is required (100/10 = 10 + 5 =

15); at 120 knots, approximately 18° of bank is needed for a

standard-rate turn. Cross-check the turn rate indicator, located

on the HSI, to determine if that bank angle is sufﬁ cient to

deliver a standard rate turn. Slight modiﬁ cations may need

to be made to the bank angle in order to achieve the desired

performance. The primary bank instrument in this case is the

turn rate indicator since the goal is to achieve a standard rate

turn. The turn rate indicator is the only instrument that can

speciﬁ cally indicate a standard rate turn. The attitude indicator

is used only to establish a bank angle (control instrument) but

can be utilized as a supporting instrument by cross-checking

the bank angle to determine if the bank is greater or less than

what was calculated.

As the aircraft rolls into the bank, the vertical component of

lift will begin to decrease. [Figure 5-67] As this happens,

additional lift must be generated to maintain level ﬂ ight.

Apply aft control pressure on the yoke sufﬁ cient to stop any

altitude loss trend. With the increase in lift that needs to be

generated, additional induced drag will also be generated.

This additional drag will cause the aircraft to start to

decelerate. To counteract this, apply additional thrust by

adding power to the power lever. Once altitude and airspeed

is being maintained, utilize the trim wheel to eliminate any

control forces that need to be held on the control column.

When rolling out from a standard rate turn, the pilot needs

to utilize coordinated aileron and rudder and roll-out to a

wings level attitude utilizing smooth control inputs. The

roll-out rate should be the same as the roll-in rate in order to

estimate the lead necessary to arrive at the desired heading

without over- or undershooting.

During the transition from the turn back to straight ﬂ ight, the

attitude indicator becomes the primary instrument for bank.

Once the wings are level, the heading indicator becomes

the primary instrument for bank. As bank decreases, the

vertical component increases if the pitch attitude is not

decreased sufﬁ ciently to maintain level ﬂ ight. An aggressive

cross-check keeps the altimeter stationary if forward control

pressure is applied to the control column. As the bank angle is

decreased, the pitch attitude should be decreased accordingly

in order to arrive at the level pitch attitude when the aircraft

reaches zero bank. Remember to utilize the trim wheel to

eliminate any excess control forces that would otherwise

need to be held.

Common Errors

1. One common error associated with standard rate turns

is due to pilot inability to hold the appropriate bank

angle that equates to a standard rate. The primary bank

instrument during the turn is the turn rate indicator;

however the bank angle varies slightly. With an

5-52

Figure 5-67. Standard Rate Turn—Constant Airspeed.

aggressive cross-check, a pilot should be able to

minimize errors arising from over- or underbanking.

2. Another error normally encountered during standard

rate turns is inefﬁ cient or lack of adequate cross-

checking. Pilots need to establish an aggressive

cross-check in order to detect and eliminate all

deviations from altitude, airspeed, and bank angle

during a maneuver.

3. Fixation is a major error associated with attitude

instrument ﬂ ying in general. Pilots training for their

instrument rating tend to focus on what they perceive

to be the most important task at hand and abandon

their cross-check by applying all of their attention to

the turn rate indicator. A modiﬁ ed radial scan works

well to provide the pilot with adequate scanning of all

instrumentation during the maneuver.

Turns to Predetermined Headings

Turning the aircraft is one of the most basic maneuvers that a

pilot learns during initial ﬂ ight training. Learning to control

the aircraft, maintaining coordination, and smoothly rolling

out on a desired heading are all keys to proﬁ cient attitude

instrument ﬂ ying.

EFDs allow the pilot to better utilize all instrumentation during

all phases of attitude instrument ﬂ ying by consolidating all

traditional instrumentation onto the PFD. The increased size

of the attitude indicator, which stretches the entire width

of the multi-function display (MFD), allows the pilot to

maintain better pitch control while the introduction of the

turn rate indicator positioned directly on the compass rose

aids the pilot in determining when to begin a roll-out for the

desired heading.

When determining what bank angle to utilize when making a

heading change, a general rule states that for a small heading

change, do not use a bank angle that is greater than the total

number of degrees of change needed. For instance, if a heading

change of 20° is needed, a bank angle of not more than 20° is

required. Another rule of thumb that better deﬁ nes the bank

angle is half the total number of degrees of heading change

required, but never greater than standard rate. The exact bank

angle that equates to a standard rate turn varies due to true

airspeed.

With this in mind and the angle of bank calculated, the next

step is determining when to start the roll-out process. For

example:

An aircraft begins a turn from a heading of 030° to a heading

of 120°. With the given airspeed, a standard rate turn has

yielded a 15° bank. The pilot wants to begin a smooth

5-53

coordinated roll-out to the desired heading when the heading

indicator displays approximately 112°. The necessary

calculations are:

15° bank (standard rate) ÷ 2 = 7.5°

120° – 7.5° = 112.5°

By utilizing this technique the pilot is better able to judge if

any modiﬁ cations need to be made to the amount of lead once

the amount of over- or undershooting is established.

Timed Turns

Timed turns to headings are performed in the same fashion

with an EFD as with an analog equipped aircraft. The

instrumentation used to perform this maneuver is the turn rate

indicator as well as the clock. The purpose of this maneuver

is to allow the pilot to gain proﬁ ciency in scanning as well

as to further develop the pilot’s ability to control the aircraft

without standard instrumentation.

Timed turns become essential when controlling the aircraft

with a loss of the heading indicator. This may become

necessary due to a loss of the AHRS unit or the magnetometer.

In any case, the magnetic compass will still be available for

navigation. The reason for timed turns instead of magnetic

compass turns is the simplicity of the maneuver. Magnetic

compass turns require the pilot to take into account various

errors associated with the compass; timed turns do not.

Prior to initiating a turn, determine if the standard rate

indication on the turn rate indicator will actually deliver a

3° per second turn. To accomplish this, a calibration must

be made. Establish a turn in either direction at the indicated

standard rate. Start the digital timer as the compass rolls past

a cardinal heading. Stop the timer once the compass card

rolls through another cardinal heading. Roll wings level and

compute the rate of turn. If the turn rate indicator is calibrated

and indicating correctly, 90° of heading change should take

30 seconds. If the time taken to change heading by 90° is

more or less than 30 seconds, then a deﬂ ection above or

below the standard rate line needs to be made to compensate

for the difference. Once the calibration has been completed

in one direction, proceed to the opposite direction. When

both directions have been calibrated, apply the calibrated

calculations to all timed turns.

In order to accomplish a timed turn, the amount of heading

change needs to be established. For a change in heading from

120° to a heading of 360°, the pilot calculates the difference

and divides that number by 3. In this case, 120° divided by

3° per second equals 40 seconds. This means that it would

take 40 seconds for an aircraft to change heading 120° if that

aircraft were held in a perfect standard rate turn. Timing for

the maneuver should start as the aircraft begins rolling into

the standard rate turn. Monitor all ﬂ ight instruments during

this maneuver. The primary pitch instrument is the altimeter.

The primary power instrument is the ASI and the primary

bank instrument is the turn rate indicator.

Once the calculated time expires, start a smooth coordinated

roll-out. As long as the pilot utilizes the same rate of roll-in as

roll-out, the time it takes for both will not need to be included

in the calculations. With practice the pilot should level the

wings on the desired heading. If any deviation has occurred,

make small corrections to establish the correct heading.

Compass Turns

The magnetic compass is the only instrument that requires

no other source of power for operation. In the event of an

AHRS or magnetometer failure, the magnetic compass is

the instrument the pilot uses to determine aircraft heading.

For a more detailed explanation on the use of the magnetic

compass, see page 5-21.

Steep Turns

For the purpose of instrument ﬂ ight training, a steep turn is

deﬁ ned as any turn in excess of standard rate. A standard rate

turn is deﬁ ned as 3° per second. The bank angle that equates

to a turn rate of 3° per second varies according to airspeed.

As airspeed increases, the bank angle must be increased.

The exact bank angle that equates to a standard rate turn is

unimportant. Normal standard rate turn bank angles range

from 10° to 20°. The goal of training in steep turn maneuvers

is pilot proﬁ ciency in controlling the aircraft with excessive

bank angles.

Training in excessive bank angles will challenge the pilot in

honing cross-checking skills and improve altitude control

throughout a wider range of ﬂ ight attitudes. Although the

current instrument ﬂ ight check practical test standards (PTS)

do not call for a demonstration of steep turns on the certiﬁ cation

check ﬂ ight, this does not eliminate the need for the instrument

pilot-in-training to demonstrate proﬁ ciency to an instructor.

Training in steep turns teaches the pilot to recognize and to

adapt to rapidly changing aerodynamic forces that necessitate

an increase in the rate of cross-checking all ﬂ ight instruments.

The procedures for entering, maintaining and exiting a steep

turn are the same as for shallower turns. Proficiency in

instrument cross-check and interpretation is increased due to

the higher aerodynamic forces and increased speed at which

the forces are changing.

5-54

Figure 5-68. Steep Left Turn.

Performing the Maneuver

To enter a steep turn to the left, roll into a coordinated 45°

bank turn to the left. An advantage that glass panel displays

have over analog instrumentation is a 45° bank indication on

the roll scale. This additional index on the roll scale allows

the pilot to precisely roll into the desired bank angle instead

of having to approximate it as is necessary with analog

instrumentation. [Figure 5-68]

As soon as the bank angle increases from level ﬂ ight, the

vertical component of lift begins to decrease. If the vertical

component of lift is allowed to continue to decrease, a

pronounced loss of altitude is indicated on the altimeter along

with the VSI tape, as well as the altitude trend indicator.

Additionally, the airspeed will begin to increase due to

the lowered pitch attitude. It is very important to have a

comprehensive scan developed prior to training in steep

turns. Utilization of all of the trend indicators, as well the

VSI, altimeter, and ASI, is essential in learning to ﬂ y steep

turns by reference to instruments alone.

In order to avoid a loss of altitude, the pilot begins to

slowly increase back pressure on the control yoke in order

to increase the pitch attitude. The pitch change required is

usually no more than 3° to 5°, depending on the type of

aircraft. As the pilot increases back pressure, the angle of

attack increases, thus increasing the vertical component of

lift. When a deviation in altitude is indicated, proper control

force corrections need to be made. During initial training

of steep turns, pilots have a tendency to overbank. Over

banking is when the bank angle exceeds 50°. As the outboard

wing begins to travel faster through the air it will begin to

generate a greater and greater differential in lift compared

to the inboard wing. As the bank angle continues to progress

more and more steeply past 45°, the two components of lift

(vertical and horizontal) become inversely proportionate.

Once the angle has exceeded 45°, the horizontal component

of lift is now the greater force. If altitude should continue to

decrease and the pilot only applies back yoke pressure, the

aircraft’s turn radius begins to tighten due to the increased

horizontal force. If aft control pressure continues to increase,

there will come a point where the loss of the vertical

component of lift and aerodynamic wing loading prohibits

the nose of the aircraft from being raised. Any increase in

pitch only tightens the turning radius.

The key to successfully performing a steep turn by reference

to instruments alone is the thorough understanding of the

aerodynamics involved, as well as a quick and reliable cross-

check. The pilot should utilize the trim to avoid holding

control forces for any period of time. With time and practice,

a ﬂ ight instructor can demonstrate how to successfully ﬂ y

steep turns with and without the use of trim. Once the aircraft

is trimmed for the maneuver, accomplishing the maneuver

will be virtually a hands-off effort. This allows additional

time for cross-checking and interpreting the instruments.

It is imperative when correcting for a deviation in altitude,

that the pilot modify the bank angle ±5° in order to vary the

vertical component of lift, not just adjust back pressure. These

two actions should be accomplished simultaneously.

During the recovery from steep turns to straight-and-level

ﬂ ight, aft control forces must be varied with the power control

to arrive back at entry altitude, heading and airspeed.

Steps:

1. Perform clearing turns.

2. Roll left into a 45° bank turn and immediately begin to

increase the pitch attitude by approximately 3° to 5°.

3. As the bank rolls past 30°, increase power to maintain

the entry airspeed.

4. Apply trim to eliminate any aft control wheel forces.

5. Begin rolling out of the steep turn approximately 20°

prior to the desired heading.

6. Apply forward control pressure and place the pitch

attitude in the level cruise pitch attitude.

7. Reduce power to the entry power setting to maintain

the desired airspeed.

8. Re-trim the aircraft as soon as practical or continue

into a right hand steep turn and continue from step 3.

5-55

Figure 5-69. Unusual Attitude Recovery Protection. Note the brown horizon line is visible at the bottom.

9. Once the maneuver is complete, establish cruise ﬂ ight

and accomplish all appropriate checklist items.

Unusual Attitude Recovery Protection

Unusual attitudes are some of the most hazardous situations

for a pilot to be in. Without proper recovery training

on instrument interpretation and aircraft control, a pilot

can quickly aggravate an abnormal ﬂ ight attitude into a

potentially fatal accident.

Analog gauges require the pilot to scan between instruments

to deduce the aircraft attitude. Individually, these gauges

lack the necessary information needed for a successful

recovery.

EFDs have additional features to aid in recognition and

recovery from unusual ﬂ ight attitudes. The PFD displays

all the ﬂ ight instruments on one screen. Each instrument is

superimposed over a full-screen representation of the attitude

indicator. With this conﬁ guration, the pilot no longer needs

to transition from one instrument to another.

The new unusual attitude recovery protection allows the pilot

to be able to quickly determine the aircraft’s attitude and make

a safe, proper and prompt recovery. Situational awareness is

increased by the introduction of the large full-width artiﬁ cial

horizon depicted on the PFD. This now allows for the attitude

indicator to be in view during all portions of the scan.

One problem with analog gauges is that the attitude indicator

displays a complete blue or brown segment when the pitch

attitude is increased toward 90° nose-up or nose-down.

With the EFDs, the attitude indicator is designed to retain a

portion of both sky and land representation at all times. This

improvement allows the pilot to always know the quickest

way to return to the horizon. Situational awareness is greatly

increased.

NOTE: The horizon line starts moving downward at

approximately 47° pitch up. From this point on, the brown

segment will remain visible to show the pilot the quickest

way to return to the level pitch attitude. [Figure 5-69]

NOTE: The horizon line starts moving upward at

approximately 27° pitch down. From this point on, the blue

segment will remain visible to show the pilot the quickest

way to return to the level pitch attitude. [Figure 5-70]

It is imperative to understand that the white line on the

attitude indicator is the horizon line. The break between the

blue and brown symbols is only a reference and should not

be thought of as the artiﬁ cial horizon.

Another important advancement is the development of the

unusual attitude recovery protection that is built into the PFD

software and made capable by the AHRS. In the case of a nose-

high unusual attitude, the unusual attitude recovery protection

displays red chevrons which point back to the horizon line.

5-56

Figure 5-70. Horizon line starts moving upward at 27°. Note that the blue sky remains visible at 17° nose-down.

These chevrons are positioned at 50° up on the attitude indicator.

The chevrons appear when the aircraft approaches a nose-high

attitude of 30°. The software automatically de-clutters the PFD

leaving only airspeed, heading, attitude, altimeter, VSI tape,

and the trend vectors. The de-cluttered information reappears

when the pitch attitude falls below 25°.

For nose-low unusual attitudes, the chevrons are displayed

when the pitch exceeds 15° nose-down. If the pitch continues

to decrease, the unusual attitude recovery protection de-

clutters the screen at 20° nose-down. The de-cluttered

information reappears when the pitch increases above 15°.

Additionally, there are bank limits that trigger the unusual

attitude protection. If the aircraft’s bank increases beyond

60°, a continuation of the roll index occurs to indicate the

shortest direction to roll the wings back to level. At 65°, the

PFD de-clutters. All information reappears when the bank

decreases below 60°.

In Figure 5-71, the aircraft has rolled past 60°. Observe the

white line that continues from the end of the bank index.

This line appears to indicate the shortest distance back to

wings level.

When experiencing a failure of the AHRS unit, all unusual

attitude protection is lost. The failure of the AHRS results

in the loss of all heading and attitude indications on the PFD.

In addition, all modes of the autopilot, except for roll and

altitude hold, are lost.

The following picture series represents how important this

technology is in increasing situational awareness, and how

critical it is in improving safety.

Figure 5-72 shows the unusual attitude protection with

valid AHRS and air data computer (ADC) inputs. The

bright red chevrons pointing down to the horizon indicate

a nose-high unusual attitude that can be easily recognized

and corrected.

NOTE: The red chevrons point back to the level pitch attitude.

The trend indicators show where the airspeed and altitude will

be in 6 seconds. The trend indicator on the heading indicator

shows which direction the aircraft is turning. The slip/skid

indicator clearly shows if the aircraft is coordinated. This

information helps the pilot determine which type of unusual

attitude the aircraft has taken.

Now look at Figure 5-73. The display shows the same

airspeed as the picture above; however, the AHRS unit has

failed. The altimeter and the VSI tape are the only clear

indications that the aircraft is in a nose-high attitude. The

one key instrument that is no longer present is the slip/skid

indicator. There is not a standby turn coordinator installed

in the aircraft for the pilot to reference.

The magnetic compass indicates a heading is being

maintained; however, it is not as useful as a turn coordinator

or slip/skid indicator.

5-57

Figure 5-71. Aircraft Rolled Past 60°.

Figure 5-72. Unusual Attitude Protection With Valid AHRS.

5-58

Figure 5-73. AHRS Unit Failed.

Figure 5-74 depicts an AHRS and ADC failure. In this failure

scenario, there are no indications of the aircraft’s attitude. The

manufacturer recommends turning on the autopilot which is

simply a wing leveler.

With a failure of the primary instrumentation on the PFD, the

only references available are the stand-by instruments. The

standby instrumentation consists of an analog ASI, attitude

indicator, altimeter, and magnetic compass. There is no

standby turn coordinator installed.

In extreme nose-high or nose-low pitch attitudes, as well

as high bank angles, the analog attitude indicator has the

potential to tumble, rendering it unusable.

Autopilot Usage

The autopilot is equipped with inputs from a turn coordinator

installed behind the MFD screen. This turn coordinator is

installed solely for the use of the autopilot to facilitate the

roll mode. Roll mode, which is simply a wing leveler. This

protection will always be available, barring a failure of the

turn coordinator (to aid the pilot if the aircraft attains an

unusual attitude).

NOTE: The pilot is not able to gain access to the turn

coordinator. This instrument is installed behind the MFD

panel. [Figure 5-75]

Most EFD equipped aircraft are coming from the factory

with autopilots installed. However, the purchaser of the

aircraft can specify if an autopilot is to be installed. Extreme

caution should be utilized when ﬂ ying an EFD equipped

aircraft without an autopilot in IMC with an AHRS and

ADC failure.

The autopilot should be utilized to reduce workload, which

affords the pilot more time to monitor the ﬂ ight. Utilization

of the autopilot also decreases the chances of entry into an

unusual attitude.

Flying an EFD equipped aircraft without the use of an

autopilot has been shown to increase workload and decrease

situational awareness for pilots ﬁ rst learning to ﬂ ying the

new system.

Common Errors Leading to Unusual Attitudes

The following errors have the potential to disrupt a pilot’s

situational awareness and lead to unusual attitudes.

1. Improper trimming techniques. A failure to keep the

aircraft trimmed for level ﬂ ight at all times can turn

a momentary distraction into an emergency situation

if the pilot stops cross-checking.

2. Poor crew resource management (CRM) skills. Failure

to perform all single-pilot resource management

duties efﬁ ciently. A major cause of CRM related

accidents comes from the failure of the pilot to

maintain an organized ﬂ ight deck. Items that are

being utilized for the ﬂ ight portion should be neatly

arranged for easy access. A disorganized ﬂ ight deck

5-59

Figure 5-74. AHRS ADC Failure.

Figure 5-75. This autopilot requires roll information from a turn coordinator.

5-60

can lead to a distraction that causes the pilot to cease

cross-checking the instruments long enough to enter

an unusual attitude.

3. Fixation is displayed when a pilot focuses far too

much attention on one instrument because he or

she perceives something is wrong or a deviation is

occurring. It is important for the instrument pilot to

remember that a cross-check of several instruments

for corroboration is more valuable than checking a

single instrument.

4. Attempting to recover by sensory sensations other

than sight. Recovery by instinct almost always leads

to erroneous corrections due to the illusions that are

prevalent during instrument ﬂ ight.

5. Failure to practice basic attitude instrument ﬂ ying.

When a pilot does not fly instrument approach

procedures or even basic attitude instrument ﬂ ying

maneuvers for long periods of time, skill levels

diminish. Pilots should avoid ﬂ ying in IMC if they are

not proﬁ cient. They should seek a qualiﬁ ed instructor

to receive additional instruction prior to entry into

IMC.

Instrument Takeoff

The reason for learning to ﬂ y by reference to instruments

alone is to expand a pilot’s abilities to operate an aircraft

in visibility less than VFR. Another valuable maneuver

to learn is the instrument takeoff. This maneuver requires

the pilot to maneuver the aircraft during the takeoff roll by

reference to ﬂ ight instruments alone with no outside visual

reference. With practice, this maneuver becomes as routine

as a standard rate turn.

The reason behind practicing instrument takeoffs is to reduce

the disorientation that can occur during the transitional phase

of quickly moving the eyes from the outside references inside

to the ﬂ ight instruments.

One EFD system currently offers what is trademarked as

synthetic vision. Synthetic vision is a three-dimensional

computer-generated representation of the terrain that lies

ahead of the aircraft. The display shows runways as well

as a depiction of the terrain features based on a GPS terrain

database. Similar to a video game, the display generates a

runway the pilot can maneuver down in order to maintain

directional control. As long as the pilot tracks down the

computer-generated runway, the aircraft will remain aligned

with the actual runway.

Not all EFD systems have such an advanced visioning system.

With all other systems, the pilot needs to revert to the standard

procedures for instrument takeoffs. Each aircraft may require

a modiﬁ cation to the maneuver; therefore, always obtain

training on any new equipment to be used.

In order to accomplish an instrument takeoff, the aircraft

needs to be maneuvered on the centerline of the runway facing

the direction of departure with the nose or tail wheel straight.

Assistance from the instructor may be necessary if the pilot

has been taxiing while wearing a view limiting device. Lock

the tail wheel, if so equipped, and hold the brakes ﬁ rmly to

prevent the aircraft from creeping. Cross-check the heading

indicator on the PFD with the magnetic compass and adjust

for any deviations noted on the compass card. Set the heading

to the nearest 5° mark closest to the runway heading. This

allows the pilot to quickly detect any deviations from the

desired heading and allows prompt corrective actions during

the takeoff roll. Using the omnibearing select (OBS) mode

on the GPS, rotate the OBS selector until the needle points

to the runway heading. This adds additional situational

awareness during the takeoff roll. Smoothly apply power to

generate sufﬁ cient rudder authority for directional control.

Release the brakes and continue to advance the power to the

takeoff setting.

As soon as the brakes are released, any deviation in heading

needs to be corrected immediately. Avoid using brakes to

control direction as this increases the takeoff roll, as well as

provides the potential of overcontrolling the aircraft.

Continuously cross-check the ASI and the heading indicator

as the aircraft accelerates. As the aircraft approaches 15-25

knots below the rotation speed, smoothly apply aft elevator

pressure to increase the pitch attitude to the desired takeoff

attitude (approximately 7° for most small airplanes). With

the pitch attitude held constant, continue to cross-check the

ﬂ ight instruments and allow the aircraft to ﬂ y off of the

runway. Do not pull the aircraft off of the runway. Pulling

the aircraft off of the runway imposes left turning tendencies

due to P-Factor, which will yaw the aircraft to the left and

destabilize the takeoff.

Maintain the desired pitch and bank attitudes by referencing

the attitude indicator and cross-check the VSI tape for an

indication of a positive rate of climb. Take note of the magenta

6-second altimeter trend indicator. The trend should show

positive. Barring turbulence, all trend indications should

be stabilized. The airspeed trend indicator should not be

visible at this point if the airspeed is being held constant. An

activation of the airspeed trend indicator shows that the pitch

attitude is not being held at the desired value and, therefore,

the airspeed is changing. The desired performance is to be

climbing at a constant airspeed and vertical speed rate. Use

the ASI as the primary instrument for the pitch indication.

5-61

Once the aircraft has reached a safe altitude (approximately

100 feet for insufﬁ cient runway available for landing should

an engine failure occur) retract the landing gear and ﬂ aps

while referencing the ASI and attitude indicator to maintain

the desired pitch. As the conﬁ guration is changed, an increase

in aft control pressure is needed in order to maintain the

desired pitch attitude. Smoothly increase the aft control

pressure to compensate for the change in conﬁ guration.

Anticipate the changes and increase the rate of cross-check.

The airspeed tape and altitude tape increases while the VSI

tape is held constant. Allow the aircraft to accelerate to the

desired climb speed. Once the desired climb speed is reached,

reduce the power to the climb power setting as printed in

the POH/AFM. Trim the aircraft to eliminate any control

pressures.

Common Errors in Instrument Takeoffs

Common errors associated with the instrument takeoff

include, but are not limited to, the following:

1. Failure to perform an adequate ﬂ ight deck check

before the takeoff. Pilots have attempted instrument

takeoff with inoperative airspeed indicators (pitot

tube obstructed), controls locked, and numerous

other oversights due to haste or carelessness. It is

imperative to cross-check the ASI as soon as possible.

No airspeed will be indicated until 20 knots of true

airspeed is generated in some systems.

2. Improper alignment on the runway. This may result

from improper brake applications, allowing the

airplane to creep after alignment, or from alignment

with the nosewheel or tailwheel cocked. In any case,

the result is a built-in directional control problem as

the takeoff starts.

3. Improper application of power. Abrupt applications of

power complicate directional control. Power should be

applied in a smooth and continuous manner to arrive

at the takeoff power setting within approximately 3

seconds.

4. Improper use of brakes. Incorrect seat or rudder pedal

adjustment, with feet in an uncomfortable position,

frequently causes inadvertent application of brakes

and excessive heading changes.

5. Overcontrolling rudder pedals. This fault may be

caused by late recognition of heading changes, tension

on the controls, misinterpretation of the heading

indicator (and correcting in the wrong direction),

failure to appreciate changing effectiveness of rudder

control as the aircraft accelerates, and other factors. If

heading changes are observed and corrected instantly

with small movement of the rudder pedals, swerving

tendencies can be reduced.

6. Failure to maintain attitude after becoming airborne.

If the pilot reacts to seat-of-the-pants sensations when

the airplane lifts off, pitch control is guesswork.

The pilot may either allow excessive pitch or apply

excessive forward-elevator pressure, depending on

the reaction to trim changes.

7. Inadequate cross-check. Fixations are likely during the

trim changes, attitude changes, gear and ﬂ ap retractions,

and power changes. Once an instrument or a control

input is applied, continue the cross-check and note the

effect control during the next cross-check sequence.

8. Inadequate interpretation of instruments. Failure

to understand instrument indications immediately

indicates that further study of the maneuver is

necessary.

Basic Instrument Flight Patterns

After attaining a reasonable degree of proﬁ ciency in basic

maneuvers, apply these skills to the various combinations

of individual maneuvers. The practice flight patterns,

beginning on page 5-30, are directly applicable to operational

instrument ﬂ ying.

5-62

6-1

Introduction

Attitude instrument ﬂ ying in helicopters is essentially visual

ﬂ ying with the ﬂ ight instruments substituted for the various

reference points on the helicopter and the natural horizon.

Control changes, required to produce a given attitude by

reference to instruments, are identical to those used in

helicopter visual ﬂ ight rules (VFR) ﬂ ight, and pilot thought

processes are the same. Basic instrument training is intended to

be a building block toward attaining an instrument rating.

Helicopter Attitude

Instrument Flying

Chapter 6

6-2

Figure 6-1. In most situations, the cross-check pattern includes the attitude indicator between the cross-check of each of the other

instruments. A typical cross-check might progress as follows: attitude indicator, altimeter, attitude indicator, vertical speed indicator,

attitude indicator, heading indicator, attitude indicator, and so on.

Flight Instruments

When flying a helicopter with reference to the flight

instruments, proper instrument interpretation is the basis

for aircraft control. Skill, in part, depends on understanding

how a particular instrument or system functions, including

its indications and limitations (see Chapter 3, Flight

Instruments). With this knowledge, a pilot can quickly

interpret an instrument indication and translate that

information into a control response.

Instrument Flight

To achieve smooth, positive control of the helicopter during

instrument ﬂ ight, three fundamental skills must be developed.

They are instrument cross-check, instrument interpretation,

and aircraft control.

Instrument Cross-Check

Cross-checking, sometimes referred to as scanning, is the

continuous and logical observation of instruments for attitude

and performance information. In attitude instrument ﬂ ying,

an attitude is maintained by reference to the instruments,

which produces the desired result in performance. Due to

human error, instrument error, and helicopter performance

differences in various atmospheric and loading conditions,

it is difﬁ cult to establish an attitude and have performance

remain constant for a long period of time. These variables

make it necessary to constantly check the instruments and

make appropriate changes in the helicopter’s attitude. The

actual technique may vary depending on what instruments

are installed and where they are installed, as well as pilot

experience and proﬁ ciency level. This discussion concentrates

on the six basic ﬂ ight instruments. [Figure 6-1]

At ﬁ rst, there may be a tendency to cross-check rapidly,

looking directly at the instruments without knowing exactly

what information is needed. However, with familiarity and

practice, the instrument cross-check reveals deﬁ nite trends

during speciﬁ c ﬂ ight conditions. These trends help a pilot

control the helicopter as it makes a transition from one ﬂ ight

condition to another.

When full concentration is applied to a single instrument, a

problem called ﬁ xation is encountered. This results from a

natural human inclination to observe a speciﬁ c instrument

carefully and accurately, often to the exclusion of other

instruments. Fixation on a single instrument usually results

in poor control. For example, while performing a turn, there

is a tendency to watch only the turn-and-slip indicator instead

of including other instruments in the cross-check. This

ﬁ xation on the turn-and-slip indicator often leads to a loss of

altitude through poor pitch-and-bank control. Look at each

6-3

instrument only long enough to understand the information

it presents, and then proceed to the next one. Similarly, too

much emphasis can be placed on a single instrument, instead

of relying on a combination of instruments necessary for

helicopter performance information. This differs from ﬁ xation

in that other instruments are included in a cross-check, but too

much attention is placed on one particular instrument.

During performance of a maneuver, there is sometimes

a failure to anticipate signiﬁ cant instrument indications

following attitude changes. For example, during level off

from a climb or descent, a pilot may concentrate on pitch

control, while forgetting about heading or roll information.

This error, called omission, results in erratic control of

heading and bank.

In spite of these common errors, most pilots can adapt well to

ﬂ ight by instrument reference after instruction and practice.

Many ﬁ nd that they can control the helicopter more easily

and precisely by instruments.

Instrument Interpretation

The ﬂ ight instruments together give a picture of what is

happening. No one instrument is more important than the

next; however, during certain maneuvers or conditions,

those instruments that provide the most pertinent and useful

information are termed primary instruments. Those which

back up and supplement the primary instruments are termed

supporting instruments. For example, since the attitude

indicator is the only instrument that provides instant and

direct aircraft attitude information, it should be considered

primary during any change in pitch or bank attitude. After

the new attitude is established, other instruments become

primary, and the attitude indicator usually becomes the

supporting instrument.

Aircraft Control

Controlling a helicopter is the result of accurately interpreting

the flight instruments and translating these readings

into correct control responses. Aircraft control involves

adjustment to pitch, bank, power, and trim in order to achieve

a desired ﬂ ight path.

Pitch attitude control is controlling the movement of

the helicopter about its lateral axis. After interpreting

the helicopter’s pitch attitude by reference to the pitch

instruments (attitude indicator, altimeter, airspeed

indicator, and vertical speed indicator (VSI)), cyclic control

adjustments are made to affect the desired pitch attitude. In

this chapter, the pitch attitudes depicted are approximate

and vary with different helicopters.

Bank attitude control is controlling the angle made by the

lateral tilt of the rotor and the natural horizon, or the movement

of the helicopter about its longitudinal axis. After interpreting

the helicopter’s bank instruments (attitude indicator, heading

indicator, and turn indicator), cyclic control adjustments are

made to attain the desired bank attitude.

Power control is the application of collective pitch with

corresponding throttle control, where applicable. In straight-

and-level ﬂ ight, changes of collective pitch are made to

correct for altitude deviation if the error is more than 100

feet, or the airspeed is off by more than 10 knots. If the error

is less than that amount, a pilot should use a slight cyclic

climb or descent.

In order to ﬂ y a helicopter by reference to the instruments, it

is important to know the approximate power settings required

for a particular helicopter in various load conﬁ gurations and

ﬂ ight conditions.

Trim, in helicopters, refers to the use of the cyclic centering

button, if the helicopter is so equipped, to relieve all

possible cyclic pressures. Trim also refers to the use of pedal

adjustment to center the ball of the turn indicator. Pedal trim

is required during all power changes.

The proper adjustment of collective pitch and cyclic friction

helps a pilot relax during instrument ﬂ ight. Friction should

be adjusted to minimize overcontrolling and to prevent

creeping, but not applied to such a degree that control

movement is limited. In addition, many helicopters equipped

for instrument ﬂ ight contain stability augmentation systems

or an autopilot to help relieve pilot workload.

Straight-and-Level Flight

Straight-and-level unaccelerated ﬂ ight consists of maintaining

the desired altitude, heading, airspeed, and pedal trim.

Pitch Control

The pitch attitude of a helicopter is the angular relation of

its longitudinal axis to the natural horizon. If available, the

attitude indicator is used to establish the desired pitch attitude.

In level ﬂ ight, pitch attitude varies with airspeed and center of

gravity (CG). At a constant altitude and a stabilized airspeed,

the pitch attitude is approximately level. [Figure 6-2]

Attitude Indicator

The attitude indicator gives a direct indication of the pitch

attitude of the helicopter. In visual ﬂ ight, attain the desired

pitch attitude by using the cyclic to raise and lower the nose

6-4

Figure 6-3. The initial pitch correction at normal cruise is one bar

width or less.

Figure 6-2. The ﬂ ight instruments for pitch control are the airspeed indicator, attitude indicator, altimeter, and vertical speed

indicator.

of the helicopter in relation to the natural horizon. During

instrument ﬂ ight, follow exactly the same procedure in

raising or lowering the miniature aircraft in relation to the

horizon bar.

There is some delay between control application and resultant

instrument change. This is the normal control lag in the

helicopter and should not be confused with instrument lag.

The attitude indicator may show small misrepresentations

of pitch attitude during maneuvers involving acceleration,

deceleration, or turns. This precession error can be detected

quickly by cross-checking the other pitch instruments.

If the miniature aircraft is properly adjusted on the ground, it

may not require readjustment in ﬂ ight. If the miniature aircraft

is not on the horizon bar after level off at normal cruising

airspeed, adjust it as necessary while maintaining level ﬂ ight

with the other pitch instruments. Once the miniature aircraft

has been adjusted in level ﬂ ight at normal cruising airspeed,

leave it unchanged so it gives an accurate picture of pitch

attitude at all times.

When making initial pitch attitude corrections to maintain

altitude, the changes of attitude should be small and smoothly

applied. The initial movement of the horizon bar should not

exceed one bar width high or low. [Figure 6-3] If a further

adjustment is required, an additional correction of one-half bar

normally corrects any deviation from the desired altitude. This

one-and-one-half bar correction is normally the maximum

pitch attitude correction from level ﬂ ight attitude.

After making the correction, cross-check the other pitch

instruments to determine whether the pitch attitude change

is sufﬁ cient. If additional correction is needed to return to

altitude, or if the airspeed varies more than 10 knots from

that desired, adjust the power.

Altimeter

The altimeter gives an indirect indication of the pitch

attitude of the helicopter in straight-and-level ﬂ ight. Since

the altitude should remain constant in level ﬂ ight, deviation

from the desired altitude indicates a need for a change in

pitch attitude and power as necessary. When losing altitude,

raise the pitch attitude and adjust power as necessary. When

gaining altitude, lower the pitch attitude and adjust power

as necessary. Indications for power changes are explained

in the next paragraph.

The rate at which the altimeter moves helps to determine pitch

attitude. A very slow movement of the altimeter indicates

a small deviation from the desired pitch attitude, while a

6-5

fast movement of the altimeter indicates a large deviation

from the desired pitch attitude. Make any corrective action

promptly, with small control changes. Also, remember that

movement of the altimeter should always be corrected by

two distinct changes. The ﬁ rst is a change of attitude to stop

the altimeter movement; the second is a change of attitude to

return smoothly to the desired altitude. If altitude and airspeed

are more than 100 feet and 10 knots low, respectively, apply

power in addition to an increase of pitch attitude. If the

altitude and airspeed are high by more than 100 feet and 10

knots, reduce power and lower the pitch attitude.

There is a small lag in the movement of the altimeter;

however, for all practical purposes, consider that the altimeter

gives an immediate indication of a change, or a need for

change in pitch attitude. Since the altimeter provides the

most pertinent information regarding pitch in level ﬂ ight, it

is considered primary for pitch.

Vertical Speed Indicator (VSI)

The VSI gives an indirect indication of the pitch attitude of

the helicopter and should be used in conjunction with the

other pitch instruments to attain a high degree of accuracy

and precision. The instrument indicates zero when in level

ﬂ ight. Any movement of the needle from the zero position

shows a need for an immediate change in pitch attitude to

return it to zero. Always use the VSI in conjunction with

the altimeter in level ﬂ ight. If a movement of the VSI is

detected, immediately use the proper corrective measures

to return it to zero. If the correction is made promptly, there

is usually little or no change in altitude. If the needle of the

VSI does not indicate zero, the altimeter indicates a gain or

loss of altitude.

The initial movement of the vertical speed needle is

instantaneous and indicates the trend of the vertical movement

of the helicopter. A period of time is necessary for the VSI to

reach its maximum point of deﬂ ection after a correction has

been made. This time element is commonly referred to as

instrument lag. The lag is directly proportional to the speed

and magnitude of the pitch change. When employing smooth

control techniques and small adjustments in pitch attitude are

made, lag is minimized, and the VSI is easy to interpret.

Overcontrolling can be minimized by ﬁ rst neutralizing the

controls and allowing the pitch attitude to stabilize, then

readjusting the pitch attitude by noting the indications of the

other pitch instruments.

Occasionally, the VSI may be slightly out of calibration.

This could result in the instrument indicating a slight climb

or descent even when the helicopter is in level ﬂ ight. If the

instrument cannot be calibrated properly, this error must be

taken into consideration when using the VSI for pitch control.

For example, if a descent of 100 feet per minute (fpm) is the

vertical speed indication when the helicopter is in level ﬂ ight,

use that indication as level ﬂ ight. Any deviation from that

reading would indicate a change in attitude.

Airspeed Indicator

The airspeed indicator gives an indirect indication of

helicopter pitch attitude. With a given power setting and

pitch attitude, the airspeed remains constant. If the airspeed

increases, the nose is too low and should be raised. If the

airspeed decreases, the nose is too high and should be

lowered. A rapid change in airspeed indicates a large change

in pitch attitude, and a slow change in airspeed indicates a

small change in pitch attitude. There is very little lag in the

indications of the airspeed indicator. If, while making attitude

changes, there is some lag between control application and

change of airspeed, it is most likely due to cyclic control lag.

Generally, a departure from the desired airspeed, due to an

inadvertent pitch attitude change, also results in a change in

altitude. For example, an increase in airspeed due to a low

pitch attitude results in a decrease in altitude. A correction in

the pitch attitude regains both airspeed and altitude.

Bank Control

The bank attitude of a helicopter is the angular relation of

its lateral axis to the natural horizon. To maintain a straight

course in visual ﬂ ight, keep the lateral axis of the helicopter

level with the natural horizon. Assuming the helicopter is in

coordinated ﬂ ight, any deviation from a laterally level attitude

produces a turn. [Figure 6-4]

Attitude Indicator

The attitude indicator gives a direct indication of the bank

attitude of the helicopter. For instrument ﬂ ight, the miniature

aircraft and the horizon bar of the attitude indicator are

substituted for the actual helicopter and the natural horizon.

Any change in bank attitude of the helicopter is indicated

instantly by the miniature aircraft. For proper interpretation

of this instrument, imagine being in the miniature aircraft. If

the helicopter is properly trimmed and the rotor tilts, a turn

begins. The turn can be stopped by leveling the miniature

aircraft with the horizon bar. The ball in the turn-and-slip

indicator should always be kept centered through proper

pedal trim.

The angle of bank is indicated by the pointer on the banking

scale at the top of the instrument. [Figure 6-5] Small bank

angles, which may not be seen by observing the miniature

aircraft, can easily be determined by referring to the banking

scale pointer.

6-6

Figure 6-5. The banking scale at the top of the attitude indicator indicates varying degrees of bank. In this example, the helicopter is

banked approximately 15° to the right.

Figure 6-4. The ﬂ ight instruments used for bank control are the attitude, heading, and turn indicators.

Pitch-and-bank attitudes can be determined simultaneously

on the attitude indicator. Even though the miniature aircraft

is not level with the horizon bar, pitch attitude can be

established by observing the relative position of the miniature

aircraft and the horizon bar.

The attitude indicator may show small misrepresentations

of bank attitude during maneuvers that involve turns. This

precession error can be detected immediately by closely

cross-checking the other bank instruments during these

maneuvers. Precession is normally noticed when rolling

out of a turn. If, upon completion of a turn, the miniature

aircraft is level and the helicopter is still turning, make a

small change of bank attitude to center the turn needle and

stop the movement of the heading indicator.

Heading Indicator

In coordinated ﬂ ight, the heading indicator gives an indirect

indication of a helicopter’s bank attitude. When a helicopter is

banked, it turns. When the lateral axis of a helicopter is level,

it ﬂ ies straight. Therefore, in coordinated ﬂ ight when the

heading indicator shows a constant heading, the helicopter is

level laterally. A deviation from the desired heading indicates

a bank in the direction the helicopter is turning. A small angle

of bank is indicated by a slow change of heading; a large angle

of bank is indicated by a rapid change of heading. If a turn

is noticed, apply opposite cyclic until the heading indicator

6-7

Figure 6-6. Coordinated ﬂ ight is indicated by centering of the ball.

indicates the desired heading, simultaneously ensuring the

ball is centered. When making the correction to the desired

heading, do not use a bank angle greater than that required

to achieve a standard rate turn. In addition, if the number

of degrees of change is small, limit the bank angle to the

number of degrees to be turned. Bank angles greater than

these require more skill and precision in attaining the desired

results. During straight-and-level ﬂ ight, the heading indicator

is the primary reference for bank control.

Turn Indicator

During coordinated ﬂ ight, the needle of the turn-and-slip

indicator gives an indirect indication of the bank attitude

of the helicopter. When the needle is displaced from the

vertical position, the helicopter is turning in the direction of

the displacement. Thus, if the needle is displaced to the left,

the helicopter is turning left. Bringing the needle back to

the vertical position with the cyclic produces straight ﬂ ight.

A close observation of the needle is necessary to accurately

interpret small deviations from the desired position.

Cross-check the ball of the turn-and-slip indicator to determine

if the helicopter is in coordinated ﬂ ight. [Figure 6-6] If

the rotor is laterally level and pedal pressure properly

compensates for torque, the ball remains in the center. To

center the ball, level the helicopter laterally by reference to

the other bank instruments, then center the ball with pedal

trim. Torque correction pressures vary as power changes are

made. Always check the ball after such changes.

Common Errors During Straight-and-Level Flight

1. Failure to maintain altitude

2. Failure to maintain heading

3. Overcontrolling pitch and bank during corrections

4. Failure to maintain proper pedal trim

5. Failure to cross-check all available instruments

Power Control During Straight-and-Level Flight

Establishing speciﬁ c power settings is accomplished through

collective pitch adjustments and throttle control, where

necessary. For reciprocating-powered helicopters, power

indication is observed on the manifold pressure gauge.

For turbine-powered helicopters, power is observed on the

torque gauge. (Although most Instrument Flight Rules (IFR)-

certiﬁ ed helicopters are turbine powered, depictions within

this chapter use a reciprocating-powered helicopter as this

is where training is most likely conducted.)

At any given airspeed, a speciﬁ c power setting determines

whether the helicopter is in level ﬂ ight, in a climb, or in a

descent. For example, cruising airspeed maintained with

cruising power results in level ﬂ ight. If a pilot increases the

power setting and holds the airspeed constant, the helicopter

climbs. Conversely, if the pilot decreases power and holds

the airspeed constant, the helicopter descends.

6-8

Figure 6-7. Flight instrument indications in straight-and-level ﬂ ight with power increasing.

If the altitude is held constant, power determines the airspeed.

For example, at a constant altitude, cruising power results

in cruising airspeed. Any deviation from the cruising power

setting results in a change of airspeed. When power is added

to increase airspeed, the nose of the helicopter pitches up and

yaws to the right in a helicopter with a counterclockwise main

rotor blade rotation. [Figure 6-7] When power is reduced to

decrease airspeed, the nose pitches down and yaws to the

left. [Figure 6-8] The yawing effect is most pronounced in

single-rotor helicopters, and is absent in helicopters with

counter-rotating rotors. To counteract the yawing tendency

of the helicopter, apply pedal trim during power changes.

To maintain a constant altitude and airspeed in level ﬂ ight,

coordinate pitch attitude and power control. The relationship

between altitude and airspeed determines the need for a

change in power and/or pitch attitude. If the altitude is

constant and the airspeed is high or low, change the power to

obtain the desired airspeed. During the change in power, make

an accurate interpretation of the altimeter, then counteract

any deviation from the desired altitude by an appropriate

change of pitch attitude. If the altitude is low and the airspeed

is high, or vice versa, a change in pitch attitude alone may

return the helicopter to the proper altitude and airspeed. If

both airspeed and altitude are low, or if both are high, changes

in both power and pitch attitude are necessary.

To make power control easy when changing airspeed, it is

necessary to know the approximate power settings for the

various airspeeds at which the helicopter is ﬂ own. When the

airspeed is to be changed by any appreciable amount, adjust

the power so that it is over or under that setting necessary

to maintain the new airspeed. As the power approaches the

desired setting, include the manifold pressure in the cross-

check to determine when the proper adjustment has been

accomplished. As the airspeed is changing, adjust the pitch

attitude to maintain a constant altitude. A constant heading

should be maintained throughout the change. As the desired

airspeed is approached, adjust power to the new cruising

power setting and further adjust pitch attitude to maintain

altitude. The instrument indications for straight-and-level

ﬂ ight at normal cruise and during the transition from normal

cruise to slow cruise are illustrated in Figures 6-9 and 6-10.

After the airspeed stabilizes at slow cruise, the attitude

indicator shows an approximate level pitch attitude.

The altimeter is the primary pitch instrument during level

ﬂ ight, whether ﬂ ying at a constant airspeed or during a

change in airspeed. Altitude should not change during

airspeed transitions, and the heading indicator remains the

primary bank instrument. Whenever the airspeed is changed

by an appreciable amount, the manifold pressure gauge is

momentarily the primary instrument for power control.

When the airspeed approaches the desired reading, the

airspeed indicator again becomes the primary instrument

for power control.

6-9

Figure 6-8. Flight instrument indications in straight-and-level ﬂ ight with power decreasing.

Figure 6-9. Flight instrument indications in straight-and-level ﬂ ight at normal cruise speed.

6-10

Figure 6-10. Flight instrument indications in straight-and-level ﬂ ight with airspeed decreasing.

Entry

To enter a constant airspeed climb from cruise airspeed when

the climb speed is lower than cruise speed, simultaneously

increase power to the climb power setting and adjust pitch

attitude to the approximate climb attitude. The increase in

power causes the helicopter to start climbing and only very

slight back cyclic pressure is needed to complete the change

from level to climb attitude. The attitude indicator should

be used to accomplish the pitch change. If the transition

from level ﬂ ight to a climb is smooth, the VSI shows an

immediate upward trend and then stops at a rate appropriate

to the stabilized airspeed and attitude. Primary and supporting

instruments for climb entry are illustrated in Figure 6-11.

When the helicopter stabilizes at a constant airspeed and

attitude, the airspeed indicator becomes primary for pitch.

The manifold pressure continues to be primary for power and

should be monitored closely to determine if the proper climb

power setting is being maintained. Primary and supporting

instruments for a stabilized constant airspeed climb are shown

in Figure 6-12.

The technique and procedures for entering a constant rate

climb are very similar to those previously described for a

constant airspeed climb. For training purposes, a constant

To produce straight-and-level ﬂ ight, the cross-check of the

pitch-and-bank instruments should be combined with the

power control instruments. With a constant power setting, a

normal cross-check should be satisfactory. When changing

power, the speed of the cross-check must be increased to

cover the pitch-and-bank instruments adequately. This is

necessary to counteract any deviations immediately.

Common Errors During Airspeed Changes

1. Improper use of power

2. Overcontrolling pitch attitude

3. Failure to maintain heading

4. Failure to maintain altitude

5. Improper pedal trim

Straight Climbs (Constant Airspeed and

Constant Rate)

For any power setting and load condition, there is only

one airspeed that gives the most efﬁ cient rate of climb.

To determine this, consult the climb data for the type of

helicopter being ﬂ own. The technique varies according to

the airspeed on entry and whether a constant airspeed or

constant rate climb is made.

6-11

Figure 6-11. Flight instrument indications during climb entry for a constant-airspeed climb.

Figure 6-12. Flight instrument indications in a stabilized constant-airspeed climb.

6-12

Figure 6-13. Flight Instrument Indications in a Stabilized Constant-Rate Climb.

rate climb is entered from climb airspeed. Use the rate

appropriate for the particular helicopter being flown.

Normally, in helicopters with low climb rates, 500 fpm is

appropriate. In helicopters capable of high climb rates, use

a rate of 1,000 fpm.

To enter a constant rate climb, increase power to the

approximate setting for the desired rate. As power is

applied, the airspeed indicator is primary for pitch until the

vertical speed approaches the desired rate. At this time, the

VSI becomes primary for pitch. Change pitch attitude by

reference to the attitude indicator to maintain the desired

vertical speed. When the VSI becomes primary for pitch, the

airspeed indicator becomes primary for power. Primary and

supporting instruments for a stabilized constant rate climb are

illustrated in Figure 6-13. Adjust power to maintain desired

airspeed. Pitch attitude and power corrections should be

closely coordinated. To illustrate this, if the vertical speed

is correct but the airspeed is low, add power. As power is

increased, it may be necessary to lower the pitch attitude

slightly to avoid increasing the vertical rate. Adjust the pitch

attitude smoothly to avoid overcontrolling. Small power

corrections are usually sufﬁ cient to bring the airspeed back

to the desired indication.

Level Off

The level off from a constant airspeed climb must be started

before reaching the desired altitude. Although the amount

of lead varies with the type of helicopter being ﬂ own and

pilot technique, the most important factor is vertical speed.

As a rule of thumb, use 10 percent of the vertical velocity

as the lead point. For example, if the rate of climb is 500

fpm, initiate the level off approximately 50 feet before the

desired altitude. When the proper lead altitude is reached, the

altimeter becomes primary for pitch. Adjust the pitch attitude

to the level ﬂ ight attitude for that airspeed. Cross-check the

altimeter and VSI to determine when level ﬂ ight has been

attained at the desired altitude. If cruise airspeed is higher

than climb airspeed, leave the power at the climb power

setting until the airspeed approaches cruise airspeed, and

then reduce it to the cruise power setting. The level off from

a constant rate climb is accomplished in the same manner as

the level off from a constant airspeed climb.

Straight Descents (Constant Airspeed

and Constant Rate)

A descent may be performed at any normal airspeed the

helicopter can attain, but the airspeed must be determined

prior to entry. The technique is determined by the type of

descent, a constant airspeed or a constant rate.

Entry

If airspeed is higher than descending airspeed, and a constant

airspeed descent is desired, reduce power to a descent

power setting and maintain a constant altitude using cyclic

pitch control. This slows the helicopter. As the helicopter

6-13

approaches the descending airspeed, the airspeed indicator

becomes primary for pitch and the manifold pressure is

primary for power. Holding the airspeed constant causes the

helicopter to descend. For a constant rate descent, reduce the

power to the approximate setting for the desired rate. If the

descent is started at the descending airspeed, the airspeed

indicator is primary for pitch until the VSI approaches the

desired rate. At this time, the VSI becomes primary for

pitch, and the airspeed indicator becomes primary for power.

Coordinate power and pitch attitude control as previously

described on page 6-10 for constant rate climbs.

Level Off

The level off from a constant airspeed descent may be

made at descending airspeed or at cruise airspeed, if this is

higher than descending airspeed. As in a climb level off, the

amount of lead depends on the rate of descent and control

technique. For a level off at descending airspeed, the lead

should be approximately 10 percent of the vertical speed. At

the lead altitude, simultaneously increase power to the setting

necessary to maintain descending airspeed in level ﬂ ight. At

this point, the altimeter becomes primary for pitch, and the

airspeed indicator becomes primary for power.

To level off at an airspeed higher than descending airspeed,

increase the power approximately 100 to 150 feet prior to

reaching the desired altitude. The power setting should be that

which is necessary to maintain the desired airspeed in level

ﬂ ight. Hold the vertical speed constant until approximately

50 feet above the desired altitude. At this point, the altimeter

becomes primary for pitch and the airspeed indicator becomes

primary for power. The level off from a constant rate descent

should be accomplished in the same manner as the level off

from a constant airspeed descent.

Common Errors During Straight Climbs and

Descents

1. Failure to maintain heading

2. Improper use of power

3. Poor control of pitch attitude

4. Failure to maintain proper pedal trim

5. Failure to level off on desired altitude

Turns

Turns made by reference to the ﬂ ight instruments should

be made at a precise rate. Turns described in this chapter

are those not exceeding a standard rate of 3° per second

as indicated on the turn-and-slip indicator. True airspeed

determines the angle of bank necessary to maintain a standard

rate turn. A rule of thumb to determine the approximate angle

of bank required for a standard rate turn is to use 15 percent

of the airspeed. A simple way to determine this amount is

to divide the airspeed by 10 and add one-half the result. For

example, at 60 knots approximately 9° of bank is required

(60 ÷ 10 = 6, 6 + 3 = 9); at 80 knots approximately 12° of

bank is needed for a standard rate turn.

To enter a turn, apply lateral cyclic in the direction of the

desired turn. The entry should be accomplished smoothly,

using the attitude indicator to establish the approximate bank

angle. When the turn indicator indicates a standard rate turn,

it becomes primary for bank. The attitude indicator now

becomes a supporting instrument. During level turns, the

altimeter is primary for pitch, and the airspeed indicator is

primary for power. Primary and supporting instruments for a

stabilized standard rate turn are illustrated in Figure 6-14. If

an increase in power is required to maintain airspeed, slight

forward cyclic pressure may be required since the helicopter

tends to pitch up as collective pitch is increased. Apply pedal

trim, as required, to keep the ball centered.

To recover to straight-and-level ﬂ ight, apply cyclic in the

direction opposite the turn. The rate of roll-out should be the

same as the rate used when rolling into the turn. As the turn

recovery is initiated, the attitude indicator becomes primary

for bank. When the helicopter is approximately level, the

heading indicator becomes primary for bank as in straight-

and-level ﬂ ight. Cross-check the airspeed indicator and ball

closely to maintain the desired airspeed and pedal trim.

Turn to a Predetermined Heading

A helicopter turns as long as its lateral axis is tilted;

therefore, the recovery must start before the desired heading

is reached. The amount of lead varies with the rate of turn

and piloting technique.

As a guide, when making a 3° per second rate of turn, use a

lead of one-half the bank angle. For example, if using a 12°

bank angle, use half of that, or 6°, as the lead point prior to the

desired heading. Use this lead until the exact amount required

by a particular technique can be determined. The bank angle

should never exceed the number of degrees to be turned.

As in any standard rate turn, the rate of recovery should be

the same as the rate of entry. During turns to predetermined

headings, cross-check the primary and supporting pitch, bank,

and power instruments closely.

Timed Turns

A timed turn is a turn in which the clock and turn-and-slip

indicator are used to change heading a deﬁ nite number of

degrees in a given time. For example, using a standard rate

turn, a helicopter turns 45° in 15 seconds. Using a half-

6-14

Figure 6-14. Flight Instrument Indications in a Standard-Rate Turn to the Left.

standard rate turn, the helicopter turns 45° in 30 seconds.

Timed turns can be used if the heading indicator becomes

inoperative.

Prior to performing timed turns, the turn coordinator should

be calibrated to determine the accuracy of its indications.

To do this, establish a standard rate turn by referring to the

turn-and-slip indicator. Then, as the sweep second hand of

the clock passes a cardinal point (12, 3, 6, or 9), check the

heading on the heading indicator. While holding the indicated

rate of turn constant, note the heading changes at 10-second

intervals. If the helicopter turns more or less than 30° in

that interval, a smaller or larger deﬂ ection of the needle is

necessary to produce a standard rate turn. After the turn-

and-slip indicator has been calibrated during turns in each

direction, note the corrected deﬂ ections, if any, and apply

them during all timed turns.

Use the same cross-check and control technique in making

timed turns that is used to make turns to a predetermined

heading, but substitute the clock for the heading indicator.

The needle of the turn-and-slip indicator is primary for bank

control, the altimeter is primary for pitch control, and the

airspeed indicator is primary for power control. Begin the

roll-in when the clock’s second hand passes a cardinal point;

hold the turn at the calibrated standard rate indication, or

half-standard rate for small changes in heading; then begin

the roll-out when the computed number of seconds has

elapsed. If the roll-in and roll-out rates are the same, the time

taken during entry and recovery need not be considered in

the time computation.

If practicing timed turns with a full instrument panel, check

the heading indicator for the accuracy of the turns. If executing

turns without the heading indicator, use the magnetic compass

at the completion of the turn to check turn accuracy, taking

compass deviation errors into consideration.

Change of Airspeed in Turns

Changing airspeed in turns is an effective maneuver for

increasing proﬁ ciency in all three basic instrument skills.

Since the maneuver involves simultaneous changes in all

components of control, proper execution requires a rapid

cross-check and interpretation, as well as smooth control.

Proﬁ ciency in the maneuver also contributes to conﬁ dence in

the instruments during attitude and power changes involved

in more complex maneuvers.

Pitch and power control techniques are the same as those

used during airspeed changes in straight-and-level ﬂ ight.

As discussed previously, the angle of bank necessary for a

given rate of turn is proportional to the true airspeed. Since

the turns are executed at standard rate, the angle of bank

must be varied in direct proportion to the airspeed change in

order to maintain a constant rate of turn. During a reduction

of airspeed, decrease the angle of bank and increase the pitch

attitude to maintain altitude and a standard rate turn.

6-15

Altimeter and turn indicator readings should remain constant

throughout the turn. The altimeter is primary for pitch control,

and the turn needle is primary for bank control. Manifold

pressure is primary for power control while the airspeed is

changing. As the airspeed approaches the new indication, the

airspeed indicator becomes primary for power control.

Two methods of changing airspeed in turns may be used.

In the ﬁ rst method, airspeed is changed after the turn is

established. In the second method, the airspeed change

is initiated simultaneously with the turn entry. The ﬁ rst

method is easier, but regardless of the method used, the rate

of cross-check must be increased as power is reduced. As

the helicopter decelerates, check the altimeter and VSI for

needed pitch changes, and the bank instruments for needed

bank changes. If the needle of the turn-and-slip indicator

shows a deviation from the desired deﬂ ection, change the

bank. Adjust pitch attitude to maintain altitude. When the

airspeed approaches that desired, the airspeed indicator

becomes primary for power control. Adjust the power to

maintain the desired airspeed. Use pedal trim to ensure the

maneuver is coordinated.

Until control technique is very smooth, frequently cross-

check the attitude indicator to keep from overcontrolling

and to provide approximate bank angles appropriate for the

changing airspeeds.

Compass Turns

The use of gyroscopic heading indicators makes heading

control very easy. However, if the heading indicator fails

or the helicopter is not equipped with one, use the magnetic

compass for heading reference. When making compass-only

turns, a pilot needs to adjust for the lead or lag created by

acceleration and deceleration errors so that the helicopter

rolls out on the desired heading. When turning to a heading

of north, the lead for the roll-out must include the number of

degrees of latitude plus the lead normally used in recovery

from turns. During a turn to a south heading, maintain the

turn until the compass passes south the number of degrees

of latitude, minus the normal roll-out lead. For example,

when turning from an easterly direction to north, where the

latitude is 30°, start the roll-out when the compass reads

37° (30° plus one-half the 15° angle of bank, or whatever

amount is appropriate for the rate of roll-out). When turning

from an easterly direction to south, start the roll-out when

the magnetic compass reads 203° (180° plus 30° minus one-

half the angle of bank). When making similar turns from a

westerly direction, the appropriate points at which to begin

the roll-out would be 323° for a turn to north, and 157° for

a turn to south.

30° Bank Turn

A turn using 30° of bank is seldom necessary or advisable

in instrument meteorological conditions (IMC), and is

considered an unusual attitude in a helicopter. However, it

is an excellent maneuver to practice to increase the ability to

react quickly and smoothly to rapid changes of attitude. Even

though the entry and recovery techniques are the same as for

any other turn, it is more difﬁ cult to control pitch because

of the decrease in vertical lift as the bank increases. Also,

because of the decrease in vertical lift, there is a tendency

to lose altitude and/or airspeed. Therefore, to maintain a

constant altitude and airspeed, additional power is required.

Do not initiate a correction, however, until the instruments

indicate the need for one. During the maneuver, note the

need for a correction on the altimeter and VSI, check the

attitude indicator, and then make the necessary adjustments.

After making a change, check the altimeter and VSI again to

determine whether or not the correction was adequate.

Climbing and Descending Turns

For climbing and descending turns, the techniques described

previously for straight climbs, descents, and standard rate

turns are combined. For practice, simultaneously turn and

start the climb or descent. The primary and supporting

instruments for a stabilized constant airspeed left climbing

turn are illustrated in Figure 6-15. The level off from a

climbing or descending turn is the same as the level off from

a straight climb or descent. To return to straight-and-level

ﬂ ight, stop the turn and then level off, or level off and then

stop the turn, or simultaneously level off and stop the turn.

During climbing and descending turns, keep the ball of the

turn indicator centered with pedal trim.

Common Errors During Turns

1. Failure to maintain desired turn rate

2. Failure to maintain altitude in level turns

3. Failure to maintain desired airspeed

4. Variation in the rate of entry and recovery

5. Failure to use proper lead in turns to a heading

6. Failure to properly compute time during timed turns

7. Failure to use proper leads and lags during the compass

turns

8. Improper use of power

9. Failure to use proper pedal trim

6-16

Figure 6-15. Flight Instrument Indications for a Stabilized Left Climbing Turn at a Constant Airspeed.

Unusual Attitudes

Any maneuver not required for normal helicopter instrument

ﬂ ight is an unusual attitude and may be caused by any one

or combination of factors such as turbulence, disorientation,

instrument failure, confusion, preoccupation with ﬂ ight deck

duties, carelessness in cross-checking, errors in instrument

interpretation, or lack of proﬁ ciency in aircraft control. Due

to the instability characteristics of the helicopter, unusual

attitudes can be extremely critical. As soon as an unusual

attitude is detected, make a recovery to straight-and-level

ﬂ ight as soon as possible with a minimum loss of altitude.

To recover from an unusual attitude, a pilot should correct

bank-and-pitch attitude and adjust power as necessary. All

components are changed almost simultaneously, with little

lead of one over the other. A pilot must be able to perform

this task with and without the attitude indicator. If the

helicopter is in a climbing or descending turn, adjust bank,

pitch, and power. The bank attitude should be corrected

by referring to the turn-and-slip indicator and attitude

indicator. Pitch attitude should be corrected by reference to

the altimeter, airspeed indicator, VSI, and attitude indicator.

Adjust power by referring to the airspeed indicator and

manifold pressure.

Since the displacement of the controls used in recovery from

unusual attitudes may be greater than those used for normal

ﬂ ight, make careful adjustments as straight-and-level ﬂ ight

is approached. Cross-check the other instruments closely to

avoid overcontrolling.

Common Errors During Unusual Attitude

Recoveries

1. Failure to make proper pitch correction

2. Failure to make proper bank correction

3. Failure to make proper power correction

4. Overcontrolling pitch and/or bank attitude

5. Overcontrolling power

6. Excessive loss of altitude

Emergencies

Emergencies during instrument ﬂ ight are handled similarly

to those occurring during VFR ﬂ ight. A thorough knowledge

of the helicopter and its systems, as well as good aeronautical

knowledge and judgment, is the best preparation for

emergency situations. Safe operations begin with preﬂ ight

planning and a thorough preﬂ ight inspection. Plan a route

of ﬂ ight to include adequate landing sites in the event of an

emergency landing. Make sure all resources, such as maps,

publications, ﬂ ashlights, and ﬁ re extinguishers are readily

available for use in an emergency.

During any emergency, ﬁ rst ﬂ y the aircraft. This means ensure

the helicopter is under control, and determine emergency

6-17

landing sites. Then perform the emergency checklist memory

items, followed by items written in the rotorcraft ﬂ ight

manual (RFM). When all these items are under control, notify

air trafﬁ c control (ATC). Declare any emergency on the last

assigned ATC frequency. If one was not issued, transmit on

the emergency frequency 121.5. Set the transponder to the

emergency squawk code 7700. This code triggers an alarm

or special indicator in radar facilities.

When experiencing most in-ﬂ ight emergencies, such as low

fuel or complete electrical failure, land as soon as possible.

In the event of an electrical ﬁ re, turn off all nonessential

equipment and land immediately. Some essential electrical

instruments, such as the attitude indicator, may be required

for a safe landing. A navigation radio failure may not require

an immediate landing if the ﬂ ight can continue safely. In

this case, land as soon as practical. ATC may be able to

provide vectors to a safe landing area. For speciﬁ c details

on what to do during an emergency, refer to the RFM for

the helicopter.

Autorotations

Both straight-ahead and turning autorotations should be

practiced by reference to instruments. This training ensures

prompt corrective action to maintain positive aircraft control

in the event of an engine failure.

To enter autorotation, reduce collective pitch smoothly to

maintain a safe rotor RPM and apply pedal trim to keep the

ball of the turn-and-slip indicator centered. The pitch attitude

of the helicopter should be approximately level as shown by

the attitude indicator. The airspeed indicator is the primary

pitch instrument and should be adjusted to the recommended

autorotation speed. The heading indicator is primary for bank

in a straight-ahead autorotation. In a turning autorotation, a

standard rate turn should be maintained by reference to the

needle of the turn-and-slip indicator.

Common Errors During Autorotations

1. Uncoordinated entry due to improper pedal trim

2. Poor airspeed control due to improper pitch attitude

3. Poor heading control in straight-ahead autorotations

4. Failure to maintain proper rotor RPM

5. Failure to maintain a standard rate turn during turning

autorotations

Servo Failure

Most helicopters certiﬁ ed for single-pilot IFR ﬂ ight are required

to have autopilots, which greatly reduces pilot workload. If an

autopilot servo fails, however, resume manual control of the

helicopter. The amount of workload increase depends on which

servo fails. If a cyclic servo fails, a pilot may want to land

immediately because the workload increases tremendously. If

an antitorque or collective servo fails, continuing to the next

suitable landing site might be possible.

Instrument Takeoff

The procedures and techniques described here should be

modiﬁ ed as necessary to conform to those set forth in the

operating instructions for the particular helicopter being

flown. During training, instrument takeoffs should not

be attempted except when receiving instruction from an

appropriately certiﬁ cated, proﬁ cient ﬂ ight instructor pilot.

Adjust the miniature aircraft in the attitude indicator, as

appropriate, for the aircraft being ﬂ own. After the helicopter

is aligned with the runway or takeoff pad, to prevent forward

movement of a helicopter equipped with a wheel-type landing

gear, set the parking brakes or apply the toe brakes. If the

parking brake is used, it must be unlocked after the takeoff

has been completed. Apply sufﬁ cient friction to the collective

pitch control to minimize overcontrolling and to prevent

creeping. Excessive friction should be avoided since it limits

collective pitch movement.

After checking all instruments for proper indications, start

the takeoff by applying collective pitch and a predetermined

power setting. Add power smoothly and steadily to gain

airspeed and altitude simultaneously and to prevent settling to

the ground. As power is applied and the helicopter becomes

airborne, use the antitorque pedals initially to maintain the

desired heading. At the same time, apply forward cyclic to

begin accelerating to climbing airspeed. During the initial

acceleration, the pitch attitude of the helicopter, as read on the

attitude indicator, should be one- to two-bar widths low. The

primary and supporting instruments after becoming airborne

are illustrated in Figure 6-16. As the airspeed increases to the

appropriate climb airspeed, adjust pitch gradually to climb

attitude. As climb airspeed is reached, reduce power to the

climb power setting and transition to a fully coordinated

straight climb.

During the initial climb out, minor heading corrections

should be made with pedals only until sufﬁ cient airspeed is

attained to transition to fully coordinated ﬂ ight. Throughout

the instrument takeoff, instrument cross-check and

interpretations must be rapid and accurate, and aircraft control

positive and smooth.

6-18

Figure 6-16. Flight Instrument Indications During an Instrument Takeoff.

Common Errors During Instrument Takeoffs

1. Failure to maintain heading

2. Overcontrolling pedals

3. Failure to use required power

4. Failure to adjust pitch attitude as climbing airspeed is

reached

Changing Technology

Advances in technology have brought about changes in

the instrumentation found in all types of aircraft, including

helicopters. Electronic displays commonly referred to as

“glass cockpits” are becoming more common. Primary ﬂ ight

displays (PFDs) and multi-function displays (MFDs) are

changing not only what information is available to a pilot

but also how that information is displayed.

Illustrations of technological advancements in instrumentation

are described as follows. In Figure 6-17, a typical PFD

depicts an aircraft flying straight-and-level at 3,000

feet and 100 knots. Figure 6-18 illustrates a nose-low

pitch attitude in a right turn. MFDs can be conﬁ gured to

provide navigation information such as the moving map in

Figure 6-19 or information pertaining to aircraft systems as

in Figure 6-20.

6-19

Figure 6-17. PFD Indications During Straight-and-Level Flight.

Figure 6-18. PFD Indications During a Nose-Low Pitch Attitude in a Right Turn.

6-20

Figure 6-19. MFD Display of a Moving Map.

Figure 6-20. MFD Display of Aircraft Systems.

7-1

Introduction

This chapter provides the basic radio principles applicable to

navigation equipment, as well as an operational knowledge

of how to use these systems in instrument flight. This

information provides the framework for all instrument

procedures, including standard instrument departure

procedures (SIDS), departure procedures (DPs), holding

patterns, and approaches, because each of these maneuvers

consists mainly of accurate attitude instrument ﬂ ying and

accurate tracking using navigation systems.

Navigation

Systems

Chapter 7

7-2

Figure 7-1. Ground, Space, and Sky Wave Propogation.

Basic Radio Principles

A radio wave is an electromagnetic (EM) wave with

frequency characteristics that make it useful. The wave

will travel long distances through space (in or out of the

atmosphere) without losing too much strength. An antenna

is used to convert electric current into a radio wave so it can

travel through space to the receiving antenna, which converts

it back into an electric current for use by a receiver.

How Radio Waves Propagate

All matter has a varying degree of conductivity or resistance

to radio waves. The Earth itself acts as the greatest resistor

to radio waves. Radiated energy that travels near the ground

induces a voltage in the ground that subtracts energy from the

wave, decreasing the strength of the wave as the distance from

the antenna becomes greater. Trees, buildings, and mineral

deposits affect the strength to varying degrees. Radiated

energy in the upper atmosphere is likewise affected as the

energy of radiation is absorbed by molecules of air, water,

and dust. The characteristics of radio wave propagation vary

according to the signal frequency and the design, use, and

limitations of the equipment.

Ground Wave

A ground wave travels across the surface of the Earth. You

can best imagine a ground wave’s path as being in a tunnel

or alley bounded by the surface of the Earth and by the

ionosphere, which keeps the ground wave from going out

into space. Generally, the lower the frequency, the farther

the signal will travel.

Ground waves are usable for navigation purposes because

they travel reliably and predictably along the same route

day after day, and are not inﬂ uenced by too many outside

factors. The ground wave frequency range is generally from

the lowest frequencies in the radio range (perhaps as low as

100 Hz) up to approximately 1,000 kHz (1 MHz). Although

there is a ground wave component to frequencies above this,

up to 30 MHz, the ground wave at these higher frequencies

loses strength over very short distances.

Sky Wave

The sky wave, at frequencies of 1 to 30 MHz, is good for

long distances because these frequencies are refracted or

“bent” by the ionosphere, causing the signal to be sent back

to Earth from high in the sky and received great distances

away. [Figure 7-1] Used by high frequency (HF) radios in

aircraft, messages can be sent across oceans using only 50

to 100 watts of power. Frequencies that produce a sky wave

are not used for navigation because the pathway of the signal

from transmitter to receiver is highly variable. The wave is

“bounced” off of the ionosphere, which is always changing

due to the varying amount of the sun’s radiation reaching it

(night/day and seasonal variations, sunspot activity, etc.). The

sky wave is, therefore, unreliable for navigation purposes.

For aeronautical communication purposes, the sky wave

(HF) is about 80 to 90 percent reliable. HF is being gradually

replaced by more reliable satellite communication.

Space Wave

When able to pass through the ionosphere, radio waves

of 15 MHz and above (all the way up to many GHz), are

considered space waves. Most navigation systems operate

with signals propagating as space waves. Frequencies above

100 MHz have nearly no ground or sky wave components.

They are space waves, but (except for global positioning

system (GPS)) the navigation signal is used before it reaches

the ionosphere so the effect of the ionosphere, which can

cause some propagation errors, is minimal. GPS errors

caused by passage through the ionosphere are signiﬁ cant

and are corrected for by the GPS receiver system.

Space waves have another characteristic of concern to users.

Space waves reﬂ ect off hard objects and may be blocked if

the object is between the transmitter and the receiver. Site

and terrain error, as well as propeller/rotor modulation error

in very high omnidirectional range (VOR) systems is caused

by this bounce. Instrument landing system (ILS) course

distortion is also the result of this phenomenon, which led

to the need for establishment of ILS critical areas.

7-3

Figure 7-2. ADF Indicator Instrument and Receiver.

Generally, space waves are “line of sight” receivable, but

those of lower frequencies will “bend” somewhat over the

horizon. The VOR signal at 108 to 118 MHz is a lower

frequency than distance measuring equipment (DME) at 962

to 1213 MHz. Therefore, when an aircraft is ﬂ own “over the

horizon” from a VOR/DME station, the DME will normally

be the ﬁ rst to stop functioning.

Disturbances to Radio Wave Reception

Static distorts the radio wave and interferes with normal

reception of communications and navigation signals. Low-

frequency airborne equipment such as automatic direction

ﬁ nder (ADF) and LORAN are particularly subject to static

disturbance. Using very high frequency (VHF) and ultra-

high frequency (UHF) frequencies avoids many of the

discharge noise effects. Static noise heard on navigation

or communication radio frequencies may be a warning of

interference with navigation instrument displays. Some of

the problems caused by precipitation static (P-static) are:

• Complete loss of VHF communications.

• Erroneous magnetic compass readings.

• Aircraft ﬂ ying with one wing low while using the

autopilot.

• High-pitched squeal on audio.

• Motorboat sound on audio.

• Loss of all avionics.

• Inoperative very-low frequency (VLF) navigation

system.

• Erratic instrument readouts.

• Weak transmissions and poor radio reception.

• St. Elmo’s Fire.

Traditional Navigation Systems

Nondirectional Radio Beacon (NDB)

The nondirectional radio beacon (NDB) is a ground-based

radio transmitter that transmits radio energy in all directions.

The ADF, when used with an NDB, determines the bearing

from the aircraft to the transmitting station. The indicator

may be mounted in a separate instrument in the aircraft

panel. [Figure 7-2] The ADF needle points to the NDB

ground station to determine the relative bearing (RB) to the

transmitting station. It is the number of degrees measured

clockwise between the aircraft’s heading and the direction

from which the bearing is taken. The aircraft’s magnetic

heading (MH) is the direction the aircraft is pointed with

respect to magnetic north. The magnetic bearing (MB) is the

direction to or from a radio transmitting station measured

relative to magnetic north.

NDB Components

The ground equipment, the NDB, transmits in the frequency

range of 190 to 535 kHz. Most ADFs will also tune the AM

broadcast band frequencies above the NDB band (550 to

1650 kHz). However, these frequencies are not approved

for navigation because stations do not continuously identify

themselves, and they are much more susceptible to sky

wave propagation especially from dusk to dawn. NDB

stations are capable of voice transmission and are often used

for transmitting the automated weather observing system

(AWOS). The aircraft must be in operational range of the

NDB. Coverage depends on the strength of the transmitting

station. Before relying on ADF indications, identify the

station by listening to the Morse code identiﬁ er. NDB stations

are usually two letters or an alpha-numeric combination.

ADF Components

The airborne equipment includes two antennas, a receiver,

and the indicator instrument. The “sense” antenna (non-

directional) receives signals with nearly equal efﬁ ciency

from all directions. The “loop” antenna receives signals

better from two directions (bidirectional). When the loop

and sense antenna inputs are processed together in the ADF

radio, the result is the ability to receive a radio signal well in

all directions but one, thus resolving all directional ambiguity.

The indicator instrument can be one of four kinds: ﬁ xed-

card ADF, rotatable compass-card ADF, or radio magnetic

7-4

Figure 7-3. Relative bearing (RB) on a ﬁ xed-card indicator. Note

that the card always indicates 360°, or north. In this case, the

relative bearing to the station is 135° to the right. If the aircraft

were on a magnetic heading of 360°, then the magnetic bearing

(MB) would also be 135°.

Figure 7-4. Relative bearing (RB) on a movable-card indicator. By

placing the aircraft’s magnetic heading (MH) of 045° under the

top index, the relative bearing (RB) of 135° to the right will also

be the magnetic bearing (no wind conditions) which will take you

to the transmitting station.

indicator (RMI) with either one needle or dual needle. Fixed-

card ADF (also known as the relative bearing indicator (RBI))

always indicates zero at the top of the instrument, with the

needle indicating the RB to the station. Figure 7-3 indicates

an RB of 135°; if the MH is 045°, the MB to the station is

180°. (MH + RB = MB to the station.)

The movable-card ADF allows the pilot to rotate the

aircraft’s present heading to the top of the instrument so

that the head of the needle indicates MB to the station and

the tail indicates MB from the station. Figure 7-4 indicates

a heading of 045°, MB to the station of 180°, and MB from

the station of 360°.

The RMI differs from the movable-card ADF in that it

automatically rotates the azimuth card (remotely controlled

by a gyrocompass) to represent aircraft heading. The RMI

has two needles, which can be used to indicate navigation

information from either the ADF or the VOR receiver. When

a needle is being driven by the ADF, the head of the needle

indicates the MB TO the station tuned on the ADF receiver.

The tail of the needle is the bearing FROM the station. When

a needle of the RMI is driven by a VOR receiver, the needle

indicates where the aircraft is radially with respect to the

VOR station. The needle points to the bearing TO the station,

as read on the azimuth card. The tail of the needle points to

the radial of the VOR the aircraft is currently on or crossing.

Figure 7-5 indicates a heading of 005°, the MB to the station

is 015°, and the MB from the station is 195°.

Function of ADF

The ADF can be used to plot your position, track inbound

and outbound, and intercept a bearing. These procedures

are used to execute holding patterns and nonprecision

instrument approaches.

Orientation

The ADF needle points TO the station, regardless of aircraft

heading or position. The RB indicated is thus the angular

relationship between the aircraft heading and the station,

measured clockwise from the nose of the aircraft. Think of

the nose/tail and left/right needle indications, visualizing the

ADF dial in terms of the longitudinal axis of the aircraft.

When the needle points to 0°, the nose of the aircraft points

directly to the station; with the pointer on 210°, the station

is 30° to the left of the tail; with the pointer on 090°, the

station is off the right wingtip. The RB alone does not indicate

aircraft position. The RB must be related to aircraft heading

in order to determine direction to or from the station.

Station Passage

When you are near the station, slight deviations from

the desired track result in large deﬂ ections of the needle.

Therefore, it is important to establish the correct drift

correction angle as soon as possible. Make small heading

corrections (not over 5°) as soon as the needle shows a

deviation from course, until it begins to rotate steadily toward

a wingtip position or shows erratic left/right oscillations. You

7-5

Figure 7-5. Radio magnetic indicator (RMI). Because the aircraft’s

magnetic heading is automatically changed, the relative bearing

(RB), in this case 095°, will indicate the magnetic bearing (095°)

to the station (no wind conditions) and the magnetic heading that

will take you there.

are abeam a station when the needle points 90° off your track.

Hold your last corrected heading constant and time station

passage when the needle shows either wingtip position or

settles at or near the 180° position. The time interval from

the ﬁ rst indications of station proximity to positive station

passage varies with altitude—a few seconds at low levels to

3 minutes at high altitude.

Homing

The ADF may be used to “home” in on a station. Homing

is ﬂ ying the aircraft on any heading required to keep the

needle pointing directly to the 0° RB position. To home in

on a station, tune the station, identify the Morse code signal,

and then turn the aircraft to bring the ADF azimuth needle to

the 0° RB position. Turns should be made using the heading

indicator. When the turn is complete, check the ADF needle

and make small corrections as necessary.

Figure 7-6 illustrates homing starting from an initial MH of

050° and an RB of 300°, indicating a 60° left turn is needed

to produce an RB of zero. Turn left, rolling out at 50° minus

60° equals 350°. Small heading corrections are then made

to zero the ADF needle.

If there is no wind, the aircraft will home to the station on a

direct track over the ground. With a crosswind, the aircraft

will follow a circuitous path to the station on the downwind

side of the direct track to the station.

Tracking

Tracking uses a heading that will maintain the desired track

to or from the station regardless of crosswind conditions.

Interpretation of the heading indicator and needle is done to

maintain a constant MB to or from the station.

To track inbound, turn to the heading that will produce a zero

RB. Maintain this heading until off-course drift is indicated

by displacement of the needle, which will occur if there is a

crosswind (needle moving left = wind from the left; needle

moving right = wind from the right). A rapid rate of bearing

change with a constant heading indicates either a strong

crosswind or close proximity to the station or both. When

there is a deﬁ nite (2° to 5°) change in needle reading, turn

in the direction of needle deﬂ ection to intercept the initial

MB. The angle of interception must be greater than the

number of degrees of drift, otherwise the aircraft will slowly

drift due to the wind pushing the aircraft. If repeated often

enough, the track to the station will appear circular and the

distance greatly increased as compared to a straight track.

The intercept angle depends on the rate of drift, the aircraft

speed, and station proximity. Initially, it is standard to double

the RB when turning toward your course.

For example, if your heading equals your course and the

needle points 10° left, turn 20° left, twice the initial RB.

[Figure 7-7] This will be your intercept angle to capture the

RB. Hold this heading until the needle is deﬂ ected 20° in

the opposite direction. That is, the deﬂ ection of the needle

equals the interception angle (in this case 20°). The track has

been intercepted, and the aircraft will remain on track as long

as the RB remains the same number of degrees as the wind

correction angle (WCA), the angle between the desired track

and the heading of the aircraft necessary to keep the aircraft

tracking over the desired track. Lead the interception to avoid

overshooting the track. Turn 10° toward the inbound course.

You are now inbound with a 10° left correction angle.

NOTE: In Figure 7-7, for the aircraft closest to the station, the

WCA is 10° left and the RB is 10° right. If those values do

not change, the aircraft will track directly to the station. If you

observe off-course deﬂ ection in the original direction, turn

again to the original interception heading. When the desired

course has been re-intercepted, turn 5° toward the inbound

course, proceeding inbound with a 15° drift correction. If the

initial 10° drift correction is excessive, as shown by needle

deﬂ ection away from the wind, turn to parallel the desired

course and let the wind drift you back on course. When the

needle is again zeroed, turn into the wind with a reduced

drift correction angle.

7-6

Figure 7-6. ADF Homing With a Crosswind.

7-7

Figure 7-7. ADF Tracking Inbound.

7-8

Operational Errors of ADF

Some of the common pilot-induced errors associated with

ADF navigation are listed below to help you avoid making

the same mistakes. The errors are:

1. Improper tuning and station identiﬁ cation. Many pilots

have made the mistake of homing or tracking to the

wrong station.

2. Positively identifying any malfunctions of the RMI

slaving system or ignoring the warning ﬂ ag.

3. Dependence on homing rather than proper tracking.

This commonly results from sole reliance on the ADF

indications, rather than correlating them with heading

indications.

4. Poor orientation, due to failure to follow proper steps

in orientation and tracking.

5. Careless interception angles, very likely to happen if

you rush the initial orientation procedure.

6. Overshooting and undershooting predetermined MBs,

often due to forgetting the course interception angles

used.

7. Failure to maintain selected headings. Any heading

change is accompanied by an ADF needle change.

The instruments must be read in combination before

any interpretation is made.

8. Failure to understand the limitations of the ADF and

the factors that affect its use.

9. Overcontrolling track corrections close to the station

(chasing the ADF needle), due to failure to understand

or recognize station approach.

10. Failure to keep the heading indicator set so it agrees

with the magnetic compass.

Very High Frequency Omnidirectional Range

(VOR)

VOR is the primary navigational aid (NAVAID) used by civil

aviation in the National Airspace System (NAS). The VOR

ground station is oriented to magnetic north and transmits

azimuth information to the aircraft, providing 360 courses

TO or FROM the VOR station. When DME is installed with

the VOR, it is referred to as a VOR/DME and provides both

azimuth and distance information. When military tactical air

navigation (TACAN) equipment is installed with the VOR,

it is known as a VORTAC and provides both azimuth and

distance information.

To track outbound, the same principles apply: needle moving

left = wind from the left, needle moving right = wind from the

right. Wind correction is made toward the needle deﬂ ection.

The only exception is while the turn to establish the WCA is

being made, the direction of the azimuth needle deﬂ ections is

reversed. When tracking inbound, needle deﬂ ection decreases

while turning to establish the WCA, and needle deﬂ ection

increases when tracking outbound. Note the example of

course interception and outbound tracking in Figure 7-8.

Intercepting Bearings

ADF orientation and tracking procedures may be applied to

intercept a speciﬁ ed inbound or outbound MB. To intercept

an inbound bearing of 355°, the following steps may be used.

[Figure 7-9]

1. Determine your position in relation to the station by

paralleling the desired inbound bearing. In this case,

turn to a heading of 355°. Note that the station is to

the right front of the aircraft.

2. Determine the number of degrees of needle deﬂ ection

from the nose of the aircraft. In this case, the needle’s

RB from the aircraft’s nose is 40° to the right. A rule

of thumb for interception is to double this RB amount

as an interception angle (80°).

3. Turn the aircraft toward the desired MB the number of

degrees determined for the interception angle which

as indicated (in two above) is twice the initial RB

(40°), or in this case 80°. Therefore, the right turn will

be 80° from the initial MB of 355°, or a turn to 075°

magnetic (355° + 80° + 075°).

4. Maintain this interception heading of 075° until the

needle is deﬂ ected the same number of degrees “left”

from the zero position as the angle of interception

080°, (minus any lead appropriate for the rate at which

the bearing is changing).

5. Turn left 80° and the RB (in a no wind condition and

with proper compensation for the rate of the ADF

needle movement) should be 0°, or directly off the

nose. Additionally, the MB should be 355° indicating

proper interception of the desired course.

NOTE: The rate of an ADF needle movement or any bearing

pointer for that matter will be faster as aircraft position

becomes closer to the station or waypoint (WP).

Interception of an outbound MB can be accomplished by the

same procedures as for the inbound intercept, except that

it is necessary to substitute the 180° position for the zero

position on the needle.

7-9

Figure 7-8. ADF Interception and Tracking Outbound.

7-10

Figure 7-10. VOR Radials.

Figure 7-9. Interception of Bearing.

the aircraft altitude, class of facility, location of the facility,

terrain conditions within the usable area of the facility, and

other factors. Above and beyond certain altitude and distance

limits, signal interference from other VOR facilities and a

weak signal make it unreliable. Coverage is typically at least

40 miles at normal minimum instrument ﬂ ight rules (IFR)

altitudes. VORs with accuracy problems in parts of their

service volume are listed in Notices to Airmen (NOTAMs)

and in the Airport/Facility Directory (A/FD) under the name

of the NAVAID.

VOR Components

The ground equipment consists of a VOR ground station,

which is a small, low building topped with a ﬂ at white disc,

upon which are located the VOR antennas and a ﬁ berglass

cone-shaped tower. [Figure 7-11] The station includes an

automatic monitoring system. The monitor automatically

turns off defective equipment and turns on the standby

transmitter. Generally, the accuracy of the signal from the

ground station is within 1°.

VOR facilities are aurally identiﬁ ed by Morse code, or

voice, or both. The VOR can be used for ground-to-air

communication without interference with the navigation

signal. VOR facilities operate within the 108.0 to 117.95 MHz

frequency band and assignment between 108.0 and 112.0

The courses oriented FROM the station are called radials. The

VOR information received by an aircraft is not inﬂ uenced

by aircraft attitude or heading. [Figure 7-10] Radials can

be envisioned to be like the spokes of a wheel on which the

aircraft is on one speciﬁ c radial at any time. For example,

aircraft A (heading 180°) is inbound on the 360° radial; after

crossing the station, the aircraft is outbound on the 180°

radial at A1. Aircraft B is shown crossing the 225° radial.

Similarly, at any point around the station, an aircraft can be

located somewhere on a speciﬁ c VOR radial. Additionally,

a VOR needle on an RMI will always point to the course

that will take you to the VOR station where conversely the

ADF needle points to the station as a RB from the aircraft. In

the example above, the ADF needle at position A would be

pointed straight ahead, at A1 to the aircraft’s 180° position

(tail) and at B, to the aircraft’s right.

The VOR receiver measures and presents information to

indicate bearing TO or FROM the station. In addition to the

navigation signals transmitted by the VOR, a Morse code

signal is transmitted concurrently to identify the facility, as

well as voice transmissions for communication and relay of

weather and other information.

VORs are classiﬁ ed according to their operational uses. The

standard VOR facility has a power output of approximately

200 watts, with a maximum usable range depending upon

7-11

Figure 7-12. The VOR Indicator Instrument.

Figure 7-11. VOR Transmitter (Ground Station).

Figure 7-13. A Typical Horizontal Situation Indicator (HSI).

MHz is in even-tenth increments to preclude any conﬂ ict

with ILS localizer frequency assignment, which uses the

odd tenths in this range.

The airborne equipment includes an antenna, a receiver, and

the indicator instrument. The receiver has a frequency knob to

select any of the frequencies between 108.0 to 117.95 MHz.

The On/Off/volume control turns on the navigation receiver

and controls the audio volume. The volume has no effect on

the operation of the receiver. You should listen to the station

identiﬁ er before relying on the instrument for navigation.

VOR indicator instruments have at least the essential

components shown in the instrument illustrated in

Figure 7-12.

Omnibearing Selector (OBS)

The desired course is selected by turning the OBS knob until

the course is aligned with the course index mark or displayed

in the course window.

Course Deviation Indicator (CDI)

The deviation indicator is composed of an instrument face

and a needle hinged to move laterally across the instrument

face. The needle centers when the aircraft is on the selected

radial or its reciprocal. Full needle deﬂ ection from the center

position to either side of the dial indicates the aircraft is 12°

or more off course, assuming normal needle sensitivity. The

outer edge of the center circle is 2° off course; with each dot

representing an additional 2°.

TO/FROM Indicator

The TO/FROM indicator shows whether the selected course

will take the aircraft TO or FROM the station. It does not

indicate whether the aircraft is heading to or from the

station.

Flags or Other Signal Strength Indicators

The device that indicates a usable or an unreliable signal may

be an “OFF” ﬂ ag. It retracts from view when signal strength

is sufﬁ cient for reliable instrument indications. Alternately,

insufﬁ cient signal strength may be indicated by a blank or

OFF in the TO/FROM window.

The indicator instrument may also be a horizontal situation

indicator (HSI) which combines the heading indicator

and CDI. [Figure 7-13] The combination of navigation

information from VOR/Localizer (LOC) or from LORAN

or GPS, with aircraft heading information provides a visual

picture of the aircraft’s location and direction. This decreases

pilot workload especially with tasks such as course intercepts,

ﬂ ying a back-course approach, or holding pattern entry. (See

7-12

Figure 7-14. An HSI display as seen on the pilot’s primary ﬂ ight display (PFD) on an electronic ﬂ ight instrument. Note that only attributes

related to the HSI are labeled.

Chapter 3, Flight Instruments, for operational characteristics.)

[Figure 7-14]

Function of VOR

Orientation

The VOR does not account for the aircraft heading. It only

relays the aircraft direction from the station and will have the

same indications regardless of which way the nose is pointing.

Tune the VOR receiver to the appropriate frequency of the

selected VOR ground station, turn up the audio volume, and

identify the station’s signal audibly. Then, rotate the OBS

to center the CDI needle and read the course under or over

the index.

In Figure 7-12, 360° TO is the course indicated, while in

Figure 7-15, 180° TO is the course. The latter indicates that

the aircraft (which may be heading in any direction) is, at this

moment, located at any point on the 360° radial (line from the

station) except directly over the station or very close to it, as

between points I and S in Figure 7-15. The CDI will deviate

from side to side as the aircraft passes over or nearly over

the station because of the volume of space above the station

where the zone of confusion exists. This zone of confusion is

caused by lack of adequate signal directly above the station

due to the radiation pattern of the station’s antenna, and

because the resultant of the opposing reference and variable

signals is small and constantly changing.

The CDI in Figure 7-15 indicates 180°, meaning that the

aircraft is on the 180° or the 360° radial of the station. The TO/

FROM indicator resolves the ambiguity. If the TO indicator is

showing, then it is 180° TO the station. The FROM indication

indicates the radial of the station the aircraft is presently on.

Movement of the CDI from center, if it occurs at a relatively

constant rate, indicates the aircraft is moving or drifting off the

180°/360° line. If the movement is rapid or ﬂ uctuating, this

is an indication of impending station passage (the aircraft is

near the station). To determine the aircraft’s position relative

to the station, rotate the OBS until FROM appears in the

window, and then center the CDI needle. The index indicates

the VOR radial where the aircraft is located. The inbound (to

the station) course is the reciprocal of the radial.

If the VOR is set to the reciprocal of the intended course,

the CDI will reﬂ ect reverse sensing. To correct for needle

deﬂ ection, turn away from the needle. To avoid this reverse

sensing situation, set the VOR to agree with the intended

course.

7-13

Figure 7-15. CDI Interpretation. The CDI as typically found on analog systems (right) and as found on electronic ﬂ ight instruments

(left).

7-14

A single NAVAID will allow a pilot to determine the aircraft’s

position relative to a radial. Indications from a second

NAVAID are needed in order to narrow the aircraft’s position

down to an exact location on this radial.

Tracking TO and FROM the Station

To track to the station, rotate the OBS until TO appears, then

center the CDI. Fly the course indicated by the index. If the CDI

moves off center to the left, follow the needle by correcting

course to the left, beginning with a 20° correction.

When flying the course indicated on the index, a left

deﬂ ection of the needle indicates a crosswind component

from the left. If the amount of correction brings the needle

back to center, decrease the left course correction by half. If

the CDI moves left or right now, it should do so much more

slowly, and smaller heading corrections can be made for the

next iteration.

Keeping the CDI centered will take the aircraft to the station.

To track to the station, the OBS value at the index is not

changed. To home to the station, the CDI needle is periodically

centered, and the new course under the index is used for the

aircraft heading. Homing will follow a circuitous route to the

station, just as with ADF homing.

To track FROM the station on a VOR radial, you should

ﬁ rst orient the aircraft’s location with respect to the station

and the desired outbound track by centering the CDI needle

with a FROM indication. The track is intercepted by either

ﬂ ying over the station or establishing an intercept heading.

The magnetic course of the desired radial is entered under the

index using the OBS and the intercept heading held until the

CDI centers. Then the procedure for tracking to the station is

used to ﬂ y outbound on the speciﬁ ed radial.

Course Interception

If the desired course is not the one being ﬂ own, ﬁ rst orient

the aircraft’s position with respect to the VOR station and the

course to be ﬂ own, and then establish an intercept heading.

The following steps may be used to intercept a predetermined

course, either inbound or outbound. Steps 1–3 may be omitted

when turning directly to intercept the course without initially

turning to parallel the desired course.

1. Turn to a heading to parallel the desired course, in the

same direction as the course to be ﬂ own.

2. Determine the difference between the radial to be

intercepted and the radial on which the aircraft is

located (205° – 160° = 045°).

3. Double the difference to determine the interception

angle, which will not be less than 20° nor greater

than 90° (45° x 2 = 090°). 205° + 090° = 295° for the

intercept)

4. Rotate the OBS to the desired radial or inbound

course.

5. Turn to the interception heading.

6. Hold this heading constant until the CDI center, which

indicates the aircraft is on course. (With practice in

judging the varying rates of closure with the course

centerline, pilots learn to lead the turn to prevent

overshooting the course.)

7. Turn to the MH corresponding to the selected

course, and follow tracking procedures inbound or

outbound.

Course interception is illustrated in Figure 7-16.

VOR Operational Errors

Typical pilot-induced errors include:

1. Careless tuning and identiﬁ cation of station.

2. Failure to check receiver for accuracy/sensitivity.

3. Turning in the wrong direction during an orientation.

This error is common until visualizing position rather

than heading.

4. Failure to check the ambiguity (TO/FROM) indicator,

particularly during course reversals, resulting

in reverse sensing and corrections in the wrong

direction.

5. Failure to parallel the desired radial on a track

interception problem. Without this step, orientation

to the desired radial can be confusing. Since pilots

think in terms of left and right of course, aligning the

aircraft position to the radial/course is essential.

6. Overshooting and undershooting radials on interception

problems.

7. Overcontrolling corrections during tracking, especially

close to the station.

8. Misinterpretation of station passage. On VOR

receivers not equipped with an ON/OFF flag, a

voice transmission on the combined communication

and navigation radio (NAV/COM) in use for VOR

may cause the same TO/FROM ﬂ uctuations on the

ambiguity meter as shown during station passage.

Read the whole receiver—TO/FROM, CDI, and

OBS—before you make a decision. Do not utilize a

VOR reading observed while transmitting.

9. Chasing the CDI, resulting in homing instead of

tracking. Careless heading control and failure to

bracket wind corrections make this error common.

7-15

Figure 7-16. Course Interception (VOR).

7-16

VOR Accuracy

The effectiveness of the VOR depends upon proper use and

adjustment of both ground and airborne equipment.

The accuracy of course alignment of the VOR is generally

plus or minus 1°. On some VORs, minor course roughness

may be observed, evidenced by course needle or brief ﬂ ag

alarm. At a few stations, usually in mountainous terrain,

the pilot may occasionally observe a brief course needle

oscillation, similar to the indication of “approaching station.”

Pilots ﬂ ying over unfamiliar routes are cautioned to be on

the alert for these vagaries, and in particular, to use the TO/

FROM indicator to determine positive station passage.

Certain propeller revolutions per minute (RPM) settings

or helicopter rotor speeds can cause the VOR CDI to

ﬂ uctuate as much as plus or minus 6°. Slight changes to

the RPM setting will normally smooth out this roughness.

Pilots are urged to check for this modulation phenomenon

prior to reporting a VOR station or aircraft equipment for

unsatisfactory operation.

VOR Receiver Accuracy Check

VOR system course sensitivity may be checked by noting

the number of degrees of change as the OBS is rotated to

move the CDI from center to the last dot on either side. The

course selected should not exceed 10° or 12° either side. In

addition, Title 14 of the Code of Federal Regulations (14

CFR) part 91 provides for certain VOR equipment accuracy

checks, and an appropriate endorsement, within 30 days prior

to ﬂ ight under IFR. To comply with this requirement and to

ensure satisfactory operation of the airborne system, use the

following means for checking VOR receiver accuracy:

1. VOR test facility (VOT) or a radiated test signal from

an appropriately rated radio repair station.

2. Certiﬁ ed checkpoints on the airport surface.

3. Certiﬁ ed airborne checkpoints.

VOR Test Facility (VOT)

The Federal Aviation Administration (FAA) VOT transmits

a test signal which provides users a convenient means to

determine the operational status and accuracy of a VOR

receiver while on the ground where a VOT is located.

Locations of VOTs are published in the A/FD. Two means of

identiﬁ cation are used. One is a series of dots and the other is

a continuous tone. Information concerning an individual test

signal can be obtained from the local ﬂ ight service station

(FSS.) The airborne use of VOT is permitted; however, its

use is strictly limited to those areas/altitudes speciﬁ cally

authorized in the A/FD or appropriate supplement.

To use the VOT service, tune in the VOT frequency 108.0

MHz on the VOR receiver. With the CDI centered, the

OBS should read 0° with the TO/FROM indication showing

FROM or the OBS should read 180° with the TO/FROM

indication showing TO. Should the VOR receiver operate an

RMI, it would indicate 180° on any OBS setting.

A radiated VOT from an appropriately rated radio repair

station serves the same purpose as an FAA VOT signal, and

the check is made in much the same manner as a VOT with

some differences.

The frequency normally approved by the Federal

Communications Commission (FCC) is 108.0 MHz;

however, repair stations are not permitted to radiate the

VOR test signal continuously. The owner or operator of the

aircraft must make arrangements with the repair station to

have the test signal transmitted. A representative of the repair

station must make an entry into the aircraft logbook or other

permanent record certifying to the radial accuracy and the

date of transmission.

Certiﬁ ed Checkpoints

Airborne and ground checkpoints consist of certiﬁ ed radials

that should be received at speciﬁ c points on the airport surface

or over speciﬁ c landmarks while airborne in the immediate

vicinity of the airport. Locations of these checkpoints are

published in the A/FD.

Should an error in excess of ±4° be indicated through use of

a ground check, or ±6° using the airborne check, IFR ﬂ ight

shall not be attempted without ﬁ rst correcting the source of

the error. No correction other than the correction card ﬁ gures

supplied by the manufacturer should be applied in making

these VOR receiver checks.

If a dual system VOR (units independent of each other except

for the antenna) is installed in the aircraft, one system may

be checked against the other. Turn both systems to the same

VOR ground facility and note the indicated bearing to that

station. The maximum permissible variation between the two

indicated bearings is 4°.

Distance Measuring Equipment (DME)

When used in conjunction with the VOR system, DME makes

it possible for pilots to determine an accurate geographic

position of the aircraft, including the bearing and distance

TO or FROM the station. The aircraft DME transmits

interrogating radio frequency (RF) pulses, which are received

by the DME antenna at the ground facility. The signal triggers

ground receiver equipment to respond to the interrogating

7-17

Figure 7-17. DME Arc Interception.

aircraft. The airborne DME equipment measures the elapsed

time between the interrogation signal sent by the aircraft and

reception of the reply pulses from the ground station. This

time measurement is converted into distance in nautical miles

(NM) from the station.

Some DME receivers provide a groundspeed in knots by

monitoring the rate of change of the aircraft’s position relative

to the ground station. Groundspeed values are accurate only

when tracking directly to or from the station.

DME Components

VOR/DME, VORTAC, ILS/DME, and LOC/DME

navigation facilities established by the FAA provide course

and distance information from collocated components under

a frequency pairing plan. DME operates on frequencies

in the UHF spectrum between 962 MHz and 1213 MHz.

Aircraft receiving equipment which provides for automatic

DME selection assures reception of azimuth and distance

information from a common source when designated VOR/

DME, VORTAC, ILS/DME, and LOC/DME are selected.

Some aircraft have separate VOR and DME receivers, each

of which must be tuned to the appropriate navigation facility.

The airborne equipment includes an antenna and a receiver.

The pilot-controllable features of the DME receiver

include:

Channel (Frequency) Selector

Many DMEs are channeled by an associated VHF radio, or

there may be a selector switch so a pilot can select which

VHF radio is channeling the DME. For a DME with its

own frequency selector, use the frequency of the associated

VOR/DME or VORTAC station.

On/Off/Volume Switch

The DME identiﬁ er will be heard as a Morse code identiﬁ er

with a tone somewhat higher than that of the associated VOR

or LOC. It will be heard once for every three or four times

the VOR or LOC identiﬁ er is heard. If only one identiﬁ er is

heard about every 30 seconds, the DME is functional, but

the associated VOR or LOC is not.

Mode Switch

The mode switch selects between distance (DIST) or distance

in NMs, groundspeed, and time to station. There may also

be one or more HOLD functions which permit the DME to

stay channeled to the station that was selected before the

switch was placed in the hold position. This is useful when

you make an ILS approach at a facility that has no collocated

DME, but there is a VOR/DME nearby.

Altitude

Some DMEs correct for slant-range error.

Function of DME

A DME is used for determining the distance from a ground

DME transmitter. Compared to other VHF/UHF NAVAIDs,

a DME is very accurate. The distance information can be

used to determine the aircraft position or ﬂ ying a track that

is a constant distance from the station. This is referred to as

a DME arc.

DME Arc

There are many instrument approach procedures (IAPs) that

incorporate DME arcs. The procedures and techniques given

here for intercepting and maintaining such arcs are applicable

to any facility that provides DME information. Such a facility

may or may not be collocated with the facility that provides

ﬁ nal approach guidance.

As an example of ﬂ ying a DME arc, refer to Figure 7-17 and

follow these steps:

1. Track inbound on the OKT 325° radial, frequently

checking the DME mileage readout.

2. A 0.5 NM lead is satisfactory for groundspeeds of 150

knots or less; start the turn to the arc at 10.5 miles. At

higher groundspeeds, use a proportionately greater

lead.

7-18

Figure 7-18. Using DME and RMI To Maintain an Arc.

3. Continue the turn for approximately 90°. The roll-out

heading will be 055° in a no wind condition.

4. During the last part of the intercepting turn, monitor

the DME closely. If the arc is being overshot (more

than 1.0 NM), continue through the originally planned

roll-out heading. If the arc is being undershot, roll-out

of the turn early.

The procedure for intercepting the 10 DME when outbound

is basically the same, the lead point being 10 NM minus 0.5

NM, or 9.5 NM.

When ﬂ ying a DME arc with wind, it is important to keep a

continuous mental picture of the aircraft’s position relative to

the facility. Since the wind-drift correction angle is constantly

changing throughout the arc, wind orientation is important.

In some cases, wind can be used in returning to the desired

track. High airspeeds require more pilot attention because of

the higher rate of deviation and correction.

Maintaining the arc is simpliﬁ ed by keeping slightly inside

the curve; thus, the arc is turning toward the aircraft and

interception may be accomplished by holding a straight

course. When outside the curve, the arc is “turning away”

and a greater correction is required.

To ﬂ y the arc using the VOR CDI, center the CDI needle

upon completion of the 90° turn to intercept the arc. The

aircraft’s heading will be found very near the left or right

side (270° or 90° reference points) of the instrument. The

readings at that side location on the instrument will give

primary heading information while on the arc. Adjust the

aircraft heading to compensate for wind and to correct for

7-19

distance to maintain the correct arc distance. Recenter the

CDI and note the new primary heading indicated whenever

the CDI gets 2°–4° from center.

With an RMI, in a no wind condition, pilots should

theoretically be able to ﬂ y an exact circle around the facility

by maintaining an RB of 90° or 270°. In actual practice,

a series of short legs are ﬂ own. To maintain the arc in

Figure 7-18, proceed as follows:

1. With the RMI bearing pointer on the wingtip reference

(90° or 270° position) and the aircraft at the desired

DME range, maintain a constant heading and allow the

bearing pointer to move 5°–10° behind the wingtip.

This will cause the range to increase slightly.

2. Turn toward the facility to place the bearing pointer

5–10° ahead of the wingtip reference, and then

maintain heading until the bearing pointer is again

behind the wingtip. Continue this procedure to

maintain the approximate arc.

3. If a crosswind causes the aircraft to drift away from

the facility, turn the aircraft until the bearing pointer is

ahead of the wingtip reference. If a crosswind causes

the aircraft to drift toward the facility, turn until the

bearing is behind the wingtip.

4. As a guide in making range corrections, change the RB

10°–20° for each half-mile deviation from the desired

arc. For example, in no-wind conditions, if the aircraft

is 1/2 to 1 mile outside the arc and the bearing pointer

is on the wingtip reference, turn the aircraft 20° toward

the facility to return to the arc.

Without an RMI, orientation is more difﬁ cult since there is

no direct azimuth reference. However, the procedure can be

ﬂ own using the OBS and CDI for azimuth information and

the DME for arc distance.

Intercepting Lead Radials

A lead radial is the radial at which the turn from the arc to the

inbound course is started. When intercepting a radial from

a DME arc, the lead will vary with arc radius and ground

speed. For the average general aviation aircraft, ﬂ ying arcs

such as those depicted on most approach charts at speeds

of 150 knots or less, the lead will be under 5°. There is no

difference between intercepting a radial from an arc and

intercepting it from a straight course.

With an RMI, the rate of bearing movement should be

monitored closely while ﬂ ying the arc. Set the course of the

radial to be intercepted as soon as possible and determine

the approximate lead. Upon reaching this point, start the

intercepting turn. Without an RMI, the technique for radial

interception is the same except for azimuth information,

which is available only from the OBS and CDI.

The technique for intercepting a localizer from a DME arc

is similar to intercepting a radial. At the depicted lead radial

(LR 070° or LR 084° in Figures 7-19, 7-20, and 7-21), a

pilot having a single VOR/LOC receiver should set it to the

localizer frequency. If the pilot has dual VOR/LOC receivers,

one unit may be used to provide azimuth information and the

other set to the localizer frequency. Since these lead radials

provide 7° of lead, a half-standard rate turn should be used

until the LOC needle starts to move toward center.

DME Errors

A DME/DME ﬁ x (a location based on two DME lines of

position from two DME stations) provides a more accurate

aircraft location than using a VOR and a DME ﬁ x.

DME signals are line-of-sight; the mileage readout is the

straight line distance from the aircraft to the DME ground

facility and is commonly referred to as slant range distance.

Slant range refers to the distance from the aircraft’s antenna

to the ground station (A line at an angle to the ground

transmitter. GPS systems provide distance as the horizontal

measurement from the WP to the aircraft. Therefore, at 3,000

feet and 0.5 miles the DME (slant range) would read 0.6 NM

while the GPS distance would show the actual horizontal

distance of .5 DME. This error is smallest at low altitudes

and/or at long ranges. It is greatest when the aircraft is closer

to the facility, at which time the DME receiver will display

altitude (in NM) above the facility. Slant range error is

negligible if the aircraft is one mile or more from the ground

facility for each 1,000 feet of altitude above the elevation of

the facility.

Area Navigation (RNAV)

Area navigation (RNAV) equipment includes VOR/DME,

LORAN, GPS, and inertial navigation systems (INS). RNAV

equipment is capable of computing the aircraft position,

actual track, groundspeed, and then presenting meaningful

information to the pilot. This information may be in the form

of distance, cross-track error, and time estimates relative to

the selected track or WP. In addition, the RNAV equipment

installations must be approved for use under IFR. The Pilot’s

Operating Handbook/Airplane Flight Manual (POH/AFM)

should always be consulted to determine what equipment is

installed, the operations that are approved, and the details of

equipment use. Some aircraft may have equipment that allows

input from more than one RNAV source, thereby providing

a very accurate and reliable navigation source.

7-20

Figure 7-19. An aircraft is displayed heading southwest to intercept the localizer approach, using the 16 NM DME Arc off of ORM.

7-21

Figure 7-20. The same aircraft illustrated in Figure 7-19 shown on the ORM radial near TIGAE intersection turning inbound for the

localizer.

7-22

Figure 7-21. Aircraft is illustrated inbound on the localizer

course.

Figure 7-22. RNAV Computation.

7-23

Figure 7-23. Onboard RNAV receivers have changed signiﬁ cantly.

Originally, RNAV receivers typically computed combined data

from VOR, VORTAC, and/or DME. That is generally not the case

now. Today, GPS such as the GNC 300 and the Bendix King KLS

88 LORAN receivers compute waypoints based upon embedded

databases and aircraft positional information.

VOR/DME RNAV

VOR RNAV is based on information generated by the present

VORTAC or VOR/DME system to create a WP using an

airborne computer. As shown in Figure 7-22, the value of

side A is the measured DME distance to the VOR/DME. Side

B, the distance from the VOR/DME to the WP, and angle 1

(VOR radial or the bearing from the VORTAC to the WP)

are values set in the ﬂ ight deck control. The bearing from

the VOR/DME to the aircraft, angle 2, is measured by the

VOR receiver. The airborne computer continuously compares

angles 1 and 2 and determines angle 3 and side C, which is

the distance in NMs and magnetic course from the aircraft

to the WP. This is presented as guidance information on the

ﬂ ight deck display.

VOR/DME RNAV Components

Although RNAV ﬂ ight deck instrument displays vary among

manufacturers, most are connected to the aircraft CDI with a

switch or knob to select VOR or RNAV guidance. There is

usually a light or indicator to inform the pilot whether VOR

or RNAV is selected. [Figure 7-23] The display includes the

WP, frequency, mode in use, WP radial and distance, DME

distance, groundspeed, and time to station.

Most VOR/DME RNAV systems have the following airborne

controls:

1. Off/On/Volume control to select the frequency of the

VOR/DME station to be used.

2. MODE select switch used to select VOR/DME mode,

with:

a. Angular course width deviation (standard VOR

operation); or

b. Linear cross-track deviation as standard (±5 NM

full scale CDI).

3. RNAV mode, with direct to WP with linear cross-track

deviation of ±5 NM.

4. RNAV/APPR (approach mode) with linear deviation

of ±1.25 NM as full scale CDI deﬂ ection.

5. WP select control. Some units allow the storage of more

than one WP; this control allows selection of any WP

in storage.

6. Data input controls. These controls allow user input

of WP number or ident, VOR or LOC frequency, WP

radial and distance.

While DME groundspeed readout is accurate only when

tracking directly to or from the station in VOR/DME mode,

in RNAV mode the DME groundspeed readout is accurate on

any track.

Function of VOR/DME RNAV

The advantages of the VOR/DME RNAV system stem from

the ability of the airborne computer to locate a WP wherever it

is convenient, as long as the aircraft is within reception range

of both nearby VOR and DME facilities. A series of these

WPs make up an RNAV route. In addition to the published

routes, a random RNAV route may be ﬂ own under IFR if it is

approved by air trafﬁ c control (ATC). RNAV DPs and standard

terminal arrival routes (STARs) are contained in the DP and

STAR booklets.

VOR/DME RNAV approach procedure charts are also

available. Note in the VOR/DME RNAV chart excerpt shown

in Figure 7-24 that the WP identiﬁ cation boxes contain the

following information: WP name, coordinates, frequency,

identiﬁ er, radial distance (facility to WP), and reference facility

elevation. The initial approach ﬁ x (IAF), ﬁ nal approach ﬁ x

(FAF), and missed approach point (MAP) are labeled.

To ﬂ y a route or to execute an approach under IFR, the RNAV

equipment installed in the aircraft must be approved for the

appropriate IFR operations.

In vertical navigation (VNAV) mode, vertical guidance is

provided, as well as horizontal guidance in some installations. A

WP is selected at a point where the descent begins, and another

WP is selected where the descent ends. The RNAV equipment

computes the rate of descent relative to the groundspeed; on

some installations, it displays vertical guidance information

on the GS indicator. When using this type of equipment

during an instrument approach, the pilot must keep in mind

that the vertical guidance information provided is not part of

the nonprecision approach. Published nonprecision approach

altitudes must be observed and complied with, unless otherwise

directed by ATC.

7-24

Figure 7-25. Aircraft/DME/Waypoint Relationship.

Figure 7-24. VOR/DME RNAV Rwy 25 Approach (Excerpt).

To ﬂ y to a WP using RNAV, observe the following procedure

[Figure 7-25]:

1. Select the VOR/DME frequency.

2. Select the RNAV mode.

3. Select the radial of the VOR that passes through the WP

(225°).

4. Select the distance from the DME to the WP (12

NM).

5. Check and conﬁ rm all inputs, and center the CDI needle

with the TO indicator showing.

6. Maneuver the aircraft to ﬂ y the indicated heading

plus or minus wind correction to keep the CDI needle

centered.

7. The CDI needle will indicate distance off course of 1

NM per dot; the DME readout will indicate distance in

NM from the WP; the groundspeed will read closing

speed (knots) to the WP; and the time to station (TTS)

will read time to the WP.

VOR/DME RNAV Errors

The limitation of this system is the reception volume.

Published approaches have been tested to ensure this is not

a problem. Descents/approaches to airports distant from the

VOR/DME facility may not be possible because, during

the approach, the aircraft may descend below the reception

altitude of the facility at that distance.

Long Range Navigation (LORAN)

LORAN uses a network of land-based transmitters to provide

an accurate long-range navigation system. The FAA and the

United States Coast Guard (USCG) arranged the stations

into chains. The signal from station is a carefully structured

sequence of brief RF pulses centered at 100 kHz. At that

frequency, signals travel considerable distances as ground

waves, from which accurate navigation information is

available. The airborne receiver monitors all of the stations

within the selected chain, then measures the arrival time

difference (TD) between the signals. All of the points having

the same TD from a station pair create a line of position

7-25

Figure 7-26. A control panel from a military aircraft after LORAN

was ﬁ rst put into use. The receiver is remotely mounted and weighs

over 25 pounds. Its size is about six times that of the LORAN fully

integrated receiver.

(LOP). The aircraft position is determined at the intersection

of two or more LOPs. Then the computer converts the

known location to latitude and longitude coordinates.

[Figure 7-26]

While continually computing latitude/longitude ﬁ xes, the

computer is able to determine and display:

1. Track over the ground since last computation;

2. Groundspeed by dividing distance covered since last

computation by the time since last computation (and

averaging several of these);

3. Distance to destination;

4. Destination time of arrival; and

5. Cross-track error.

The Aeronautical Information Manual (AIM) provides a

detailed explanation of how LORAN works. LORAN is

a very accurate navigation system if adequate signals are

received. There are two types of accuracy that must be

addressed in any discussion of LORAN accuracy.

Repeatable accuracy is the accuracy measured when a user

notes the LORAN position, moves away from that location,

then uses the LORAN to return to that initial LORAN

position. Distance from that initial position is the error.

Propagation and terrain errors will be essentially the same as

when the ﬁ rst position was taken, so those errors are factored

out by using the initial position. Typical repeatable accuracy

for LORAN can be as good as 0.01 NM, or 60 feet, if the

second position is determined during the day and within a

short period of time (a few days).

Absolute accuracy refers to the ability to determine present

position in space independently, and is most often used by

pilots. When the LORAN receiver is turned on and position

is determined, absolute accuracy applies. Typical LORAN

absolute accuracy will vary from about 0.1 NM to as much

as 2.5 NM depending on distance from the station, geometry

of the TD LOP crossing angles, terrain and environmental

conditions, signal-to-noise ratio (signal strength), and some

design choices made by the receiver manufacturer.

Although LORAN use diminished with the introduction

of Global Navigation Satellite Systems such as the United

States’ GPS, its use has since increased. Three items aided

in this resurgence:

• In 1996, a commission called the Gore Commission

evaluated GPS’ long-term use as a sole navigation

aid. Although GPS was hailed originally as the

eventual sole NAVAID, which would replace the need

for most currently existing NAVAIDs by the year

2020, the Commission questioned single-link failure

potential and its effect on the NAS. For this reason,

the forecasted decommissioning of the VOR has been

amended and their expectant lifecycle extended into

the future. Additionally, the use of LORAN continues

to be evaluated for facilitating carrying GPS corrective

timing signals.

• The GPS is controlled by the DOD presenting certain

unforecasted uncertainties for commercial use on an

uninterrupted basis.

As a result of these and other key factors, it was determined that

LORAN would remain. In recognition of GPS vulnerabilities

as a GNSS, there are plans to maintain other systems that

could provide en route and terminal accuracy such as LORAN.

Therefore as LORAN is further modernized it’s a possibility

that it may be used to augment GPS and provide backup to

GPS during unlikely but potential outages. Or if combined

with GPS and other systems such as newer miniaturized low-

cost inertial navigation systems (INS), superior accuracy and

seamless backup will always be available.

LORAN Components

The LORAN receiver incorporates a radio receiver, signal

processor, navigation computer, control/display, and antenna.

When turned on, the receivers go through an initialization

or warm-up period, then inform the user they are ready to

be programmed. LORAN receivers vary widely in their

appearance, method of user programming, and navigation

information display. Therefore, it is necessary to become

familiar with the unit, including programming and output

interpretation. The LORAN operating manual should be in the

aircraft at all times and available to the pilot. IFR-approved

LORAN units require that the manual be aboard and that the

pilot be familiar with the unit’s functions, before ﬂ ight.

7-26

Figure 7-27. A typical example (GNS 480) of a stand-alone GPS

receiver and display.

Function of LORAN

After initialization, select for the present location WP

(the airport), and select GO TO in order to determine if

the LORAN is functioning properly. Proper operation is

indicated by a low distance reading (0 to 0.5 NM). The

simplest mode of navigation is referred to as GO TO: you

select a WP from one of the databases and choose the

GO TO mode. Before use in ﬂ ight, verify that the latitude

and longitude of the chosen WP is correct by reference to

another approved information source. An updatable LORAN

database that supports the appropriate operations (e.g., en

route, terminal, and instrument approaches) is required when

operating under IFR.

In addition to displaying bearing, distance, time to the WP,

and track and speed over the ground, the LORAN receiver

may have other features such as flight planning (WP

sequential storage), emergency location of several nearest

airports, vertical navigation capabilities, and more.

LORAN Errors

System Errors

LORAN is subject to interference from many external

sources, which can cause distortion of or interference with

LORAN signals. LORAN receiver manufacturers install

“notch ﬁ lters” to reduce or eliminate interference. Proximity

to 60 Hz alternating current power lines, static discharge,

P-static, electrical noise from generators, alternators, strobes,

and other onboard electronics may decrease the signal-

to-noise ratio to the point where the LORAN receiver’s

performance is degraded.

Proper installation of the antenna, good electrical bonding,

and an effective static discharge system are the minimum

requirements for LORAN receiver operation. Most receivers

have internal tests that verify the timing alignment of the

receiver clock with the LORAN pulse, and measure and

display signal-to-noise ratio. A signal will be activated to alert

the pilot if any of the parameters for reliable navigation are

exceeded on LORAN sets certiﬁ ed for IFR operations.

LORAN is most accurate when the signal travels over sea

water during the day and least accurate when the signal

comes over land and large bodies of fresh water or ice at

night; furthermore, the accuracy degrades as distance from

the station increases. However, LORAN accuracy is generally

better than VOR accuracy.

Operational Errors

Some of the typical pilot-induced errors of LORAN operation

are:

1. Use of a nonapproved LORAN receiver for IFR

operations. The pilot should check the aircraft’s POH/

AFM LORAN supplement to be certain the unit’s

functions are well understood (this supplement must

be present in the aircraft for approved IFR operations).

There should be a copy of FAA Form 337, Major

Repair and Alteration, present in the aircraft’s records,

showing approval of use of this model LORAN for

IFR operations in this aircraft.

2. Failure to double-check the latitude/longitude values

for a WP to be used. Whether the WP was accessed

from the airport, NDB, VOR, or intersection database,

the values of latitude and longitude should still be

checked against the values in the A/FD or other

approved source. If the WP data is entered in the user

database, its accuracy must be checked before use.

3. Attempting to use LORAN information with degraded

signals.

Advanced Technologies

Global Navigation Satellite System (GNSS)

The Global Navigation Satellite System (GNSS) is a

constellation of satellites providing a high-frequency signal

which contains time and distance that is picked up by a

receiver thereby. [Figure 7-27] The receiver which picks up

multiple signals from different satellites is able to triangulate

its position from these satellites.

7-27

Figure 7-28. Typical GPS Satellite Array.

Three GNSSs exist today: the GPS, a United States system;

the Russian GNSS (GLONASS); and Galileo, a European

system.

1. GLONASS is a network of 24 satellites, which can be

picked up by any GLONASS receiver, allowing the

user to pinpoint their position.

2. Galileo is a network of 30 satellites that continuously

transmit high-frequency radio signals containing time

and distance data that can be picked up by a Galileo

receiver with operational expectancy by 2008.

3. The GPS came on line in 1992 with 24 satellites, and

today utilizes 30 satellites.

Global Positioning System (GPS)

The GPS is a satellite-based radio navigation system, which

broadcasts a signal that is used by receivers to determine

precise position anywhere in the world. The receiver tracks

multiple satellites and determines a measurement that is then

used to determine the user location. [Figure 7-28]

The Department of Defense (DOD) developed and deployed

GPS as a space-based positioning, velocity, and time system.

The DOD is responsible for operation of the GPS satellite

constellation, and constantly monitors the satellites to ensure

proper operation. The GPS system permits Earth-centered

coordinates to be determined and provides aircraft position

referenced to the DOD World Geodetic System of 1984

(WGS-84). Satellite navigation systems are unaffected

by weather and provide global navigation coverage that

fully meets the civil requirements for use as the primary

means of navigation in oceanic airspace and certain remote

areas. Properly certiﬁ ed GPS equipment may be used as a

supplemental means of IFR navigation for domestic en route,

terminal operations, and certain IAPs. Navigational values,

such as distance and bearing to a WP and groundspeed, are

computed from the aircraft’s current position (latitude and

longitude) and the location of the next WP. Course guidance

is provided as a linear deviation from the desired track of a

Great Circle route between deﬁ ned WPs.

GPS may not be approved for IFR use in other countries.

Prior to its use, pilots should ensure that GPS is authorized

by the appropriate countries.

GPS Components

GPS consists of three distinct functional elements: space,

control, and user.

The space element consists of over 30 Navstar satellites. This

group of satellites is called a constellation. The satellites

are in six orbital planes (with four in each plane) at about

11,000 miles above the Earth. At least ﬁ ve satellites are

in view at all times. The GPS constellation broadcasts a

pseudo-random code timing signal and data message that the

aircraft equipment processes to obtain satellite position and

status data. By knowing the precise location of each satellite

and precisely matching timing with the atomic clocks on

the satellites, the aircraft receiver/processor can accurately

measure the time each signal takes to arrive at the receiver

and, therefore, determine aircraft position.

The control element consists of a network of ground-based

GPS monitoring and control stations that ensure the accuracy

of satellite positions and their clocks. In its present form, it

has ﬁ ve monitoring stations, three ground antennas, and a

master control station.

The user element consists of antennas and receiver/processors

on board the aircraft that provide positioning, velocity,

and precise timing to the user. GPS equipment used while

operating under IFR must meet the standards set forth in

Technical Standard Order (TSO) C-129 (or equivalent); meet

the airworthiness installation requirements; be “approved” for

that type of IFR operation; and be operated in accordance with

the applicable POH/AFM or ﬂ ight manual supplement.

An updatable GPS database that supports the appropriate

operations (e.g., en route, terminal, and instrument

approaches) is required when operating under IFR. The

aircraft GPS navigation database contains WPs from the

7-28

geographic areas where GPS navigation has been approved

for IFR operations. The pilot selects the desired WPs from

the database and may add user-deﬁ ned WPs for the ﬂ ight.

Equipment approved in accordance with TSO C-115a, visual

ﬂ ight rules (VFR), and hand-held GPS systems do not meet

the requirements of TSO C-129 and are not authorized for

IFR navigation, instrument approaches, or as a principal

instrument ﬂ ight reference. During IFR operations, these

units (TSO C-115a) may be considered only an aid to

situational awareness.

Prior to GPS/WAAS IFR operation, the pilot must review

appropriate NOTAMs and aeronautical information. This

information is available on request from an Automated

Flight Service Station. The FAA will provide NOTAMs to

advise pilots of the status of the WAAS and level of service

available.

Function of GPS

GPS operation is based on the concept of ranging and

triangulation from a group of satellites in space which act

as precise reference points. The receiver uses data from a

minimum of four satellites above the mask angle (the lowest

angle above the horizon at which it can use a satellite).

The aircraft GPS receiver measures distance from a satellite

using the travel time of a radio signal. Each satellite transmits

a speciﬁ c code, called a course/acquisition (CA) code, which

contains information about satellite position, the GPS system

time, and the health and accuracy of the transmitted data.

Knowing the speed at which the signal traveled (approximately

186,000 miles per second) and the exact broadcast time,

the distance traveled by the signal can be computed from

the arrival time. The distance derived from this method of

computing distance is called a pseudo-range because it is not

a direct measurement of distance, but a measurement based

on time. In addition to knowing the distance to a satellite, a

receiver needs to know the satellite’s exact position in space,

its ephemeris. Each satellite transmits information about its

exact orbital location. The GPS receiver uses this information

to establish the precise position of the satellite.

Using the calculated pseudo-range and position information

supplied by the satellite, the GPS receiver/processor

mathematically determines its position by triangulation

from several satellites. The GPS receiver needs at least four

satellites to yield a three-dimensional position (latitude,

longitude, and altitude) and time solution. The GPS receiver

computes navigational values (distance and bearing to

a WP, groundspeed, etc.) by using the aircraft’s known

latitude/longitude and referencing these to a database built

into the receiver.

The GPS receiver veriﬁ es the integrity (usability) of the

signals received from the GPS constellation through receiver

autonomous integrity monitoring (RAIM) to determine if a

satellite is providing corrupted information. RAIM needs

a minimum of ﬁ ve satellites in view, or four satellites and

a barometric altimeter baro-aiding to detect an integrity

anomaly. For receivers capable of doing so, RAIM needs

six satellites in view (or ﬁ ve satellites with baro-aiding)

to isolate a corrupt satellite signal and remove it from the

navigation solution.

Generally, there are two types of RAIM messages. One

type indicates that there are not enough satellites available

to provide RAIM and another type indicates that the RAIM

has detected a potential error that exceeds the limit for the

current phase of ﬂ ight. Without RAIM capability, the pilot

has no assurance of the accuracy of the GPS position.

Aircraft using GPS navigation equipment under IFR for

domestic en route, terminal operations, and certain IAPs,

must be equipped with an approved and operational alternate

means of navigation appropriate to the ﬂ ight. The avionics

necessary to receive all of the ground-based facilities

appropriate for the route to the destination airport and any

required alternate airport must be installed and operational.

Ground-based facilities necessary for these routes must also

be operational. Active monitoring of alternative navigation

equipment is not required if the GPS receiver uses RAIM for

integrity monitoring. Active monitoring of an alternate means

of navigation is required when the RAIM capability of the

GPS equipment is lost. In situations where the loss of RAIM

capability is predicted to occur, the ﬂ ight must rely on other

approved equipment, delay departure, or cancel the ﬂ ight.

GPS Substitution

IFR En Route and Terminal Operations

GPS systems, certified for IFR en route and terminal

operations, may be used as a substitute for ADF and DME

receivers when conducting the following operations within

the United States NAS.

1. Determining the aircraft position over a DME ﬁ x. This

includes en route operations at and above 24,000 feet

mean sea level (MSL) (FL 240) when using GPS for

navigation.

2. Flying a DME arc.

3. Navigating TO/FROM an NDB/compass locator.

4. Determining the aircraft position over an NDB/compass

locator.

5. Determining the aircraft position over a ﬁ x deﬁ ned by

an NDB/compass locator bearing crossing a VOR/LOC

course.

7-29

6. Holding over an NDB/compass locator.

GPS Substitution for ADF or DME

Using GPS as a substitute for ADF or DME is subject to the

following restrictions:

1. This equipment must be installed in accordance with

appropriate airworthiness installation requirements

and operated within the provisions of the applicable

POH/AFM, or supplement.

2. The required integrity for these operations must be

provided by at least en route RAIM, or equivalent.

3. WPs, ﬁ xes, intersections, and facility locations to be

used for these operations must be retrieved from the

GPS airborne database. The database must be current.

If the required positions cannot be retrieved from the

airborne database, the substitution of GPS for ADF

and/or DME is not authorized

4. Procedures must be established for use when RAIM

outages are predicted or occur. This may require the

ﬂ ight to rely on other approved equipment or require

the aircraft to be equipped with operational NDB and/or

DME receivers. Otherwise, the ﬂ ight must be rerouted,

delayed, canceled, or conducted under VFR.

5. The CDI must be set to terminal sensitivity (1 NM)

when tracking GPS course guidance in the terminal

area.

6. A non-GPS approach procedure must exist at the

alternate airport when one is required. If the non-GPS

approaches on which the pilot must rely require DME

or ADF, the aircraft must be equipped with DME or

ADF avionics as appropriate.

7. Charted requirements for ADF and/or DME can be met

using the GPS system, except for use as the principal

instrument approach navigation source.

NOTE: The following provides guidance, which is not

speciﬁ c to any particular aircraft GPS system. For speciﬁ c

system guidance, refer to the POH/AFM, or supplement, or

contact the system manufacturer.

To Determine Aircraft Position Over a DME Fix:

1. Verify aircraft GPS system integrity monitoring

is functioning properly and indicates satisfactory

integrity.

2. If the ﬁ x is identiﬁ ed by a ﬁ ve-letter name which is

contained in the GPS airborne database, select either

the named ﬁ x as the active GPS WP or the facility

establishing the DME ﬁ x as the active GPS WP. When

using a facility as the active WP, the only acceptable

facility is the DME facility which is charted as the one

used to establish the DME ﬁ x. If this facility is not in

the airborne database, it is not authorized for use.

3. If the ﬁ x is identiﬁ ed by a ﬁ ve-letter name which is not

contained in the GPS airborne database, or if the ﬁ x is

not named, select the facility establishing the DME ﬁ x

or another named DME ﬁ x as the active GPS WP.

4. When selecting the named ﬁ x as the active GPS WP,

a pilot is over the ﬁ x when the GPS system indicates

the active WP.

5. If selecting the DME providing facility as the active

GPS WP, a pilot is over the ﬁ x when the GPS distance

from the active WP equals the charted DME value, and

the aircraft is established on the appropriate bearing

or course.

To Fly a DME Arc:

1. Verify aircraft GPS system integrity monitoring

is functioning properly and indicates satisfactory

integrity.

2. Select from the airborne database the facility providing

the DME arc as the active GPS WP. The only

acceptable facility is the DME facility on which the arc

is based. If this facility is not in your airborne database,

you are not authorized to perform this operation.

3. Maintain position on the arc by reference to the GPS

distance instead of a DME readout.

To Navigate TO or FROM an NDB/Compass

Locator:

1. Verify aircraft GPS system integrity monitoring

is functioning properly and indicates satisfactory

integrity.

2. Select the NDB/compass locator facility from the

airborne database as the active WP. If the chart depicts

the compass locator collocated with a ﬁ x of the same

name, use of that ﬁ x as the active WP in place of the

compass locator facility is authorized.

3. Select and navigate on the appropriate course to or

from the active WP.

To Determine Aircraft Position Over an NDB/

Compass Locator:

1. Verify aircraft GPS system integrity monitoring

is functioning properly and indicates satisfactory

integrity.

7-30

2. Select the NDB/compass locator facility from the

airborne database. When using an NDB/compass

locator, the facility must be charted and be in the

airborne database. If the facility is not in the airborne

database, pilots are not authorized to use a facility WP

for this operation.

3. A pilot is over the NDB/compass locator when the

GPS system indicates arrival at the active WP.

To Determine Aircraft Position Over a Fix Made up

of an NDB/Compass Locator Bearing Crossing a

VOR/LOC Course:

1. Verify aircraft GPS system integrity monitoring

is functioning properly and indicates satisfactory

integrity.

2. A ﬁ x made up by a crossing NDB/compass locator

bearing is identiﬁ ed by a ﬁ ve-letter ﬁ x name. Pilots

may select either the named ﬁ x or the NDB/compass

locator facility providing the crossing bearing to

establish the ﬁ x as the active GPS WP. When using

an NDB/compass locator, that facility must be charted

and be in the airborne database. If the facility is not

in the airborne database, pilots are not authorized to

use a facility WP for this operation.

3. When selecting the named ﬁ x as the active GPS WP,

pilot is over the ﬁ x when the GPS system indicates

the pilot is at the WP.

4. When selecting the NDB/compass locator facility

as the active GPS WP, pilots are over the ﬁ x when

the GPS bearing to the active WP is the same as

the charted NDB/compass locator bearing for the

ﬁ x ﬂ ying the prescribed track from the non-GPS

navigation source.

To Hold Over an NDB/Compass Locator:

1. Verify aircraft GPS system integrity monitoring

is functioning properly and indicates satisfactory

integrity.

2. Select the NDB/compass locator facility from the

airborne database as the active WP. When using a

facility as the active WP, the only acceptable facility

is the NDB/compass locator facility which is charted.

If this facility is not in the airborne database, its use

is not authorized.

3. Select nonsequencing (e.g., “HOLD” or “OBS”) mode

and the appropriate course in accordance with the

POH/AFM, or supplement.

4. Hold using the GPS system in accordance with the

POH/AFM, or supplement.

IFR Flight Using GPS

Preﬂ ight preparations should ensure that the GPS is properly

installed and certiﬁ ed with a current database for the type

of operation. The GPS operation must be conducted in

accordance with the FAA-approved POH/AFM or ﬂ ight

manual supplement. Flightcrew members must be thoroughly

familiar with the particular GPS equipment installed in the

aircraft, the receiver operation manual, and the POH/AFM

or ﬂ ight manual supplement. Unlike ILS and VOR, the

basic operation, receiver presentation to the pilot and some

capabilities of the equipment can vary greatly. Due to these

differences, operation of different brands, or even models

of the same brand of GPS receiver under IFR should not be

attempted without thorough study of the operation of that

particular receiver and installation. Using the equipment in

ﬂ ight under VFR conditions prior to attempting IFR operation

will allow further familiarization.

Required preﬂ ight preparations should include checking

NOTAMs relating to the IFR ﬂ ight when using GPS as a

supplemental method of navigation. GPS satellite outages

are issued as GPS NOTAMs both domestically and

internationally. Pilots may obtain GPS RAIM availability

information for an airport by speciﬁ cally requesting GPS

aeronautical information from an automated ﬂ ight service

station (AFSS) during preflight briefings. GPS RAIM

aeronautical information can be obtained for a 3-hour

period: the estimated time of arrival (ETA), and 1 hour

before to 1 hour after the ETA hour, or a 24-hour time frame

for a speciﬁ c airport. FAA briefers will provide RAIM

information for a period of 1 hour before to 1 hour after

the ETA, unless a speciﬁ c timeframe is requested by the

pilot. If ﬂ ying a published GPS departure, the pilot should

also request a RAIM prediction for the departure airport.

Some GPS receivers have the capability to predict RAIM

availability. The pilot should also ensure that the required

underlying ground-based navigation facilities and related

aircraft equipment appropriate to the route of ﬂ ight, terminal

operations, instrument approaches for the destination, and

alternate airports/heliports will be operational for the ETA.

If the required ground-based facilities and equipment will

not be available, the ﬂ ight should be rerouted, rescheduled,

canceled, or conducted under VFR.

Except for programming and retrieving information from

the GPS receiver, planning the ﬂ ight is accomplished in a

similar manner to conventional NAVAIDs. Departure WP,

DP, route, STAR, desired approach, IAF, and destination

airport are entered into the GPS receiver according to the

manufacturer’s instructions. During preﬂ ight, additional

information may be entered for functions such as ETA, fuel

planning, winds aloft, etc.

7-31

Figure 7-29. A GPS Stand-Alone Approach.

When the GPS receiver is turned on, it begins an internal

process of test and initialization. When the receiver is

initialized, the user develops the route by selecting a WP

or series of WPs, veriﬁ es the data, and selects the active

ﬂ ight plan. This procedure varies widely among receivers

made by different manufacturers. GPS is a complex system,

offering little standardization between receiver models. It is

the pilot’s responsibility to be familiar with the operation of

the equipment in the aircraft.

The GPS receiver provides navigational values such as track,

bearing, groundspeed, and distance. These are computed from

the aircraft’s present latitude and longitude to the location of

the next WP. Course guidance is provided between WPs. The

pilot has the advantage of knowing the aircraft’s actual track

over the ground. As long as track and bearing to the WP are

matched up (by selecting the correct aircraft heading), the

aircraft is going directly to the WP.

GPS Instrument Approaches

There is a mixture of GPS overlay approaches (approaches

with “or GPS” in the title) and GPS stand-alone approaches

in the United States.

NOTE: GPS instrument approach operations outside the

United States must be authorized by the appropriate country

authority.

While conducting these IAPs, ground-based NAVAIDs are

not required to be operational and associated aircraft avionics

need not be installed, operational, turned on, or monitored;

however, monitoring backup navigation systems is always

recommended when available.

Pilots should have a basic understanding of GPS approach

procedures and practice GPS IAPs under visual meteorological

conditions (VMC) until thoroughly proficient with all

aspects of their equipment (receiver and installation) prior

to attempting ﬂ ight in instrument meteorological conditions

(IMC). [Figure 7-29]

All IAPs must be retrievable from the current GPS database

supplied by the manufacturer or other FAA-approved

source. Flying point to point on the approach does not

assure compliance with the published approach procedure.

The proper RAIM sensitivity will not be available and the

CDI sensitivity will not automatically change to 0.3 NM.

Manually setting CDI sensitivity does not automatically

change the RAIM sensitivity on some receivers. Some

existing nonprecision approach procedures cannot be coded

for use with GPS and will not be available as overlays.

7-32

GPS approaches are requested and approved by ATC using

the GPS title, such as “GPS RWY 24” or “RNAV RWY

35.” Using the manufacturer’s recommended procedures, the

desired approach and the appropriate IAF are selected from

the GPS receiver database. Pilots should ﬂ y the full approach

from an initial approach waypoint (IAWP) or feeder ﬁ x unless

speciﬁ cally cleared otherwise. Randomly joining an approach

at an intermediate ﬁ x does not ensure terrain clearance.

When an approach has been loaded in the ﬂ ight plan, GPS

receivers will give an “arm” annunciation 30 NM straight

line distance from the airport/heliport reference point. The

approach mode should be “armed” when within 30 NM

distance so the receiver will change from en route CDI

(±5 NM) and RAIM (±2 NM) sensitivity to ±1 NM terminal

sensitivity. Where the IAWP is within 30 NM, a CDI

sensitivity change will occur once the approach mode is

armed and the aircraft is within 30 NM. Where the IAWP

is beyond the 30 NM point, CDI sensitivity will not change

until the aircraft is within 30 NM even if the approach is

armed earlier. Feeder route obstacle clearance is predicated

on the receiver CDI and RAIM being in terminal CDI

sensitivity within 30 NM of the airport/heliport reference

point; therefore, the receiver should always be armed no later

than the 30 NM annunciation.

Pilots should pay particular attention to the exact operation

of their GPS receivers for performing holding patterns and in

the case of overlay approaches, operations such as procedure

turns. These procedures may require manual intervention

by the pilot to stop the sequencing of WPs by the receiver

and to resume automatic GPS navigation sequencing once

the maneuver is complete. The same WP may appear in the

route of ﬂ ight more than once and consecutively (e.g., IAWP,

ﬁ nal approach waypoint (FAWP), missed approach waypoint

(MAWP) on a procedure turn). Care must be exercised to

ensure the receiver is sequenced to the appropriate WP for

the segment of the procedure being ﬂ own, especially if one

or more ﬂ y-over WPs are skipped (e.g., FAWP rather than

IAWP if the procedure turn is not ﬂ own). The pilot may need

to sequence past one or more ﬂ y-overs of the same WP in

order to start GPS automatic sequencing at the proper place

in the sequence of WPs.

When receiving vectors to ﬁ nal, most receiver operating

manuals suggest placing the receiver in the nonsequencing

mode on the FAWP and manually setting the course. This

provides an extended ﬁ nal approach course in cases where

the aircraft is vectored onto the ﬁ nal approach course outside

of any existing segment which is aligned with the runway.

Assigned altitudes must be maintained until established on a

published segment of the approach. Required altitudes at WPs

outside the FAWP or step-down ﬁ xes must be considered.

Calculating the distance to the FAWP may be required in

order to descend at the proper location.

When within 2 NM of the FAWP with the approach mode

armed, the approach mode will switch to active, which results

in RAIM and CDI sensitivity changing to the approach

mode. Beginning 2 NM prior to the FAWP, the full scale

CDI sensitivity will change smoothly from ±1 NM to ±0.3

NM at the FAWP. As sensitivity changes from ±1 NM to

±0.3 NM approaching the FAWP, and the CDI not centered,

the corresponding increase in CDI displacement may give

the impression the aircraft is moving further away from the

intended course even though it is on an acceptable intercept

heading. If digital track displacement information (cross-track

error) is available in the approach mode, it may help the pilot

remain position oriented in this situation. Being established

on the ﬁ nal approach course prior to the beginning of the

sensitivity change at 2 NM will help prevent problems in

interpreting the CDI display during ramp-down. Requesting

or accepting vectors, which will cause the aircraft to intercept

the ﬁ nal approach course within 2 NM of the FAWP, is not

recommended.

Incorrect inputs into the GPS receiver are especially critical

during approaches. In some cases, an incorrect entry can

cause the receiver to leave the approach mode. Overriding

an automatically selected sensitivity during an approach

will cancel the approach mode annunciation. If the approach

mode is not armed by 2 NM prior to the FAWP, the approach

mode will not become active at 2 NM prior to the FAWP and

the equipment will ﬂ ag. In these conditions, the RAIM and

CDI sensitivity will not ramp down, and the pilot should not

descend to minimum descent altitude (MDA), but ﬂ y to the

MAWP and execute a missed approach. The approach active

annunciator and/or the receiver should be checked to ensure

the approach mode is active prior to the FAWP.

A GPS missed approach requires pilot action to sequence the

receiver past the MAWP to the missed approach portion of

the procedure. The pilot must be thoroughly familiar with

the activation procedure for the particular GPS receiver

installed in the aircraft and must initiate appropriate action

after the MAWP. Activating the missed approach prior to the

MAWP will cause CDI sensitivity to change immediately to

terminal (±1 NM) sensitivity, and the receiver will continue

to navigate to the MAWP. The receiver will not sequence past

the MAWP. Turns should not begin prior to the MAWP. If

the missed approach is not activated, the GPS receiver will

display an extension of the inbound ﬁ nal approach course and

the along track distance (ATD) will increase from the MAWP

until it is manually sequenced after crossing the MAWP.

7-33

Missed approach routings in which the ﬁ rst track is via a

course rather than direct to the next WP require additional

action by the pilot to set the course. Being familiar with all

of the required inputs is especially critical during this phase

of ﬂ ight.

Departures and Instrument Departure Procedures

(DPs)

The GPS receiver must be set to terminal (±1 NM) CDI

sensitivity and the navigation routes contained in the database

in order to ﬂ y published IFR charted departures and DPs.

Terminal RAIM should be provided automatically by the

receiver. (Terminal RAIM for departure may not be available

unless the WPs are part of the active ﬂ ight plan rather than

proceeding direct to the ﬁ rst destination.) Certain segments

of a DP may require some manual intervention by the pilot,

especially when radar vectored to a course or required to

intercept a speciﬁ c course to a WP. The database may not

contain all of the transitions or departures from all runways

and some GPS receivers do not contain DPs in the database.

It is necessary that helicopter procedures be ﬂ own at 70 knots

or less since helicopter departure procedures and missed

approaches use a 20:1 obstacle clearance surface (OCS),

which is double the ﬁ xed-wing OCS. Turning areas are based

on this speed also. Missed approach routings in which the

ﬁ rst track is via a course rather than direct to the next WP

require additional action by the pilot to set the course. Being

familiar with all of the required inputs is especially critical

during this phase of ﬂ ight.

GPS Errors

Normally, with 30 satellites in operation, the GPS

constellation is expected to be available continuously

worldwide. Whenever there are fewer than 24 operational

satellites, GPS navigational capability may not be available

at certain geographic locations. Loss of signals may also

occur in valleys surrounded by high terrain, and any time

the aircraft’s GPS antenna is “shadowed” by the aircraft’s

structure (e.g., when the aircraft is banked).

Certain receivers, transceivers, mobile radios, and portable

receivers can cause signal interference. Some VHF

transmissions may cause “harmonic interference.” Pilots

can isolate the interference by relocating nearby portable

receivers, changing frequencies, or turning off suspected

causes of the interference while monitoring the receiver’s

signal quality data page.

GPS position data can be affected by equipment characteristics

and various geometric factors, which typically cause errors

of less than 100 feet. Satellite atomic clock inaccuracies,

receiver/processors, signals reflected from hard objects

(multi-path), ionospheric and tropospheric delays, and

satellite data transmission errors may cause small position

errors or momentary loss of the GPS signal.

System Status

The status of GPS satellites is broadcast as part of the data

message transmitted by the GPS satellites. GPS status

information is also available by means of the United States

Coast Guard navigation information service: (703) 313-

5907, or on the internet at http://www.navcen.uscg.gov/.

Additionally, satellite status is available through the Notice

to Airmen (NOTAM) system.

The GPS receiver veriﬁ es the integrity (usability) of the

signals received from the GPS constellation through receiver

autonomous integrity monitoring (RAIM) to determine if

a satellite is providing corrupted information. At least one

satellite, in addition to those required for navigation, must

be in view for the receiver to perform the RAIM function;

thus, RAIM needs a minimum of ﬁ ve satellites in view, or

four satellites and a barometric altimeter (baro-aiding) to

detect an integrity anomaly. For receivers capable of doing

so, RAIM needs six satellites in view (or ﬁ ve satellites with

baro-aiding) to isolate the corrupt satellite signal and remove

it from the navigation solution.

RAIM messages vary somewhat between receivers; however,

there are two most commonly used types. One type indicates

that there are not enough satellites available to provide

RAIM integrity monitoring and another type indicates that

the RAIM integrity monitor has detected a potential error

that exceeds the limit for the current phase of ﬂ ight. Without

RAIM capability, the pilot has no assurance of the accuracy

of the GPS position.

Selective Availability. Selective Availability (SA) is a method

by which the accuracy of GPS is intentionally degraded.

This feature is designed to deny hostile use of precise GPS

positioning data. SA was discontinued on May 1, 2000,

but many GPS receivers are designed to assume that SA

is still active. New receivers may take advantage of the

discontinuance of SA based on the performance values in

ICAO Annex 10, and do not need to be designed to operate

outside of that performance.

7-34

GPS Familiarization

Pilots should practice GPS approaches under visual

meteorological conditions (VMC) until thoroughly proﬁ cient

with all aspects of their equipment (receiver and installation)

prior to attempting ﬂ ight by IFR in instrument meteorological

conditions (IMC). Some of the tasks which the pilot should

practice are:

1. Utilizing the receiver autonomous integrity monitoring

(RAIM) prediction function;

2. Inserting a DP into the ﬂ ight plan, including setting

terminal CDI sensitivity, if required, and the conditions

under which terminal RAIM is available for departure

(some receivers are not DP or STAR capable);

3. Programming the destination airport;

4. Programming and flying the overlay approaches

(especially procedure turns and arcs);

5. Changing to another approach after selecting an

approach;

6. Programming and flying “direct” missed

approaches;

7. Programming and flying “routed” missed

approaches;

8. Entering, flying, and exiting holding patterns,

particularly on overlay approaches with a second WP

in the holding pattern;

9. Programming and ﬂ ying a “route” from a holding

pattern;

10. Programming and flying an approach with radar

vectors to the intermediate segment;

11. Indication of the actions required for RAIM failure

both before and after the FAWP; and

12. Programming a radial and distance from a VOR (often

used in departure instructions).

Differential Global Positioning Systems (DGPS)

Differential global positioning systems (DGPS) are designed

to improve the accuracy of global navigation satellite systems

(GNSS) by measuring changes in variables to provide satellite

positioning corrections.

Because multiple receivers receiving the same set of satellites

produce similar errors, a reference receiver placed at a known

location can compute its theoretical position accurately and

can compare that value to the measurements provided by the

navigation satellite signals. The difference in measurement

between the two signals is an error that can be corrected by

providing a reference signal correction.

As a result of this differential input accuracy of the

satellite system can be increased to meters. The Wide Area

Augmentation System (WAAS) and Local Area Augmentation

System (LAAS) are examples of differential global positioning

systems.

Wide Area Augmentation System (WAAS)

The WAAS is designed to improve the accuracy, integrity,

and availability of GPS signals. WAAS allows GPS to be

used, as the aviation navigation system, from takeoff through

Category I precision approaches. The International Civil

Aviation Organization (ICAO) has deﬁ ned Standards for

satellite-based augmentation systems (SBAS), and Japan

and Europe are building similar systems that are planned

to be interoperable with WAAS: EGNOS, the European

Geostationary Navigation Overlay System, and MSAS,

the Japanese Multifunctional Transport Satellite (MTSAT)

Satellite-based Augmentation System. The result will be a

worldwide seamless navigation capability similar to GPS but

with greater accuracy, availability, and integrity.

Unlike traditional ground-based navigation aids, WAAS

will cover a more extensive service area in which surveyed

wide-area ground reference stations are linked to the WAAS

network. Signals from the GPS satellites are monitored by

these stations to determine satellite clock and ephemeris

corrections. Each station in the network relays the data to a

wide-area master station where the correction information is

computed. A correction message is prepared and uplinked to

a geostationary satellite (GEO) via a ground uplink and then

broadcast on the same frequency as GPS to WAAS receivers

within the broadcast coverage area. [Figure 7-30]

In addition to providing the correction signal, WAAS

provides an additional measurement to the aircraft receiver,

improving the availability of GPS by providing, in effect,

an additional GPS satellite in view. The integrity of GPS is

improved through real-time monitoring, and the accuracy

is improved by providing differential corrections to reduce

errors. [Figure 7-31] As a result, performance improvement

is sufﬁ cient to enable approach procedures with GPS/WAAS

glide paths. At this time the FAA has completed installation of

25 wide area ground reference systems, two master stations,

and four ground uplink stations.

General Requirements

WAAS avionics must be certified in accordance with

TSO-C145A, Airborne Navigation Sensors Using the GPS

Augmented by the WAAS; or TSO-146A for stand-alone

systems. GPS/WAAS operation must be conducted in

accordance with the FAA-approved aircraft ﬂ ight manual

(AFM) and flight manual supplements. Flight manual

supplements must state the level of approach procedure that

the receiver supports.

7-35

Figure 7-30. WAAS Satellite Representation.

7-36

Figure 7-32. LAAS Representation.

Figure 7-31. WAAS Satellite Representation.

Instrument Approach Capabilities

WAAS receivers support all basic GPS approach functions

and will provide additional capabilities with the key beneﬁ t

to generate an electronic glide path, independent of ground

equipment or barometric aiding. This eliminates several

problems such as cold temperature effects, incorrect altimeter

setting or lack of a local altimeter source, and allows approach

procedures to be built without the cost of installing ground

stations at each airport. A new class of approach procedures

which provide vertical guidance requirements for precision

approaches has been developed to support satellite navigation

use for aviation applications. These new procedures called

Approach with Vertical Guidance (APV) include approaches

such as the LNAV/VNAV procedures presently being ﬂ own

with barometric vertical navigation.

Local Area Augmentation System (LAAS)

LAAS is a ground-based augmentation system which uses

a GPS reference facility located on or in the vicinity of

the airport being serviced. This facility has a reference

receiver that measures GPS satellite pseudo-range and

timing and retransmits the signal. Aircraft landing at

LAAS-equipped airports are able to conduct approaches to

Category I level and above for properly equipped aircraft.

[Figures 7-32 and 7-33]

Inertial Navigation System (INS)

Inertial Navigation System (INS) is a system that navigates

precisely without any input from outside of the aircraft. It is

fully self-contained. The INS is initialized by the pilot, who

enters into the system the exact location of the aircraft on the

ground before the ﬂ ight. The INS is also programmed with

WPs along the desired route of ﬂ ight.

7-37

Figure 7-33. LAAS Representation.

INS Components

INS is considered a stand-alone navigation system, especially

when more than one independent unit is onboard. The

airborne equipment consists of an accelerometer to measure

acceleration—which, when integrated with time, gives

velocity—and gyros to measure direction.

Later versions of the INS, called inertial reference systems

(IRS) utilize laser gyros and more powerful computers;

therefore, the accelerometer mountings no longer need to

be kept level and aligned with true north. The computer

system can handle the added workload of dealing with the

computations necessary to correct for gravitational and

directional errors. Consequently, these newer systems are

sometimes called strap down systems, as the accelerometers

and gyros are strapped down to the airframe, rather than being

mounted on a structure that stays ﬁ xed with respect to the

horizon and true north.

INS Errors

The principal error associated with INS is degradation of

position with time. INS computes position by starting with

accurate position input which is changed continuously as

accelerometers and gyros provide speed and direction inputs.

Both accelerometers and gyros are subject to very small

errors; as time passes, those errors probably accumulate.

While the best INS/IRS display errors of 0.1 to 0.4 NM after

ﬂ ights across the North Atlantic of 4 to 6 hours, smaller and

less expensive systems are being built that show errors of 1

to 2 NM per hour. This accuracy is more than sufﬁ cient for

a navigation system that can be combined with and updated

by GPS. The synergy of a navigation system consisting of an

INS/IRS unit in combination with a GPS resolves the errors

and weaknesses of both systems. GPS is accurate all the time

it is working but may be subject to short and periodic outages.

INS is made more accurate because it is continually updated

and continues to function with good accuracy if the GPS has

moments of lost signal.

Instrument Approach Systems

Most navigation systems approved for en route and terminal

operations under IFR, such as VOR, NDB, and GPS, may

also be approved to conduct IAPs. The most common

systems in use in the United States are the ILS, simpliﬁ ed

directional facility (SDF), localizer directional aid (LDA),

and microwave landing system (MLS). These systems

operate independently of other navigation systems. There are

new systems being developed, such as WAAS and LAAS.

Other systems have been developed for special use.

Instrument Landing Systems (ILS)

The ILS system provides both course and altitude guidance

to a speciﬁ c runway. The ILS system is used to execute

a precision instrument approach procedure or precision

approach. [Figure 7-34] The system consists of the following

components:

1. A localizer providing horizontal (left/right) guidance

along the extended centerline of the runway.

2. A glide slope (GS) providing vertical (up/down)

guidance toward the runway touchdown point, usually

at a 3° slope.

3. Marker beacons providing range information along

the approach path.

4. Approach lights assisting in the transition from

instrument to visual ﬂ ight.

The following supplementary elements, though not speciﬁ c

components of the system, may be incorporated to increase

safety and utility:

1. Compass locators providing transition from en route

NAVAIDs to the ILS system and assisting in holding

procedures, tracking the localizer course, identifying

the marker beacon sites, and providing a FAF for ADF

approaches.

2. DME collocated with the GS transmitter providing

positive distance-to-touchdown information or DME

associated with another nearby facility (VOR or stand-

alone), if speciﬁ ed in the approach procedure.

ILS approaches are categorized into three different types of

approaches based on the equipment at the airport and the

experience level of the pilot. Category I approaches provide

for approach height above touchdown of not less than 200 feet.

Category II approaches provide for approach to a height above

7-38

Figure 7-34. Instrument Landing Systems.

7-39

Figure 7-35. Localizer Coverage Limits.

touchdown of not less than 100 feet. Category III approaches

provide lower minimums for approaches without a decision

height minimum. While pilots need only be instrument rated

and the aircraft be equipped with the appropriate airborne

equipment to execute Category I approaches, Category II

and III approaches require special certiﬁ cation for the pilots,

ground equipment, and airborne equipment.

ILS Components

Ground Components

The ILS uses a number of different ground facilities. These

facilities may be used as a part of the ILS system, as well as

part of another approach. For example, the compass locator

may be used with NDB approaches.

Localizer

The localizer (LOC) ground antenna array is located on the

extended centerline of the instrument runway of an airport,

located at the departure end of the runway to prevent it from

being a collision hazard. This unit radiates a ﬁ eld pattern,

which develops a course down the centerline of the runway

toward the middle markers (MMs) and outer markers

(OMs), and a similar course along the runway centerline in

the opposite direction. These are called the front and back

courses, respectively. The localizer provides course guidance,

transmitted at 108.1 to 111.95 MHz (odd tenths only),

throughout the descent path to the runway threshold from a

distance of 18 NM from the antenna to an altitude of 4,500

feet above the elevation of the antenna site. [Figure 7-35]

The localizer course width is defined as the angular

displacement at any point along the course between a full

“ﬂ y-left” (CDI needle fully deﬂ ected to the left) and a full

“ﬂ y-right” indication (CDI needle fully deﬂ ected to the right).

Each localizer facility is audibly identiﬁ ed by a three-letter

designator, transmitted at frequent regular intervals. The ILS

identiﬁ cation is preceded by the letter “I” (two dots). For

example, the ILS localizer at Springﬁ eld, Missouri transmits

the identiﬁ er ISGF. The localizer includes a voice feature on

its frequency for use by the associated ATC facility in issuing

approach and landing instructions.

The localizer course is very narrow, normally 5°. This

results in high needle sensitivity. With this course width,

a full-scale deﬂ ection shows when the aircraft is 2.5° to

either side of the centerline. This sensitivity permits accurate

orientation to the landing runway. With no more than one-

quarter scale deﬂ ection maintained, the aircraft will be

aligned with the runway.

Glide Slope (GS)

GS describes the systems that generate, receive, and indicate

the ground facility radiation pattern. The glide path is the

straight, sloped line the aircraft should ﬂ y in its descent from

where the GS intersects the altitude used for approaching the

FAF, to the runway touchdown zone. The GS equipment

is housed in a building approximately 750 to 1,250 feet

down the runway from the approach end of the runway, and

between 400 and 600 feet to one side of the centerline.

7-40

Figure 7-36. Localizer receiver indications and aircraft

displacement.

The course projected by the GS equipment is essentially the

same as would be generated by a localizer operating on its

side. The GS projection angle is normally adjusted to 2.5°

to 3.5° above horizontal, so it intersects the MM at about

200 feet and the OM at about 1,400 feet above the runway

elevation. At locations where standard minimum obstruction

clearance cannot be obtained with the normal maximum GS

angle, the GS equipment is displaced farther from the approach

end of the runway if the length of the runway permits; or, the

GS angle may be increased up to 4°.

Unlike the localizer, the GS transmitter radiates signals only

in the direction of the ﬁ nal approach on the front course. The

system provides no vertical guidance for approaches on the

back course. The glide path is normally 1.4° thick. At 10

NM from the point of touchdown, this represents a vertical

distance of approximately 1,500 feet, narrowing to a few feet

at touchdown.

Marker Beacons

Two VHF marker beacons, outer and middle, are normally

used in the ILS system. [Figure 7-36] A third beacon, the

inner, is used where Category II operations are certiﬁ ed. A

marker beacon may also be installed to indicate the FAF on

the ILS back course.

The OM is located on the localizer front course 4–7 miles

from the airport to indicate a position at which an aircraft, at

the appropriate altitude on the localizer course, will intercept

the glide path. The MM is located approximately 3,500 feet

from the landing threshold on the centerline of the localizer

front course at a position where the GS centerline is about 200

feet above the touchdown zone elevation. The inner marker

(IM), where installed, is located on the front course between

the MM and the landing threshold. It indicates the point at

which an aircraft is at the decision height on the glide path

during a Category II ILS approach. The back-course marker,

where installed, indicates the back-course FAF.

Compass Locator

Compass locators are low-powered NDBs and are received

and indicated by the ADF receiver. When used in conjunction

with an ILS front course, the compass locator facilities are

collocated with the outer and/or MM facilities. The coding

identiﬁ cation of the outer locator consists of the ﬁ rst two

letters of the three-letter identiﬁ er of the associated LOC.

For example, the outer locator at Dallas/Love Field (DAL) is

identiﬁ ed as “DA.” The middle locator at DAL is identiﬁ ed

by the last two letters “AL.”

Approach Lighting Systems (ALS)

Normal approach and letdown on the ILS is divided into two

distinct stages: the instrument approach stage using only radio

guidance, and the visual stage, when visual contact with the

ground runway environment is necessary for accuracy and

safety. The most critical period of an instrument approach,

particularly during low ceiling/visibility conditions, is the

point at which the pilot must decide whether to land or

execute a missed approach. As the runway threshold is

approached, the visual glide path will separate into individual

lights. At this point, the approach should be continued by

reference to the runway touchdown zone markers. The ALS

provides lights that will penetrate the atmosphere far enough

from touchdown to give directional, distance, and glide path

information for safe visual transition.

Visual identification of the ALS by the pilot must be

instantaneous, so it is important to know the type of ALS

before the approach is started. Check the instrument approach

chart and the A/FD for the particular type of lighting facilities

at the destination airport before any instrument ﬂ ight. With

reduced visibility, rapid orientation to a strange runway can

be difﬁ cult, especially during a circling approach to an airport

with minimum lighting facilities, or to a large terminal airport

located in the midst of distracting city and ground facility

lights. Some of the most common ALS systems are shown

in Figure 7-37.

A high-intensity ﬂ asher system, often referred to as “the

rabbit,” is installed at many large airports. The ﬂ ashers consist

of a series of brilliant blue-white bursts of light ﬂ ashing in

sequence along the approach lights, giving the effect of a ball

of light traveling towards the runway. Typically, “the rabbit”

makes two trips toward the runway per second.

Runway end identiﬁ er lights (REIL) are installed for rapid and

positive identiﬁ cation of the approach end of an instrument

runway. The system consists of a pair of synchronized

ﬂ ashing lights placed laterally on each side of the runway

threshold facing the approach area.

7-41

Figure 7-37. Precision and Nonprecision ALS Conﬁ guration.

The visual approach slope indicator (VASI) gives visual

descent guidance information during the approach to a

runway. The standard VASI consists of light bars that

project a visual glide path, which provides safe obstruction

clearance within the approach zone. The normal GS angle

is 3°; however, the angle may be as high as 4.5° for proper

obstacle clearance. On runways served by ILS, the VASI

angle normally coincides with the electronic GS angle.

Visual left/right course guidance is obtained by alignment

with the runway lights. The standard VASI installation

consists of either 2-, 3-, 4-, 6-, 12-, or 16-light units arranged

in downwind and upwind light bars. Some airports serving

long-bodied aircraft have three-bar VASIs which provide two

visual glidepaths to the same runway. The ﬁ rst glide path

encountered is the same as provided by the standard VASI.

The second glide path is about 25 percent higher than the ﬁ rst

and is designed for the use of pilots of long-bodied aircraft.

The basic principle of VASI is that of color differentiation

between red and white. Each light projects a beam having

a white segment in the upper part and a red segment in the

lower part of the beam. From a position above the glide path

the pilot sees both bars as white. Lowering the aircraft with

respect to the glide path, the color of the upwind bars changes

from white to pink to red. When on the proper glide path,

the landing aircraft will overshoot the downwind bars and

undershoot the upwind bars. Thus the downwind (closer)

bars are seen as white and the upwind bars as red. From a

position below the glide path, both light bars are seen as

red. Moving up to the glide path, the color of the downwind

7-42

Figure 7-38. Standard two-bar VASI.

bars changes from red to pink to white. When below the

glide path, as indicated by a distinct all-red signal, a safe

obstruction clearance might not exist. A standard two-bar

VASI is illustrated in Figure 7-38.

ILS Airborne Components

Airborne equipment for the ILS system includes receivers

for the localizer, GS, marker beacons, ADF, DME, and the

respective indicator instruments.

The typical VOR receiver is also a localizer receiver with

common tuning and indicating equipment. Some receivers

have separate function selector switches, but most switch

between VOR and LOC automatically by sensing if odd

tenths between 108 and 111.95 MHz have been selected.

Otherwise, tuning of VOR and localizer frequencies is

accomplished with the same knobs and switches, and the CDI

indicates “on course” as it does on a VOR radial.

Though some GS receivers are tuned separately, in a typical

installation the GS is tuned automatically to the proper

frequency when the localizer is tuned. Each of the 40 localizer

channels in the 108.10 to 111.95 MHz band is paired with a

corresponding GS frequency.

When the localizer indicator also includes a GS needle, the

instrument is often called a cross-pointer indicator. The

crossed horizontal (GS) and vertical (localizer) needles are

free to move through standard ﬁ ve-dot deﬂ ections to indicate

position on the localizer course and glide path.

When the aircraft is on the glide path, the needle is horizontal,

overlying the reference dots. Since the glide path is much

narrower than the localizer course (approximately 1.4° from

full up to full down deﬂ ection), the needle is very sensitive

to displacement of the aircraft from on-path alignment. With

the proper rate of descent established upon GS interception,

very small corrections keep the aircraft aligned.

The localizer and GS warning ﬂ ags disappear from view on

the indicator when sufﬁ cient voltage is received to actuate the

needles. The ﬂ ags show when an unstable signal or receiver

malfunction occurs.

The OM is identiﬁ ed by a low-pitched tone, continuous dashes

at the rate of two per second, and a purple/blue marker beacon

light. The MM is identiﬁ ed by an intermediate tone, alternate

dots and dashes at the rate of 95 dot/dash combinations per

minute, and an amber marker beacon light. The IM, where

installed, is identiﬁ ed by a high-pitched tone, continuous dots

at the rate of six per second, and a white marker beacon light.

The back-course marker (BCM), where installed, is identiﬁ ed

by a high-pitched tone with two dots at a rate of 72 to 75 two-

dot combinations per minute, and a white marker beacon light.

Marker beacon receiver sensitivity is selectable as high or low

on many units. The low-sensitivity position gives the sharpest

indication of position and should be used during an approach.

The high-sensitivity position provides an earlier warning that

the aircraft is approaching the marker beacon site.

ILS Function

The localizer needle indicates, by deﬂ ection, whether the

aircraft is right or left of the localizer centerline, regardless of

the position or heading of the aircraft. Rotating the OBS has

no effect on the operation of the localizer needle, although

it is useful to rotate the OBS to put the LOC inbound course

under the course index. When inbound on the front course, or

outbound on the back course, the course indication remains

directional. (See Figure 7-39, aircraft C, D, and E.)

Unless the aircraft has reverse sensing capability and it is in

use, when ﬂ ying inbound on the back course or outbound

on the front course, heading corrections to on-course are

made opposite the needle deﬂ ection. This is commonly

described as “ﬂ ying away from the needle.” (See Figure 7-39,

aircraft A and B.) Back course signals should not be used

for an approach unless a back course approach procedure

is published for that particular runway and the approach is

authorized by ATC.

Once you have reached the localizer centerline, maintain

the inbound heading until the CDI moves off center. Drift

corrections should be small and reduced proportionately as

the course narrows. By the time you reach the OM, your drift

correction should be established accurately enough on a well-

executed approach to permit completion of the approach,

with heading corrections no greater then 2°.

The heaviest demand on pilot technique occurs during

descent from the OM to the MM, when you maintain

the localizer course, adjust pitch attitude to maintain the

7-43

Figure 7-39. Localizer Course Indications. To follow indications displayed in the aircraft, start from A and proceed through E.

7-44

Figure 7-40. Illustrates a GS receiver indication and aircraft displacement. An analog system is on the left and the same indication on

the Garmin PFD on the right.

proper rate of descent, and adjust power to maintain proper

airspeed. Simultaneously, the altimeter must be checked

and preparation made for visual transition to land or for a

missed approach. You can appreciate the need for accurate

instrument interpretation and aircraft control within the ILS

as a whole, when you notice the relationship between CDI

and glide path needle indications, and aircraft displacement

from the localizer and glide path centerlines.

Deﬂ ection of the GS needle indicates the position of the

aircraft with respect to the glide path. When the aircraft is

above the glide path, the needle is deﬂ ected downward. When

the aircraft is below the glide path, the needle is deﬂ ected

upward. [Figure 7-40]

ILS Errors

The ILS and its components are subject to certain errors,

which are listed below. Localizer and GS signals are subject to

the same type of bounce from hard objects as space waves.

1. Reﬂ ection. Surface vehicles and even other aircraft

ﬂ ying below 5,000 feet above ground level (AGL)

may disturb the signal for aircraft on the approach.

2. False courses. In addition to the desired course, GS

facilities inherently produce additional courses at

higher vertical angles. The angle of the lowest of these

false courses will occur at approximately 9°–12°. An

aircraft ﬂ ying the LOC/GS course at a constant altitude

would observe gyrations of both the GS needle and GS

warning ﬂ ag as the aircraft passed through the various

false courses. Getting established on one of these

false courses will result in either confusion (reversed

GS needle indications) or in the need for a very high

descent rate. However, if the approach is conducted

at the altitudes speciﬁ ed on the appropriate approach

chart, these false courses will not be encountered.

Marker Beacons

The very low power and directional antenna of the marker

beacon transmitter ensures that the signal will not be received

any distance from the transmitter site. Problems with signal

reception are usually caused by the airborne receiver not

being turned on, or by incorrect receiver sensitivity.

Some marker beacon receivers, to decrease weight and cost,

are designed without their own power supply. These units

utilize a power source from another radio in the avionics

stack, often the ADF. In some aircraft, this requires the

ADF to be turned on in order for the marker beacon receiver

to function, yet no warning placard is required. Another

7-45

source of trouble may be the “High/Low/Off” three-position

switch, which both activates the receiver and selects receiver

sensitivity. Usually, the “test” feature only tests to see if

the light bulbs in the marker beacon lights are working.

Therefore, in some installations, there is no functional way

for the pilot to ascertain the marker beacon receiver is actually

on except to ﬂ y over a marker beacon transmitter, and see if

a signal is received and indicated (e.g., audibly, and visually

via marker beacon lights).

Operational Errors

1. Failure to understand the fundamentals of ILS ground

equipment, particularly the differences in course

dimensions. Since the VOR receiver is used on the

localizer course, the assumption is sometimes made

that interception and tracking techniques are identical

when tracking localizer courses and VOR radials.

Remember that the CDI sensing is sharper and faster

on the localizer course.

2. Disorientation during transition to the ILS due to poor

planning and reliance on one receiver instead of on all

available airborne equipment. Use all the assistance

available; a single receiver may fail.

3. Disorientation on the localizer course, due to the ﬁ rst

error noted above.

4. Incorrect localizer interception angles. A large

interception angle usually results in overshooting,

and possible disorientation. When intercepting,

if possible, turn to the localizer course heading

immediately upon the first indication of needle

movement. An ADF receiver is an excellent aid to

orient you during an ILS approach if there is a locator

or NDB on the inbound course.

5. Chasing the CDI and glide path needles, especially

when you have not sufﬁ ciently studied the approach

before the ﬂ ight.

Simpliﬁ ed Directional Facility (SDF)

The SDF provides a ﬁ nal approach course similar to the ILS

localizer. The SDF course may or may not be aligned with

the runway and the course may be wider than a standard

ILS localizer, resulting in less precision. Usable off-course

indications are limited to 35° either side of the course

centerline. Instrument indications in the area between 35°

and 90° from the course centerline are not controlled and

should be disregarded.

The SDF must provide signals sufﬁ cient to allow satisfactory

operation of a typical aircraft installation within a sector

which extends from the center of the SDF antenna system

to distances of 18 NM covering a sector 10° either side of

centerline up to an angle 7° above the horizontal. The angle

of convergence of the ﬁ nal approach course and the extended

runway centerline must not exceed 30°. Pilots should note

this angle since the approach course originates at the antenna

site, and an approach continued beyond the runway threshold

would lead the aircraft to the SDF offset position rather than

along the runway centerline.

The course width of the SDF signal emitted from the

transmitter is ﬁ xed at either 6° or 12°, as necessary, to provide

maximum ﬂ yability and optimum approach course quality.

A three-letter identiﬁ er is transmitted in code on the SDF

frequency; there is no letter “I” (two dots) transmitted before

the station identiﬁ er, as there is with the LOC. For example,

the identiﬁ er for Lebanon, Missouri, SDF is LBO.

Localizer Type Directional Aid (LDA)

The LDA is of comparable utility and accuracy to a localizer

but is not part of a complete ILS. The LDA course width is

between 3° and 6° and thus provides a more precise approach

course than an SDF installation. Some LDAs are equipped

with a GS. The LDA course is not aligned with the runway,

but straight-in minimums may be published where the angle

between the runway centerline and the LDA course does not

exceed 30°. If this angle exceeds 30°, only circling minimums

are published. The identiﬁ er is three letters preceded by “I”

transmitted in code on the LDA frequency. For example, the

identiﬁ er for Van Nuys, California, LDA is I-BUR.

Microwave Landing System (MLS)

The MLS provides precision navigation guidance for exact

alignment and descent of aircraft on approach to a runway.

It provides azimuth, elevation, and distance. Both lateral

and vertical guidance may be displayed on conventional

course deviation indicators or incorporated into multipurpose

ﬂ ight deck displays. Range information can be displayed

by conventional DME indicators and also incorporated into

multipurpose displays. [Figure 7-41]

The system may be divided into ﬁ ve functions, which are

approach azimuth, back azimuth, approach elevation, range;

and data communications. The standard conﬁ guration of

MLS ground equipment includes an azimuth station to

perform functions as indicated above. In addition to providing

azimuth navigation guidance, the station transmits basic data,

which consists of information associated directly with the

operation of the landing system, as well as advisory data on

the performance of the ground equipment.

Approach Azimuth Guidance

The azimuth station transmits MLS angle and data on one

of 200 channels within the frequency range of 5031 to 5091

7-46

Figure 7-41. MLS Coverage Volumes, 3-D Representation.

MHz. The equipment is normally located about 1,000 feet

beyond the stop end of the runway, but there is considerable

flexibility in selecting sites. For example, for heliport

operations the azimuth transmitter can be collocated with

the elevation transmitter. The azimuth coverage extends

laterally at least 40° on either side of the runway centerline

in a standard conﬁ guration, in elevation up to an angle of 15°

and to at least 20,000 feet, and in range to at least 20 NM.

MLS requires separate airborne equipment to receive and

process the signals from what is normally installed in general

aviation aircraft today. It has data communications capability,

and can provide audible information about the condition

of the transmitting system and other pertinent data such as

weather, runway status, etc. The MLS transmits an audible

identiﬁ er consisting of four letters beginning with the letter

M, in Morse code at a rate of at least six per minute. The

MLS system monitors itself and transmits ground-to-air data

messages about the system’s operational condition. During

periods of routine or emergency maintenance, the coded

identiﬁ cation is missing from the transmissions. At this time

there are only a few systems installed.

Required Navigation Performance

RNP is a navigation system that provides a speciﬁ ed level

of accuracy deﬁ ned by a lateral area of conﬁ ned airspace

in which an RNP-certiﬁ ed aircraft operates. The continuing

growth of aviation places increasing demands on airspace

capacity and emphasizes the need for the best use of the

available airspace. These factors, along with the accuracy of

modern aviation navigation systems and the requirement for

increased operational efﬁ ciency in terms of direct routings

and track-keeping accuracy, have resulted in the concept

of required navigation performance—a statement of the

navigation performance accuracy necessary for operation

within a deﬁ ned airspace. RNP can include both performance

and functional requirements, and is indicated by the RNP type.

These standards are intended for designers, manufacturers,

and installers of avionics equipment, as well as service

providers and users of these systems for global operations.

The minimum aviation system performance speciﬁ cation

(MASPS) provides guidance for the development of airspace

and operational procedures needed to obtain the beneﬁ ts of

improved navigation capability. [Figure 7-42]

The RNP type deﬁ nes the total system error (TSE) that

is allowed in lateral and longitudinal dimensions within

a particular airspace. The TSE, which takes account of

navigation system errors (NSE), computation errors, display

errors and ﬂ ight technical errors (FTE), must not exceed the

speciﬁ ed RNP value for 95 percent of the ﬂ ight time on any

part of any single ﬂ ight. RNP combines the accuracy standards

laid out in the ICAO Manual (Doc 9613) with specific

accuracy requirements, as well as functional and performance

standards, for the RNAV system to realize a system that

can meet future air trafﬁ c management requirements. The

functional criteria for RNP address the need for the ﬂ ight paths

of participating aircraft to be both predictable and repeatable

to the declared levels of accuracy. More information on RNP

is contained in subsequent chapters.

The term RNP is also applied as a descriptor for airspace,

routes, and procedures (including departures, arrivals,

and IAPs). The descriptor can apply to a unique approach

procedure or to a large region of airspace. RNP applies to

navigation performance within a designated airspace, and

includes the capability of both the available infrastructure

(navigation aids) and the aircraft.

RNP type is used to specify navigation requirements for the

airspace. The following are ICAO RNP Types: RNP-1.0,

RNP-4.0, RNP-5.0, and RNP-10.0. The required performance

is obtained through a combination of aircraft capability and

the level of service provided by the corresponding navigation

infrastructure. From a broad perspective:

Aircraft Capability + Level of Service = Access

In this context, aircraft capability refers to the airworthiness

certiﬁ cation and operational approval elements (including

avionics, maintenance, database, human factors, pilot

procedures, training, and other issues). The level of service

element refers to the NAS infrastructure, including published

routes, signal-in-space performance and availability, and air

7-47

Figure 7-42. Required Navigation Performance.

7-48

Figure 7-43. Typical Display and Control Unit(s) in General Aviation. The Universal UNS-1 (left) controls and integrates all other

systems. The Avidyne (center) and Garmin systems (right) illustrate and are typical of completely integrated systems. Although the

Universal CDU is not typically found on smaller general aviation aircraft, the difference in capabilities of the CDUs and stand-alone

sytems is diminishing each year.

trafﬁ c management. When considered collectively, these

elements result in providing access. Access provides the

desired beneﬁ t (airspace, procedures, routes of ﬂ ight, etc.).

RNP levels are actual distances from the centerline of the

ﬂ ight path, which must be maintained for aircraft and obstacle

separation. Although additional FAA-recognized RNP

levels may be used for speciﬁ c operations, the United States

currently supports three standard RNP levels:

• RNP 0.3 – Approach

• RNP 1.0 – Departure, Terminal

• RNP 2.0 – En route

RNP 0.3 represents a distance of 0.3 NM either side of a

speciﬁ ed ﬂ ight path centerline. The speciﬁ c performance

that is required on the final approach segment of an

instrument approach is an example of this RNP level. At

the present time, a 0.3 RNP level is the lowest level used in

normal RNAV operations. Speciﬁ c airlines, using special

procedures, are approved to use RNP levels lower than

RNP 0.3, but those levels are used only in accordance with

their approved operations speciﬁ cations (OpsSpecs). For

aircraft equipment to qualify for a speciﬁ c RNP type, it

must maintain navigational accuracy at least 95 percent of

the total ﬂ ight time.

Flight Management Systems (FMS)

A ﬂ ight management system (FMS) is not a navigation

system in itself. Rather, it is a system that automates the

tasks of managing the onboard navigation systems. FMS may

perform other onboard management tasks, but this discussion

is limited to its navigation function.

FMS is an interface between ﬂ ight crews and ﬂ ight-deck

systems. FMS can be thought of as a computer with a large

database of airport and NAVAID locations and associated

data, aircraft performance data, airways, intersections,

DPs, and STARs. FMS also has the ability to accept and

store numerous user-deﬁ ned WPs, ﬂ ight routes consisting

of departures, WPs, arrivals, approaches, alternates, etc.

FMS can quickly deﬁ ne a desired route from the aircraft’s

current position to any point in the world, perform ﬂ ight

plan computations, and display the total picture of the ﬂ ight

route to the crew.

FMS also has the capability of controlling (selecting) VOR,

DME, and LOC NAVAIDs, and then receiving navigational

data from them. INS, LORAN, and GPS navigational data

may also be accepted by the FMS computer. The FMS may

act as the input/output device for the onboard navigation

systems, so that it becomes the “go-between” for the crew

and the navigation systems.

Function of FMS

At startup, the crew programs the aircraft location, departure

runway, DP (if applicable), WPs deﬁ ning the route, approach

procedure, approach to be used, and routing to alternate. This

may be entered manually, be in the form of a stored ﬂ ight

plan, or be a ﬂ ight plan developed in another computer and

transferred by disk or electronically to the FMS computer.

The crew enters this basic information in the control/display

unit (CDU). [Figure 7-43]

Once airborne, the FMS computer channels the appropriate

NAVAIDs and takes radial/distance information, or

channels two NAVAIDs, taking the more accurate distance

information. FMS then indicates position, track, desired

heading, groundspeed and position relative to desired track.

Position information from the FMS updates the INS. In more

sophisticated aircraft, the FMS provides inputs to the HSI,

RMI, glass ﬂ ight deck navigation displays, head-up display

(HUD), autopilot, and autothrottle systems.

7-49

Figure 7-44. Example of a Head-Up Display (top) and a Head-Down

Display (bottom). The head-up display presents information in front

of the pilot along his/her normal ﬁ eld of view while a head-down

display may present information beyond the normal head-up ﬁ eld

of view.

Head-Up Display (HUD)

The HUD is a display system that provides a projection of

navigation and air data (airspeed in relation to approach

reference speed, altitude, left/right and up/down GS) on a

transparent screen between the pilot and the windshield. Other

information may be displayed, including a runway target in

relation to the nose of the aircraft. This allows the pilot to see

the information necessary to make the approach while also

being able to see out the windshield, which diminishes the

need to shift between looking at the panel to looking outside.

Virtually any information desired can be displayed on the

HUD if it is available in the aircraft’s ﬂ ight computer, and

if the display is user deﬁ nable. [Figure 7-44]

Radar Navigation (Ground Based)

Radar works by transmitting a pulse of RF energy in a speciﬁ c

direction. The return of the echo or bounce of that pulse from

a target is precisely timed. From this, the distance traveled

by the pulse and its echo is determined and displayed on a

radar screen in such a manner that the distance and bearing to

this target can be instantly determined. The radar transmitter

must be capable of delivering extremely high power levels

toward the airspace under surveillance, and the associated

radar receiver must be able to detect extremely small signal

levels of the returning echoes.

The radar display system provides the controller with a map-

like presentation upon which appear all the radar echoes

of aircraft within detection range of the radar facility. By

means of electronically generated range marks and azimuth-

indicating devices, the controller can locate each radar target

with respect to the radar facility, or can locate one radar target

with respect to another.

Another device, a video-mapping unit, generates an actual

airway or airport map and presents it on the radar display

equipment. Using the video-mapping feature, the air trafﬁ c

controller not only can view the aircraft targets, but can see

these targets in relation to runways, navigation aids, and

hazardous ground obstructions in the area. Therefore, radar

becomes a NAVAID, as well as the most signiﬁ cant means

of trafﬁ c separation.

In a display presenting perhaps a dozen or more targets, a

primary surveillance radar system cannot identify one speciﬁ c

radar target, and it may have difﬁ culty “seeing” a small target

at considerable distance—especially if there is a rain shower

or thunderstorm between the radar site and the aircraft. This

problem is solved with the Air Trafﬁ c Control Radar Beacon

System (ATCRBS), sometimes called secondary surveillance

radar (SSR), which utilizes a transponder in the aircraft. The

ground equipment is an interrogating unit, in which the beacon

antenna is mounted so it rotates with the surveillance antenna.

The interrogating unit transmits a coded pulse sequence that

actuates the aircraft transponder. The transponder answers the

coded sequence by transmitting a preselected coded sequence

back to the ground equipment, providing a strong return signal

and positive aircraft identiﬁ cation, as well as other special data

such as aircraft altitude.

Functions of Radar Navigation

The radar systems used by ATC are air route surveillance

radar (ARSR), airport surveillance radar (ASR), and precision

approach radar (PAR) and airport surface detection equipment

7-50

(ASDE). Surveillance radars scan through 360° of azimuth

and present target information on a radar display located in

a tower or center. This information is used independently or

in conjunction with other navigational aids in the control of

air trafﬁ c.

ARSR is a long-range radar system designed primarily to cover

large areas and provide a display of aircraft while en route

between terminal areas. The ARSR enables air route trafﬁ c

control center (ARTCC) controllers to provide radar service

when the aircraft are within the ARSR coverage. In some

instances, ARSR may enable ARTCC to provide terminal radar

services similar to but usually more limited than those provided

by a radar approach control.

ASR is designed to provide relatively short-range coverage in

the general vicinity of an airport and to serve as an expeditious

means of handling terminal area trafﬁ c through observation

of precise aircraft locations on a radarscope. Nonprecision

instrument approaches are available at airports that have an

approved surveillance radar approach procedure. ASR provides

radar vectors to the ﬁ nal approach course and then azimuth

information to the pilot during the approach. In addition to

range (distance) from the runway, the pilot is advised of MDA,

when to begin descent, and when the aircraft is at the MDA. If

requested, recommended altitudes will be furnished each mile

while on ﬁ nal.

PAR is designed to be used as a landing aid displaying range,

azimuth, and elevation information rather than as an aid for

sequencing and spacing aircraft. PAR equipment may be

used as a primary landing aid, or it may be used to monitor

other types of approaches. Two antennas are used in the PAR

array, one scanning a vertical plane, and the other scanning

horizontally. Since the range is limited to 10 miles, azimuth to

20°, and elevation to 7°, only the ﬁ nal approach area is covered.

The controller’s scope is divided into two parts. The upper half

presents altitude and distance information, and the lower half

presents azimuth and distance.

PAR is a system in which a controller provides highly accurate

navigational guidance in azimuth and elevation to a pilot. Pilots

are given headings to ﬂ y to direct them to and keep their aircraft

aligned with the extended centerline of the landing runway.

They are told to anticipate glide path interception approximately

10–30 seconds before it occurs and when to start descent.

The published decision height (DH) is given only if the pilot

requests it. If the aircraft is observed to deviate above or below

the glide path, the pilot is given the relative amount of deviation

by use of terms “slightly” or “well” and is expected to adjust

the aircraft’s rate of descent/ascent to return to the glide path.

Trend information is also issued with respect to the elevation

of the aircraft and may be modiﬁ ed by the terms “rapidly” and

“slowly” (e.g., “well above glide path, coming down rapidly”).

Range from touchdown is given at least once each mile. If an

aircraft is observed by the controller to proceed outside of

speciﬁ ed safety zone limits in azimuth and/or elevation and

continue to operate outside these prescribed limits, the pilot will

be directed to execute a missed approach or to ﬂ y a speciﬁ ed

course unless the pilot has the runway environment (runway,

approach lights, etc.) in sight. Navigational guidance in azimuth

and elevation is provided to the pilot until the aircraft reaches

the published decision altitude (DA)/DH. Advisory course and

glide path information is furnished by the controller until the

aircraft passes over the landing threshold, at which point the

pilot is advised of any deviation from the runway centerline.

Radar service is automatically terminated upon completion of

the approach.

Airport Surface Detection Equipment

Radar equipment is speciﬁ cally designed to detect all principal

features on the surface of an airport, including aircraft and

vehicular trafﬁ c, and to present the entire image on a radar

indicator console in the control tower. It is used to augment

visual observation by tower personnel of aircraft and/or

vehicular movements on runways and taxiways.

Radar Limitations

1. It is very important for the aviation community to

recognize the fact that there are limitations to radar

service and that ATC controllers may not always be able

to issue trafﬁ c advisories concerning aircraft which are

not under ATC control and cannot be seen on radar.

2. The characteristics of radio waves are such that they

normally travel in a continuous straight line unless

they are “bent” by abnormal atmospheric phenomena

such as temperature inversions; reﬂ ected or attenuated

by dense objects such as heavy clouds, precipitation,

ground obstacles, mountains, etc.; or screened by high

terrain features.

3. Primary radar energy that strikes dense objects will be

reﬂ ected and displayed on the operator’s scope, thereby

blocking out aircraft at the same range and greatly

weakening or completely eliminating the display of

targets at a greater range.

4. Relatively low altitude aircraft will not be seen if they

are screened by mountains or are below the radar beam

due to curvature of the Earth.

5. The amount of reﬂ ective surface of an aircraft will

determine the size of the radar return. Therefore, a small

light airplane or a sleek jet ﬁ ghter will be more difﬁ cult

to see on primary radar than a large commercial jet or

military bomber.

7-51

6. All ARTCC radar in the conterminous United States and

many ASR have the capability to interrogate Mode C

and display altitude information to the controller from

appropriately equipped aircraft. However, a number of

ASR do not have Mode C display capability; therefore,

altitude information must be obtained from the pilot.

7-52

8-1

Introduction

The National Airspace System (NAS) is the network of

United States airspace: air navigation facilities, equipment,

services, airports or landing areas, aeronautical charts,

information/services, rules, regulations, procedures, technical

information, manpower, and material. Included are system

components shared jointly with the military. The system’s

present conﬁ guration is a reﬂ ection of the technological

advances concerning the speed and altitude capability of jet

aircraft, as well as the complexity of microchip and satellite-

based navigation equipment. To conform to international

aviation standards, the United States adopted the primary

elements of the classification system developed by the

International Civil Aviation Organization (ICAO).

This chapter is a general discussion of airspace classiﬁ cation;

en route, terminal, and approach procedures; and operations

within the NAS. Detailed information on the classiﬁ cation

of airspace, operating procedures, and restrictions is found

in the Aeronautical Information Manual (AIM).

The National

Airspace System

Chapter 8

8-2

Airspace Classiﬁ cation

Airspace in the United States [Figure 8-1] is designated as

follows:

1. Class A. Generally, airspace from 18,000 feet mean

sea level (MSL) up to and including ﬂ ight level (FL)

600, including the airspace overlying the waters

within 12 nautical miles (NM) of the coast of the

48 contiguous states and Alaska. Unless otherwise

authorized, all pilots must operate their aircraft under

instrument ﬂ ight rules (IFR).

2. Class B. Generally, airspace from the surface to 10,000

feet MSL surrounding the nation’s busiest airports in

terms of airport operations or passenger enplanements.

The conﬁ guration of each Class B airspace area is

individually tailored, consists of a surface area and two

or more layers (some Class B airspace areas resemble

upside-down wedding cakes), and is designed to

contain all published instrument procedures once

an aircraft enters the airspace. An air trafﬁ c control

(ATC) clearance is required for all aircraft to operate

in the area, and all aircraft that are so cleared receive

separation services within the airspace.

3. Class C. Generally, airspace from the surface to

4,000 feet above the airport elevation (charted

in MSL) surrounding those airports that have an

operational control tower, are serviced by a radar

approach control, and have a certain number of IFR

operations or passenger enplanements. Although the

conﬁ guration of each Class C area is individually

tailored, the airspace usually consists of a surface

area with a 5 NM radius, an outer circle with a 10 NM

radius that extends from 1,200 feet to 4,000 feet above

the airport elevation and an outer area. Each aircraft

must establish two-way radio communications with

the ATC facility providing air trafﬁ c services prior

to entering the airspace and thereafter maintain those

communications while within the airspace.

4. Class D. Generally, that airspace from the surface

to 2,500 feet above the airport elevation (charted

in MSL) surrounding those airports that have an

operational control tower. The configuration of

each Class D airspace area is individually tailored

and when instrument procedures are published,

the airspace will normally be designed to contain

the procedures. Arrival extensions for instrument

approach procedures (IAPs) may be Class D or Class

E airspace. Unless otherwise authorized, each aircraft

must establish two-way radio communications with

the ATC facility providing air trafﬁ c services prior

to entering the airspace and thereafter maintain those

communications while in the airspace.

5. Class E. Generally, if the airspace is not Class A, B,

C, or D, and is controlled airspace, then it is Class E

airspace. Class E airspace extends upward from either

the surface or a designated altitude to the overlying

or adjacent controlled airspace. When designated as a

surface area, the airspace will be conﬁ gured to contain

all instrument procedures. Also in this class are federal

airways, airspace beginning at either 700 or 1,200 feet

above ground level (AGL) used to transition to and

from the terminal or en route environment, and en

route domestic and offshore airspace areas designated

below 18,000 feet MSL. Unless designated at a lower

altitude, Class E airspace begins at 14,500 MSL over

the United States, including that airspace overlying the

waters within 12 NM of the coast of the 48 contiguous

states and Alaska, up to but not including 18,000 feet

MSL, and the airspace above FL 600.

6. Class G. Airspace not designated as Class A, B, C, D,

or E. Class G airspace is essentially uncontrolled by

ATC except when associated with a temporary control

tower.

Special Use Airspace

Special use airspace is the designation for airspace in which

certain activities must be conﬁ ned, or where limitations

may be imposed on aircraft operations that are not part

of those activities. Certain special use airspace areas can

create limitations on the mixed use of airspace. The special

use airspace depicted on instrument charts includes the

area name or number, effective altitude, time and weather

conditions of operation, the controlling agency, and the chart

panel location. On National Aeronautical Charting Group

(NACG) en route charts, this information is available on one

of the end panels.

Prohibited areas contain airspace of deﬁ ned dimensions

within which the ﬂ ight of aircraft is prohibited. Such areas

are established for security or other reasons associated with

the national welfare. These areas are published in the Federal

charted as a “P” followed by a number (e.g., “P-123”).

Restricted areas are areas where operations are hazardous to

nonparticipating aircraft and contain airspace within which

the ﬂ ight of aircraft, while not wholly prohibited, is subject

to restrictions. Activities within these areas must be conﬁ ned

because of their nature, or limitations may be imposed upon

aircraft operations that are not a part of those activities, or

both. Restricted areas denote the existence of unusual, often

invisible, hazards to aircraft (e.g., artillery ﬁ ring, aerial

8-3

Figure 8-1. Airspace Classiﬁ cations.

8-4

gunnery, or guided missiles). IFR ﬂ ights may be authorized

to transit the airspace and are routed accordingly. Penetration

of restricted areas without authorization from the using

or controlling agency may be extremely hazardous to the

aircraft and its occupants. ATC facilities apply the following

procedures when aircraft are operating on an IFR clearance

(including those cleared by ATC to maintain visual ﬂ ight

rules (VFR)-On-Top) via a route that lies within joint-use

restricted airspace:

1. If the restricted area is not active and has been released

to the Federal Aviation Administration (FAA), the

ATC facility will allow the aircraft to operate in the

restricted airspace without issuing speciﬁ c clearance

for it to do so.

2. If the restricted area is active and has not been

released to the FAA, the ATC facility will issue a

clearance which will ensure the aircraft avoids the

restricted airspace.

Restricted areas are charted with an “R” followed by a

number (e.g., “R-5701”) and are depicted on the en route

chart appropriate for use at the altitude or FL being ﬂ own.

Warning areas are similar in nature to restricted areas;

however, the United States government does not have sole

jurisdiction over the airspace. A warning area is airspace of

deﬁ ned dimensions, extending from 12 NM outward from

the coast of the United States, containing activity that may

be hazardous to nonparticipating aircraft. The purpose of

such areas is to warn nonparticipating pilots of the potential

danger. A warning area may be located over domestic or

international waters or both. The airspace is designated with

a “W” followed by a number (e.g., “W-123”).

Military operations areas (MOAs) consist of airspace with

deﬁ ned vertical and lateral limits established for the purpose

of separating certain military training activities from IFR

trafﬁ c. Whenever an MOA is being used, nonparticipating

IFR trafﬁ c may be cleared through an MOA if IFR separation

can be provided by ATC. Otherwise, ATC will reroute or

restrict nonparticipating IFR trafﬁ c. MOAs are depicted on

sectional, VFR terminal area, and en route low altitude charts

and are not numbered (e.g., “Boardman MOA”).

Alert areas are depicted on aeronautical charts with an

“A” followed by a number (e.g., “A-123”) to inform

nonparticipating pilots of areas that may contain a high

volume of pilot training or an unusual type of aerial activity.

Pilots should exercise caution in alert areas. All activity

within an alert area shall be conducted in accordance with

regulations, without waiver, and pilots of participating

aircraft, as well as pilots transiting the area, shall be equally

responsible for collision avoidance.

Military Training Routes (MTRs) are routes used by military

aircraft to maintain proﬁ ciency in tactical ﬂ ying. These routes

are usually established below 10,000 feet MSL for operations

at speeds in excess of 250 knots. Some route segments may

be deﬁ ned at higher altitudes for purposes of route continuity.

Routes are identiﬁ ed as IFR (IR), and VFR (VR), followed by

a number. MTRs with no segment above 1,500 feet AGL are

identiﬁ ed by four number characters (e.g., IR1206, VR1207,

etc.). MTRs that include one or more segments above 1,500

feet AGL are identiﬁ ed by three number characters (e.g.,

IR206, VR207). IFR Low Altitude En Route Charts depict

all IR routes and all VR routes that accommodate operations

above 1,500 feet AGL. IR routes are conducted in accordance

with IFR regardless of weather conditions.

Temporary ﬂ ight restrictions (TFRs) are put into effect

when trafﬁ c in the airspace would endanger or hamper air

or ground activities in the designated area. For example, a

forest ﬁ re, chemical accident, ﬂ ood, or disaster-relief effort

could warrant a TFR, which would be issued as a Notice to

Airmen (NOTAM).

National Security Areas (NSAs) consist of airspace with

defined vertical and lateral dimensions established at

locations where there is a requirement for increased security

and safety of ground facilities. Flight in NSAs may be

temporarily prohibited by regulation under the provisions of

Title 14 of the Code of Federal Regulations (14 CFR) part 99

and prohibitions will be disseminated via NOTAM.

Federal Airways

The primary means for routing aircraft operating under IFR

is the federal airways system.

Each federal airway is based on a centerline that extends from

one NAVAID/waypoint/ﬁ x/intersection to another NAVAID/

waypoint/ﬁ x/intersection speciﬁ ed for that airway. A federal

airway includes the airspace within parallel boundary lines

four NM to each side of the centerline. As in all instrument

ﬂ ight, courses are magnetic, and distances are in NM. The

airspace of a federal airway has a ﬂ oor of 1,200 feet AGL,

unless otherwise speciﬁ ed. A federal airway does not include

the airspace of a prohibited area.

Victor airways include the airspace extending from 1,200 feet

AGL up to, but not including 18,000 feet MSL. The airways

are designated on Sectional and IFR low altitude en route

charts with the letter “V” followed by a number (e.g., “V23”).

Typically, Victor airways are given odd numbers when oriented

north/south and even numbers when oriented east/west. If more

than one airway coincides on a route segment, the numbers are

listed serially (e.g., “V287-495-500”). [Figure 8-2]

8-5

Figure 8-2. Victor Airways and Charted IFR Altitudes.

Jet routes exist only in Class A airspace, from 18,000 feet

MSL to FL 450, and are depicted on high-altitude en route

charts. The letter “J” precedes a number to label the airway

(e.g., J12).

RNAV routes have been established in both the low-altitude

and the high-altitude structures in recent years and are

depicted on the en route low and high chart series. High

altitude RNAV routes are identiﬁ ed with a “Q” preﬁ x (except

the Q-routes in the Gulf of Mexico) and low altitude RNAV

routes are identiﬁ ed with a “T” preﬁ x. RNAV routes and data

are depicted in aeronautical blue.

In addition to the published routes, a random RNAV route may

be ﬂ own under IFR if it is approved by ATC. Random RNAV

routes are direct routes, based on area navigation capability,

between waypoints deﬁ ned in terms of latitude/longitude

coordinates, degree-distance ﬁ xes, or offsets from established

routes/airways at a speciﬁ ed distance and direction.

Radar monitoring by ATC is required on all random

RNAV routes. These routes can only be approved in a radar

environment. Factors that will be considered by ATC in

approving random RNAV routes include the capability to

provide radar monitoring, and compatibility with trafﬁ c

volume and flow. ATC will radar monitor each flight;

however, navigation on the random RNAV route is the

responsibility of the pilot.

Other Routing

Preferred IFR routes have been established between

major terminals to guide pilots in planning their routes of

ﬂ ight, minimizing route changes and aiding in the orderly

management of air trafﬁ c on federal airways. Low and high

8-6

altitude preferred routes are listed in the Airport/Facility

Directory (A/FD). To use a preferred route, reference the

departure and arrival airports; if a routing exists for your

ﬂ ight, then airway instructions will be listed.

Tower En Route Control (TEC) is an ATC program that

uses overlapping approach control radar services to provide

IFR clearances. By using TEC, a pilot is routed by airport

control towers. Some advantages include abbreviated ﬁ ling

procedures and reduced trafﬁ c separation requirements. TEC

is dependent upon the ATC’s workload, and the procedure

varies among locales.

The latest version of Advisory Circular (AC) 90-91, North

American Route Program (NRP), provides guidance to users

of the NAS for participation in the NRP. All ﬂ ights operating

at or above FL 290 within the conterminous United States

and Canada are eligible to participate in the NRP, the primary

purpose of which is to allow operators to plan minimum time/

cost routes that may be off the prescribed route structure. NRP

aircraft are not subject to route-limiting restrictions (e.g.,

published preferred IFR routes) beyond a 200 NM radius of

their point of departure or destination.

IFR En Route Charts

The objective of IFR en route ﬂ ight is to navigate within the

lateral limits of a designated airway at an altitude consistent

with the ATC clearance. Your ability to ﬂ y instruments

safely and competently in the system is greatly enhanced by

understanding the vast array of data available to the pilot on

instrument charts. The NACG maintains and produces the

charts for the United States government.

En route high-altitude charts provide aeronautical information

for en route instrument navigation (IFR) at or above 18,000

feet MSL. Information includes the portrayal of Jet and

RNAV routes, identiﬁ cation and frequencies of radio aids,

selected airports, distances, time zones, special use airspace,

and related information. Established Jet routes from 18,000

feet MSL to FL 450 use NAVAIDs not more than 260 NM

apart. The charts are revised every 56 days.

To effectively depart from one airport and navigate en route

under instrument conditions a pilot needs the appropriate IFR

en route low-altitude chart(s). The IFR low altitude en route

chart is the instrument equivalent of the Sectional chart. When

folded, the cover of the NACG en route chart displays an

index map of the United States showing the coverage areas.

Cities near congested airspace are shown in black type and

their associated area chart is listed in the box in the lower

left-hand corner of the map coverage box. Also noted is an

explanation of the off-route obstruction clearance altitude

(OROCA). The effective date of the chart is printed on the

other side of the folded chart. Information concerning MTRs

is also included on the chart cover. The en route charts are

revised every 56 days.

When the NACG en route chart is unfolded, the legend is

displayed and provides information concerning airports,

NAVAIDs, communications, air traffic services, and

airspace.

Airport Information

Airport information is provided in the legend, and the symbols

used for the airport name, elevation, and runway length are

similar to the sectional chart presentation. Associated city

names are shown for public airports only. FAA identiﬁ ers are

shown for all airports. ICAO identiﬁ ers are also shown for

airports outside of the contiguous United States. Instrument

approaches can be found at airports with blue or green

symbols, while the brown airport symbol denotes airports

that do not have instrument approaches. Stars are used to

indicate the part-time nature of tower operations, ATIS

frequencies, part-time or on request lighting facilities, and

part-time airspace classiﬁ cations. A box after an airport name

with a “C” or “D” inside indicates Class C and D airspace,

respectively, per Figure 8-3.

Charted IFR Altitudes

The minimum en route altitude (MEA) ensures a navigation

signal strong enough for adequate reception by the aircraft

navigation (NAV) receiver and obstacle clearance along the

airway. Communication is not necessarily guaranteed with

MEA compliance. The obstacle clearance, within the limits of

the airway, is typically 1,000 feet in non-mountainous areas

and 2,000 feet in designated mountainous areas. MEAs can

be authorized with breaks in the signal coverage; if this is the

case, the NACG en route chart notes “MEA GAP” parallel

to the affected airway. MEAs are usually bidirectional;

however, they can be single-directional. Arrows are used to

indicate the direction to which the MEA applies.

The minimum obstruction clearance altitude (MOCA), as

the name suggests, provides the same obstruction clearance

as an MEA; however, the NAV signal reception is ensured

only within 22 NM of the closest NAVAID deﬁ ning the route.

The MOCA is listed below the MEA and indicated on NACG

charts by a leading asterisk (e.g., “*3400”—see Figure 8-2,

V287 at bottom left).

The minimum reception altitude (MRA) identiﬁ es the lowest

altitude at which an intersection can be determined from an

off-course NAVAID. If the reception is line-of-sight based,

signal coverage will only extend to the MRA or above.

However, if the aircraft is equipped with distance measuring

equipment (DME) and the chart indicates the intersection can

8-7

Figure 8-3. En Route Airport Legend.

be identiﬁ ed with such equipment, the pilot could deﬁ ne the

ﬁ x without attaining the MRA. On NACG charts, the MRA

is indicated by the symbol and the altitude preceded by

“MRA” (e.g., “MRA 9300”). [Figure 8-2]

The minimum crossing altitude (MCA) will be charted when

a higher MEA route segment is approached. The MCA is

usually indicated when a pilot is approaching steeply rising

terrain, and obstacle clearance and/or signal reception is

compromised. In this case, the pilot is required to initiate

a climb so the MCA is reached by the time the intersection

is crossed. On NACG charts, the MCA is indicated by the

symbol , and the Victor airway number, altitude, and

the direction to which it applies (e.g. “V24 8000 SE”).

The maximum authorized altitude (MAA) is the highest

altitude at which the airway can be ﬂ own with assurance

of receiving adequate navigation signals. Chart depictions

appear as “MAA-15000.”

When an MEA, MOCA, and/or MAA change on a segment

other than at a NAVAID, a sideways “T” is depicted

on the chart. If there is an airway break without the symbol,

one can assume the altitudes have not changed (see the upper

left area of Figure 8-2). When a change of MEA to a higher

MEA is required, the climb may commence at the break,

ensuring obstacle clearance. [Figure 8-4]

Navigation Features

Types of NAVAIDs

Very high frequency omnidirectional ranges (VORs) are the

principal NAVAIDs that support the Victor and Jet airways.

Many other navigation tools are also available to the pilot.

For example, nondirectional beacons (NDBs) can broadcast

signals accurate enough to provide stand-alone approaches,

and DME allows the pilot to pinpoint a reporting point on the

airway. Though primarily navigation tools, these NAVAIDs

can also transmit voice broadcasts.

Tactical air navigation (TACAN) channels are represented

as the two- or three-digit numbers following the three-letter

identifier in the NAVAID boxes. The NACG terminal

procedures provide a frequency-pairing table for the

TACAN-only sites. On NACG charts, very-high frequencies

and ultra-high frequencies (VHF/UHF) NAVAIDs (e.g.,

VORs) are depicted in black, while low frequencies and

medium frequencies (LF/MF) are depicted as brown.

[Figure 8-5]

Identifying Intersections

Intersections along the airway route are established by a

variety of NAVAIDs. An open triangle indicates the

location of an ATC reporting point at an intersection. If the

triangle is solid, a report is compulsory. [Figure 8-4]

8-8

Figure 8-4. Legend From En Route Low Attitude Chart, Air Trafﬁ c Services and Airspace Information Section.

8-9

Figure 8-5. Legend From En Route Low Attitude Chart.

8-10

necessary to enable trafﬁ c ﬂ ow. When a holding pattern is

charted, the controller may provide the holding direction and

the statement “as published.” [Figure 8-4]

Boundaries separating the jurisdiction of Air Route Trafﬁ c

Control Centers (ARTCC) are depicted on charts with blue

serrations. The name

of the controlling facility is printed on the

corresponding side of the division line.

ARTCC remote sites are depicted as blue serrated boxes

and contain the center name, sector name, and the sector

frequency. [Figure 8-4]

Weather Information and Communication Features

En route NAVAIDs also provide weather information and

serve communication functions.

When a NAVAID is shown as a

shadowed box, an automated ﬂ ight

service station (AFSS) of the same

name is directly associated with the facility. If an AFSS is

located without an associated NAVAID, the shadowed box is

smaller and contains only the name and identiﬁ er. The AFSS

frequencies are provided above the

box. (Frequencies 122.2 and 255.4,

and emergency frequencies 121.5 and

243.0 are not listed.)

A Remote Communications Outlet (RCO) associated with

a NAVAID is designated by a thin-

lined box with the controlling AFSS

frequency above the box, and the

name under the box. Without an

associated facility, the thin-lined

RCO box contains the AFSS name

and remote frequency.

Automated Surface Observing Station (ASOS), Automated

Weather Observing Station (AWOS), Hazardous Inﬂ ight

Weather Advisory Service

(HIWAS) and Transcribed

Weather Broadcast (TWEB) are

continuously transmitted over

selected NAVAIDs and depicted in the NAVAID box. ASOS/

AWOS are depicted by a white “A”, HIWAS by a “H” and

TWEB broadcasts by a “T” in a solid black circle in the upper

right or left corner.

New Technologies

Technological advances have made multifunction displays

and moving maps more common in newer aircraft. Even older

aircraft are being retroﬁ tted to include “glass” in the ﬂ ight

deck. [Figure 8-6] Moving maps improve pilot situational

awareness by providing a picture of aircraft location in

NDBs, localizers, and off-route VORs are used to establish

intersections. NDBs are sometimes collocated with

intersections, in which case passage of the NDB would mark

the intersection. A bearing to an off-route NDB also can

provide intersection identiﬁ cation. A localizer course used to

identify an intersection is depicted by a feathered arrowhead

symbol on the en route chart.

If feathered markings appear on the left-hand side of the

arrowhead, a back course (BC)

signal is transmitted. On NACG en route charts, the localizer

symbol is only depicted to identify an intersection.

Off-route VORs remain the most common means of

identifying intersections when traveling on an airway. Arrows

depicted next to the intersection indicate the NAVAID to

be used for identiﬁ cation. Another means of identifying an

intersection is with the use of DME. A hollow arrowhead

indicates DME is authorized for intersection identiﬁ cation. If

the DME mileage at the intersection is a cumulative distance

of route segments, the mileage is totaled and indicated by

a D-shaped symbol with a mileage number inside.

[Figure 8-4] Approved IFR GPS units can also be used to

report intersections.

Other Route Information

DME and GPS provide valuable route information concerning

such factors as mileage, position, and groundspeed. Even

without this equipment, information is provided on the

charts for making the necessary calculations using time and

distance. The en route chart depicts point-to-point distances

on the airway system. Distances from VOR to VOR are

charted with a number inside of a box. To differentiate

distances when two airways coincide, the word “TO” with the

three-letter VOR identiﬁ er appear to the left of the distance

boxes.

VOR changeover points (COPs) are depicted on the charts by

this symbol: The numbers indicate the distance at which

to change the VOR frequency. The frequency change might

be required due to signal reception or conﬂ icting frequencies.

If a COP does not appear on an airway, the frequency should

be changed midway between the facilities. A COP at an

intersection may indicate a course change.

Occasionally an “x” will appear at a separated segment of

an airway that is not an intersection. The “x” is a mileage

breakdown or computer navigation ﬁ x and may indicate a

course change.

Today’s computerized system of ATC has greatly reduced

the need for holding en route. However,

published holding patterns are still found on

charts at junctures where ATC has deemed it

Holding Pattern

NAME

Name

000.0 000.0

8-11

Figure 8-6. Moving Map Display.

Figure 8-7. Example of an Electronic Flight Bag.

relation to NAVAIDS, waypoints, airspace, terrain, and

hazardous weather. GPS systems can be certiﬁ ed for terminal

area and en route use as well as approach guidance.

Additional breakthroughs in display technology are the new

electronic chart systems or electronic ﬂ ight bags that facilitate

the use of electronic documents in the general aviation

ﬂ ight deck. [Figure 8-7] An electronic chart or ﬂ ight bag

is a self-powered electronic library that stores and displays

en route charts and other essential documents on a screen.

These electronic devices can store the digitized United States

terminal procedures, en route charts, the complete airport

facility directory, in addition to Title 14 of the Code of Federal

Regulations (14 CFR) and the AIM. Full touch-screen based

computers allow pilots to view airport approach and area

charts electronically while ﬂ ying. It replaces paper charts as

well as other paper materials including minimum equipment

lists (MELs), standard operating procedures (SOPs), standard

instrument departures (SIDs), standard terminal arrival

routes (STARs), checklists, and ﬂ ight deck manuals. As with

paper ﬂ ight publications, the electronic database needs to be

current to provide accurate information regarding NAVAIDS,

waypoints, and terminal procedures. Databases are updated

every 28 days and are available from various commercial

vendors. Pilots should be familiar with equipment operation,

capabilities, and limitations prior to use.

8-12

Terminal Procedures Publications

While the en route charts provide the information necessary

to safely transit broad regions of airspace, the United States

Terminal Procedures Publication (TPP) enables pilots to

guide their aircraft in the airport area. Whether departing or

arriving, these procedures exist to make the controllers’ and

pilots’ jobs safer and more efﬁ cient. Available in booklets

by region (published by NACG), the TPP includes approach

procedures, STARs, Departure Procedures (DPs), and airport

diagrams.

Departure Procedures (DPs)

There are two types of DPs, Obstacle Departure Procedures

(ODP) and SIDs. [Figure 8-8] Both types of DPs provide

obstacle clearance protection to aircraft in instrument

meteorological conditions (IMC), while reducing

communications and departure delays. DPs are published in

text and/or charted graphic form. Regardless of the format, all

DPs provide a way to depart the airport and transition to the

en route structure safely. When possible, pilots are strongly

encouraged to ﬁ le and ﬂ y a DP at night, during marginal

visual meteorological conditions (VMC) and IMC.

All DPs provide obstacle clearance provided the aircraft

crosses the end of the runway at least 35 feet AGL; climbs

to 400 feet above airport elevation before turning; and climbs

at least 200 feet per nautical mile (FPNM), unless a higher

climb gradient is speciﬁ ed to the assigned altitude. ATC may

vector an aircraft off a previously assigned DP; however, the

200 FPNM or the FPNM speciﬁ ed in the DP is required.

Textual ODPs are listed by city and airport in the IFR

Take-Off Minimums and DPs Section of the TPP. SIDs are

depicted in the TPP following the approach procedures for

the airport.

Standard Terminal Arrival Routes (STARs)

STARs depict prescribed routes to transition the instrument

pilot from the en route structure to a ﬁ x in the terminal area

from which an instrument approach can be conducted. If a

pilot does not have the appropriate STAR, write “No STAR”

in the ﬂ ight plan. However, if the controller is busy, the pilot

might be cleared along the same route and, if necessary,

the controller will have the pilot copy the entire text of the

procedure.

STARs are listed alphabetically at the beginning of the

NACG booklet. Figure 8-9 shows an example of a STAR, and

the legend for STARs and DPs printed in NACG booklets.

Instrument Approach Procedure (IAP)

Charts

The IAP chart provides the method to descend and land safely

in low visibility conditions. The FAA establishes an IAP

after thorough analyses of obstructions, terrain features, and

navigational facilities. Maneuvers, including altitude changes,

course corrections, and other limitations, are prescribed in the

IAP. The approach charts reﬂ ect the criteria associated with

the United States Standard for Terminal Instrument Approach

Procedures (TERPs), which prescribes standardized methods

for use in designing instrument ﬂ ight procedures.

In addition to the NACG, other governmental and corporate

entities produce approach procedures. The United States

military IAPs are established and published by the

Department of Defense and are available to the public

upon request. Special IAPs are approved by the FAA for

individual operators and are not available to the general

public. Foreign country standard IAPs are established and

published according to the individual country’s publication

procedures. The information presented in the following

sections will highlight features of the United States Terminal

Procedures Publications.

The instrument approach chart is divided into six main

sections, which include the margin identification, pilot

briefing (and notes), plan view, profile view, landing

minimums, and airport diagram. [Figure 8-10] An

examination of each section follows.

Margin Identiﬁ cation

The margin identiﬁ cation, at the top and bottom of the chart,

depicts the airport location and procedure identiﬁ cation.

The civil approach plates are organized by city, then airport

name and state. For example, Orlando Executive in Orlando,

Florida is alphabetically listed under “O” for Orlando.

Military approaches are organized by airport name ﬁ rst.

The chart’s amendment status appears below the city and state

in the bottom margin. The amendment number is followed

by the ﬁ ve-digit julian-date of the last chart change.“05300”

is read, “the 300th day of 2005”. At the center of the top

margin is the FAA chart reference number and the approving

authority. At the bottom center, the airport’s latitude and

longitude coordinates are provided.

8-13

Figure 8-8. Obstacle Departure Procedures (ODP) and Standard Instrument Departures (SID).

8-14

Figure 8-9. DP Chart Legend and STAR.

8-15

Figure 8-10. Instrument Approach Chart.

8-16

The procedure chart title (top and bottom margin area of

Figure 8-10) is derived from the type of navigational facility

providing ﬁ nal approach course guidance. A runway number

is listed when the approach course is aligned within 30º of the

runway centerline. This type of approach allows a straight-

in landing under the right conditions. The type of approach

followed by a letter identiﬁ es approaches that do not have

straight-in landing minimums. Examples include procedure

titles at the same airport, which have only circling minimums.

The ﬁ rst approach of this type created at the airport will be

labeled with the letter A, and the lettering will continue in

alphabetical order (e.g., “VOR-A or “LDA-B”). The letter

designation signiﬁ es the expectation is for the procedure to

culminate in a circling approach to land. As a general rule,

circling-only approaches are designed for one of the two

following reasons:

• The ﬁ nal approach course alignment with the runway

centerline exceeds 30º.

• The descent gradient is greater than 400 feet per

NM from the FAF to the threshold crossing height

(TCH). When this maximum gradient is exceeded, the

circling-only approach procedure may be designed to

meet the gradient criteria limits.

Further information on this topic can be found in the

Instrument Procedures Handbook, Chapter 5, under Approach

Naming Conventions.

To distinguish between the left, right, and center runways, an

“L,” “R,” or “C” follows the runway number (e.g., “ILS RWY

16R”). In some cases, an airport might have more than one

circling approach, shown as VOR-A, VOR/DME-B, etc.

More than one navigational system separated by a slash

indicates more than one type of equipment is required to

execute the ﬁ nal approach (e.g., VOR/DME RWY 31). More

than one navigational system separated by “or” indicates either

type of equipment may be used to execute the ﬁ nal approach

(e.g., VOR or GPS RWY 15). Multiple approaches of the same

type, to the same runway and using the same guidance, have

an additional letter from the end of the alphabet, number, or

term in the title (e.g., ILS Z RWY 28, SILVER ILS RWY

28, or ILS 2 RWY 28). VOR/DME RNAV approaches are

identiﬁ ed as VOR/DME RNAV RWY (runway number).

Helicopters have special IAPs, designated with COPTER in

the procedure identiﬁ cation (e.g., COPTER LOC/DME 25L).

Other types of navigation systems may be required to execute

other portions of the approach prior to intercepting the ﬁ nal

approach segment or during the missed approach.

The Pilot Brieﬁ ng

The pilot brieﬁ ng is located at the top of the chart and

provides the pilot with information required to complete the

published approach procedure. Included in the pilot brieﬁ ng

are the NAVAID providing approach guidance, its frequency,

the ﬁ nal approach course, and runway information. A notes

section contains additional procedural information. For

example, a procedural note might indicate restrictions for

circling maneuvers. Some other notes might concern a local

altimeter setting and the resulting change in the minimums.

The use of RADAR may also be noted in this section.

Additional notes may be found in the plan view.

When a triangle containing a “T” ( ) appears in the notes

section, it signiﬁ es the airport has nonstandard IFR takeoff

minimums. Pilots should refer to the DPs section of the TPP

to determine takeoff minimums.

When a triangle containing an “A” ( ) appears in the notes

section, it signiﬁ es the airport has nonstandard IFR alternate

minimums. Civil pilots should refer to the Alternate Minimums

Section of the TPP to determine alternate minimums. Military

pilots should refer to appropriate regulations.

When a triangle containing an “A” NA ( ) appears in

the notes area, it signiﬁ es that Alternate Minimums are Not

Authorized due to unmonitored facility or the absence of

weather reporting service.

Communication frequencies are listed in the order in which

they would be used during the approach. Frequencies for

weather and related facilities are included, where applicable,

such as automatic terminal information service (ATIS),

automated surface observing system (ASOS), automated

weather observation system (AWOS), and AFSSs.

The Plan View

The plan view provides a graphical overhead view of the

procedure, and depicts the routes that guide the pilot from

the en route segments to the initial approach ﬁ x (IAF).

[Figure 8-10] During the initial approach, the aircraft has

departed the en route phase of ﬂ ight and is maneuvering

to enter an intermediate or ﬁ nal segment of the instrument

approach. An initial approach can be made along prescribed

routes within the terminal area, which may be along an arc,

radial, course, heading, radar vector, or a combination thereof.

Procedure turns and high altitude teardrop penetrations

are initial approach segments. Features of the plan view,

including the procedure turn, obstacle elevation, minimum

safe altitude (MSA), and procedure track, are depicted in

Figure 8-11. Terrain will be depicted in the plan view portion

of all IAPs if the terrain within the plan view exceeds 4,000

feet above the airport elevation, or if within a 6 nautical mile

radius of the airport reference point the terrain rises at least

2,000 feet above the airport elevation.

8-17

Figure 8-11. IAP Plan View and Symbol Legends.

8-18

Some NACG charts contain a reference or distance circle

with a speciﬁ ed radius (10 NM is most common). Normally,

approach features within the plan view are shown to scale;

however, only the data within the reference circle is always

drawn to scale.

Concentric dashed circles, or concentric rings around the

distance circle, are used when the information necessary to

the procedure will not ﬁ t to scale within the limits of the plan

view area. They serve as a means to systematically arrange

this information in its relative position outside and beyond

the reference circle. These concentric rings are labeled en

route facilities and feeder facilities.

The primary airport depicted in the plan view is drawn with

enough detail to show the runway orientation and ﬁ nal

approach course alignment. Airports other than the primary

approach airport are not normally depicted in the NACG

plan view.

Known spot elevations are indicated on the plan view with a

dot in MSL altitude. The largest dot and number combination

indicates the highest elevation. An inverted “V” with a dot

in the center depicts an obstacle. The highest obstacle is

indicated with a bolder, larger version of the same symbol.

[Figure 8-11]

The MSA circle appears in the plan view, except in approaches

for which the Terminal Arrival Area (TAA) format is used or

appropriate NAVAIDs (e.g., VOR or NDB)

are unavailable. The MSA is provided for

emergency purposes only and guarantees

1,000 feet obstruction clearance in the sector

indicated with reference to the bearings in the

circle. For conventional navigation systems,

the MSA is normally based on the primary omnidirectional

facility (NAVAID) on which the IAP is predicated. The MSA

depiction on the approach chart contains the facility identiﬁ er

of the NAVAID used to determine the MSA altitudes. For

RNAV approaches, the MSA is based on the runway waypoint

for straight-in approaches, or the airport waypoint for circling

approaches. For GPS approaches, the MSA center header will

be the missed approach waypoint. The MSL altitudes appear

in boxes within the circle, which is typically a 25 NM radius

unless otherwise indicated. The MSA circle header refers to

the letter identiﬁ er of the NAVAID or waypoint that describes

the center of the circle.

NAVAIDs necessary for the completion of the instrument

procedure include the facility name, letter identiﬁ er, and

Morse code sequence. They may also furnish the frequency,

Morse code, and channel. A heavy-lined NAVAID box depicts

the primary NAVAID used for the approach. An “I” in front

of the NAVAID identiﬁ er (in Figure 8-11, “I-AVL”) listed in

the NAVAID box indicates a localizer. The requirement for

an ADF, DME, or RADAR in the approach is noted in the

plan view.

Intersections, ﬁ xes, radials, and course lines describe route

and approach sequencing information. The main procedure

or ﬁ nal approach course is a thick, solid line. A

DME arc, which is part of the main procedure course, is

also represented as a thick, solid line. A feeder

route is depicted with a medium line and provides

heading, altitude, and distance information. (All three

components must be designated on the chart to provide a

navigable course.) Radials, such as lead radials, are shown

by thin lines. The missed approach track is drawn

using a thin, hash marked line with a directional arrow.

A visual ﬂ ight path segment

appears as a thick dashed line with a directional arrow.

IAFs are charted IAF when associated with

a NAVAID or when freestanding.

The missed approach holding pattern track is represented with

a thin-dashed line. When collocated, the missed approach

holding pattern and procedure turn holding pattern are

indicated as a solid, black line. Arrival holding patterns are

depicted as thin, solid lines.

Terminal Arrival Area (TAA)

The design objective of the TAA procedure is to provide

a transition method for arriving aircraft with GPS/RNAV

equipment. TAAs will also eliminate or reduce the need

for feeder routes, departure extensions, and procedure

turns or course reversal. The TAA is controlled airspace

established in conjunction with the standard or modiﬁ ed

RNAV approach conﬁ gurations.

The standard TAA has three areas: straight-in, left base, and

right base. The arc boundaries of the three areas of the TAA

are published portions of the approach and allow aircraft to

transition from the en route structure direct to the nearest

IAF. When crossing the boundary of each of these areas or

when released by ATC within the area, the pilot is expected

to proceed direct to the appropriate waypoint IAF for the

approach area being ﬂ own. A pilot has the option in all areas

of proceeding directly to the holding pattern.

The TAA has a “T” structure that normally provides a NoPT

for aircraft using the approach. [Figure 8-12] The TAA

provides the pilot and air trafﬁ c controller with an efﬁ cient

method for routing trafﬁ c from the en route to the terminal

structure. The basic “T” contained in the TAA normally

aligns the procedure on runway centerline, with the missed

8-19

Figure 8-12. Basic “T” Design of Terminal Arrival Area (TAA) and Legend.

8-20

Figure 8-13. 45° Procedure Turn. Figure 8-14. Holding in Lieu of Procedure Turn.

approach point (MAP) located at the threshold, the FAF 5

NM from the threshold, and the intermediate ﬁ x (IF) 5 NM

from the FAF.

In order to accommodate descent from a high en route altitude

to the initial segment altitude, a hold in lieu of a procedure

turn provides the aircraft with an extended distance for the

necessary descent gradient. The holding pattern constructed

for this purpose is always established on the center IAF

waypoint. Other modiﬁ cations may be required for parallel

runways, or special operational requirements. When

published, the RNAV chart will depict the TAA through

the use of icons representing each TAA associated with the

RNAV procedure. These icons are depicted in the plan view

of the approach, generally arranged on the chart in accordance

with their position relative to the aircraft’s arrival from the

en route structure.

Course Reversal Elements in Plan View and

Proﬁ le View

Course reversals included in an IAP are depicted in one of

three different ways: a 45°/180° procedure turn, a holding

pattern in lieu of procedure turn, or a teardrop procedure.

The maneuvers are required when it is necessary to reverse

direction to establish the aircraft inbound on an intermediate

or final approach course. Components of the required

procedure are depicted in the plan view and the proﬁ le view.

The maneuver must be completed within the distance and

at the minimum altitude speciﬁ ed in the proﬁ le view. Pilots

should coordinate with the appropriate ATC facility relating

to course reversal during the IAP.

Procedure Turns

A procedure turn barbed arrow indicates

the direction or side of the outbound course on which

the procedure turn is made. [Figure 8-13] Headings are

provided for course reversal using the 45° procedure turn.

However, the point at which the turn may be commenced,

and the type and rate of turn is left to the discretion of the

pilot. Some of the options are the 45° procedure turn, the

racetrack pattern, the teardrop procedure turn, or the 80°/260°

course reversal. The absence of the procedure turn barbed

arrow in the plan view indicates that a procedure turn is

not authorized for that procedure. A maximum procedure

turn speed of not greater than 200 knots indicated airspeed

(KIAS) should be observed when turning outbound over the

IAF and throughout the procedure turn maneuver to ensure

staying within the obstruction clearance area. The normal

procedure turn distance is 10 NM. This may be reduced to

a minimum of 5 NM where only Category A or helicopter

aircraft are operated, or increased to as much as 15 NM to

accommodate high performance aircraft. Descent below the

procedure turn altitude begins after the aircraft is established

on the inbound course.

The procedure turn is not required when the symbol “NoPT”

appears, when radar vectoring to the final approach is

provided, when conducting a timed approach, or when the

procedure turn is not authorized. Pilots should contact the

appropriate ATC facility when in doubt if a procedure turn

is required.

Holding in Lieu of Procedure Turn

A holding pattern in lieu of a procedure turn may be speciﬁ ed

for course reversal in some procedures. [Figure 8-14] In such

cases, the holding pattern is established over an intermediate

ﬁ x or a ﬁ nal approach ﬁ x (FAF). The holding pattern distance

8-21

Figure 8-15. Teardrop Procedure.

or time speciﬁ ed in the proﬁ le view must be observed.

Maximum holding airspeed limitations as set forth for all

holding patterns apply. The holding pattern maneuver is

completed when the aircraft is established on the inbound

course after executing the appropriate entry. If cleared for

the approach prior to returning to the holding ﬁ x and the

aircraft is at the prescribed altitude, additional circuits of the

holding pattern are neither necessary nor expected by ATC.

If pilots elect to make additional circuits to lose excessive

altitude or to become better established on course, it is their

responsibility to advise ATC upon receipt of their approach

clearance. When holding in lieu of a procedure turn, the

holding pattern must be followed, except when RADAR

VECTORING to the ﬁ nal approach course is provided or

when NoPT is shown on the approach course.

Teardrop Procedure

When a teardrop procedure turn is depicted and a course

reversal is required, unless otherwise authorized by ATC,

this type of procedure must be executed. [Figure 8-15] The

teardrop procedure consists of departure from an IAF on the

published outbound course followed by a turn toward and

intercepting the inbound course at or prior to the intermediate

ﬁ x or point. Its purpose is to permit an aircraft to reverse

direction and lose considerable altitude within reasonably

limited airspace. Where no ﬁ x is available to mark the

beginning of the intermediate segment, it shall be assumed

to commence at a point 10 NM prior to the FAF. When the

facility is located on the airport, an aircraft is considered to

be on ﬁ nal approach upon completion of the penetration turn.

However, the ﬁ nal approach segment begins on the ﬁ nal

approach course 10 NM from the facility.

The Proﬁ le View

The proﬁ le view is a depiction of the procedure from the side

and illustrates the vertical approach path altitudes, headings,

distances, and ﬁ xes. [Figures 8-10, 8-11, and 8-12] The

view includes the minimum altitude and the maximum

distance for the procedure turn, altitudes over prescribed

ﬁ xes, distances between ﬁ xes, and the missed approach

procedure. The proﬁ le view aids in the pilot’s interpretation

of the IAP. The profile view is not drawn to scale.

[Figures 8-10, 8-11, 8-12, and 8-16]

The precision approach glide slope (GS) intercept altitude

is a minimum altitude for GS interception after completion

of the procedure turn, illustrated by an altitude number and

“zigzag” line. It applies to precision approaches, and except

where otherwise prescribed, also applies as a minimum

altitude for crossing the FAF when the GS is inoperative

or not used. Precision approach proﬁ les also depict the GS

angle of descent, threshold-crossing height (TCH), and GS

altitude at the outer marker (OM).

For nonprecision approaches, a ﬁ nal descent is initiated and

the ﬁ nal segment begins at either the FAF or the ﬁ nal approach

point (FAP). The FAF is identiﬁ ed by use of the Maltese cross

symbol in the proﬁ le view. [Figure 8-11] When no FAF

is depicted, the ﬁ nal approach point is the point at which the

aircraft is established inbound on the ﬁ nal approach course.

[Figure 8-16]

Stepdown ﬁ xes in nonprecision procedures are provided

between the FAF and the airport for authorizing a lower

minimum descent altitude (MDA) after passing an

obstruction. Stepdown ﬁ xes can be identiﬁ ed by NAVAID,

NAVAID ﬁ x, waypoint or radar, and are depicted by a hash

marked line. Normally, there is only one stepdown ﬁ x

between the FAF and the MAP, but there can be several.

If the stepdown ﬁ x cannot be identiﬁ ed for any reason, the

minimum altitude at the stepdown ﬁ x becomes the MDA for

the approach. However, circling minimums apply if they are

higher than the stepdown ﬁ x minimum altitude, and a circling

approach is required.

The visual descent point (VDP) is a defined point on

the final approach course of a nonprecision straight-in

approach procedure. A normal descent from the MDA to

the runway touchdown point may be commenced, provided

visual reference is established. The VDP is identiﬁ ed on

the proﬁ le view of the approach chart by the symbol “V.”

[Figure 8-12]

The MAP varies depending upon the approach ﬂ own. For

the ILS, the MAP is at the decision altitude/decision height

(DA/DH). For nonprecision procedures, the pilot determines

8-22

Figure 8-16. More IAP Proﬁ le View Features.

8-23

Figure 8-17. Vertical Descent Angle (VDA).

the MAP by timing from FAF when the approach aid is away

from the airport, by a ﬁ x or NAVAID when the navigation

facility is located on the ﬁ eld, or by waypoints as deﬁ ned

by GPS or VOR/DME RNAV. The pilot may execute the

MAP early, but pilots should, unless otherwise cleared by

ATC, ﬂ y the IAP as speciﬁ ed on the approach plate to the

MAP at or above the MDA or DA/DH before executing a

turning maneuver.

A complete description of the missed approach procedure

appears in the pilot brieﬁ ng section. [Figure 8-16] Icons

indicating what is to be accomplished at the MAP are located

in the proﬁ le view. When initiating a missed approach, the

pilot will be directed to climb straight ahead (e.g., “Climb to

2,000”) or commence a turning climb to a speciﬁ ed altitude

(e.g., “Climbing right turn to 2,000”). In some cases, the

procedure will direct the pilot to climb straight ahead to

an initial altitude, then turn or enter a climbing turn to the

holding altitude (e.g., “Climb to 900, then climbing right turn

to 2,500 direct ABC VOR and hold”).

When the missed approach procedure speciﬁ es holding at

a facility or ﬁ x, the pilot proceeds according to the missed

approach track and pattern depicted on the plan view. An

alternate missed approach procedure may also be issued by

ATC. The textual description will also specify the NAVAID(s)

or radials that identify the holding ﬁ x.

The profile view also depicts minimum, maximum,

recommended, and mandatory block altitudes used in

approaches. The minimum altitude is depicted with the altitude

underscored. On ﬁ nal approach, aircraft are required

to maintain an altitude at or above the depicted altitude until

reaching the subsequent ﬁ x. The maximum altitude will be

depicted with the altitude overscored, and aircraft

must remain at or below the depicted altitude. Mandatory

altitudes will be depicted with the altitude both underscored

and overscored, and altitude is to be maintained at the

depicted value. Recommended altitudes are advisory altitudes

and are neither over- nor underscored. When an over- or

underscore spans two numbers, a mandatory block altitude is

indicated, and aircraft are required to maintain altitude within

the range of the two numbers. [Figures 8-11 and 8-12]

The Vertical Descent Angle (VDA) found on nonprecision

approach charts provides the pilot with information required

to establish a stabilized approach descent from the FAF

or stepdown ﬁ x to the threshold crossing height (TCH).

[Figure 8-17] Pilots can use the published angle and

estimated or actual ground speed to ﬁ nd a target rate of descent

using the rate of descent table in the back of the TPP.

Landing Minimums

The minimums section sets forth the lowest altitude and

visibility requirements for the approach, whether precision

or nonprecision, straight-in or circling, or radar vectored.

When a ﬁ x is incorporated in a nonprecision ﬁ nal segment,

two sets of minimums may be published, depending upon

how the ﬁ x can be identiﬁ ed. Two sets of minimums may

also be published when a second altimeter source is used

in the procedure. The minimums ensure that ﬁ nal approach

obstacle clearance is provided from the start of the ﬁ nal

segment to the runway or MAP, whichever occurs last. The

same minimums apply to both day and night operations unless

different minimums are speciﬁ ed in the Notes section of the

pilot brieﬁ ng. Published circling minimums provide obstacle

clearance when pilots remain within the appropriate area of

protection. [Figure 8-18]

Minimums are specified for various aircraft approach

categories based upon a value 1.3 times the stalling speed

of the aircraft in the landing conﬁ guration at maximum

certiﬁ ed gross landing weight. If it is necessary to maneuver

at speeds in excess of the upper limit of a speed range for a

category, the minimums for the next higher category should

be used. For example, an aircraft that falls into category A,

but is circling to land at a speed in excess of 91 knots, should

use approach category B minimums when circling to land.

[Figure 8-19]

The minimums for straight-in and circling appear directly

under each aircraft category. [Figure 8-19] When there is

no solid division line between minimums for each category

on the rows for straight-in or circling, the minimums apply

to the two or more categories.

The terms used to describe the minimum approach altitudes

differ between precision and nonprecision approaches.

8-24

Figure 8-18. IAP Proﬁ le Legend.

8-25

Figure 8-19. Descent Rate Table.

8-26

Figure 8-20. Terms/Landing Minima Data.

8-27

Precision approaches use decision height (DH), which

is referenced to the height above threshold elevation

(HAT). Nonprecision approaches use MDA, referenced

to “feet MSL.” The MDA is also referenced to HAT for

straight-in approaches, or height above airport (HAA) for

circling approaches. On NACG charts, the ﬁ gures listed

parenthetically are for military operations and are not used

in civil aviation.

Visibility ﬁ gures are provided in statute miles or runway

visual range (RVR), which is reported in hundreds of feet.

RVR is measured by a transmissometer, which represents the

horizontal distance measured at points along the runway. It

is based on the sighting of either high intensity runway lights

or on the visual contrast of other targets, whichever yields

the greater visual range. RVR is horizontal visual range, not

slant visual range, and is used in lieu of prevailing visibility

in determining minimums for a particular runway. It is

illustrated in hundreds of feet if less than a mile (i.e., “24”

is an RVR of 2,400 feet). [Figures 8-19 and 8-20]

Visibility ﬁ gures are depicted after the DA/DH or MDA in the

minimums section. If visibility in statute miles is indicated,

an altitude number, hyphen, and a whole or fractional

number appear; for example, 530-1, which indicates “530

feet MSL” and 1 statute mile visibility. This is the descent

minimum for the approach. The RVR value is separated

from the minimum altitude with a slash, such as “1065/24,”

which indicates 1,065 feet MSL and an RVR of 2,400 feet.

If RVR is prescribed for the procedure, but not available, a

conversion table is used to provide the equivalent visibility

in this case, of 1/2 statute mile visibility. [Figure 8-20] The

conversion table is also available in the TPP.

When an alternate airport is required, standard IFR alternate

minimums apply. For aircraft other than helicopters, precision

approach procedures require a 600-feet ceiling and two

statute miles visibility; nonprecision approaches require an

800-feet ceiling and two statute miles visibility. Helicopter

alternate minimums are a ceiling that is 200 feet above the

minimum for the approach to be ﬂ own and visibility of at

least one statute mile, but not less than the minimum visibility

for the approach to be ﬂ own. When a black triangle with a

white “A” appears in the notes section of the pilot brieﬁ ng,

it indicates non-standard IFR alternate minimums exist for

the airport. If an “NA” appears after the “A,” then

alternate minimums are not authorized. This information is

found in the beginning of the TPP.

In addition to the COPTER approaches, instrument-equipped

helicopters may fly standard approach procedures. The

required visibility minimum may be reduced to one-half the

published visibility minimum for category A aircraft, but

in no case may it be reduced to less than 1/4 mile or 1,200

feet RVR.

Two terms are speciﬁ c to helicopters. Height above landing

(HAL) means height above a designated helicopter landing

area used for helicopter IAPs. “Point in space approach”

refers to a helicopter IAP to a MAP more than 2,600 feet

from an associated helicopter landing area.

Airport Sketch /Airport Diagram

The airport sketch, located on the bottom right side of the

chart, includes many helpful features. IAPs for some of the

larger airports devote an entire page to an airport diagram.

Airport sketch information concerning runway orientation,

lighting, final approach bearings, airport beacon, and

obstacles all serve to guide the pilot in the ﬁ nal phases of

ﬂ ight. See Figure 8-21 for a legend of airport diagram/airport

sketch features (see also Figure 8-10 for an example of an

airport diagram).

The airport elevation is indicated in a separate box at the

top left of the airport sketch. The touchdown zone elevation

(TDZE), which is the highest elevation within the ﬁ rst 3,000

feet of the runway, is designated at the approach end of the

procedure’s runway.

Beneath the airport sketch is a time and speed table when

applicable. The table provides the distance and the amount

of time required to transit the distance from the FAF to the

MAP for selected groundspeeds.

The approach lighting systems and the visual approach lights

are depicted on the airport sketch. White on black symbols

are used for identifying pilot-controlled lighting (PCL).

Runway lighting aids are also noted (e.g., REIL, HIRL), as

is the runway centerline lighting (RCL). [Figure 8-22]

The airport diagram shows the paved runway conﬁ guration

in solid black, while the taxiways and aprons are shaded

gray. Other runway environment features are shown, such

as the runway identiﬁ cation, dimensions, magnetic heading,

displaced threshold, arresting gear, usable length, and slope.

Inoperative Components

Certain procedures can be ﬂ own with inoperative components.

According to the Inoperative Components Table, for

example, an ILS approach with a malfunctioning Medium

Intensity Approach Lighting System with Runway Alignment

Indicator Lights (MALSR = MALS with RAIL) can be

ﬂ own if the minimum visibility is increased by 1/4 mile.

[Figure 8-23] A note in this section might read, “Inoperative

Table does not apply to ALS or HIRL Runway 13L.”

8-28

Figure 8-21. Airport Legend and Diagram.

8-29

Figure 8-22. Approach Lighting Legend.

8-30

Figure 8-23. IAP Inoperative Components Table.

8-31

Figure 8-24. RNAV Instrument Approach Charts.

8-32

RNAV Instrument Approach Charts

To avoid unnecessary duplication and proliferation of

approach charts, approach minimums for unaugmented

GPS, Wide Area Augmentation System (WAAS), Local

Area Augmentation System (LAAS), will be published

on the same approach chart as lateral navigation/vertical

navigation (LNAV/VNAV). Other types of equipment may

be authorized to conduct the approach based on the minima

notes in the front of the TPP approach chart books. Approach

charts titled “RNAV RWY XX” may be used by aircraft

with navigation systems that meet the required navigational

performance (RNP) values for each segment of the approach.

[Figure 8-24]

The chart may contain as many as four lines of approach

minimums: global landing system (GLS), WAAS and LAAS,

LNAV/VNAV, LNAV, and circling. LNAV/VNAV is an

instrument approach with lateral and vertical guidance with

integrity limits similar to barometric vertical navigation

(BARO VNAV).

RNAV procedures that incorporate a ﬁ nal approach stepdown

ﬁ x may be published without vertical navigation on a separate

chart also titled RNAV. During a transition period when GPS

procedures are undergoing revision to a new title, both RNAV

and GPS approach charts and formats will be published. ATC

clearance for the RNAV procedure will authorize a properly

certiﬁ cated pilot to utilize any landing minimums for which

the aircraft is certiﬁ ed.

Chart terminology will change slightly to support the new

procedure types:

1. DA replaces the term DH. DA conforms to the

international convention where altitudes relate to

MSL and heights relate to AGL. DA will eventually

be published for other types of IAPs with vertical

guidance, as well. DA indicates to the pilot that the

published descent proﬁ le is ﬂ own to the DA (MSL),

where a missed approach will be initiated if visual

references for landing are not established. Obstacle

clearance is provided to allow a momentary descent

below DA while transitioning from the ﬁ nal approach to

the missed approach. The aircraft is expected to follow

the missed approach instructions while continuing

along the published ﬁ nal approach course to at least

the published runway threshold waypoint or MAP (if

not at the threshold) before executing any turns.

2. MDA will continue to be used only for the LNAV and

circling procedures.

3. Threshold crossing height (TCH) has been traditionally

used in precision approaches as the height of the GS

above threshold. With publication of LNAV/VNAV

minimums and RNAV descent angles, including

graphically depicted descent profiles, TCH also

applies to the height of the “descent angle,” or glide

path, at the threshold. Unless otherwise required for

larger type aircraft, which may be using the IAP, the

typical TCH will be 30 to 50 feet.

The minima format changes slightly:

1. Each line of minima on the RNAV IAP will be titled

to reﬂ ect the RNAV system applicable (e.g., GLS,

LNAV/VNAV, and LNAV). Circling minima will

also be provided.

2. The minima title box will also indicate the nature of

the minimum altitude for the IAP. For example: DA

will be published next to the minima line title for

minimums supporting vertical guidance, and MDA

will be published where the minima line supports only

lateral guidance. During an approach where an MDA

is used, descent below MDA is not authorized.

3. Where two or more systems share the same minima,

each line of minima will be displayed separately.

For more information concerning government charts, the

NACG can be contacted by telephone, or via their internet

address at:

National Aeronautical Charting Group

Telephone 800-626-3677

http://naco.faa.gov/

9-1

The Air Trafﬁ c

Control System

Introduction

This chapter covers the communication equipment,

communication procedures, and air trafﬁ c control (ATC)

facilities and services available for a ﬂ ight under instrument

ﬂ ight rules (IFR) in the National Airspace System (NAS).

Chapter 9

9-2

Figure 9-2. Audio Panel.

Figure 9-1. Typical NAV/COM Installation.

Communication Equipment

Navigation/Communication (NAV/COM)

Equipment

Civilian pilots communicate with ATC on frequencies in

the very high frequency (VHF) range between 118.000 and

136.975 MHz. To derive full beneﬁ t from the ATC system,

radios capable of 25 kHz spacing are required (e.g., 134.500,

134.575, 134.600). If ATC assigns a frequency that cannot

be selected, ask for an alternative frequency.

Figure 9-1 illustrates a typical radio panel installation,

consisting of a communications transceiver on the left and a

navigational receiver on the right. Many radios allow the pilot

to have one or more frequencies stored in memory and one

frequency active for transmitting and receiving (called simplex

operation). It is possible to communicate with some automated

ﬂ ight service stations (AFSS) by transmitting on 122.1 MHz

(selected on the communication radio) and receiving on a

VHF omnidirectional range (VOR) frequency (selected on

the navigation radio). This is called duplex operation.

An audio panel allows a pilot to adjust the volume of the

selected receiver(s) and to select the desired transmitter.

[Figure 9-2] The audio panel has two positions for receiver

selection, cabin speaker, and headphone (some units might

have a center “off” position). Use of a hand-held microphone

and the cabin speaker introduces the distraction of reaching

for and hanging up the microphone. A headset with a boom

microphone is recommended for clear communications. The

microphone should be positioned close to the lips to reduce

9-3

Figure 9-3. Boom Microphone, Headset, and Push-To-Talk

Switch.

Figure 9-4. Combination GPS-Com Unit.

the possibility of ambient ﬂ ight deck noise interfering with

transmissions to the controller. Headphones deliver the

received signal directly to the ears; therefore, ambient noise

does not interfere with the pilot’s ability to understand the

transmission. [Figure 9-3]

Switching the transmitter selector between COM1 and

COM2 changes both transmitter and receiver frequencies.

It is necessary only when a pilot wants to monitor one

frequency while transmitting on another. One example is

listening to automatic terminal information service (ATIS)

on one receiver while communicating with ATC on the

other. Monitoring a navigation receiver to check for proper

identiﬁ cation is another reason to use the switch panel.

Most audio switch panels also include a marker beacon

receiver. All marker beacons transmit on 75 MHz, so there

is no frequency selector.

Figure 9-4 illustrates an increasingly popular form of

NAV/COM radio; it contains a global positioning system

(GPS) receiver and a communications transceiver. Using its

navigational capability, this unit can determine when a ﬂ ight

crosses an airspace boundary or ﬁ x and can automatically

select the appropriate communications frequency for that

location in the communications radio.

Radar and Transponders

ATC radars have a limited ability to display primary returns,

which is energy reﬂ ected from an aircraft’s metallic structure.

Their ability to display secondary returns (transponder replies

to ground interrogation signals) makes possible the many

advantages of automation.

A transponder is a radar beacon transmitter/receiver installed

in the instrument panel. ATC beacon transmitters send out

interrogation signals continuously as the radar antenna

rotates. When an interrogation is received by a transponder, a

coded reply is sent to the ground station where it is displayed

on the controller’s scope. A reply light on the transponder

panel ﬂ ickers every time it receives and replies to a radar

interrogation. Transponder codes are assigned by ATC.

When a controller asks a pilot to “ident” and the ident button

is pushed, the return on the controller’s scope is intensiﬁ ed for

precise identiﬁ cation of a ﬂ ight. When requested, brieﬂ y push

the ident button to activate this feature. It is good practice

for pilots to verbally conﬁ rm that they have changed codes

or pushed the ident button.

Mode C (Altitude Reporting)

Primary radar returns indicate only range and bearing from

the radar antenna to the target; secondary radar returns can

display altitude, Mode C, on the control scope if the aircraft

is equipped with an encoding altimeter or blind encoder. In

either case, when the transponder’s function switch is in the

ALT position the aircraft’s pressure altitude is sent to the

controller. Adjusting the altimeter’s Kollsman window has

no effect on the altitude read by the controller.

Transponders, when installed, must be ON at all times when

operating in controlled airspace; altitude reporting is required

by regulation in Class B and Class C airspace and inside a

30-mile circle surrounding the primary airport in Class B

airspace. Altitude reporting should also be ON at all times.

9-4

Figure 9-5. Phonetic Pronunciation Guide.

Communication Procedures

Clarity in communication is essential for a safe instrument

ﬂ ight. This requires pilots and controllers to use terms that

are understood by both—the Pilot/Controller Glossary in the

Aeronautical Information Manual (AIM) is the best source of

terms and deﬁ nitions. The AIM is revised twice a year and

new deﬁ nitions are added, so the glossary should be reviewed

frequently. Because clearances and instructions are comprised

largely of letters and numbers, a phonetic pronunciation guide

has been developed for both. [Figure 9-5]

ATCs must follow the guidance of the Air Trafﬁ c Control

Manual when communicating with pilots. The manual

presents the controller with different situations and prescribes

precise terminology that must be used. This is advantageous

for pilots because once they have recognized a pattern

or format they can expect future controller transmissions

to follow that format. Controllers are faced with a wide

variety of communication styles based on pilot experience,

proﬁ ciency, and professionalism.

Pilots should study the examples in the AIM, listen to

other pilots communicate, and apply the lessons learned

to their own communications with ATC. Pilots should ask

for clariﬁ cation of a clearance or instruction. If necessary,

use plain English to ensure understanding, and expect the

controller to reply in the same way. A safe instrument ﬂ ight

is the result of cooperation between controller and pilot.

Communication Facilities

The controller’s primary responsibility is separation of

aircraft operating under IFR. This is accomplished with ATC

facilities which include the AFSS, airport trafﬁ c control tower

(ATCT), terminal radar approach control (TRACON), and

air route trafﬁ c control center (ARTCC).

Automated Flight Service Stations (AFSS)

A pilot’s ﬁ rst contact with ATC is usually through AFSS,

either by radio or telephone. AFSSs provide pilot brieﬁ ngs,

receive and process ﬂ ight plans, relay ATC clearances,

originate Notices to Airmen (NOTAMs), and broadcast

aviation weather. Some facilities provide En Route Flight

Advisory Service (EFAS), take weather observations,

and advise United States Customs and Immigration of

international ﬂ ights.

Telephone contact with Flight Service can be obtained

by dialing 1-800-WX-BRIEF. This number can be used

anywhere in the United States and connects to the nearest

AFSS based on the area code from which the call originates.

There are a variety of methods of making radio contact:

direct transmission, remote communication outlets (RCOs),

ground communication outlets (GCOs), and by using duplex

transmissions through navigational aids (NAVAIDs). The

best source of information on frequency usage is the Airport/

Facility Directory (A/FD) and the legend panel on sectional

charts also contains contact information.

9-5

Figure 9-6. Flight Strip.

The briefer sends a flight plan to the host computer at

the ARTCC (Center). After processing the flight plan,

the computer will send ﬂ ight strips to the tower, to the

radar facility that will handle the departure route, and to

the Center controller whose sector the ﬂ ight ﬁ rst enters.

Figure 9-6 shows a typical strip. These strips are delivered

approximately 30 minutes prior to the proposed departure

time. Strips are delivered to en route facilities 30 minutes

before the ﬂ ight is expected to enter their airspace. If a

ﬂ ight plan is not opened, it will “time out” 2 hours after the

proposed departure time.

When departing an airport in Class G airspace, a pilot receives

an IFR clearance from the AFSS by radio or telephone. It

contains either a clearance void time, in which case an aircraft

must be airborne prior to that time, or a release time. Pilots

should not take-off prior to the release time. Pilots can help

the controller by stating how soon they expect to be airborne.

If the void time is, for example, 10 minutes past the hour and

an aircraft is airborne at exactly 10 minutes past the hour,

the clearance is void—a pilot must take off prior to the void

time. A speciﬁ c void time may be requested when ﬁ ling a

ﬂ ight plan.

ATC Towers

Several controllers in the tower cab are involved in handling

an instrument ﬂ ight. Where there is a dedicated clearance

delivery position, that frequency is found in the A/FD and

on the instrument approach chart for the departure airport.

Where there is no clearance delivery position, the ground

controller performs this function. At the busiest airports, pre-

taxi clearance is required; the frequency for pre-taxi clearance

can be found in the A/FD. Taxi clearance should be requested

not more than 10 minutes before proposed taxi time.

It is recommended that pilots read their IFR clearance back to

the clearance delivery controller. Instrument clearances can

be overwhelming when attempting to copy them verbatim,

but they follow a format that allows a pilot to be prepared

when responding “Ready to copy.” The format is: clearance

limit (usually the destination airport); route, including any

departure procedure; initial altitude; frequency (for departure

control); and transponder code. With the exception of the

transponder code, a pilot knows most of these items before

engine start. One technique for clearance copying is writing

C-R-A-F-T.

Assume an IFR ﬂ ight plan has been ﬁ led from Seattle,

Washington to Sacramento, California via V-23 at 7,000

feet. Trafﬁ c is taking off to the north from Seattle-Tacoma

(Sea-Tac) airport and, by monitoring the clearance delivery

frequency, a pilot can determine the departure procedure

being assigned to southbound ﬂ ights. The clearance limit

is the destination airport, so write “SAC” after the letter C.

Write “SEATTLE TWO – V23” after R for Route, because

departure control issued this departure to other ﬂ ights. Write

“7” after the A, the departure control frequency printed on

the approach charts for Sea-Tac after F, and leave the space

after the letter T blank—the transponder code is generated by

computer and can seldom be determined in advance. Then,

call clearance delivery and report “Ready to copy.”

As the controller reads the clearance, check it against what

is already written down; if there is a change, draw a line

through that item and write in the changed item. Chances

are the changes are minimal, and most of the clearance is

copied before keying the microphone. Still, it is worthwhile

to develop clearance shorthand to decrease the verbiage that

must be copied (see Appendix 1).

Pilots are required to have either the text of a departure

procedure (DP) or a graphic representation (if one is

available), and should review it before accepting a clearance.

This is another reason to ﬁ nd out ahead of time which DP is

in use. If the DP includes an altitude or a departure control

frequency, those items are not included in the clearance.

The last clearance received supersedes all previous clearances.

For example, if the DP says “Climb and maintain 2,000 feet,

expect higher in 6 miles,” but upon contacting the departure

controller a new clearance is received: “Climb and maintain

8,000 feet,” the 2,000 feet restriction has been canceled. This

rule applies in both terminal and Center airspace.

9-6

Figure 9-7. Combined Radar and Beacon Antenna. Figure 9-8. Minimum Vectoring Altitude Chart.

When reporting ready to copy an IFR clearance before the

strip has been received from the Center computer, pilots

are advised “clearance on request.” The controller initiates

contact when it has been received. This time can be used for

taxi and pre-takeoff checks.

The local controller is responsible for operations in the Class

D airspace and on the active runways. At some towers,

designated as IFR towers, the local controller has vectoring

authority. At visual ﬂ ight rules (VFR) towers, the local

controller accepts inbound IFR ﬂ ights from the terminal radar

facility and cannot provide vectors. The local controller also

coordinates ﬂ ights in the local area with radar controllers.

Although Class D airspace normally extends 2,500 feet above

ﬁ eld elevation, towers frequently release the top 500 feet to

the radar controllers to facilitate overﬂ ights. Accordingly,

when a ﬂ ight is vectored over an airport at an altitude that

appears to enter the tower controller’s airspace, there is no

need to contact the tower controller—all coordination is

handled by ATC.

The departure radar controller may be in the same building

as the control tower, but it is more likely that the departure

radar position is remotely located. The tower controller will

not issue a takeoff clearance until the departure controller

issues a release.

Terminal Radar Approach Control (TRACON)

TRACONs are considered terminal facilities because they

provide the link between the departure airport and the en route

structure of the NAS. Terminal airspace normally extends 30

nautical miles (NM) from the facility, with a vertical extent

of 10,000 feet; however, dimensions vary widely. Class B

and Class C airspace dimensions are provided on aeronautical

charts. At terminal radar facilities the airspace is divided

into sectors, each with one or more controllers, and each

sector is assigned a discrete radio frequency. All terminal

facilities are approach controls and should be addressed

as “Approach” except when directed to do otherwise (e.g.,

“Contact departure on 120.4”).

Terminal radar antennas are located on or adjacent to the

airport. Figure 9-7 shows a typical conﬁ guration. Terminal

controllers can assign altitudes lower than published

procedural altitudes called minimum vectoring altitudes

(MVAs). These altitudes are not published or accessible to

pilots, but are displayed at the controller’s position, as shown

in Figure 9-8. However, when pilots are assigned an altitude

that seems to be too low, they should query the controller

before descending.

When a pilot accepts a clearance and reports ready for takeoff,

a controller in the tower contacts the TRACON for a release.

An aircraft is not cleared for takeoff until the departure

controller can ﬁ t the ﬂ ight into the departure ﬂ ow. A pilot may

have to hold for release. When takeoff clearance is received,

the departure controller is aware of the ﬂ ight and is waiting

for a call. All of the information the controller needs is on

the departure strip or the computer screen there is no need to

repeat any portion of the clearance to that controller. Simply

establish contact with the facility when instructed to do so by

the tower controller. The terminal facility computer picks up

the transponder and initiates tracking as soon as it detects the

9-7

assigned code. For this reason, the transponder should remain

on standby until takeoff clearance has been received.

The aircraft appears on the controller’s radar display as a

target with an associated data block that moves as the aircraft

moves through the airspace. The data block includes aircraft

identiﬁ cation, aircraft type, altitude, and airspeed.

A TRACON controller uses Airport Surveillance Radar

(ASR) to detect primary targets and Automated Radar

Terminal Systems (ARTS) to receive transponder signals; the

two are combined on the controller’s scope. [Figure 9-9]

At facilities with ASR-3 equipment, radar returns from

precipitation are not displayed as varying levels of intensity,

and controllers must rely on pilot reports and experience

to provide weather avoidance information. With ASR-9

equipment, the controller can select up to six levels of

intensity. Light precipitation does not require avoidance

tactics but precipitation levels of moderate, heavy or

extreme should cause pilots to plan accordingly. Along

with precipitation the pilot must additionally consider the

temperature, which if between -20° and +5° C will cause icing

even during light precipitation. The returns from higher levels

of intensity may obscure aircraft data blocks, and controllers

may select the higher levels only on pilot request. When

uncertainty exists about the weather ahead, ask the controller

if the facility can display intensity levels—pilots of small

aircraft should avoid intensity levels 3 or higher.

Tower En Route Control (TEC)

At many locations, instrument ﬂ ights can be conducted

entirely in terminal airspace. These TEC routes are generally

for aircraft operating below 10,000 feet, and they can be

found in the A/FD. Pilots desiring to use TEC should include

that designation in the remarks section of the ﬂ ight plan.

Pilots are not limited to the major airports at the city pairs

listed in the A/FD. For example, a tower en route ﬂ ight from

an airport in New York (NYC) airspace could terminate

at any airport within approximately 30 miles of Bradley

International (BDL) airspace, such as Hartford (HFD).

[Figure 9-10]

A valuable service provided by the automated radar

equipment at terminal radar facilities is the Minimum Safe

Altitude Warnings (MSAW). This equipment predicts an

aircraft’s position in 2 minutes based on present path of

ﬂ ight—the controller issues a safety alert if the projected

path encounters terrain or an obstruction. An unusually

rapid descent rate on a nonprecision approach can trigger

such an alert.

Air Route Trafﬁ c Control Center (ARTCC)

ARTCC facilities are responsible for maintaining separation

between IFR ﬂ ights in the en route structure. Center radars

(Air Route Surveillance Radar (ARSR)) acquire and track

transponder returns using the same basic technology as

terminal radars. [Figure 9-11]

Earlier Center radars display weather as an area of slashes

(light precipitation) and Hs (moderate rainfall), as illustrated

in Figure 9-12. Because the controller cannot detect higher

levels of precipitation, pilots should be wary of areas showing

moderate rainfall. Newer radar displays show weather as

three levels of blue. Controllers can select the level of weather

to be displayed. Weather displays of higher levels of intensity

can make it difﬁ cult for controllers to see aircraft data blocks,

so pilots should not expect ATC to keep weather displayed

continuously.

Center airspace is divided into sectors in the same manner

as terminal airspace; additionally, most Center airspace is

divided by altitudes into high and low sectors. Each sector

has a dedicated team of controllers and a selection of radio

frequencies, because each Center has a network of remote

transmitter/receiver sites. All Center frequencies can be found

in the back of the A/FD in the format shown in Figure 9-13;

they are also found on en route charts.

Each ARTCC’s area of responsibility covers several states;

when ﬂ ying from the vicinity of one remote communication

site toward another, expect to hear the same controller on

different frequencies.

Center Approach/Departure Control

The majority of airports with instrument approaches do not

lie within terminal radar airspace, and when operating to

or from these airports pilots communicate directly with the

Center controller. Departing from a tower-controlled airport,

the tower controller provides instructions for contacting the

appropriate Center controller. When departing an airport

without an operating control tower, the clearance includes

instructions such as “Upon entering controlled airspace,

contact Houston Center on 126.5.” Pilots are responsible

for terrain clearance until reaching the controller’s MVA.

Simply hearing “Radar contact” does not relieve a pilot of

this responsibility.

If obstacles in the departure path require a steeper-than-

standard climb gradient (200 FPNM), then the controller

advises the pilot. However, it is the pilot’s responsibility to

check the departure airport listing in the A/FD to determine if

there are trees or wires in the departure path. When in doubt,

ask the controller for the required climb gradient.

9-8

Figure 9-9. The top image is a display as seen by controllers in an Air Trafﬁ c Facility. The one illustrated is an ARTS III (Automated

Radar Terminal System). The display shown provides an explanation of the symbols in the graphic. The lower ﬁ gure is an example of

the Digital Bright Radar Indicator Tower Equipment (DBRITE) screen as seen by tower personnel. It provides tower controllers with

a visual display of the airport surveillance radar, beacon signals, and data received from ARTS III. The display shown provides an

explanation of the symbols in the graphic.

9-9

Figure 9-10. A Portion of the New York Area Tower En Route List. (From the A/FD)

9-10

Figure 9-11. Center Radar Displays. Figure 9-12. A Center Controller’s Scope.

Figure 9-13. Center Symbology.

A common clearance in these situations is “When able,

proceed direct to the Astoria VOR…” The words “when able”

mean to proceed to the waypoint, intersection, or NAVAID

when the pilot is able to navigate directly to that point using

onboard available systems providing proper guidance, usable

signal, etc. If provided such guidance while ﬂ ying VFR, the

pilot remains responsible for terrain and obstacle clearance.

Using the standard climb gradient, an aircraft is 2 miles

from the departure end of the runway before it is safe to

turn (400 feet above ground level (AGL)). When a Center

controller issues a heading, a direct route, or says “direct

when able,” the controller becomes responsible for terrain

and obstruction clearance.

Another common Center clearance is “Leaving (altitude)

ﬂ y (heading) or proceed direct when able.” This keeps the

terrain/obstruction clearance responsibility in the ﬂ ight deck

until above the minimum IFR altitude. A controller cannot

issue an IFR clearance until an aircraft is above the minimum

IFR altitude unless it is able to climb in VFR conditions.

On a Center controller’s scope, 1 NM is about 1/28 of an inch.

When a Center controller is providing Approach/Departure

control services at an airport many miles from the radar

antenna, estimating headings and distances is very difﬁ cult.

Controllers providing vectors to ﬁ nal must set the range on

their scopes to not more than 125 NM to provide the greatest

possible accuracy for intercept headings. Accordingly, at

locations more distant from a Center radar antenna, pilots

should expect a minimum of vectoring.

9-11

ATC radar systems cannot detect turbulence. Generally,

turbulence can be expected to occur as the rate of rainfall or

intensity of precipitation increases. Turbulence associated

with greater rates of rainfall/precipitation is normally more

severe than any associated with lesser rates of rainfall/

precipitation. Turbulence should be expected to occur near

convective activity, even in clear air. Thunderstorms are a

form of convective activity that implies severe or greater

turbulence. Operation within 20 miles of thunderstorms

should be approached with great caution, as the severity of

turbulence can be markedly greater than the precipitation

intensity might indicate.

Weather Avoidance Assistance

ATC’s ﬁ rst duty priority is to separate aircraft and issue

safety alerts. ATC provides additional services to the extent

possible, contingent upon higher priority duties and other

factors including limitations of radar, volume of trafﬁ c,

frequency congestion, and workload. Subject to the above

factors/limitations, controllers issue pertinent information

on weather or chaff areas; and if requested, assist pilots, to

the extent possible, in avoiding areas of precipitation. Pilots

should respond to a weather advisory by acknowledging the

advisory and, if desired, requesting an alternate course of

action, such as:

1. Request to deviate off course by stating the direction

and number of degrees or miles needed to deviate from

the original course;

2. Request a change of altitude; or

3. Request routing assistance to avoid the affected

area. Because ATC radar systems cannot detect the

presence or absence of clouds and turbulence, such

assistance conveys no guarantee that the pilot will not

encounter hazards associated with convective activity.

Pilots wishing to circumnavigate precipitation areas

by a specific distance should make their desires

clearly known to ATC at the time of the request for

services. Pilots must advise ATC when they can

resume normal navigation.

IFR pilots shall not deviate from their assigned course or

altitude without an ATC clearance. Plan ahead for possible

course deviations because hazardous convective conditions

can develop quite rapidly. This is important to consider

because the precipitation data displayed on ARTCC radar

scopes can be up to 6 minutes old and thunderstorms can

develop at rates exceeding 6,000 feet per minute (fpm). When

encountering weather conditions that threaten the safety of

the aircraft, the pilot may exercise emergency authority as

ATC Inﬂ ight Weather Avoidance

Assistance

ATC Radar Weather Displays

ATC radar systems are able to display areas of precipitation

by sending out a beam of radio energy that is reﬂ ected back to

the radar antenna when it strikes an object or moisture which

may be in the form of rain drops, hail, or snow. The larger

the object, or the denser its reﬂ ective surface, the stronger the

return will be. Radar weather processors indicate the intensity

of reﬂ ective returns in terms of decibels with respect to the

radar reﬂ ectively factor (dBZ).

ATC systems cannot detect the presence or absence of

clouds. ATC radar systems can often determine the intensity

of a precipitation area, but the speciﬁ c character of that area

(snow, rain, hail, VIRGA, etc.) cannot be determined. For

this reason, ATC refers to all weather areas displayed on

ATC radar scopes as “precipitation.”

All ATC facilities using radar weather processors with the

ability to determine precipitation intensity describes the

intensity to pilots as:

1. “LIGHT” (< 30 dBZ)

2. “MODERATE” (30 to 40 dBZ)

3. “HEAVY” (>40 to 50 dBZ)

4. “EXTREME” (>50 dBZ)

ARTCC controllers do not use the term “LIGHT” because

their systems do not display “LIGHT” precipitation

intensities. ATC facilities that, due to equipment limitations,

cannot display the intensity levels of precipitation, will

describe the location of the precipitation area by geographic

position, or position relative to the aircraft. Since the intensity

level is not available, the controller states, “INTENSITY

UNKNOWN.”

ARTCC facilities normally use a Weather and Radar

Processor (WARP) to display a mosaic of data obtained from

multiple NEXRAD sites. The WARP processor is only used

in ARTCC facilities.

There is a time delay between actual conditions and those

displayed to the controller. For example, the precipitation

data on the ARTCC controller’s display could be up to 6

minutes old. When the WARP is not available, a secondary

system, the narrowband ARSR is utilized. The ARSR system

can display two distinct levels of precipitation intensity that

is described to pilots as “MODERATE” (30 to 40 dBZ) and

“HEAVY to EXTREME” (>40 dBZ).

9-12

Figure 9-14. High Resolution ATC Displays Used in PRM.

stated in 14 CFR part 91, section 91.3 should an immediate

deviation from the assigned clearance be necessary and time

does not permit approval by ATC.

Generally, when weather disrupts the ﬂ ow of air trafﬁ c,

greater workload demands are placed on the controller.

Requests for deviations from course and other services

should be made as far in advance as possible to better assure

the controller’s ability to approve these requests promptly.

When requesting approval to detour around weather activity,

include the following information to facilitate the request:

1. The proposed point where detour commences;

2. The proposed route and extent of detour (direction

and distance);

3. The point where original route will be resumed;

4. Flight conditions (IMC or VMC);

5. Whether the aircraft is equipped with functioning

airborne radar; and

6. Any further deviation that may become necessary.

To a large degree, the assistance that might be rendered

by ATC depends upon the weather information available

to controllers. Due to the extremely transitory nature of

hazardous weather, the controller’s displayed precipitation

information may be of limited value.

Obtaining IFR clearance or approval to circumnavigate

hazardous weather can often be accommodated more readily

in the en route areas away from terminals because there

is usually less congestion and, therefore, greater freedom

of action. In terminal areas, the problem is more acute

because of trafﬁ c density, ATC coordination requirements,

complex departure and arrival routes, and adjacent airports.

As a consequence, controllers are less likely to be able to

accommodate all requests for weather detours in a terminal

area. Nevertheless, pilots should not hesitate to advise

controllers of any observed hazardous weather and should

speciﬁ cally advise controllers if they desire circumnavigation

of observed weather.

Pilot reports (PIREPs) of ﬂ ight conditions help deﬁ ne the

nature and extent of weather conditions in a particular area.

These reports are disseminated by radio and electronic means

to other pilots. Provide PIREP information to ATC regarding

pertinent ﬂ ight conditions, such as:

1. Turbulence;

2. Visibility;

3. Cloud tops and bases; and

4. The presence of hazards such as ice, hail, and

lightning.

Approach Control Facility

An approach control facility is a terminal ATC facility

that provides approach control service in the terminal area.

Services are provided for arriving and departing VFR and

IFR aircraft and, on occasion, en route aircraft. In addition,

for airports with parallel runways with ILS or LDA

approaches, the approach control facility provides monitoring

of the approaches.

Approach Control Advances

Precision Runway Monitor (PRM)

Over the past few years, a new technology has been installed

at airports that permits a decreased separation distance

between parallel runways. The system is called a Precision

Runway Monitor (PRM) and is comprised of high-update

radar, high-resolution ATC displays, and PRM-certiﬁ ed

controllers. [Figure 9-14]

Precision Runway Monitor (PRM) Radar

The PRM uses a Monopulse Secondary Surveillance Radar

(MSSR) that employs electronically scanned antennas.

Because the PRM has no scan rate restrictions, it is capable

of providing a faster update rate (up to 0.5 second) over

conventional systems, thereby providing better target

presentation in terms of accuracy, resolution, and track

prediction. The system is designed to search, track, process,

and display SSR-equipped aircraft within airspace of over

30 miles in range and over 15,000 feet in elevation. Visual

and audible alerts are generated to warn controllers to take

corrective actions.

9-13

Figure 9-15. Aircraft Management Using PRM. (Note the no transgression zone (NTZ) and how the aircraft are separated.)

PRM Beneﬁ ts

Typically, PRM is used with dual approaches with centerlines

separated less than 4,300 feet but not less than 3,000 feet

(under most conditions). [Figure 9-15] Separating the two

ﬁ nal approach courses is a No Transgression Zone (NTZ)

with surveillance of that zone provided by two controllers,

one for each active approach. The system tracking software

provides PRM monitor controllers with aircraft identiﬁ cation,

position, speed, projected position, as well as visual and

aural alerts.

Control Sequence

The IFR system is ﬂ exible and accommodating if pilots do

their homework, have as many frequencies as possible written

down before they are needed, and have an alternate in mind

if the ﬂ ight cannot be completed as planned. Pilots should

familiarize themselves with all the facilities and services

available along the planned route of ﬂ ight. [Figure 9-16]

Always know where the nearest VFR conditions can be

found, and be prepared to head in that direction if the situation

deteriorates.

A typical IFR ﬂ ight, with departure and arrival at airports

with control towers, would use the ATC facilities and services

in the following sequence:

1. AFSS: Obtain a weather brieﬁ ng for a departure,

destination and alternate airports, and en route

conditions, and then file a flight plan by calling

1-800-WX-BRIEF.

2. ATIS: Preﬂ ight complete, listen for present conditions

and the approach in use.

3. Clearance Delivery: Prior to taxiing, obtain a departure

clearance.

4. Ground Control: Noting that the ﬂ ight is IFR, receive

taxi instructions.

5. Tower: Pre-takeoff checks complete, receive clearance

to takeoff.

6. Departure Control: Once the transponder “tags up”

with the ARTS, the tower controller instructs the pilot

to contact Departure to establish radar contact.

9-14

7. ARTCC: After departing the departure controller’s

airspace, aircraft is handed off to Center, who

coordinates the flight while en route. Pilots may

be in contact with multiple ARTCC facilities; they

coordinate the hand-offs.

8. EFAS/HIWAS: Coordinate with ATC before

leaving their frequency to obtain inﬂ ight weather

information.

9. ATIS: Coordinate with ATC before leaving their

frequency to obtain ATIS information.

10. Approach Control: Center hands off to approach

control where pilots receive additional information

and clearances.

11. Tower: Once cleared for the approach, pilots are

instructed to contact tower control; the ﬂ ight plan is

canceled by the tower controller upon landing.

A typical IFR ﬂ ight, with departure and arrival at airports

without operating control towers, would use the ATC

facilities and services in the following sequence:

1. AFSS: Obtain a weather briefing for departure,

destination, and alternate airports, and en route

conditions, and then file a flight plan by calling

1-800-WX-BRIEF. Provide the latitude/longitude

description for small airports to ensure that Center is

able to locate departure and arrival locations.

2. AFSS or UNICOM: ATC clearances can be ﬁ led and

received on the UNICOM frequency if the licensee

has made arrangements with the controlling ARTCC;

otherwise, ﬁ le with AFSS via telephone. Be sure all

preﬂ ight preparations are complete before ﬁ ling. The

clearance includes a clearance void time. Pilots must

be airborne prior to the void time.

3. ARTCC: After takeoff, establish contact with Center.

During the flight, pilots may be in contact with

multiple ARTCC facilities; ATC coordinates the hand-

offs.

4. EFAS/HIWAS: Coordinate with ATC before

leaving their frequency to obtain in-ﬂ ight weather

information.

5. Approach Control: Center hands off to approach

control where pilots receive additional information and

clearances. If a landing under visual meteorological

conditions (VMC) is possible, pilots may cancel their

IFR clearance before landing.

Letters of Agreement (LOA)

The ATC system is indeed a system, and very little happens

by chance. As a ﬂ ight progresses, controllers in adjoining

sectors or adjoining Centers coordinate its handling by

telephone or by computer. Where there is a boundary between

the airspace controlled by different facilities, the location and

altitude for hand-off is determined by Letters of Agreement

(LOA) negotiated between the two facility managers. This

information is not available to pilots in any Federal Aviation

Administration (FAA) publication. For this reason, it is good

practice to note on the en route chart the points at which hand-

offs occur. Each time a ﬂ ight is handed-off to a different

facility, the controller knows the altitude and location—this

was part of the hand-off procedure.

9-15

Figure 9-16. ATC Facilities, Services, and Radio Call Signs.

9-16

10-1

Introduction

This chapter is a discussion of conducting a ﬂ ight under

instrument ﬂ ight rules (IFR). It also explains the sources for

ﬂ ight planning, the conditions associated with instrument

ﬂ ight, and the procedures used for each phase of IFR ﬂ ight:

departure, en route, and approach. The chapter concludes

with an example of an IFR ﬂ ight which applies many of the

procedures discussed in the chapter.

IFR Flight

Chapter 10

10-2

Sources of Flight Planning Information

The following resources are available for a pilot planning a

ﬂ ight conducted under instrument ﬂ ight rules (IFR).

National Aeronautical Charting Group (NACG)

publications:

• IFR en route charts

• area charts

• United States (U.S.) Terminal Procedures Publications

(TPP)

The Federal Aviation Administration (FAA) publications:

• AIM

• Airport/Facility Directory (A/FD)

• Notices to Airmen Publication (NTAP) for ﬂ ight

planning in the National Airspace System (NAS)

Pilots should also consult the Pilot’s Operating Handbook/

Airplane Flight Manual (POH/AFM) for ﬂ ight planning

information pertinent to the aircraft to be ﬂ own.

A review of the contents of all the listed publications will help

determine which material should be referenced for each ﬂ ight.

As a pilot becomes more familiar with these publications, the

ﬂ ight planning process becomes quicker and easier.

Aeronautical Information Manual (AIM)

The AIM provides the aviation community with basic

ﬂ ight information and air trafﬁ c control (ATC) procedures

used in the United States NAS. An international version

called the Aeronautical Information Publication contains

parallel information, as well as speciﬁ c information on the

international airports used by the international community.

Airport/Facility Directory (A/FD)

The A/FD contains information on airports, communications,

and navigation aids pertinent to IFR ﬂ ight. It also includes

very-high frequency omnidirectional range (VOR) receiver

checkpoints, automated ﬂ ight service station (AFSS), weather

service telephone numbers, and air route trafﬁ c control center

(ARTCC) frequencies. Various special notices essential

to ﬂ ight are also included, such as land-and-hold-short

operations (LAHSO) data, the civil use of military ﬁ elds,

continuous power facilities, and special ﬂ ight procedures.

In the major terminal and en route environments, preferred

routes have been established to guide pilots in planning their

routes of ﬂ ight, to minimize route changes, and to aid in the

orderly management of air trafﬁ c using the federal airways.

The A/FD lists both high and low altitude preferred routes.

Notices to Airmen Publication (NTAP)

The NTAP is a publication containing current Notices to

Airmen (NOTAMs) which are essential to the safety of ﬂ ight,

as well as supplemental data affecting the other operational

publications listed. It also includes current Flight Data Center

(FDC) NOTAMs, which are regulatory in nature, issued to

establish restrictions to ﬂ ight or to amend charts or published

instrument approach procedures (IAPs).

POH/AFM

The POH/AFM contain operating limitations, performance,

normal and emergency procedures, and a variety of other

operational information for the respective aircraft. Aircraft

manufacturers have done considerable testing to gather and

substantiate the information in the aircraft manual. Pilots should

refer to it for information relevant to a proposed ﬂ ight.

IFR Flight Plan

As speciﬁ ed in Title 14 of the Code of Federal Regulations

(14 CFR) part 91, no person may operate an aircraft in

controlled airspace under IFR unless that person has ﬁ led an

IFR ﬂ ight plan. Flight plans may be submitted to the nearest

AFSS or air trafﬁ c control tower (ATCT) either in person,

by telephone (1-800-WX-BRIEF), by computer (using the

direct user access terminal system (DUATS)), or by radio

if no other means are available. Pilots should ﬁ le IFR ﬂ ight

plans at least 30 minutes prior to estimated time of departure

to preclude possible delay in receiving a departure clearance

from ATC. The AIM provides guidance for completing

and ﬁ ling FAA Form 7233-1, Flight Plan. These forms are

available at ﬂ ight service stations (FSSs), and are generally

found in ﬂ ight planning rooms at airport terminal buildings.

[Figure 10-1]

Filing in Flight

IFR ﬂ ight plans may be ﬁ led from the air under various

conditions, including:

1. A ﬂ ight outside controlled airspace before proceeding

into IFR conditions in controlled airspace.

2. A VFR ﬂ ight expecting IFR weather conditions en

route in controlled airspace.

In either of these situations, the ﬂ ight plan may be ﬁ led with

the nearest AFSS or directly with the ARTCC. A pilot who

ﬁ les with the AFSS submits the information normally entered

during preflight filing, except for “point of departure,”

together with present position and altitude. AFSS then

relays this information to the ARTCC. The ARTCC will

then clear the pilot from present position or from a speciﬁ ed

navigation ﬁ x.

10-3

Figure 10-1. Flight Plan Form.

A pilot who ﬁ les directly with the ARTCC reports present

position and altitude, and submits only the flight plan

information normally relayed from the AFSS to the ARTCC.

Be aware that trafﬁ c saturation frequently prevents ARTCC

personnel from accepting ﬂ ight plans by radio. In such

cases, a pilot is advised to contact the nearest AFSS to ﬁ le

the ﬂ ight plan.

Cancelling IFR Flight Plans

An IFR ﬂ ight plan may be cancelled any time a pilot is

operating in VFR conditions outside Class A airspace by

stating “cancel my IFR ﬂ ight plan” to the controller or air-to-

ground station. After cancelling an IFR ﬂ ight plan, the pilot

should change to the appropriate air-to-ground frequency,

transponder code as directed, and VFR altitude/ﬂ ight level.

ATC separation and information services (including radar

services, where applicable) are discontinued when an IFR

ﬂ ight plan is cancelled. If VFR radar advisory service is

desired, a pilot must speciﬁ cally request it. Be aware that

other procedures may apply when cancelling an IFR ﬂ ight

plan within areas such as Class C or Class B airspace.

When operating on an IFR ﬂ ight plan to an airport with

an operating control tower, a flight plan is cancelled

automatically upon landing. If operating on an IFR ﬂ ight

plan to an airport without an operating control tower, the

pilot is responsible for cancelling the ﬂ ight plan. This can

be done by telephone after landing if there is no operating

FSS or other means of direct communications with ATC.

When there is no FSS or air-to-ground communications are

not possible below a certain altitude, a pilot may cancel an

IFR ﬂ ight plan while still airborne and able to communicate

with ATC by radio. If using this procedure, be certain the

remainder of the ﬂ ight can be conducted under VFR. It is

essential that IFR ﬂ ight plans be cancelled expeditiously. This

allows other IFR trafﬁ c to utilize the airspace.

Clearances

An ATC clearance allows an aircraft to proceed under

speciﬁ ed trafﬁ c conditions within controlled airspace for the

purpose of providing separation between known aircraft.

Examples

A ﬂ ight ﬁ led for a short distance at a relatively low altitude

in an area of low trafﬁ c density might receive a clearance

as follows:

“Cessna 1230 Alpha, cleared to Doeville airport direct,

cruise 5,000.”

10-4

The term “cruise” in this clearance means a pilot is authorized

to ﬂ y at any altitude from the minimum IFR altitude up to and

including 5,000 feet, and may level off at any altitude within

this block of airspace. A climb or descent within the block may

be made at the pilot’s discretion. However, once a pilot reports

leaving an altitude within the block, the pilot may not return to

that altitude without further ATC clearance.

When ATC issues a cruise clearance in conjunction with an

unpublished route, an appropriate crossing altitude will be

speciﬁ ed to ensure terrain clearance until the aircraft reaches a

ﬁ x, point, or route where the altitude information is available.

The crossing altitude ensures IFR obstruction clearance to

the point at which the aircraft enters a segment of a published

route or IAP.

Once a ﬂ ight plan is ﬁ led, ATC will issue the clearance with

appropriate instructions, such as the following:

“Cessna 1230 Alpha is cleared to Skyline airport via

the Crossville 055 radial, Victor 18, maintain 5,000.

Clearance void if not off by 1330.”

Or a more complex clearance, such as:

“Cessna 1230 Alpha is cleared to Wichita Mid-continent

airport via Victor 77, left turn after takeoff, proceed

direct to the Oklahoma City VORTAC. Hold west on

the Oklahoma City 277 radial, climb to 5,000 in holding

pattern before proceeding on course. Maintain 5,000 to

CASHION intersection. Climb to and maintain 7,000.

Departure control frequency will be 121.05, Squawk

0412.”

Clearance delivery may issue the following “abbreviated

clearance” which includes a departure procedure (DP):

“Cessna 1230 Alpha, cleared to La Guardia as ﬁ led,

RINGOES 8 departure Phillipsburg transition, maintain

8,000. Departure control frequency will be 120.4,

Squawk 0700.”

This clearance may be readily copied in shorthand as follows:

“CAF RNGO8 PSB M80 DPC 120.4 SQ 0700.”

The information contained in this DP clearance is abbreviated

using clearance shorthand (see appendix 1). The pilot should

know the locations of the speciﬁ ed navigation facilities, together

with the route and point-to-point time, before accepting the

clearance.

The DP enables a pilot to study and understand the details

of a departure before ﬁ ling an IFR ﬂ ight plan. It provides

the information necessary to set up communication and

navigation equipment and be ready for departure before

requesting an IFR clearance.

Once the clearance is accepted, a pilot is required to comply

with ATC instructions. A clearance different from that issued

may be requested if the pilot considers another course of action

more practicable or if aircraft equipment limitations or other

considerations make acceptance of the clearance inadvisable.

A pilot should also request clariﬁ cation or amendment, as

appropriate, any time a clearance is not fully understood

or considered unacceptable for safety of ﬂ ight. The pilot is

responsible for requesting an amended clearance if ATC issues

a clearance that would cause a pilot to deviate from a rule or

regulation or would place the aircraft in jeopardy.

Clearance Separations

ATC will provide the pilot on an IFR clearance with separation

from other IFR trafﬁ c. This separation is provided:

1. Vertically—by assignment of different altitudes.

2. Longitudinally—by controlling time separation between

aircraft on the same course.

3. Laterally—by assignment of different ﬂ ight paths.

4. By radar—including all of the above.

ATC does not provide separation for an aircraft operating:

1. Outside controlled airspace.

2. On an IFR clearance:

a) With “VFR-On-Top” authorized instead of a

speciﬁ c assigned altitude.

b) Specifying climb or descent in “VFR conditions.”

c) At any time in VFR conditions, since uncontrolled

VFR flights may be operating in the same

airspace.

In addition to heading and altitude assignments, ATC will

occasionally issue speed adjustments to maintain the required

separations. For example:

“Cessna 30 Alpha, slow to 100 knots.”

A pilot who receives speed adjustments is expected to maintain

that speed plus or minus 10 knots. If for any reason the pilot

is not able to accept a speed restriction, the pilot should advise

ATC.

At times, ATC may also employ visual separation techniques

to keep aircraft safely separated. A pilot who obtains visual

contact with another aircraft may be asked to maintain visual

separation or to follow the aircraft. For example:

10-5

“Cessna 30 Alpha, maintain visual separation with that

trafﬁ c, climb and maintain 7,000.”

The pilot’s acceptance of instructions to maintain visual

separation or to follow another aircraft is an acknowledgment

that the aircraft will be maneuvered as necessary, to maintain

safe separation. It is also an acknowledgment that the pilot

accepts the responsibility for wake turbulence avoidance.

In the absence of radar contact, ATC will rely on position

reports to assist in maintaining proper separation. Using the data

transmitted by the pilot, the controller follows the progress of

each ﬂ ight. ATC must correlate the pilots’ reports to provide

separation; therefore, the accuracy of each pilot’s report can

affect the progress and safety of every other aircraft operating

in the area on an IFR ﬂ ight plan.

Departure Procedures (DPs)

Instrument departure procedures are preplanned instrument

flight rule (IFR) procedures, which provide obstruction

clearance from the terminal area to the appropriate en route

structure and provide the pilot with a way to depart the airport

and transition to the en route structure safely. Pilots operating

under 14 CFR part 91 are strongly encouraged to ﬁ le and ﬂ y a

DP when one is available. [Figure 10-2]

There are two types of DPs, Obstacle Departure Procedures

(ODP), printed either textually or graphically, and Standard

Instrument Departures (SID), always printed graphically. All

DPs, either textual or graphic, may be designed using either

conventional or RNAV criteria. RNAV procedures will have

RNAV printed in the title, e.g., SHEAD TWO DEPARTURE

(RNAV).

Obstacle Departure Procedures (ODP)

ODPs provide obstruction clearance via the least onerous route

from the terminal area to the appropriate en route structure. ODPs

are recommended for obstruction clearance and may be ﬂ own

without ATC clearance unless an alternate departure procedure

(SID or radar vector) has been speciﬁ cally assigned by ATC.

Graphic ODPs will have (OBSTACLE) printed in the procedure

title, e.g., GEYSR THREE DEPARTURE (OBSTACLE),

CROWN ONE DEPARTURE (RNAV)(OBSTACLE).

Standard Instrument Departures

Standard Instrument Departures (SID) are air trafﬁ c control

(ATC) procedures printed for pilot/controller use in graphic

form to provide obstruction clearance and a transition from

the terminal area to the appropriate en route structure. SIDs

are primarily designed for system enhancement and to reduce

pilot/controller workload. ATC clearance must be received

prior to ﬂ ying a SID.

ODPs are found in section C of each booklet published

regionally by the NACG, TPP, along with “IFR Take-off

Minimums” while SIDs are collocated with the approach

procedures for the applicable airport. Additional information

on the development of DPs can be found in paragraph 5-2-7

of the AIM. However, the following points are important

to remember.

1. The pilot of IFR aircraft operating from locations

where DP procedures are effective may expect an ATC

clearance containing a DP. The use of a DP requires

pilot possession of at least the textual description of the

approved DP.

2. If a pilot does not possess a preprinted DP or for any other

reason does not wish to use a DP, he or she is expected

to advise ATC. Notiﬁ cation may be accomplished by

ﬁ ling “NO DP” in the remarks section of the ﬁ led ﬂ ight

plan, or by advising ATC.

3. If a DP is accepted in a clearance, a pilot must comply

with it.

Radar Controlled Departures

On IFR departures from airports in congested areas, a pilot

will normally receive navigational guidance from departure

control by radar vector. When a departure is to be vectored

immediately following takeoff, the pilot will be advised before

takeoff of the initial heading to be ﬂ own. This information is

vital in the event of a loss of two-way radio communications

during departure.

The radar departure is normally simple. Following takeoff,

contact departure control on the assigned frequency when

advised to do so by the control tower. At this time departure

control veriﬁ es radar contact, and gives headings, altitude, and

climb instructions to move an aircraft quickly and safely out of

the terminal area. A pilot is expected to ﬂ y the assigned headings

and altitudes until informed by the controller of the aircraft’s

position with respect to the route given in the clearance, whom

to contact next, and to “resume own navigation.”

Departure control will provide vectors to either a navigation

facility, or an en route position appropriate to the departure

clearance, or transfer to another controller with further radar

surveillance capabilities. [Figure 10-2]

A radar controlled departure does not relieve the pilot of

responsibilities as pilot-in-command. Be prepared before

takeoff to conduct navigation according to the ATC clearance,

with navigation receivers checked and properly tuned. While

under radar control, monitor instruments to ensure continuous

orientation to the route speciﬁ ed in the clearance, and record

the time over designated checkpoints.

10-6

Figure 10-2. Departure Procedure (DP).

10-7

Position Reports

Position reports are required over each compulsory reporting

point (shown on the chart as a solid triangle) along the route

being ﬂ own regardless of altitude, including those with

a VFR-on-top clearance. Along direct routes, reports are

required of all IFR ﬂ ights over each point used to deﬁ ne

the route of ﬂ ight. Reports at reporting points (shown as an

open triangle) are made only when requested by ATC. A

pilot should discontinue position reporting over designated

reporting points when informed by ATC that the aircraft

is in “RADAR CONTACT.” Position reporting should be

resumed when ATC advises “RADAR CONTACT LOST”

or “RADAR SERVICE TERMINATED.”

Position reports should include the following items:

1. Identiﬁ cation

2. Position

3. Time

4. Altitude or ﬂ ight level (include actual altitude or ﬂ ight

level when operating on a clearance specifying VFR-

on-top)

5. Type of ﬂ ight plan (not required in IFR position reports

made directly to ARTCCs or approach control)

6. ETA and name of next reporting point

7. The name only of the next succeeding reporting point

along the route of ﬂ ight

8. Pertinent remarks

En route position reports are submitted normally to

the ARTCC controllers via direct controller-to-pilot

communications channels, using the appropriate ARTCC

frequencies listed on the en route chart.

Whenever an initial contact with a controller is to be followed

by a position report, the name of the reporting point should

be included in the call-up. This alerts the controller that such

information is forthcoming. For example:

“Atlanta Center, Cessna 1230 Alpha at JAILS

intersection.”

“Cessna 1230 Alpha Atlanta Center.”

“Atlanta Center, Cessna 1230 Alpha at JAILS

intersection, 5,000, estimating Monroeville at

1730.”

Additional Reports

In addition to required position reports, the following reports

should be made to ATC without a speciﬁ c request.

Departures From Airports Without an Operating

Control Tower

When departing from airports that have neither an operating

tower nor an FSS, a pilot should telephone the ﬂ ight plan to the

nearest ATC facility at least 30 minutes before the estimated

departure time. If weather conditions permit, depart VFR and

request IFR clearance as soon as radio contact is established

with ATC.

If weather conditions make it undesirable to ﬂ y VFR, telephone

clearance request. In this case, the controller would probably

issue a short-range clearance pending establishment of radio

contact, and might restrict the departure time to a certain period.

For example:

“Clearance void if not off by 0900.”

This would authorize departure within the allotted period and

permit a pilot to proceed in accordance with the clearance. In

the absence of any speciﬁ c departure instructions, a pilot would

be expected to proceed on course via the most direct route.

En Route Procedures

Procedures en route will vary according to the proposed route,

the trafﬁ c environment, and the ATC facilities controlling

the ﬂ ight. Some IFR ﬂ ights are under radar surveillance and

controlled from departure to arrival, and others rely entirely

on pilot navigation.

Where ATC has no jurisdiction, it does not issue an IFR

clearance. It has no control over the ﬂ ight, nor does the pilot

have any assurance of separation from other trafﬁ c.

ATC Reports

All pilots are required to report unforecast weather conditions

or other information related to safety of ﬂ ight to ATC. The

pilot-in-command of each aircraft operated in controlled

airspace under IFR shall report as soon as practical to ATC any

malfunctions of navigational, approach, or communication

equipment occurring in ﬂ ight:

1. Loss of VOR, tactical air navigation (TACAN) or

automatic direction ﬁ nder (ADF) receiver capability.

2. Complete or partial loss of instrument landing system

(ILS) receiver capability.

3. Impairment of air-to-ground communications

capability.

The pilot-in-command shall include within the report

(1) Aircraft identiﬁ cation, (2) Equipment affected, (3) Degree

to which the pilot to operate under IFR within the ATC

system is impaired, and (4) Nature and extent of assistance

desired from ATC.

10-8

Planning the Descent and Approach

ATC arrival procedures and ﬂ ight deck workload are affected

by weather conditions, trafﬁ c density, aircraft equipment,

and radar availability.

When landing at an airport with approach control services

and where two or more IAPs are published, information on

the type of approach to expect will be provided in advance of

arrival or vectors will be provided to a visual approach. This

information will be broadcast either on automated terminal

information service (ATIS) or by a controller. It will not be

furnished when the visibility is 3 miles or more and the ceiling

is at or above the highest initial approach altitude established

for any low altitude IAP for the airport.

The purpose of this information is to help the pilot plan arrival

actions; however, it is not an ATC clearance or commitment

and is subject to change. Fluctuating weather, shifting

winds, blocked runway, etc., are conditions that may result

in changes to the approach information previously received.

It is important for a pilot to advise ATC immediately if he

or she is unable to execute the approach or prefers another

type of approach.

If the destination is an airport without an operating control

tower, and has automated weather data with broadcast

capability, the pilot should monitor the automated surface

observing system/automated weather observing system

(ASOS/AWOS) frequency to ascertain the current weather for

the airport. ATC should be advised that weather information

has been received and what the pilot’s intentions are.

When the approach to be executed has been determined, the

pilot should plan for and request a descent to the appropriate

altitude prior to the initial approach ﬁ x (IAF) or transition

route depicted on the IAP. When ﬂ ying the transition route,

a pilot should maintain the last assigned altitude until ATC

gives the instructions “cleared for the approach.” Lower

altitudes can be requested to bring the transition route

altitude closer to the required altitude at the initial approach

ﬁ x. When ATC uses the phrase “at pilot’s discretion” in the

altitude information of a clearance, the pilot has the option

to start a descent at any rate, and may level off temporarily

at any intermediate altitude. However, once an altitude has

been vacated, return to that altitude is not authorized without

a clearance. When ATC has not used the term “at pilot’s

discretion” nor imposed any descent restrictions, initiate

descent promptly upon acknowledgment of the clearance.

Descend at an optimum rate (consistent with the operating

characteristics of the aircraft) to 1,000 feet above the assigned

altitude. Then attempt to descend at a rate of between 500 and

1. At all times:

a) When vacating any previously assigned altitude

or ﬂ ight level for a newly assigned altitude or

ﬂ ight level

b) When an altitude change will be made if operating

on a clearance specifying VFR-on-top

c) When unable to climb/descend at a rate of at least

500 feet per minute (fpm)

d) When an approach has been missed (Request

clearance for specific action (to alternative

airport, another approach, etc.))

e) Change in average true airspeed (at cruising

altitude) when it varies by 5 percent or ten knots

(whichever is greater) from that ﬁ led in the ﬂ ight

plan

f) The time and altitude upon reaching a holding ﬁ x

or point to which cleared

g) When leaving any assigned holding ﬁ x or point

NOTE - The reports in (f) and (g) may be omitted

by pilots of aircraft involved in instrument

training at military terminal area facilities when

radar service is being provided.

h) Any loss in controlled airspace of VOR,

TACAN, ADF, low frequency navigation

receiver capability, GPS anomalies while using

installed IFR-certified GPS/GNSS receivers,

complete or partial loss of ILS receiver capability,

or impairment of air/ground communications

capability. Reports should include aircraft

identification, equipment affected, degree to

which the capability to operate under IFR in

the ATC system is impaired, and the nature and

extent of assistance desired from ATC.

i) Any information relating to the safety of ﬂ ight.

2. When not in radar contact:

a) When leaving the ﬁ nal approach ﬁ x inbound

on ﬁ nal approach (nonprecision approach), or

when leaving the outer marker or ﬁ x used in lieu

of the outer marker inbound on ﬁ nal approach

(precision approach).

b) A corrected estimate at any time it becomes

apparent that an estimate as previously submitted

is in error in excess of 3 minutes.

Any pilot who encounters weather conditions that have not

been forecast, or hazardous conditions which have been

forecast, is expected to forward a report of such weather

to ATC.

10-9

1,500 fpm until the assigned altitude is reached. If at anytime

a pilot is unable to maintain a descent rate of at least 500 fpm,

advise ATC. Also advise ATC if it is necessary to level off

at an intermediate altitude during descent. An exception to

this is when leveling off at 10,000 feet mean sea level (MSL)

on descent, or 2,500 feet above airport elevation (prior to

entering a Class B, Class C, or Class D surface area) when

required for speed reduction.

Standard Terminal Arrival Routes (STARs)

Standard terminal arrival routes (as described in Chapter

8) have been established to simplify clearance delivery

procedures for arriving aircraft at certain areas having high

density trafﬁ c. A STAR serves a purpose parallel to that of a

DP for departing trafﬁ c. [Figure 10-3] The following points

regarding STARs are important to remember:

1. All STARs are contained in the TPP, along with the

IAP charts for the destination airport. The AIM also

describes STAR procedures.

2. If the destination is a location for which STARs

have been published, a pilot may be issued a

clearance containing a STAR whenever ATC deems

it appropriate. To accept the clearance, a pilot must

possess at least the approved textual description.

3. It is the pilot’s responsibility to either accept or refuse

an issued STAR. If a STAR will not or cannot be used,

advise ATC by placing “NO STAR” in the remarks

section of the ﬁ led ﬂ ight plan or by advising ATC.

4. If a STAR is accepted in a clearance, compliance is

mandatory.

Substitutes for Inoperative or Unusable

Components

The basic ground components of an ILS are the localizer,

glide slope, outer marker, middle marker, and inner marker

(when installed). A compass locator or precision radar may

be substituted for the outer or middle marker. Distance

measuring equipment (DME), VOR, or nondirectional beacon

(NDB) ﬁ xes authorized in the standard IAP or surveillance

radar may be substituted for the outer marker.

Additionally, IFR-certiﬁ ed global positioning system (GPS)

equipment, operated in accordance with Advisory Circular

(AC) 90-94, Guidelines for Using Global Positioning System

Equipment for IFR En Route and Terminal Operations and

for Nonprecision Instrument Approaches in the United

States National Airspace System, may be substituted for

ADF and DME equipment, except when ﬂ ying NDB IAP.

Speciﬁ cally, GPS can be substituted for ADF and DME

equipment when:

1. Flying a DME arc;

2. Navigating TO/FROM an NDB;

3. Determining the aircraft position over an NDB;

4. Determining the aircraft position over a ﬁ x made up

of a crossing NDB bearing;

5. Holding over an NDB;

6. Determining aircraft position over a DME ﬁ x.

Holding Procedures

Depending upon trafﬁ c and weather conditions, holding may

be required. Holding is a predetermined maneuver which

keeps aircraft within a speciﬁ ed airspace while awaiting

further clearance from ATC. A standard holding pattern

uses right turns, and a nonstandard holding pattern uses left

turns. The ATC clearance will always specify left turns when

a nonstandard pattern is to be ﬂ own.

Standard Holding Pattern (No Wind)

In a standard holding pattern with no winds, [Figure 10-4] the

aircraft follows the speciﬁ ed course inbound to the holding

ﬁ x, turns 180° to the right, ﬂ ies a parallel straight course

outbound for 1 minute, turns 180° to the right, and ﬂ ies the

inbound course to the ﬁ x.

Standard Holding Pattern (With Wind)

A standard symmetrical holding pattern cannot be ﬂ own

when winds exist. In those situations, the pilot is expected

to:

1. Compensate for the effect of a known wind except

when turning.

2. Adjust outbound timing to achieve a 1-minute (1-1/2

minutes above 14,000 feet) inbound leg.

Figure 10-5 illustrates the holding track followed with a left

crosswind. The effect of wind is counteracted by applying

drift corrections to the inbound and outbound legs and by

applying time allowances to the outbound leg.

Holding Instructions

If an aircraft arrives at a clearance limit before receiving

clearance beyond the ﬁ x, ATC expects the pilot to maintain

the last assigned altitude and begin holding in accordance

with the charted holding pattern. If no holding pattern is

charted and holding instructions have not been issued, enter

a standard holding pattern on the course on which the aircraft

approached the ﬁ x and request further clearance as soon

as possible. Normally, when no delay is anticipated, ATC

will issue holding instructions at least 5 minutes before the

10-10

Figure 10-3. Standard Terminal Arrival Route (STAR).

10-11

Figure 10-4. Standard Holding Pattern—No Wind.

Figure 10-5. Drift Correction in Holding Pattern.

estimated arrival at the ﬁ x. Where a holding pattern is not

charted, the ATC clearance will specify the following:

1. Direction of holding from the ﬁ x in terms of the eight

cardinal compass points (N, NE, E, SE, etc.)

2. Holding ﬁ x (the ﬁ x may be omitted if included at the

beginning of the transmission as the clearance limit)

3. Radial, course, bearing, airway, or route on which the

aircraft is to hold.

4. Leg length in miles if DME or area navigation

(RNAV) is to be used (leg length will be speciﬁ ed in

minutes on pilot request or if the controller considers

it necessary).

5. Direction of turn, if left turns are to be made, because

the pilot requests or the controller considers it

necessary.

6. Time to expect-further-clearance (EFC) and any

pertinent additional delay information.

ATC instructions will also be issued whenever:

1. It is determined that a delay will exceed 1 hour.

2. A revised EFC is necessary.

3. In a terminal area having a number of navigation

aids and approach procedures, a clearance limit may

not indicate clearly which approach procedures will

be used. On initial contact, or as soon as possible

thereafter, approach control will advise the pilot of

the type of approach to expect.

4. Ceiling and/or visibility is reported as being at or

below the highest “circling minimums” established

for the airport concerned. ATC will transmit a report

of current weather conditions and subsequent changes,

as necessary.

5. An aircraft is holding while awaiting approach

clearance, and the pilot advises ATC that reported

weather conditions are below minimums applicable

to the operation. In this event, ATC will issue suitable

instructions to aircraft desiring either to continue

holding while awaiting weather improvement or

proceed to another airport.

Standard Entry Procedures

The entry procedures given in the AIM evolved from

extensive experimentation under a wide range of operational

conditions. The standardized procedures should be followed

to ensure that an aircraft remains within the boundaries of

the prescribed holding airspace.

When a speed reduction is required, start the reduction when

3 minutes or less from the holding ﬁ x. Cross the holding ﬁ x

initially at or below the maximum holding airspeed (MHA).

The purpose of the speed reduction is to prevent overshooting

the holding airspace limits, especially at locations where

adjacent holding patterns are close together.

All aircraft may hold at the following altitudes and maximum

holding airspeeds:

Altitude Mean Sea Level (MSL) Airspeed (KIAS)

Up to 6,000 feet 200

6,001 – 14,000 feet 230

14,001 feet and above 265

10-12

Figure 10-6. Holding Pattern Entry Procedures.

The following are exceptions to the maximum holding

airspeeds:

1. Holding patterns from 6,001 to 14,000 feet may

be restricted to a maximum airspeed of 210 knots

indicated airspeed (KIAS). This nonstandard pattern

is depicted by an icon.

2. Holding patterns may be restricted to a maximum

airspeed of 175 KIAS. This nonstandard pattern is

depicted by an icon. Holding patterns restricted to

175 KIAS are generally found on IAPs applicable to

category A and B aircraft only.

3. Holding patterns at Air Force airﬁ elds only—310

KIAS maximum, unless otherwise depicted.

4. Holding patterns at Navy airﬁ elds only—230 KIAS

maximum, unless otherwise depicted.

5. The pilot of an aircraft unable to comply with

maximum airspeed restrictions should notify ATC.

While other entry procedures may enable the aircraft to

enter the holding pattern and remain within protected

airspace, the parallel, teardrop, and direct entries are the

procedures for entry and holding recommended by the FAA.

Additionally, paragraph 5-3-7 in the AIM should be reviewed.

[Figure 10-6]

1. Parallel Procedure. When approaching the holding

ﬁ x from anywhere in sector (a), the parallel entry

procedure would be to turn to a heading to parallel the

holding course outbound on the nonholding side for

1 minute, turn in the direction of the holding pattern

through more than 180°, and return to the holding ﬁ x

or intercept the holding course inbound.

2. Teardrop Procedure. When approaching the holding

ﬁ x from anywhere in sector (b), the teardrop entry

procedure would be to ﬂ y to the ﬁ x, turn outbound to

a heading for a 30° teardrop entry within the pattern

(on the holding side) for a period of 1 minute, then

turn in the direction of the holding pattern to intercept

the inbound holding course.

3. Direct Entry Procedure. When approaching the

holding ﬁ x from anywhere in sector (c), the direct

entry procedure would be to ﬂ y directly to the ﬁ x and

turn to follow the holding pattern.

A pilot should make all turns during entry and while holding at:

1. 3° per second, or

2. 30° bank angle, or

3. A bank angle provided by a ﬂ ight director system.

Time Factors

The holding pattern entry time reported to ATC is the initial

time of arrival over the ﬁ x. Upon entering a holding pattern,

the initial outbound leg is ﬂ own for 1 minute at or below

14,000 feet MSL, and for 1-1/2 minutes above 14,000

feet MSL. Timing for subsequent outbound legs should be

adjusted as necessary to achieve proper inbound leg time.

The pilot should begin outbound timing over or abeam the

ﬁ x, whichever occurs later. If the abeam position cannot

be determined, start timing when the turn to outbound is

completed. [Figure 10-7]

Time leaving the holding ﬁ x must be known to ATC before

succeeding aircraft can be cleared to the vacated airspace.

Leave the holding ﬁ x:

1. When ATC issues either further clearance en route or

approach clearance;

2. As prescribed in 14 CFR part 91 (for IFR operations;

two-way radio communications failure, and

responsibility and authority of the pilot-in-command);

3. After the IFR ﬂ ight plan has been cancelled, if the

aircraft is holding in VFR conditions.

DME Holding

The same entry and holding procedures apply to DME

holding, but distances (nautical miles) are used instead of

time values. The length of the outbound leg will be speciﬁ ed

by the controller, and the end of this leg is determined by

the DME readout.

Approaches

Compliance With Published Standard Instrument

Approach Procedures

Compliance with the approach procedures shown on the

approach charts provides necessary navigation guidance

information for alignment with the ﬁ nal approach courses,

10-13

Figure 10-7. Holding—Outbound Timing.

as well as obstruction clearance. Under certain conditions, a

course reversal maneuver or procedure turn may be necessary.

However, this procedure is not authorized when:

1. The symbol “NoPT” appears on the approach course

on the plan view of the approach chart.

2. Radar vectoring is provided to the final approach

course.

3. A holding pattern is published in lieu of a procedure

turn.

4. Executing a timed approach from a holding ﬁ x.

5. Otherwise directed by ATC.

Instrument Approaches to Civil Airports

Unless otherwise authorized, when an instrument letdown to

an airport is necessary, the pilot should use a standard IAP

prescribed for that airport. IAPs are depicted on IAP charts

and are found in the TPP.

ATC approach procedures depend upon the facilities available

at the terminal area, the type of instrument approach executed,

and the existing weather conditions. The ATC facilities,

navigation aids (NAVAIDs), and associated frequencies

appropriate to each standard instrument approach are given

on the approach chart. Individual charts are published for

standard approach procedures associated with the following

types of facilities:

1. Nondirectional beacon (NDB)

2. Very-high frequency omnirange (VOR)

3. Very-high frequency omnirange with distance

measuring equipment (VORTAC or VOR/DME)

4. Localizer (LOC)

5. Instrument landing system (ILS)

6. Localizer-type directional aid (LDA)

7. Simpliﬁ ed directional facility (SDF)

8. Area navigation (RNAV)

9. Global positioning system (GPS)

An IAP can be ﬂ own in one of two ways: as a full approach

or with the assistance of radar vectors. When the IAP is ﬂ own

as a full approach, pilots conduct their own navigation using

the routes and altitudes depicted on the instrument approach

chart. A full approach allows the pilot to transition from

the en route phase, to the instrument approach, and then to

a landing with minimal assistance from ATC. This type of

procedure may be requested by the pilot but is most often

used in areas without radar coverage. A full approach also

provides the pilot with a means of completing an instrument

approach in the event of a communications failure.

When an approach is ﬂ own with the assistance of radar vectors,

ATC provides guidance in the form of headings and altitudes

which position the aircraft to intercept the ﬁ nal approach.

From this point, the pilot resumes navigation, intercepts the

ﬁ nal approach course, and completes the approach using the

IAP chart. This is often a more expedient method of ﬂ ying

the approach, as opposed to the full approach, and allows

ATC to sequence arriving trafﬁ c. A pilot operating in radar

contact can generally expect the assistance of radar vectors

to the ﬁ nal approach course.

10-14

Approach to Airport Without an Operating Control

Tower

Figure 10-8 shows an approach procedure at an airport

without an operating control tower. When approaching

such a facility, the pilot should monitor the AWOS/ASOS

if available for the latest weather conditions. When direct

communication between the pilot and controller is no longer

required, the ARTCC or approach controller will issue a

clearance for an instrument approach and advise “change to

advisory frequency approved.” When the aircraft arrives on

a “cruise” clearance, ATC will not issue further clearance

for approach and landing.

If an approach clearance is required, ATC will authorize

the pilot to execute his or her choice of standard instrument

approach (if more than one is published for the airport)

with the phrase “Cleared for the approach” and the

communications frequency change required, if any. From

this point on, there will be no contact with ATC. The pilot

is responsible for closing the IFR ﬂ ight plan before landing,

if in VFR conditions, or by telephone after landing.

Unless otherwise authorized by ATC, a pilot is expected to

execute the complete IAP shown on the chart.

Approach to Airport With an Operating Tower,

With No Approach Control

When an aircraft approaches an airport with an operating

control tower, but no approach control, ATC will issue

a clearance to an approach/outer ﬁ x with the appropriate

information and instructions as follows:

1. Name of the ﬁ x

2. Altitude to be maintained

3. Holding information and expected approach clearance

time, if appropriate

4. Instructions regarding further communications,

including:

a) facility to be contacted

b) time and place of contact

c) frequency/ies to be used

If ATIS is available, a pilot should monitor that frequency

for information such as ceiling, visibility, wind direction and

velocity, altimeter setting, instrument approach, and runways

in use prior to initial radio contact with the tower. If ATIS is

not available, ATC will provide weather information from

the nearest reporting station.

Approach to an Airport With an Operating Tower,

With an Approach Control

Where radar is approved for approach control service, it is

used to provide vectors in conjunction with published IAPs.

Radar vectors can provide course guidance and expedite

trafﬁ c to the ﬁ nal approach course of any established IAP.

Figure 10-9 shows an IAP chart with maximum ATC

facilities available.

Approach control facilities that provide this radar service

operate in the following manner:

1. Arriving aircraft are either cleared to an outer ﬁ x most

appropriate to the route being ﬂ own with vertical

separation and, if required, given holding information;

or,

2. When radar hand-offs are effected between ARTCC

and approach control, or between two approach

control facilities, aircraft are cleared to the airport, or

to a ﬁ x so located that the hand-off will be completed

prior to the time the aircraft reaches the ﬁ x.

a) When the radar hand-offs are utilized, successive

arriving ﬂ ights may be handed off to approach

control with radar separation in lieu of vertical

separation.

b) After hand-off to approach control, an aircraft

is vectored to the appropriate ﬁ nal approach

course.

3. Radar vectors and altitude/ﬂ ight levels are issued

as required for spacing and separating aircraft; do

not deviate from the headings issued by approach

control.

4. Aircraft are normally informed when it becomes

necessary to be vectored across the ﬁ nal approach

course for spacing or other reasons. If approach

course crossing is imminent and the pilot has not

been informed that the aircraft will be vectored across

the ﬁ nal approach course, the pilot should query the

controller. The pilot is not expected to turn inbound on

the ﬁ nal approach course unless an approach clearance

has been issued. This clearance is normally issued with

the ﬁ nal vector for interception of the ﬁ nal approach

course, and the vector enables the pilot to establish the

aircraft on the ﬁ nal approach course prior to reaching

the ﬁ nal approach ﬁ x.

5. Once the aircraft is established inbound on the ﬁ nal

approach course, radar separation is maintained with

other aircraft, and the pilot is expected to complete

the approach using the NAVAID designated in the

clearance (ILS, VOR, NDB, GPS, etc.) as the primary

means of navigation.

10-15

Figure 10-8. Monroeville, AL (MVC) VOR or GPS Rwy 3 Approach: An Approach Procedure at an Airport Without an Operating

Control Tower.

10-16

Figure 10-9. Gulfport, MS (GPT) ILS or LOC Rwy 14 Approach: An Instrument Procedure Chart With Maximum ATC Facilities

Available.

10-17

Figure 10-10. Radar Instrument Approach Minimums for Troy, AL.

6. After passing the ﬁ nal approach ﬁ x inbound, the

pilot is expected to proceed direct to the airport and

complete the approach, or to execute the published

missed approach procedure.

7. Radar service is automatically terminated when the

landing is completed or when the pilot is instructed to

change to advisory frequency at uncontrolled airports,

whichever occurs ﬁ rst.

Radar Approaches

With a radar approach, the pilot receives course and altitude

guidance from a controller who monitors the progress of the

ﬂ ight with radar. This is an option should the pilot experience

an emergency or distress situation.

The only airborne radio equipment required for radar

approaches is a functioning radio transmitter and receiver.

The radar controller vectors the aircraft to align it with the

runway centerline. The controller continues the vectors to

keep the aircraft on course until the pilot can complete the

approach and landing by visual reference to the surface.

There are two types of radar approaches: Precision (PAR)

and Surveillance (ASR).

A radar approach may be given to any aircraft upon request

and may be offered to pilots of aircraft in distress or to expedite

trafﬁ c; however, an ASR might not be approved unless

there is an ATC operational requirement, or in an unusual

or emergency situation. Acceptance of a PAR or ASR by a

pilot does not waive the prescribed weather minimums for the

airport or for the particular aircraft operator concerned. The

decision to make a radar approach when the reported weather

is below the established minimums rests with the pilot.

PAR and ASR minimums are published on separate pages

in the FAA Terminal Procedures Publication (TPP).

Figure 10-10.

Precision Approach (PAR) is one in which a controller

provides highly accurate navigational guidance in azimuth

and elevation to a pilot.

The controller gives the pilot headings to ﬂ y that direct the

aircraft to, and keep the aircraft aligned with, the extended

centerline of the landing runway. The pilot is told to anticipate

glide path interception approximately 10 to 30 seconds before

it occurs and when to start descent. The published decision

height (DH) will be given only if the pilot requests it. If

the aircraft is observed to deviate above or below the glide

path, the pilot is given the relative amount of deviation by

use of terms “slightly” or “well” and is expected to adjust

the aircraft’s rate of descent/ascent to return to the glide

path. Trend information is also issued with respect to the

elevation of the aircraft and may be modiﬁ ed by the terms

“rapidly” and “slowly”; e.g., “well above glide path, coming

down rapidly.”

Range from touchdown is given at least once each mile. If

an aircraft is observed by the controller to proceed outside

of speciﬁ ed safety zone limits in azimuth and/or elevation

and continue to operate outside these prescribed limits, the

pilot will be directed to execute a missed approach or to ﬂ y a

10-18

speciﬁ ed course unless the pilot has the runway environment

(runway, approach lights, etc.) in sight. Navigational

guidance in azimuth and elevation is provided to the pilot

until the aircraft reaches the published DH. Advisory course

and glide path information is furnished by the controller

until the aircraft passes over the landing threshold. At this

point the pilot is advised of any deviation from the runway

centerline. Radar service is automatically terminated upon

completion of the approach.

Surveillance Approach (ASR) is one in which a controller

provides navigational guidance in azimuth only.

The controller furnishes the pilot with headings to ﬂ y to

align the aircraft with the extended centerline of the landing

runway. Since the radar information used for a surveillance

approach is considerably less precise than that used for a

precision approach, the accuracy of the approach will not

be as great and higher minimums will apply. Guidance in

elevation is not possible but the pilot will be advised when to

commence descent to the Minimum Descent Altitude (MDA)

or, if appropriate, to an intermediate step-down ﬁ x Minimum

Crossing Altitude and subsequently to the prescribed MDA.

In addition, the pilot will be advised of the location of the

Missed Approach Point (MAP) prescribed for the procedure

and the aircraft’s position each mile on ﬁ nal from the runway,

airport or heliport or MAP, as appropriate.

If requested by the pilot, recommended altitudes will be

issued at each mile, based on the descent gradient established

for the procedure, down to the last mile that is at or above

the MDA. Normally, navigational guidance will be provided

until the aircraft reaches the MAP.

Radar service is automatically terminated at the completion

of a radar approach.

No-Gyro Approach is available to a pilot under radar control

who experiences circumstances wherein the directional gyro or

other stabilized compass is inoperative or inaccurate. When this

occurs, the pilot should so advise ATC and request a no-gyro

vector or approach. The pilot of an aircraft not equipped with a

directional gyro or other stabilized compass who desires radar

handling may also request a no-gyro vector or approach. The

pilot should make all turns at standard rate and should execute

the turn immediately upon receipt of instructions. For example,

“TURN RIGHT,” “STOP TURN.” When a surveillance or

precision approach is made, the pilot will be advised after the

aircraft has been turned onto ﬁ nal approach to make turns at

half standard rate.

Radar Monitoring of Instrument Approaches

PAR facilities operated by the FAA and the military services

at some joint-use (civil and military) and military installations

monitor aircraft on instrument approaches and issue radar

advisories to the pilot when weather is below VFR minimums

(1,000 and 3), at night, or when requested by a pilot. This

service is provided only when the PAR Final Approach

Course coincides with the ﬁ nal approach of the navigational

aid and only during the operational hours of the PAR. The

radar advisories serve only as a secondary aid since the pilot

has selected the navigational aid as the primary aid for the

approach.

Prior to starting ﬁ nal approach, the pilot will be advised of

the frequency on which the advisories will be transmitted.

If, for any reason, radar advisories cannot be furnished, the

pilot will be so advised.

Advisory information, derived from radar observations,

includes information on:

1. Passing the ﬁ nal approach ﬁ x inbound (nonprecision

approach) or passing the outer marker or ﬁ x used

in lieu of the outer marker inbound (precision

approach).

2. Trend advisories with respect to elevation and/or

azimuth radar position and movement will be

provided.

3. If, after repeated advisories, the aircraft proceeds

outside the PAR safety limit or if a radical deviation is

observed, the pilot will be advised to execute a missed

approach unless the prescribed visual reference with

the surface is established.

Radar service is automatically terminated upon completion

of the approach. [Figure 10-11]

Timed Approaches From a Holding Fix

Timed approaches from a holding ﬁ x are conducted when

many aircraft are waiting for an approach clearance. Although

the controller will not speciﬁ cally state “timed approaches

are in progress,” the assigning of a time to depart the FAF

inbound (nonprecision approach), or the outer marker or

ﬁ x used in lieu of the outer marker inbound (precision

approach), indicates that timed approach procedures are

being utilized.

10-19

Figure 10-11. ILS RWY 7 Troy, AL.

10-20

In lieu of holding, the controller may use radar vectors to the

ﬁ nal approach course to establish a distance between aircraft

that will ensure the appropriate time sequence between the

FAF and outer marker, or ﬁ x used in lieu of the outer marker

and the airport. Each pilot in the approach sequence will

be given advance notice of the time they should leave the

holding point on approach to the airport. When a time to

leave the holding point is received, the pilot should adjust

the ﬂ ight path in order to leave the ﬁ x as closely as possible

to the designated time.

Timed approaches may be conducted when the following

conditions are met:

1. A control tower is in operation at the airport where

the approaches are conducted.

2. Direct communications are maintained between the

pilot and the Center or approach controller until the

pilot is instructed to contact the tower.

3. If more than one missed approach procedure is

available, none require a course reversal.

4. If only one missed approach procedure is available,

the following conditions are met:

a) Course reversal is not required; and

b) Reported ceiling and visibility are equal to or

greater than the highest prescribed circling

minimums for the IAP.

5. When cleared for the approach, pilots should not

execute a procedure turn.

Approaches to Parallel Runways

Procedures permit ILS instrument approach operations to dual

or triple parallel runway conﬁ gurations. A parallel approach

is an ATC procedure that permits parallel ILS approach to

airports with parallel runways separated by at least 2,500

feet between centerlines. Wherever parallel approaches

are in progress, pilots are informed that approaches to both

runways are in use.

Simultaneous approaches are permitted to runways:

1. With centerlines separated by 4,300 to 9,000 feet;

2. That are equipped with ﬁ nal monitor controllers;

3. That require radar monitoring to ensure separation

between aircraft on the adjacent parallel approach

course.

The approach procedure chart will include the note

“simultaneous approaches authorized RWYS 14L and 14R,”

identifying the appropriate runways. When advised that

simultaneous parallel approaches are in progress, pilots must

advise approach control immediately of malfunctioning or

inoperative components.

Parallel approach operations demand heightened pilot

situational awareness. The close proximity of adjacent

aircraft conducting simultaneous parallel approaches

mandates strict compliance with all ATC clearances and

approach procedures. Pilots should pay particular attention

to the following approach chart information: name and

number of the approach, localizer frequency, inbound course,

glide slope intercept altitude, DA/DH, missed approach

instructions, special notes/procedures, and the assigned

runway location and proximity to adjacent runways. Pilots

also need to exercise strict radio discipline, which includes

continuous monitoring of communications and the avoidance

of lengthy, unnecessary radio transmissions.

Side-Step Maneuver

ATC may authorize a side-step maneuver to either one of

two parallel runways that are separated by 1,200 feet or less,

followed by a straight-in landing on the adjacent runway.

Aircraft executing a side-step maneuver will be cleared

for a speciﬁ ed nonprecision approach and landing on the

adjacent parallel runway. For example, “Cleared ILS runway

7 left approach, side-step to runway 7 right.” The pilot is

expected to commence the side-step maneuver as soon as

possible after the runway or runway environment is in sight.

Landing minimums to the adjacent runway will be based on

nonprecision criteria and therefore higher than the precision

minimums to the primary runway, but will normally be lower

than the published circling minimums.

Circling Approaches

Landing minimums listed on the approach chart under

“CIRCLING” apply when it is necessary to circle the airport,

maneuver for landing, or when no straight-in minimums are

speciﬁ ed on the approach chart. [Figure 10-11]

The circling minimums published on the instrument approach

chart provide a minimum of 300 feet of obstacle clearance in

the circling area. [Figure 10-12] During a circling approach,

the pilot should maintain visual contact with the runway of

intended landing and ﬂ y no lower than the circling minimums

until positioned to make a ﬁ nal descent for a landing. It is

important to remember that circling minimums are only

minimums. If the ceiling allows it, ﬂ y at an altitude that

more nearly approximates VFR trafﬁ c pattern altitude. This

will make any maneuvering safer and bring the view of the

landing runway into a more normal perspective.

Figure 10-13 shows patterns that can be used for circling

approaches. Pattern “A” can be ﬂ own when the ﬁ nal approach

10-21

Figure 10-12. Circling Approach Area Radii.

Figure 10-13. Circling Approaches.

course intersects the runway centerline at less than a 90°

angle, and the runway is in sight early enough to establish a

base leg. If the runway becomes visible too late to ﬂ y pattern

“A,” circle as shown in “B.” Fly pattern “C” if it is desirable

to land opposite the direction of the ﬁ nal approach, and the

runway is sighted in time for a turn to downwind leg. If the

runway is sighted too late for a turn to downwind, ﬂ y pattern

“D.” Regardless of the pattern ﬂ own, the pilot must maneuver

the aircraft to remain within the designated circling area.

Refer to section A (“Terms and Landing Minima Data”) in

the front of each TPP for a description of circling approach

categories.

The criteria for determining the pattern to be ﬂ own are

based on personal ﬂ ying capabilities and knowledge of the

performance characteristics of the aircraft. In each instance,

the pilot must consider all factors: airport design, ceiling and

visibility, wind direction and velocity, ﬁ nal approach course

alignment, distance from the ﬁ nal approach ﬁ x to the runway,

and ATC instructions.

IAP Minimums

Pilots may not operate an aircraft at any airport below

the authorized MDA or continue an approach below the

authorized DA/DH unless:

1. The aircraft is continuously in a position from which

a descent to a landing on the intended runway can

be made at a normal descent rate using normal

maneuvers;

2. The ﬂ ight visibility is not less than that prescribed for

the approach procedure being used; and

3. At least one of the following visual references for

the intended runway is visible and identiﬁ able to the

pilot:

a) Approach light system

b) Threshold

c) Threshold markings

d) Threshold lights

e) Runway end identiﬁ er lights (REIL)

f) Visual approach slope indicator (VASI)

g) Touchdown zone or touchdown zone markings

h) Touchdown zone lights

i) Runway or runway markings

j) Runway lights

Missed Approaches

A missed approach procedure is formulated for each

published instrument approach and allows the pilot to return

to the airway structure while remaining clear of obstacles.

The procedure is shown on the approach chart in text and

graphic form. Since the execution of a missed approach

occurs when the ﬂ ight deck workload is at a maximum, the

10-22

procedure should be studied and mastered before beginning

the approach.

When a missed approach procedure is initiated, a climb pitch

attitude should be established while setting climb power.

Conﬁ gure the aircraft for climb, turn to the appropriate

heading, advise ATC that a missed approach is being

executed, and request further clearances.

If the missed approach is initiated prior to reaching the

missed approach point (MAP), unless otherwise cleared by

ATC, continue to ﬂ y the IAP as speciﬁ ed on the approach

chart. Fly to the MAP at or above the MDA or DA/DH before

beginning a turn.

If visual reference is lost while circling-to-land from an

instrument approach, execute the appropriate missed

approach procedure. Make the initial climbing turn toward

the landing runway and then maneuver to intercept and ﬂ y

the missed approach course.

Pilots should immediately execute the missed approach

procedure:

1. Whenever the requirements for operating below DA/

DH or MDA are not met when the aircraft is below

MDA, or upon arrival at the MAP and at any time

after that until touchdown;

2. Whenever an identiﬁ able part of the airport is not visible

to the pilot during a circling maneuver at or above MDA;

3. When so directed by ATC.

Landing

According to 14 CFR part 91, no pilot may land when the ﬂ ight

visibility is less than the visibility prescribed in the standard

IAP being used. ATC will provide the pilot with the current

visibility reports appropriate to the runway in use. This may be

in the form of prevailing visibility, runway visual value (RVV),

or runway visual range (RVR). However, only the pilot can

determine if the ﬂ ight visibility meets the landing requirements

indicated on the approach chart. If the ﬂ ight visibility meets

the minimum prescribed for the approach, then the approach

may be continued to a landing. If the ﬂ ight visibility is less than

that prescribed for the approach, then the pilot must execute a

missed approach, regardless of the reported visibility.

The landing minimums published on IAP charts are based on

full operation of all components and visual aids associated

with the instrument approach chart being used. Higher

minimums are required with inoperative components or

visual aids. For example, if the ALSF-1 approach lighting

system were inoperative, the visibility minimums for an ILS

would need to be increased by one-quarter mile. If more

than one component is inoperative, each minimum is raised

to the highest minimum required by any single component

that is inoperative. ILS glide slope inoperative minimums

are published on instrument approach charts as localizer

minimums. Consult the “Inoperative Components or Visual

Aids Table” (printed on the inside front cover of each TPP),

for a complete description of the effect of inoperative

components on approach minimums.

Instrument Weather Flying

Flying Experience

The more experience a pilot has in VFR and IFR ﬂ ight,

the more proﬁ cient a pilot becomes. VFR experience can

be gained by flying in terminal areas with high traffic

activity. This type of ﬂ ying forces the pilot to polish the

skill of dividing his or her attention between aircraft control,

navigation, communications, and other ﬂ ight deck duties.

IFR experience can be gained through night ﬂ ying which

also promotes both instrument proﬁ ciency and conﬁ dence.

The progression from ﬂ ying at night under clear, moonlit

conditions to ﬂ ying at night without moonlight, natural

horizon, or familiar landmarks teaches a pilot to trust the

aircraft instruments with minimal dependence upon what

can be seen outside the aircraft. It is a pilot’s decision to

proceed with an IFR ﬂ ight or to wait for more acceptable

weather conditions.

Recency of Experience

Currency as an instrument pilot is an equally important

consideration. No person may act as pilot in command of an

aircraft under IFR or in weather conditions less than VFR

minimums unless he or she has met the requirements of part

91. Remember, these are minimum requirements.

Airborne Equipment and Ground Facilities

Regulations specify minimum equipment for ﬁ ling an IFR

ﬂ ight plan. It is the pilot’s responsibility to determine the

adequacy of the aircraft and navigation/communication

(NAV/COM) equipment for the proposed IFR flight.

Performance limitations, accessories, and general condition

of the equipment are directly related to the weather, route,

altitude, and ground facilities pertinent to the ﬂ ight, as well

as to the ﬂ ight deck workload.

Weather Conditions

In addition to the weather conditions that might affect a

VFR ﬂ ight, an IFR pilot must consider the effects of other

weather phenomena (e.g., thunderstorms, turbulence, icing,

and visibility).

10-23

Figure 10-14. Maintaining an instrument scan in severe turbulence can be difﬁ cult.

Turbulence

Inﬂ ight turbulence can range from occasional light bumps

to extreme airspeed and altitude variations that make aircraft

control difﬁ cult. To reduce the risk factors associated with

turbulence, pilots must learn methods of avoidance, as

well as piloting techniques for dealing with an inadvertent

encounter.

Turbulence avoidance begins with a thorough preﬂ ight weather

brieﬁ ng. Many reports and forecasts are available to assist

the pilot in determining areas of potential turbulence. These

include the Severe Weather Warning (WW), SIGMET (WS),

Convective SIGMET (WST), AIRMET (WA), Severe Weather

Outlook (AC), Center Weather Advisory (CWA), Area Forecast

(FA), and Pilot Reports (UA or PIREPs). Since thunderstorms

are always indicative of turbulence, areas of known and forecast

thunderstorm activity will always be of interest to the pilot. In

addition, clear air turbulence (CAT) associated with jet streams,

strong winds over rough terrain, and fast moving cold fronts are

good indicators of turbulence.

Pilots should be alert while in ﬂ ight for the signposts of

turbulence. For example, clouds with vertical development

such as cumulus, towering cumulus, and cumulonimbus are

indicators of atmospheric instability and possible turbulence.

Standing lenticular clouds lack vertical development but

indicate strong mountain wave turbulence. While en route,

pilots can monitor hazardous inflight weather advisory

service (HIWAS) broadcast for updated weather advisories,

or contact the nearest AFSS or En Route Flight Advisory

Service (EFAS) for the latest turbulence-related PIREPs.

To avoid turbulence associated with strong thunderstorms,

circumnavigate cells by at least 20 miles. Turbulence may

also be present in the clear air above a thunderstorm. To

avoid this, ﬂ y at least 1,000 feet above the top for every 10

knots of wind at that level, or ﬂ y around the storm. Finally,

do not underestimate the turbulence beneath a thunderstorm.

Never attempt to ﬂ y under a thunderstorm. The possible

results of turbulence and wind shear under the storm could

be disastrous.

When moderate to severe turbulence is encountered, aircraft

control is difﬁ cult, and a great deal of concentration is

required to maintain an instrument scan. [Figure 10-14] Pilots

should immediately reduce power and slow the aircraft to

the recommended turbulence penetration speed as described

in the POH/AFM. To minimize the load factor imposed on

the aircraft, the wings should be kept level and the aircraft’s

pitch attitude should be held constant. The aircraft is allowed

to ﬂ uctuate up and down, because maneuvering to maintain

a constant altitude only increases the stress on the aircraft.

If necessary, the pilot should advise ATC of the ﬂ uctuations

and request a block altitude clearance. In addition, the power

should remain constant at a setting that will maintain the

recommended turbulence penetration airspeed.

10-24

Figure 10-15. Temperature Ranges for Ice Formation.

The best source of information on the location and intensity

of turbulence are PIREPs. Therefore, pilots are encouraged to

familiarize themselves with the turbulence reporting criteria

found in the AIM, which also describes the procedure for

volunteering PIREPs relating to turbulence.

Structural Icing

The very nature of flight in Instrument Meteorological

Conditions means operating in visible moisture such as clouds.

At the right temperatures, this moisture can freeze on the

aircraft, causing increased weight, degraded performance, and

unpredictable aerodynamic characteristics. Understanding,

avoidance, and early recognition followed by prompt action

are the keys to avoiding this potentially hazardous situation.

Structural icing refers to the accumulation of ice on the exterior

of the aircraft and is broken down into three classiﬁ cations:

rime ice, clear ice, and mixed ice. For ice to form, there must

be moisture present in the air, and the air must be cooled to

a temperature of 0° C (32° F) or less. Aerodynamic cooling

can lower the surface temperature of an airfoil and cause ice

to form on the airframe even though the ambient temperature

is slightly above freezing.

Rime ice forms if the droplets are small and freeze immediately

when contacting the aircraft surface. This type of ice usually

forms on areas such as the leading edges of wings or struts.

It has a somewhat rough-looking appearance and a milky-

white color.

Clear ice is usually formed from larger water droplets or

freezing rain that can spread over a surface. This is the most

dangerous type of ice since it is clear, hard to see, and can

change the shape of the airfoil.

Mixed ice is a mixture of clear ice and rime ice. It has the

bad characteristics of both types and can form rapidly. Ice

particles become embedded in clear ice, building a very rough

accumulation. The table in Figure 10-15 lists the temperatures

at which the various types of ice will form.

Structural icing is a condition that can only get worse.

Therefore, during an inadvertent icing encounter, it is

important the pilot act to prevent additional ice accumulation.

Regardless of the level of anti-ice or deice protection offered

by the aircraft, the ﬁ rst course of action should be to leave

the area of visible moisture. This might mean descending

to an altitude below the cloud bases, climbing to an altitude

that is above the cloud tops, or turning to a different course.

If this is not possible, then the pilot must move to an altitude

where the temperature is above freezing. Pilots should report

icing conditions to ATC and request new routing or altitude

if icing will be a hazard. Refer to the AIM for information

on reporting icing intensities.

Fog

Instrument pilots must learn to anticipate conditions leading

to the formation of fog and take appropriate action early in

the progress of the ﬂ ight. Before a ﬂ ight, close examination

of current and forecast weather should alert the pilot to the

possibility of fog formation. When fog is a consideration,

pilots should plan adequate fuel reserves and alternate

landing sites. En route, the pilot must stay alert for fog

formation through weather updates from EFAS, ATIS, and

ASOS/AWOS sites.

Two conditions will lead to the formation of fog. Either the

air is cooled to saturation, or sufﬁ cient moisture is added

to the air until saturation occurs. In either case, fog can

form when the temperature/dewpoint spread is 5° or less.

Pilots planning to arrive at their destination near dusk with

decreasing temperatures should be particularly concerned

about the possibility of fog formation.

Volcanic Ash

Volcanic eruptions create volcanic ash clouds containing

an abrasive dust that poses a serious safety threat to ﬂ ight

operations. Adding to the danger is the fact that these ash

clouds are not easily discernible from ordinary clouds when

encountered at some distance from the volcanic eruption.

When an aircraft enters a volcanic ash cloud, dust particles

and smoke may become evident in the cabin, often along with

the odor of an electrical ﬁ re. Inside the volcanic ash cloud,

the aircraft may also experience lightning and St. Elmo’s ﬁ re

on the windscreen. The abrasive nature of the volcanic ash

can pit the windscreens, thus reducing or eliminating forward

visibility. The pitot-static system may become clogged,

causing instrument failure. Severe engine damage is probable

in both piston and jet-powered aircraft.

Every effort must be made to avoid volcanic ash. Since

volcanic ash clouds are carried by the wind, pilots should plan

their ﬂ ights to remain upwind of the ash-producing volcano.

Visual detection and airborne radar are not considered

a reliable means of avoiding volcanic ash clouds. Pilots

witnessing volcanic eruptions or encountering volcanic

ash should immediately pass this information along in

the form of a pilot report. The National Weather Service

10-25

Figure 10-16. A thunderstorm packs just about every weather hazard

known to aviation into one vicious bundle.

monitors volcanic eruptions and estimates ash trajectories.

This information is passed along to pilots in the form of

SIGMETs.

As for many other hazards to ﬂ ight, the best source of

volcanic information comes from PIREPs. Pilots who witness

a volcanic eruption or encounter volcanic ash in flight

should immediately inform the nearest agency. Volcanic

Ash Forecast Transport and Dispersion (VAFTAD) charts

are also available; these depict volcanic ash cloud locations

in the atmosphere following an eruption, and also forecast

dispersion of the ash concentrations over 6- and 12-hour time

intervals. See AC 00-45, Aviation Weather Services.

Thunderstorms

A thunderstorm packs just about every weather hazard known

to aviation into one vicious bundle. Turbulence, hail, rain,

snow, lightning, sustained updrafts and downdrafts, and icing

conditions are all present in thunderstorms. Do not take off in

the face of an approaching thunderstorm or ﬂ y an aircraft that is

not equipped with thunderstorm detection in clouds or at night

in areas of suspected thunderstorm activity. [Figure 10-16]

There is no useful correlation between the external visual

appearance of thunderstorms and the severity or amount of

turbulence or hail within them. All thunderstorms should be

considered hazardous, and thunderstorms with tops above

35,000 feet should be considered extremely hazardous.

Weather radar, airborne or ground based, will normally

reﬂ ect the areas of moderate to heavy precipitation (radar

does not detect turbulence). The frequency and severity of

turbulence generally increases with the radar reﬂ ectivity

closely associated with the areas of highest liquid water

content of the storm. A ﬂ ight path through an area of strong

or very strong radar echoes separated by 20 to 30 miles or

less may not be considered free of severe turbulence.

The probability of lightning strikes occurring to aircraft is

greatest when operating at altitudes where temperatures are

between -5 ° C and +5 ° C. In addition, an aircraft ﬂ ying in the

clear air near a thunderstorm is also susceptible to lightning

strikes. Thunderstorm avoidance is always the best policy.

Wind Shear

Wind shear can be deﬁ ned as a change in wind speed and/or

wind direction in a short distance. It can exist in a horizontal

or vertical direction and occasionally in both. Wind shear can

occur at all levels of the atmosphere but is of greatest concern

during takeoffs and landings. It is typically associated

with thunderstorms and low-level temperature inversions;

however, the jet stream and weather fronts are also sources

of wind shear.

As Figure 10-17 illustrates, while an aircraft is on an

instrument approach, a shear from a tailwind to a headwind

causes the airspeed to increase and the nose to pitch up with

a corresponding balloon above the glide path. A shear from

a headwind to a tailwind has the opposite effect, and the

aircraft will sink below the glide path.

A headwind shear followed by a tailwind/downdraft shear is

particularly dangerous because the pilot has reduced power

and lowered the nose in response to the headwind shear. This

leaves the aircraft in a nose-low, power-low conﬁ guration

when the tailwind shear occurs, which makes recovery more

difﬁ cult, particularly near the ground. This type of wind

shear scenario is likely while making an approach in the

face of an oncoming thunderstorm. Pilots should be alert for

indications of wind shear early in the approach phase and be

ready to initiate a missed approach at the ﬁ rst indication. It

may be impossible to recover from a wind shear encounter

at low altitude.

To inform pilots of hazardous wind shear activity, some

airports have installed a Low-Level Wind Shear Alert

System (LLWAS) consisting of a centerﬁ eld wind indicator

and several surrounding boundary-wind indicators. With

10-26

Figure 10-17. Glide slope Deviations Due to Wind Shear Encounter.

this system, controllers are alerted of wind discrepancies

(an indicator of wind shear possibility) and provide this

information to pilots. A typical wind shear alert issued to a

pilot would be:

“Runway 27 arrival, wind shear alert, 20 knot loss 3

mile ﬁ nal, threshold wind 200 at 15”

In plain language, the controller is advising aircraft arriving

on runway 27 that at about 3 miles out they can expect a

wind shear condition that will decrease their airspeed by 20

knots and possibly encounter turbulence. Additionally, the

airport surface winds for landing runway 27 are reported as

200° at 15 knots.

Pilots encountering wind shear are encouraged to pass along

pilot reports. Refer to AIM for additional information on

wind shear PIREPs.

VFR-On-Top

Pilots on IFR flight plans operating in VFR weather

conditions may request VFR-on-top in lieu of an assigned

altitude. This permits them to select an altitude or ﬂ ight level

of their choice (subject to any ATC restrictions).

Pilots desiring to climb through a cloud, haze, smoke, or

other meteorological formation and then either cancel their

IFR ﬂ ight plan or operate VFR-on-top may request a climb

to VFR-on-top. The ATC authorization will contain a top

report (or a statement that no top report is available) and a

request to report upon reaching VFR-on-top. Additionally,

the ATC authorization may contain a clearance limit, routing,

and an alternative clearance if VFR-on-top is not reached by

a speciﬁ ed altitude.

A pilot on an IFR ﬂ ight plan, operating in VFR conditions,

may request to climb/descend in VFR conditions. When

operating in VFR conditions with an ATC authorization to

“maintain VFR-on-top/maintain VFR conditions,” pilots on

IFR ﬂ ight plans must:

1. Fly at the appropriate VFR altitude as prescribed in 14

CFR part 91.

2. Comply with the VFR visibility and distance-from-

cloud criteria in 14 CFR part 91.

3. Comply with instrument ﬂ ight rules applicable to this

ﬂ ight (minimum IFR altitudes, position reporting, radio

communications, course to be ﬂ own, adherence to ATC

clearance, etc.).

Pilots operating on a VFR-on-top clearance should advise

ATC before any altitude change to ensure the exchange of

accurate trafﬁ c information.

ATC authorization to “maintain VFR-on-top” is not intended

to restrict pilots to operating only above an obscuring

meteorological formation (layer). Rather, it permits operation

above, below, between layers, or in areas where there is no

meteorological obstruction. It is imperative pilots understand,

however, that clearance to operate “VFR-on-top/VFR

conditions” does not imply cancellation of the IFR ﬂ ight

plan.

Pilots operating VFR-on-top/VFR conditions may receive

trafﬁ c information from ATC on other pertinent IFR or

VFR aircraft. However, when operating in VFR weather

conditions, it is the pilot’s responsibility to be vigilant to see

and avoid other aircraft.

This clearance must be requested by the pilot on an IFR ﬂ ight

plan. VFR-on-top is not permitted in certain areas, such as

Class A airspace. Consequently, IFR ﬂ ights operating VFR-

on-top must avoid such airspace.

10-27

VFR Over-The-Top

VFR over-the-top must not be confused with VFR-on-

top. VFR-on-top is an IFR clearance that allows the pilot

to ﬂ y VFR altitudes. VFR over-the-top is strictly a VFR

operation in which the pilot maintains VFR cloud clearance

requirements while operating on top of an undercast layer.

This situation might occur when the departure airport and the

destination airport are reporting clear conditions, but a low

overcast layer is present in between. The pilot could conduct

a VFR departure, ﬂ y over the top of the undercast in VFR

conditions, then complete a VFR descent and landing at the

destination. VFR cloud clearance requirements would be

maintained at all times, and an IFR clearance would not be

required for any part of the ﬂ ight.

Conducting an IFR Flight

To illustrate some of the concepts introduced in this chapter,

follow along on a typical IFR ﬂ ight from the Birmingham

International Airport (BHM), Birmingham, Alabama to

Gulfport-Biloxi International Airport (GPT), Gulfport,

Mississippi. [Figure 10-18] For this trip, a Cessna 182

with a call sign of N1230A will be ﬂ own. The aircraft is

equipped with dual navigation and communication radios, a

transponder, and a GPS system approved for IFR en route,

terminal, and approach operations.

Preﬂ ight

The success of the flight depends largely upon the

thoroughness of the preﬂ ight planning. The evening before

the ﬂ ight, pay close attention to the weather forecast and

begin planning the ﬂ ight.

The Weather Channel indicates a large, low-pressure system

has settled in over the Midwest, pulling moisture up from

the Gulf of Mexico and causing low ceilings and visibility

with little chance for improvement over the next couple of

days. To begin planning, gather all the necessary charts and

materials, and verify everything is current. This includes en

route charts, approach charts, DPs, STAR charts, the GPS

database, as well as an A/FD, some navigation logs, and the

aircraft’s POH/AFM. The charts cover both the departure

and arrival airports and any contingency airports that will

be needed if the ﬂ ight cannot be completed as planned. This

is also a good time for the pilot to consider recent ﬂ ight

experience, pilot proﬁ ciency, ﬁ tness, and personal weather

minimums to ﬂ y this particular ﬂ ight.

Check the A/FD to become familiar with the departure and

arrival airport, and check for any preferred routing between

BHM and GPT. Next, review the approach charts and any

DP or STAR that pertains to the ﬂ ight. Finally, review the en

route charts for potential routing, paying close attention to the

minimum en route and obstacle clearance altitudes.

After this review, select the best option. For this ﬂ ight, the

Birmingham Three Departure [Figure 10-2] to Brookwood

VORTAC, V 209 to Kewanee VORTAC, direct to Gulfport

using GPS would be a logical route. An altitude of 4,000 feet

meets all the regulatory requirements and falls well within

the performance capabilities of the aircraft.

Next, call 1-800-WX-BRIEF to obtain an outlook-type

weather briefing for the proposed flight. This provides

forecast conditions for departure and arrival airports, as well

as the en route portion of the ﬂ ight including forecast winds

aloft. This also is a good opportunity to check the available

NOTAMs.

The weather briefer conﬁ rms the predictions of the weather

channel giving forecast conditions that are at or near

minimum landing minimums at both BHM and GPT for

the proposed departure time. The briefer provides NOTAM

information for GPT indicating that the localizer to runway

32 is scheduled to be out of service and that runway 18/36 is

closed until further notice. Also check for temporary ﬂ ight

restrictions (TFRs) along the proposed route.

After receiving a weather brieﬁ ng, continue ﬂ ight planning

and begin to transfer some preliminary information onto

the navigation log, listing each ﬁ x along the route and the

distances, frequencies, and altitudes. Consolidating this

information onto an organized navigation log will keep the

workload to a minimum during the ﬂ ight.

Next, obtain a standard weather brieﬁ ng online for the

proposed route. A check of current conditions indicates

low IFR conditions at both the departure airport and the

destination, with visibility of one-quarter mile:

SURFACE WEATHER OBSERVATIONS

METAR KBHM 111155Z VRB04KT ¼ SM FG –RA VV004

06/05 A2994 RMK A02 SLP140

METAR KGPT 111156Z 24003KT ¼ SM FG OVC001 08/07

A2962 RMK A02 SLP033

The small temperature/dewpoint spread is causing the low

visibility and ceilings. Conditions should improve later in

the day as temperatures increase. A check of the terminal

forecast conﬁ rms this theory:

TERMINAL FORECASTS

TAF KBHM 111156Z 111212 VRB04KT ¼ SM FG VV004

TEMPO1316 ¾ SM OVC004

FM1600 VRB05KT 2SM BR OVC007 TEMPO 1720 3SM

DZ BKN009

10-28

Figure 10-18. Route Planning.

10-29

FM2000 22008KT 3SM –RA OVC015 TEMP 2205 3SM

–RA OVC025 FM0500 23013KT P6SM OVC025

FM0800 23013KT P6SM BKN030 PROB40 1012 2SM BR

OVC030

TAF KGPT 111153Z 111212 24004KT ¼ SM FG OVC001

BECMG 1317 3SM BR 0VC004

FM1700 24010KT 4SM –RA OVC006 FM0400 24010 5SM

SCT080 TEMPO 0612 P6SM SKC

In addition to the terminal forecast, the area forecast also

indicates gradual improvement along the route. Since the

terminal forecast only provides information for a 5-mile

radius around a terminal area, checking the area forecast

provides a better understanding of the overall weather picture

along the route, as well as potential hazards:

SYNOPSIS AND VFR CLOUDS/WEATHER FORECASTS

SYNOPSIS… AREA OF LOW PRESSURE CNTD OV AL

RMNG GENLY STNRY BRNGNG MSTR AND WD SPRD

IFR TO E TN. ALF…LOW PRES TROF ACRS CNTR PTN

OF THE DFW FA WILL GDLY MOV EWD DURG PD.

NRN LA, AR, NRN MS

SWLY WND THRUT THE PD. 16Z CIG OVC006. SCT

–SHRA. OTLK… IFR SRN ½ … CIG SCT – BKN015

TOPS TO FL250 SWLY WND THRUT THE PD. 17Z AGL

BKN040. OTLK…MVFR CIG VIS.

LA MS CSTL WTRS

CIG OVC001 – OVC006. TOPS TO FL240. VIS ¼ - ¾ SM

FG. SWLY WND. 16Z CIG OVC010 VIS 2 SM BR. OCNL

VIS 3-5SM –RN BR OVC009. OTLK…MVFR CIG VIS.

CIG BKN020 TOPS TO FL180. VIS 1–3 SM BR. SWLY

WND. 18Z BRK030. OTLK…MVFR CIG.

At this time, there are no SIGMETs or PIREPs reported.

However, there are several AIRMETs, one for IFR

conditions, one for turbulence that covers the entire route,

and another for icing conditions which covers an area just

north of the route:

WAUS44 KKCI 111150

DFWS WA 0111150

AIRMET SIERRA FOR IFR VALID UNTIL 111800

AIRMET IFR...OK TX LA AR MS AL FL

TS IMPLY SEV OR GTR TURB SEV ICE LLWS AND

IFR CONDS.

NON MSL HGHTS DENOTED BY AGL OR CIG.

A recheck of NOTAMs for Gulfport confirms that the

localizer to runway 32 is out of service until further notice

and runway 18/36 is closed. If runway 6 is planned for the

departure, conﬁ rm that the climb restriction for the departure

can be met.

GPT 12/006 GPT LOC OS UFN

GPT 12/008 GPT MIRL RWY 18/36 OS UFN

Since the weather is substantially better to the east, Pensacola

Regional Airport is a good alternate with current conditions

and a forecast of marginal VFR.

METAR KPNS 111150Z 21010Z 3SM BKN014 OVC025

09/03 A2973

TAF KPNS 111152Z 111212 22010KT 3 SM BR OVC020

BECMG 1317 4 SM BR OVC025

FM1700 23010KT 4SM –RA OVC030

FM 0400 25014KT 5SM OVC050 TEMPO1612 P6SM

OVC080

If weather minimums are below a pilot’s personal minimums,

a delay in departure to wait for improved conditions is

a good decision. This time can be used to complete the

navigation log which is the next step in planning an IFR

ﬂ ight. [Figure 10-19]

Use the POH/AFM to compute a true airspeed, cruise power

setting, and fuel burn based on the forecast temperatures

aloft and cruising pressure altitude. Also, compute weight-

and-balance information and determine takeoff and landing

distances. There will be a crosswind if weather conditions

require a straight-in landing on runway 14 at GPT. Therefore,

compute the landing distance assuming a 10-knot crosswind

and determine if the runway length is adequate to allow

landing. Determine the estimated ﬂ ight time and fuel burn

using the winds aloft forecast and considering Pensacola

Regional Airport as an alternate airport. With full tanks, the

ﬂ ight can be made nonstop with adequate fuel for ﬂ ight to

the destination, alternate, and the reserve requirement.

Next, check the surface analysis chart which shows where the

pressure systems will be found. The weather depiction chart

shows areas of IFR conditions and can be used to ﬁ nd areas

10-30

Figure 10-19. Navigation Log.

of improving conditions. These charts provide information

a pilot will need should a diversion to VFR conditions be

required. For this ﬂ ight, the radar depicts precipitation along

the route, and the latest satellite photo conﬁ rms what the

weather depiction chart showed.

When the navigation log is ﬁ nished, complete the ﬂ ight plan

in preparation for ﬁ ling with ﬂ ight service. [Figure 10-20]

Call an AFSS for an updated weather brieﬁ ng, Birmingham

INTL airport is now reporting 700 overcast with 3 miles

visibility, and Gulfport-Biloxi is now 400 overcast with 2

miles visibility. The alternate, Pensacola Regional Airport,

continues to report adequate weather conditions with 2,000

overcast and 3 miles visibility in light rain.

10-31

Figure 10-20. Flight Plan Form.

Several pilot reports have been submitted for light icing

conditions; however, all the reports are north of the route

of ﬂ ight and correspond to the AIRMET that was issued

earlier. No pilot reports have included cloud tops, but the

area forecast predicted cloud tops to ﬂ ight level 240. Since

the weather conditions appear to be improving, a ﬂ ight plan

can be ﬁ led using the completed form.

Analyze the latest weather minimums to determine if they

exceed personal minimums. With the absence of icing

reported along the route and steadily rising temperatures,

structural icing should not be a problem. Make a note to

do an operational check of the pitot heat during preﬂ ight

and to take evasive action immediately should even light

icing conditions be encountered in ﬂ ight. This may require

returning to BHM or landing at an intermediate spot before

reaching GPT. The go/no-go decision will be constantly

reevaluated during the ﬂ ight.

Once at the airport, conduct a thorough preﬂ ight inspection.

A quick check of the logbooks indicates all airworthiness

requirements have been met to conduct this IFR flight

including an altimeter, static, and transponder test within

the preceding 24 calendar months. In addition, a log on

the clipboard indicates the VOR system has been checked

within the preceding 30 days. Turn on the master switch and

pitot heat, and quickly check the heating element before it

becomes too hot. Then, complete the rest of the walk-around

procedure. Since this will be a ﬂ ight in actual IFR conditions,

place special emphasis on IFR equipment during the walk-

around, including the alternator belt and antennas. After

completing the preﬂ ight, organize charts, pencils, paper, and

navigation log in the ﬂ ight deck for quick, easy access. This

is also the time to enter the planned ﬂ ight into the GPS.

Departure

After starting the engine, tune in ATIS and copy the

information to the navigation log. The conditions remain the

same as the updated weather brieﬁ ng with the ceiling at 700

overcast, and visibility at 3 miles. Call clearance delivery to

receive a clearance:

“Clearance Delivery, Cessna 1230A IFR to Gulfport

Biloxi with information Kilo, ready to copy.”

“Cessna 1230A is cleared to Gulfport-Biloxi via the

Birmingham Three Departure, Brookwood, Victor

209 Kewanee then direct Mindo, Gulfport. Climb and

maintain 4,000. Squawk 0321.”

10-32

Read back the clearance and review the DP. Although a

departure frequency was not given in the clearance, note that

on the DP, the departure control frequency is listed as 123.8

for the southern sector. Since a departure from runway 24

is anticipated, note the instruction to climb to 2,100 prior

to turning. After tuning in the appropriate frequencies and

setting up navigation equipment for the departure routing,

contact ground control (noting that this is IFR) and receive

the following clearance:

“Cessna 1230A taxi to runway 24 via taxiway

Mike.”

Read back the clearance and aircraft call sign. After a review

of the taxi instructions on the airport diagram, begin to taxi

and check the ﬂ ight instruments for proper indications.

Hold short of runway 24 and complete the before takeoff

checklist and engine run-up. Advise the tower when ready

for takeoff. The tower gives the following clearance:

“Cessna 30A cleared for takeoff runway 24.

Caution wake turbulence from 737 departing to the

northwest.”

Taxi into position. Note the time off on the navigation log,

verify that the heading indicator and magnetic compass are

in agreement, the transponder is in the ALT position, all the

necessary lights, equipment, and pitot heat are on. Start the

takeoff roll. To avoid the 737’s wake turbulence, make note

of its lift off point and take off prior to that point.

En Route

After departure, climb straight ahead to 2,100 feet as directed

by the Birmingham Three Departure. While continuing a

climb to the assigned altitude of 4,000 feet, the following

instructions are received from the tower:

“Cessna 30A contact Departure.”

Acknowledge the clearance and contact departure on the

frequency designated by the DP. State the present altitude

so the departure controller can check the encoded altitude

against indicated altitude:

“Birmingham Departure Cessna 1230A climbing

through 2,700 heading 240.”

Departure replies:

“Cessna 30A proceed direct to Brookwood and resume

own navigation. Contact Atlanta Center on 134.05.”

Acknowledge the clearance, contact Atlanta Center and

proceed direct to Brookwood VORTAC, using the IFR-

approved GPS equipment. En route to Kewanee, VORTAC

Atlanta Center issues the following instructions:

“Cessna 1230A contact Memphis Center on

125.975.”

Acknowledge the instructions and contact Memphis Center

with aircraft ID and present altitude. Memphis Center

acknowledges contact:

“Cessna 1230A, Meridian altimeter is 29.87. Trafﬁ c

at your 2 o’clock and 6 miles is a King Air at 5,000

climbing to 12,000.”

Even when on an IFR ﬂ ight plan, pilots are still responsible

for seeing and avoiding other aircraft. Acknowledge the call

from Memphis Center and inform them of negative contact

with trafﬁ c due to IMC.

“Roger, altimeter setting 29.87. Cessna 1230A is in

IMC negative contact with trafﬁ c.”

Continue the ﬂ ight, and at each ﬁ x note the arrival time on

the navigation log to monitor progress.

To get an update of the weather at the destination and issue

a pilot report, contact the FSS servicing the area. To ﬁ nd

the nearest AFSS, locate a nearby VOR and check above

the VOR information box for a frequency. In this case, the

nearest VOR is Kewanee VORTAC which lists a receive-

only frequency of 122.1 for Greenwood FSS. Request a

frequency change from Memphis and then attempt to contact

Greenwood on 122.1 while listening over the Kewanee

VORTAC frequency of 113.8:

“Greenwood Radio Cessna 1230A receiving on

frequency 113.8, over.”

“Cessna 30A, this is Greenwood, go ahead.”

“Greenwood Radio, Cessna 30A is currently 30 miles

south of the Kewanee VORTAC at 4,000 feet en

route to Gulfport. Requesting an update of en route

conditions and current weather at GPT, as well as

PNS.”

“Cessna 30A, Greenwood Radio, current weather at

Gulfport is 400 overcast with 3 miles visibility in light

rain. The winds are from 140 at 7 and the altimeter

is 29.86. Weather across your route is generally IFR

in light rain with ceilings ranging from 300 to 1,000

overcast with visibilities between 1 and 3 miles.

Pensacola weather is much better with ceilings now

at 2,500 and visibility 6 miles. Checking current

NOTAMs at GPT shows the localizer out of service

and runway 18/36 closed.”

10-33

“Roger, Cessna 30A copies the weather. I have a

PIREP when you are ready to copy.”

“Cessna 30A go ahead with your PIREP.”

“Cessna 30A is a Cessna 182 located on the Kewanee

195° radial at 30 miles level at 4,000 feet. I am

currently in IMC conditions with a smooth ride.

Outside air temperature is plus 1° Celsius. Negative

icing.”

“Cessna 30A thank you for the PIREP.”

With the weather check and PIREP complete, return to

Memphis Center:

“Memphis Center, Cessna 1230A is back on your

frequency.”

“Cessna 1230A, Memphis Center, roger, contact

Houston Center now on frequency 126.8.”

“Roger, contact Houston Center frequency 126.8,

Cessna 1230A.”

“Houston Center, Cessna 1230A level at 4,000

feet.”

“Cessna 30A, Houston Center area altimeter 29.88.”

Arrival

40 miles north of Gulfport, tune in ATIS on number two

communication radio. The report reveals there has been no

change in the weather and ATIS is advertising ILS runway

14 as the active approach.

Houston Center completes a hand off to Gulfport approach

control with instructions to contact approach:

“Gulfport Approach, Cessna 1230A level 4,000 feet

with information TANGO. Request GPS Runway 14

approach.”

“Cessna 30A, Gulfport Approach, descend and

maintain 3,000 feet.”

“Descend to 3,000, Cessna 30A.”

Begin a descent to 3,000 and conﬁ gure your navigation

radios for the approach. The GPS will automatically change

from the en route mode to the terminal mode. This change

will affect the sensitivity of the CDI. Tune in the VORTAC

frequency of 109.0 on the number one navigation radio, and

set in the ﬁ nal approach course of 133° on the OBS. This

setup will help with situational awareness should the GPS

lose signal.

“Cessna 30A your position is 7 miles from MINDO,

maintain 3,000 feet until MINDO, cleared for the GPS

runway 14 approach.”

Read back the clearance and concentrate on ﬂ ying the aircraft.

At MINDO descend to 2,000 as depicted on the approach

chart. At BROWA turn to the ﬁ nal approach course of

133°. Just outside the Final Approach Way Point (FAWP)

AVYUM, the GPS will change to the approach mode and

the CDI will become even more sensitive. Gulfport approach

control issues instructions to contact Gulfport tower:

“Cessna 30A contact Tower on 123.7.”

“123.7, Cessna 30A.”

“Tower, Cessna 1230A outside AVYUM on the GPS

runway 14.”

“Cessna 30A Gulfport Tower, the ceiling is now 600

overcast and the visibility is 4 miles.”

“Cleared to land runway 14, Cessna 30A.”

Continue the approach, complete the appropriate checklists,

cross AVYUM, and begin the ﬁ nal descent. At 700 feet MSL

visual contact with the airport is possible. Slow the aircraft

and conﬁ gure it to allow a normal descent to landing. As

touch down is completed, Gulfport Tower gives further

instructions:

“Cessna 30A turn left at taxiway Bravo and contact

ground on 120.4.”

“Roger, Cessna 30A.”

Taxi clear of the runway and complete the appropriate

checklists. The Tower will automatically cancel the IFR

ﬂ ight plan.

10-34

11-1

Introduction

Changing weather conditions, air trafﬁ c control (ATC), the

aircraft, and the pilot are all variables that make instrument

ﬂ ying an unpredictable and challenging operation. The safety

of the ﬂ ight depends upon the pilot’s ability to manage these

variables while maintaining positive aircraft control and

adequate situational awareness. This chapter discusses the

recognition and suggested remedies for such abnormal and

emergency events related to unforecasted, adverse weather;

aircraft system malfunctions; communication/navigation

system malfunctions; and loss of situational awareness.

Emergency

Operations

Chapter 11

11-2

Unforecast Adverse Weather

Inadvertent Thunderstorm Encounter

A pilot should avoid ﬂ ying through a thunderstorm of any

intensity. However, certain conditions may be present that

could lead to an inadvertent thunderstorm encounter. For

example, ﬂ ying in areas where thunderstorms are embedded

in large cloud masses may make thunderstorm avoidance

difﬁ cult, even when the aircraft is equipped with thunderstorm

detection equipment. Therefore, pilots must be prepared to

deal with an inadvertent thunderstorm penetration. At the

very least, a thunderstorm encounter subjects the aircraft to

turbulence that could be severe. The pilot and passengers

should tighten seat belts and shoulder harnesses and secure

any loose items in the cabin.

As with any emergency, the ﬁ rst order of business during

an inadvertent thunderstorm encounter must be to ﬂ y the

aircraft. The pilot workload is heavy; therefore, increased

concentration is necessary to maintain an instrument scan.

If a pilot inadvertently enters a thunderstorm, it is better to

maintain a course straight through the thunderstorm rather

than turning around. A straight course minimizes the amount

of time in the thunderstorm and turning maneuvers only

increase structural stress on the aircraft.

Reduce power to a setting that maintains a speed at the

recommended turbulence penetration speed as described in the

Pilot’s Operating Handbook/Airplane Flight Manual (POH/

AFM), and try to minimize additional power adjustments.

Concentrate on maintaining a level attitude while allowing

airspeed and altitude to ﬂ uctuate. Similarly, if using the

autopilot, disengage the altitude hold and speed hold modes,

as they only increase the aircraft’s maneuvering—thereby

increasing structural stress.

During a thunderstorm encounter, the potential for icing

also exists. As soon as possible, turn on anti-icing/deicing

equipment and carburetor heat, if equipped. Icing can be

rapid at any altitude and may lead to power failure and/or

loss of airspeed indication.

Lightning is also present in a thunderstorm and can

temporarily blind a pilot. To reduce this risk, turn up ﬂ ight

deck lights to the highest intensity, concentrate on the ﬂ ight

instruments, and resist the urge to look outside.

Inadvertent Icing Encounter

Because icing is unpredictable in nature, pilots may ﬁ nd

themselves in icing conditions even though they have done

everything practicable to avoid it. In order to stay alert to this

possibility while operating in visible moisture, pilots should

monitor the outside air temperature (OAT).

The effects of ice on aircraft are cumulative—thrust is

reduced, drag increases, lift lessens, and weight increases.

The results are an increase in stall speed and a deterioration

of aircraft performance. In extreme cases, two to three inches

of ice can form on the leading edge of the airfoil in less than

5 minutes. It takes only 1/2 inch of ice to reduce the lifting

power of some aircraft by 50 percent and increases the

frictional drag by an equal percentage.

A pilot can expect icing when ﬂ ying in visible precipitation,

such as rain or cloud droplets, and the temperature is

between +02 and -10° Celsius. When icing is detected, a

pilot should do one of two things, particularly if the aircraft

is not equipped with deicing equipment: leave the area of

precipitation or go to an altitude where the temperature is

above freezing. This “warmer” altitude may not always be

a lower altitude. Proper preﬂ ight action includes obtaining

information on the freezing level and the above-freezing

levels in precipitation areas.

If neither option is available, consider an immediate landing

at the nearest suitable airport. Even if the aircraft is equipped

with anti-icing/deicing equipment, it is not designed to allow

aircraft to operate indeﬁ nitely in icing conditions. Anti-

icing/deicing equipment gives a pilot more time to get out of

the icing conditions. Report icing to ATC and request new

routing or altitude. Be sure to report the type of aircraft, and

use the following terms when reporting icing to ATC:

1. Trace. Ice becomes perceptible. Rate of accumulation

is slightly greater than sublimation. Deicing/anti-icing

equipment is not utilized unless encountered for an

extended period of time (over 1 hour).

2. Light. The rate of accumulation may create a problem

if ﬂ ight is prolonged in this environment (over 1

hour). Occasional use of deicing/anti-icing equipment

removes/prevents accumulation. It does not present a

problem if deicing/anti-icing equipment is used.

3. Moderate. The rate of accumulation is such that even

short encounters become potentially hazardous and

use of deicing/anti-icing equipment or ﬂ ight diversion

is necessary.

4. Severe. The rate of accumulation is such that deicing/

anti-icing equipment fails to reduce or control the

hazard. Immediate ﬂ ight diversion is necessary.

Early ice detection is critical and is particularly difﬁ cult during

night ﬂ ight. Use a ﬂ ashlight to check for ice accumulation on

the wings. At the ﬁ rst indication of ice accumulation, take

action to get out of the icing conditions. Refer to the POH/

AFM for the proper use of anti-icing/deicing equipment.

11-3

Figure 11-2. One example of a static wick installed on aircraft

control surface to bleed off static charges built up during ﬂ ight.

This will prevent static buildup and St. Elmo’s ﬁ re by allowing

the static electricity to dissipate harmlessly.

Figure 11-1. St. Elmo’s Fire is harmless but may affect both communication and navigation radios, especially the lower frequencies

such as those used on the ADF.

Precipitation Static

Precipitation static, often referred to as P-static, occurs

when accumulated static electricity is discharged from the

extremities of the aircraft. This discharge has the potential

to create problems for the instrument pilot. These problems

range from the serious, such as erroneous magnetic compass

readings and the complete loss of very high frequency (VHF)

communications to the annoyance of high-pitched audio

squealing and St. Elmo’s ﬁ re. [Figure 11-1]

Precipitation static is caused when an aircraft encounters

airborne particles during flight (e.g., rain or snow),

and develops a negative charge. It can also result from

atmospheric electric ﬁ elds in thunderstorm clouds. When

a signiﬁ cant negative voltage level is reached, the aircraft

discharges it, which can create electrical disturbances. This

electrical discharge builds with time as the aircraft ﬂ ies in

precipitation. It is usually encountered in rain, but snow can

cause the same effect. As the static buildup increases, the

effectiveness of both communication and navigation systems

decreases to the point of potential unusability.

To reduce the problems associated with P-static, the pilot

should ensure the aircraft’s static wicks are properly maintained

and accounted for. Broken or missing static wicks should be

replaced before an instrument ﬂ ight. [Figure 11-2]

Aircraft System Malfunctions

Preventing aircraft system malfunctions that might lead

to an inﬂ ight emergency begins with a thorough preﬂ ight

11-4

Figure 11-3. G1000 PFD display in normal mode and in the reversionary mode activated upon system failure.

inspection. In addition to those items normally checked

prior to a visual ﬂ ight rules (VFR) ﬂ ight, pilots intending to

ﬂ y under instrument ﬂ ight rules (IFR) should pay particular

attention to the alternator belt, antennas, static wicks, anti-

icing/deicing equipment, pitot tube, and static ports.

During taxi, verify the operation and accuracy of all ﬂ ight

instruments. In addition, during the run-up, verify that the

operation of the pneumatic system(s) is within acceptable

parameters. It is critical that all systems are determined to be

operational before departing into IFR conditions.

Electronic Flight Display Malfunction

When a pilot becomes familiar and comfortable with the

new electronic displays, he or she also tends to become more

reliant on the system. The system then becomes a primary

source of navigation and data acquisition instead of the

supplementary source of data as initially intended.

Complete reliance on the moving map for navigation becomes

a problem during a failure of one, more, or all of the ﬂ ight

display screens. Under these conditions, the systems revert to

a composite mode (called reversionary), which eliminates the

moving map display and combines the PFD with the engine

indicating system. [Figure 11-3] If a pilot has relied on the

display for navigation information and situational awareness,

he or she lacks any concept of critical data such as the aircraft’s

position, the nearest airport, or proximity to other aircraft.

The electronic ﬂ ight display is a supplementary source of

navigation data and does not replace en route charts. To

maintain situational awareness, a pilot must follow the ﬂ ight

on the en route chart while monitoring the PFD. It is important

for the pilot to know the location of the closest airport as

well as surrounding trafﬁ c relative to the location of his or

her aircraft. This information becomes critical should the

electronic ﬂ ight display fail.

For the pilot who utilizes the electronic database as a

substitute for the Airport Facilities Directory, screen failure

or loss of electrical power can mean the pilot is no longer

able to access airport information. Once the pilot loses the

ability to call up airport information, aeronautical decision-

making is compromised.

Alternator/Generator Failure

Depending upon the aircraft being ﬂ own, an alternator failure

is indicated in different ways. Some aircraft use an ammeter

11-5

Figure 11-4. Ammeter (left) and Loadmeter (right).

Figure 11-5. Double Rocker Switch Seen on Many Aircraft.

that indicates the state of charge or discharge of the battery.

[Figure 11-4] A positive indication on the ammeter indicates

a charge condition; a negative indication reveals a discharge

condition. Other aircraft use a load meter to indicate the load

being carried by the alternator. [Figure 11-4]

Sometimes an indicator light is also installed in the aircraft to

alert the pilot to an alternator failure. On some aircraft such

as the Cessna 172, the light is located on the lower left side

making it difﬁ cult to see its illumination if charts are open

Ensure that these safety indicators are visible during ﬂ ight.

When a loss of the electrical charging system is experienced,

the pilot has approximately 40 minutes of battery life

remaining before the system fails entirely. The time

mentioned is an approximation and should not be relied upon

as speciﬁ c to all aircraft. In addition, the battery charge that

exists in a battery may not be full, altering the time available

before electrical exhaustion occurs. At no time should a pilot

consider continuing a ﬂ ight once the electrical charging

system has failed. Land at the nearest suitable airport.

Techniques for Electrical Usage

Master Battery Switch

One technique for conserving the main battery charge is

to ﬂ y the aircraft to the airport of intended landing while

operating with minimal power. If a two-position battery

master/alternator rocker switch [Figure 11-5] is installed, it

can be utilized to isolate the main battery from the electrical

system and conserve power.

Operating on the Main Battery

While en route to the airport of intended landing, reduce the

electrical load as much as practical. Turn off all unnecessary

electrical items such as duplicate radios, non-essential

lighting, etc. If unable to turn off radios, lights, etc. manually,

consider pulling circuit breakers to isolate those pieces of

equipment from the electrical system. Maximum time of

useful voltage may be between 30 and 40 minutes and is

inﬂ uenced by many factors, which degrade the useful time.

Loss of Alternator/Generator for Electronic Flight

Instrumentation

With the increase in electrical components being installed

in modern technically advanced aircraft, the power supply

and the charging system need increased attention and

understanding. Traditional round dial aircraft do not rely

as heavily on electrical power for the primary six-pack

instrumentation. Modern electronic ﬂ ight displays utilize the

electrical system to power the AHRS, ADC, engine indicating

system (EIS), etc. A loss of an alternator or generator was

considered an abnormality in traditionally equipped aircraft;

11-6

Figure 11-6. Note the double rocker switch and the standby battery

switch in this aircraft. The standby battery must be armed to work

correctly; arming should be done prior to departure.

however, a failure of this magnitude is considered an

emergency in technically advanced aircraft.

Due to the increased demand for electrical power, it is

necessary for manufacturers to install a standby battery in

conjunction with the primary battery. The standby battery is

held in reserve and kept charged in case of a failure of the

charging system and a subsequent exhaustion of the main

battery. The standby battery is brought online when the main

battery voltage is depleted to a speciﬁ c value, approximately

19 volts. Generally, the standby battery switch must be in the

ARM position for this to occur but pilots should refer to the

aircraft ﬂ ight manual for speciﬁ cs on an aircraft’s electrical

system. The standby battery powers the essential bus and

allows the primary ﬂ ight display (PFD) to be utilized.

The essential bus usually powers the following

components:

1. AHRS (Attitude and Heading Reference System)

2. ADC (Air Data Computer)

3. PFD (Primary Flight Display)

4. Navigation Radio #1

5. Communication Radio #1

6. Standby Indicator Light

Techniques for Electrical Usage

Standby Battery

One technique for conserving the main battery charge is

to ﬂ y the aircraft to the airport of intended landing while

using the standby battery. A two-position battery master/

alternator rocker switch is installed on most aircraft with

electronic ﬂ ight displays, which can be utilized to isolate

the main battery from the electrical system. By switching the

MASTER side off, the battery is taken ofﬂ ine and the standby

battery comes online to power the essential bus. However,

the standby battery switch must be in the ARM position for

this to occur. [Figure 11-6] Utilization of the standby battery

ﬁ rst reserves the main battery for use when approaching to

land. With this technique, electrical power may be available

for the use of ﬂ aps, gear, lights, etc. Do not rely on any power

to be available after the standby battery has exhausted itself.

Once the charging system has failed, ﬂ ight with a powered

electrical system is not guaranteed.

Operating on the Main Battery

While en route to the airport of intended landing, reduce the

electrical load as much as practical. Turn off all unnecessary

electrical items such as duplicate radios, non-essential

lighting, etc. If unable to turn off radios, lights, etc., manually,

consider pulling circuit breakers to isolate those pieces of

equipment from the electrical system. Keep in mind that

once the standby battery has exhausted its charge, the ﬂ ight

deck may become very dark depending on what time of

day the failure occurs. The priority during this emergency

situation is landing the aircraft as soon as possible without

jeopardizing safety.

A standby attitude indicator, altimeter, airspeed indicator

(ASI) and magnetic compass are installed in each aircraft

for use when the PFD instrumentation is unavailable.

[Figure 11-7] These would be the only instruments left

available to the pilot. Navigation would be limited to pilotage

and dead reckoning unless a hand-held transceiver with a

GPS/navigation function is onboard.

Once an alternator failure has been detected, the pilot must

reduce the electrical load on the battery and land as soon as

practical. Depending upon the electrical load and condition

of the battery, there may be sufﬁ cient power available for

45 minutes of ﬂ ight—or for only a matter of minutes. Pilots

should also know which systems on the aircraft are electric and

those that continue to operate without electrical power. Pilots

can attempt to troubleshoot alternator failure by following

the established alternator failure procedure published in the

POH/AFM. If the alternator cannot be reset, advise ATC of

the situation and inform them of the impending electrical

failure.

Analog Instrument Failure

A warning indicator or an inconsistency between indications

on the attitude indicator and the supporting performance

11-7

Figure 11-7. Emergency Instrumentation Available to the Pilot on Electronic Flight Instrumented Aircraft.

instruments usually identiﬁ es system or instrument failure.

Aircraft control must be maintained while identifying the

failed component(s). Expedite the cross-check and include

all flight instruments. The problem may be individual

instrument failure or a system failure affecting multiple

instruments.

One method of identification involves an immediate

comparison of the attitude indicator with the rate-of-turn

indicator and vertical speed indicator (VSI). Along with

providing pitch-and-bank information, this technique

compares the static system with the suction or pressure system

and the electrical system. Identify the failed component(s)

and use the remaining functional instruments to maintain

aircraft control.

Attempt to restore the inoperative component(s) by checking

the appropriate power source, changing to a backup or

alternate system, and resetting the instrument if possible.

Covering the failed instrument(s) may enhance a pilot’s

ability to maintain aircraft control and navigate the aircraft.

Usually, the next step is to advise ATC of the problem and,

if necessary, declare an emergency before the situation

deteriorates beyond the pilot’s ability to recover.

Pneumatic System Failure

One possible cause of instrument failure is a loss of the

suction or pressure source. This pressure or suction is

supplied by a vacuum pump mechanically driven off the

engine. Occasionally these pumps fail, leaving the pilot with

inoperative attitude and heading indicators.

Figure 11-8 illustrates inoperative vacuum driven attitude

and heading indicators which can fail progressively. As the

gyroscopes slow down they may wander, which, if connected

to the autopilot and/or ﬂ ight director, can cause incorrect

movement or erroneous indications. In Figure 11-8, the

aircraft is actually level and at 2,000 feet MSL. It is not in

a turn to the left which the pilot may misinterpret if he or

she fails to see the off or failed ﬂ ags. If that occurs, the pilot

may transform a normally benign situation into a hazardous

situation. Again, good decision-making by the pilot only

occurs after a careful analysis of systems.

Many small aircraft are not equipped with a warning system

for vacuum failure; therefore, the pilot should monitor the

system’s vacuum/pressure gauge. This can be a hazardous

situation with the potential to lead the unsuspecting pilot into

a dangerous unusual attitude which would require a partial

panel recovery. It is important that pilots practice instrument

ﬂ ight without reference to the attitude and heading indicators

in preparation for such a failure.

Pitot/Static System Failure

A pitot or static system failure can also cause erratic and

unreliable instrument indications. When a static system

11-8

Figure 11-8. Vacuum Failure.

problem occurs, it affects the ASI, altimeter, and the VSI.

In most aircraft, provisions have been made for the pilot to

select an alternate static source. Check the POH/AFM for

the location and operation of the alternate static source. In

the absence of an alternate static source, in an unpressurized

aircraft, the pilot could break the glass on the VSI. The VSI

is not required for instrument ﬂ ight, and breaking the glass

provides the altimeter and the ASI a source of static pressure.

This procedure could cause additional instrument errors.

Communication/Navigation System

Malfunction

Avionics equipment has become very reliable, and the

likelihood of a complete communications failure is remote.

However, each IFR ﬂ ight should be planned and executed in

anticipation of a two-way radio failure. At any given point

during a ﬂ ight, the pilot must know exactly what route to ﬂ y,

what altitude to ﬂ y, and when to continue beyond a clearance

limit. Title 14 of the Code of Federal Regulations (14 CFR)

part 91 describes the procedures to be followed in case of a

two-way radio communications failure. If operating in VFR

conditions at the time of the failure, the pilot should continue

the ﬂ ight under VFR and land as soon as practicable. If the

failure occurs in IFR conditions, or if VFR conditions cannot

be maintained, the pilot must continue the ﬂ ight:

1. Along the route assigned in the last ATC clearance

received;

2. If being radar vectored, by the direct route from the

point of radio failure to the ﬁ x, route, or airway speciﬁ ed

in the vector clearance;

3. In the absence of an assigned route, by the route

that ATC has advised may be expected in a further

clearance; or

4. In the absence of an assigned route or a route that ATC

has advised may be expected in a further clearance,

by the route ﬁ led in the ﬂ ight plan.

The pilot should maintain the highest of the following

altitudes or ﬂ ight levels for the route segment being ﬂ own:

1. The altitude or ﬂ ight level assigned in the last ATC

clearance received;

2. The minimum altitude (converted, if appropriate, to

minimum ﬂ ight level as prescribed in part 91 for IFR

operations); or

3. The altitude or ﬂ ight level ATC has advised may be

expected in a further clearance.

In addition to route and altitude, the pilot must also plan the

progress of the ﬂ ight to leave the clearance limit.

1. When the clearance limit is a ﬁ x from which an

approach begins, commence descent or descent

and approach as close as possible to the expect-

further-clearance time if one has been received. If an

expect-further-clearance time has not been received,

commence descent or descent and approach as close as

possible to the estimated time of arrival as calculated

from the ﬁ led or amended (with ATC) estimated time

en route.

11-9

Figure 11-9. The default soft key menu that is displayed on the PFD contains a “NRST” (Nearest Airport) soft key. Pressing this soft

key opens a text box which displays the nearest 25 airports.

Nearest Airports Using the PFD

With the advancements in electronic databases, diverting to

alternate airports has become easier. Simply by pressing a soft

key on the PFD, pilots can access information for up to 25 of

the nearest airports that meet the criteria set in the systems

conﬁ guration page. [Figure 11-9] Pilots are able to specify

what airports are acceptable for their aircraft requirements

based on landing surface and length of runway.

When the text box opens, the ﬂ ashing cursor is located over

the nearest airport that meets the criteria set in the auxiliary

setup page as shown in Figure 11-10. Scrolling through the

25 airports is accomplished by turning the outer FMS knob,

which is located on the lower right corner of the display

screen. Turning the FMS knob clockwise moves the blinking

cursor to the next closest airport. By continuing to turn the

knob, the pilot is able to scroll through all 25 nearest airports.

Each airport box contains the information illustrated in

Figure 11-11, which the pilot can utilize to determine which

airport best suits their individual needs.

Additional Information for a Speciﬁ c Airport

In addition to the information that is presented on the ﬁ rst

screen, the pilot can view additional information as shown in

Figure 11-12 by highlighting the airport identiﬁ er and then

pressing the enter key.

2. If the clearance limit is not a ﬁ x from which an

approach begins, leave the clearance limit at the

expect-further-clearance time if one has been received.

If no expect-further-clearance time has been received,

leave the clearance limit upon arrival over it, and

proceed to a ﬁ x from which an approach begins and

commence descent or descent and approach as close as

possible to the estimated time of arrival as calculated

from the ﬁ led or amended (with ATC) estimated time

en route. [Figure 11-8]

While following these procedures, set the transponder to

code 7600 and use all means possible to reestablish two-way

radio communication with ATC. This includes monitoring

navigational aids (NAVAIDs), attempting radio contact with

other aircraft, and attempting contact with a nearby automated

ﬂ ight service station (AFSS).

GPS Nearest Airport Function

Procedures for accessing the nearest airport information

vary by the type of display installed in an aircraft. Pilots can

obtain information relative to the nearest airport by using the

PFD, MFD, or the nearest function on the GPS receiver. The

following examples are based on a popular system. Pilots

should become familiar with the operational characteristics

of the equipment to be used.

11-10

Figure 11-11. Information shown on the nearest airport page.

Figure 11-12. Information shown on the additional information

page that will aid the pilot in making a more informed decision

about which airport to choose when diverting.

Figure 11-10. An enlargement of the box shown in the lower right

of Figure 11-9. Note that KGNV would be ﬂ ashing.

From this menu or the previous default nearest airport screen,

the pilot is able to activate the Direct-To function, which

provides a direct GPS course to the airport. In addition,

the pilot can auto-tune communication frequencies by

highlighting the appropriate frequency and then pressing

the enter key. The frequency is placed in the stand-by box

of either COM1 or COM2, whichever frequency has the

cyan box around it.

Nearest Airports Using the MFD

A second way to determine the nearest airport is by

referencing the NRST Page Group located on the MFD. This

method provides additional information to the pilot; however,

it may require additional steps to view. [Figure 11-13]

Navigating the MFD Page Groups

Most display systems are designed for ease of navigation

through the different screens on the MFD. Notice the

various page groups in the lower right-hand corner of the

MFD screen. Navigation through these four page groups

is accomplished by turning the outer FMS knob clockwise.

[Figure 11-14]

Within each page group are speciﬁ c pages that provide

additional information pertaining to that speciﬁ c group. Once

the desired page group and page is selected, the MFD remains

in that conﬁ guration until the page is changed or the CLR

button is depressed for more than 2 seconds. Holding the CLR

button returns the display to the default moving map page.

Nearest Airport Page Group

The nearest airport page contains speciﬁ c areas of interest

for the airport selected. [Figure 11-15] The pilot is furnished

information regarding runways, frequencies, and types of

approaches available.

Nearest Airports Page Soft Keys

Figure 11-16 illustrates four speciﬁ c soft keys that allow

the pilot to access independent windows of the airport page.

Selection of each of these windows can also be accomplished

by utilizing the MENU hard key.

The soft keys and functions are as follows: Scroll through

each section with the cursor, then press enter to accept the

selection.

1. APT. Allows the user access to scroll through the

25 nearest airports. The white arrow indicates which

airport is selected. The INFORMATION window

is slaved to the white arrow. The INFORMATION

window decodes the airport identiﬁ er. Scroll through

the 25 airports by turning the outer FMS knob.

11-11

Figure 11-13. The MFD is another means of viewing the nearest airports.

Figure 11-14. Page Groups. As the FMS outer knob is rotated, the

current page group is indicated by highlighting the speciﬁ c group

indicator. Notice that the MAP page group is highlighted.

2. RNWY. Moves the cursor into the Runways section

and allows the user to scroll through the available

runways at a specific airport that is selected in

conjunction with the APT soft key. A green arrow

indicates additional runways to view.

3. FREQ. Moves the cursor into the Frequencies section

and allows the pilot to highlight and auto-tune the

frequency into the selected standby box.

4. APR. Moves the cursor into the Approach section and

allows the pilot to review approaches and load them

into the ﬂ ight plan. When the APR soft key is selected,

an additional soft key appears. The LD APR (Load

Approach) soft key must be pressed once the desired

instrument approach procedure has been highlighted.

Once the soft key is pressed, the screen changes to the

PROC Page Group. From this page the pilot is able to

choose the desired approach, the transition, and choose

the option to activate the approach or just load it into

the ﬂ ight plan.

Situational Awareness

Situational awareness (SA) is not simply a mental picture of

aircraft location; rather, it is an overall assessment of each

element of the environment and how it affects a ﬂ ight. On one

end of the SA spectrum is a pilot who is knowledgeable of

every aspect of the ﬂ ight; consequently, this pilot’s decision-

making is proactive. With good SA, this pilot is able to make

decisions well ahead of time and evaluate several different

options. On the other end of the SA spectrum is a pilot who

is missing important pieces of the puzzle: “I knew exactly

where I was when I ran out of fuel.” Consequently, this

pilot’s decision-making is reactive. With poor SA, a pilot

11-12

Figure 11-15. The page group of nearest airports has been selected.

lacks a vision of future events and is forced to make decisions

quickly, often with limited options.

During a typical IFR ﬂ ight, a pilot operates at varying levels

of SA. For example, a pilot may be cruising to his or her

destination with a high level of SA when ATC issues an

unexpected standard terminal arrival route (STAR). Since the

pilot was not expecting the STAR and is not familiar with it,

SA is lowered. However, after becoming familiar with the

STAR and resuming normal navigation, the pilot returns to

a higher level of SA.

Factors that reduce SA include: distractions, unusual or

unexpected events, complacency, high workload, unfamiliar

situations, and inoperative equipment. In some situations, a

loss of SA may be beyond a pilot’s control. For example, a

pneumatic system failure and associated loss of the attitude

and heading indicators could cause a pilot to ﬁ nd his or her

aircraft in an unusual attitude. In this situation, established

procedures must be used to regain SA.

Pilots should be alert to a loss of SA anytime they are in a

reactive mindset. To regain SA, reassess the situation and

seek additional information from other sources, such as the

navigation instruments or ATC.

Summary

Electronic ﬂ ight displays have been dramatically improved

regarding how information is displayed and what information

is available to a pilot. With only the push of a button, a pilot

is able to access information that was traditionally contained

in multiple publications. (Electronic databases have replaced

paper manuals and reduced the clutter in the ﬂ ight deck.)

Multi-Function Displays (MFD) are capable of displaying

moving maps that mirror sectional charts. These detailed

displays depict all airspace including permanent temporary

ﬂ ight restrictions (TFRs).

In fact, MFDs have become so descriptive that many pilots

fall into the trap of relying solely on the moving maps for

navigation. In addition, pilots are drawing upon the database

to familiarize themselves with departure and destination

airport information.

Pilots are relying heavily on the electronic database for their

ﬂ ight planning and have moved away from the traditional

method of cross-country ﬂ ight planning. It is imperative

to understand that the electronic ﬂ ight display adds to the

overall quality of the ﬂ ight experience, but can also lead to

11-13

Figure 11-16. The four soft keys at the bottom of the MFD are airport (A), runway (B), frequency (C), and approach (D).

11-14

Figure 11-17. The Area Surrounding the Aircraft for Coverage

Using TIS.

Figure 11-18. A Typical Display on Aircraft MFD When Using TIS.

catastrophe if not utilized properly. At no time is the moving

map meant to substitute for a VFR sectional or Low Altitude

En Route chart.

Trafﬁ c Avoidance

Electronic ﬂ ight displays have the capability of displaying

transponder-equipped aircraft on the MFD as well as the

inset map on the PFD. However, due to the limitations of the

systems, not all trafﬁ c is displayed. Some TIS units display

only eight intruding targets within the service volume. The

normal service volume has altitude limitations of 3,500 feet

below the aircraft to 3,500 feet above the aircraft. The lateral

limitation is 7 NM. [Figure 11-17] Pilots unfamiliar with the

limitations of the system may rely on the aural warnings to

alert them to approaching trafﬁ c.

In addition to an outside visual scan of trafﬁ c, a pilot should

incorporate any Trafﬁ c Information electronically displayed

such as TIS. This innovation in trafﬁ c alerting reinforces and

adds synergy to the ability to see and avoid. However, it is

an aid and not a replacement for the responsibilities of the

pilot. Systems such as TIS provide a visual representation

of nearby trafﬁ c and displays a symbol on the moving map

display with relative information about altitude, vertical

trends, and direction of ﬂ ight. [Figure 11-18]

11-15

It is important to remember that most systems display only a

speciﬁ c maximum number of targets allowed. Therefore, it

does not mean that the targets displayed are the only aircraft

in the vicinity. The system displays only the closest aircraft.

In addition, the system does not display aircraft that are not

equipped with transponders. The display may not show any

aircraft; however, a Piper Cub with no transponder could be

ﬂ ying in the area. TIS coverage can be sporadic and is not

available in some areas of the United States. Trafﬁ c advisory

software is to be utilized only for increased situational

awareness and not the sole means of trafﬁ c avoidance. There is

no substitute for a good visual scan of the surrounding sky.

11-16

A-1

The following shorthand system is recommended by the

Federal Aviation Administration (FAA). Applicants for the

instrument rating may use any shorthand system, in any

language, which ensures accurate compliance with air trafﬁ c

control (ATC) instructions. No shorthand system is required

by regulation and no knowledge of shorthand is required for

the FAA Knowledge Test; however, because of the vital need

for reliable communication between the pilot and controller,

clearance information should be unmistakably clear.

The following symbols and contractions represent words

and phrases frequently used in clearances. Most are used

regularly by ATC personnel. By practicing this shorthand,

omitting the parenthetical words, you will be able to copy

long clearances as fast as they are read.

Example: CAF RH RV V18 40 SQ 0700 DPC 120.4

Cleared as ﬁ led, maintain runway heading for radar vector

to Victor 18, climb to 4,000, squawk 0700, departure control

frequency is 120.4.

Words and Phrases Shorthand

Above ..........................................................................ABV

Above (Altitude, Hundreds of Feet) ............................... 70

Adjust speed to 250 knots ......................................... 250 K

Advise .........................................................................ADZ

After (Passing) ..................................................................<

Airway (Designation) ................................................... V26

Airport .............................................................................. A

Alternate Instructions ...................................................... ( )

Altitude 6,000–17,000 .............................................60-170

And ................................................................................... &

Approach ........................................................................ AP

Approach Control ........................................................ APC

Area Navigation .......................................................RNAV

Arriving ..............................................................................

At..................................................................................... @

At or Above ....................................................................

At or Below ....................................................................

(ATC) Advises ...............................................................CA

(ATC) Clears or Cleared .................................................. C

(ATC) Requests .............................................................CR

Appendix A

Back Course ...................................................................BC

Bearing ........................................................................... BR

Before (Reaching, Passing) ...............................................>

Below .......................................................................... BLO

Below (Altitude, Hundreds of Feet) ................................ 70

Center .......................................................................... CTR

Clearance Void if Not Off By (Time) .............................v<

Cleared as Filed ........................................................... CAF

Cleared to Airport ............................................................ A

Cleared to Climb/Descend at Pilot’s Discretion ............ PD

Cleared to Cross ............................................................... X

Cleared to Depart From the Fix ....................................... D

Cleared to the Fix ..............................................................F

Cleared to Hold and Instructions Issued .......................... H

Cleared to Land .................................................................L

Cleared to the Outer Marker ............................................ O

Climb to (Altitude, Hundreds of Feet) ........................... 70

Contact Approach .......................................................... CT

Contact (Denver) Approach Control ............................ (den

Contact (Denver) Center ............................................(DEN

Course ..........................................................................CRS

Cross ................................................................................ X

Cruise .............................................................................

Delay Indeﬁ nite ............................................................ DLI

Depart (Direction, if Speciﬁ ed) ................................ T ( )

Departure Control ....................................................... DPC

Descend To (Altitude, Hundreds of Feet) ...................... 70

Direct ..............................................................................DR

Direction (Bound)

Eastbound ................................................................... EB

Westbound ................................................................. WB

Northbound .................................................................NB

Southbound ................................................................. SB

Inbound ........................................................................ IB

Outbound ....................................................................OB

DME Fix (Mile) ............................................................

Each ................................................................................EA

Enter Control Area .......................................................

Estimated Time of Arrival .......................................... ETA

Expect ............................................................................EX

Expect-Further-Clearance ............................................EFC

Clearance Shorthand

A-2

Fan Marker .................................................................... FM

Final ..................................................................................F

Final Approach ...............................................................FA

Flight Level .................................................................... FL

Flight Planned Route.................................................... FPR

For Further Clearance .................................................. FFC

For Further Headings ...................................................FFH

From .............................................................................. FM

Ground ....................................................................... GND

GPS Approach .............................................................GPS

Heading ...................................................................... HDG

Hold (Direction) .......................................................... H-W

Holding Pattern ............................................................

ILS Approach ................................................................ ILS

Increase Speed 30 Knots ........................................... +30 K

Initial Approach .................................................................I

Instrument Departure Procedure .................................... DP

Intersection .................................................................... XN

Join or Intercept Airway/Jet Route/Track or Course ........

Left Turn After Takeoff ...................................................

Locator Outer Marker ................................................ LOM

Magnetic ..........................................................................M

Maintain ........................................................................

Maintain VFR Conditions On Top ............................. VFR

Middle Compass Locator .............................................. ML

Middle Marker ............................................................. MM

Missed Approach ..........................................................MA

Nondirectional Beacon Approach ...............................NDB

Out of (Leave) Control Area ........................................

Outer Marker .................................................................OM

Over (Station) ..............................................................OKC

On Course ......................................................................OC

Precision Approach Radar .......................................... PAR

Procedure Turn ............................................................... PT

Radar Vector ..................................................................RV

Radial (080° Radial) .................................................. 080R

Reduce Speed 20 Knots .............................................-20 K

Remain This Frequency ...............................................RTF

Remain Well to Left Side .............................................. LS

Remain Well to Right Side ............................................ RS

Report Crossing .............................................................RX

Report Departing ............................................................RD

Report Leaving ...............................................................RL

Report on Course .....................................................R-CRS

Report Over ....................................................................RO

Report Passing ............................................................... RP

Report Reaching .............................................................RR

Report Starting Procedure Turn .................................RSPT

Reverse Course ..............................................................RC

Right Turn After Takeoff .................................................

Runway Heading ............................................................RH

Runway (Number) .....................................................RY18

Squawk ........................................................................... SQ

Standby .....................................................................STBY

Straight-in Approach ........................................................SI

Surveillance Radar Approach ..................................... ASR

Takeoff (Direction) ................................................... T N

Tower ................................................................................Z

Turn Left ........................................................................ TL

Turn Right ...................................................................... TR

Until ................................................................................... /

Until Advised (By) ........................................................ UA

Until Further Advised ................................................. UFA

VFR Conditions On Top ..............................................OTP

Via ................................................................................ VIA

Victor (Airway Number) .............................................. V14

Visual Approach ........................................................... VA

VOR ..............................................................................

VOR Approach ..............................................................VR

VORTAC ......................................................................

While in Control Area ..................................................

B-1

Introduction

Flight instructors may use this guide in the development of

lesson plans. The lessons are arranged in a logical learning

sequence and use the building-block technique. Each lesson

includes ground training appropriate to the ﬂ ight portion of

the lesson. It is vitally important that the ﬂ ight instructor brief

the student on the objective of the lesson and how it will be

accomplished. Debrieﬁ ng the student’s performance is also

necessary to motivate further progress. To ensure steady

progress, student pilots should master the objective of each

lesson before advancing to the next lesson. Lessons should

be arranged to take advantage of each student’s knowledge

and skills.

Flight instructors must monitor progress closely during

training to guide student pilots in how to properly divide

their attention. The importance of this division of attention

or “cross-check” cannot be overemphasized. Cross-check and

proper instrument interpretation are essential components

of “attitude instrument ﬂ ying” that enables student pilots to

accurately visualize the aircraft’s attitude at all times.

When possible, each lesson should incorporate radio

communications, basic navigation, and emergency procedures

so the student pilot is exposed to the entire IFR experience

with each ﬂ ight. Cross-reference the Instrument Training

Lesson Guide with this handbook and the Instrument

Practical Test Standards for a comprehensive instrument

rating training program.

Lesson 1—Ground and ﬂ ight evaluation

of student’s knowledge and performance

Aircraft systems

Aircraft performance

Preﬂ ight planning

Use of checklists

Basic ﬂ ight maneuvers

Radio communications procedures

Navigation systems

Appendix B

Instrument Training Lesson Guide

Lesson 2—Preﬂ ight preparation and

ﬂ ight by reference to instruments

Ground Training

Instrument system preﬂ ight procedures

Attitude instrument ﬂ ying

Fundamental instrument skills

Instrument cross-check techniques

Flight Training

Aircraft and instrument preﬂ ight inspection

Use of checklists

Fundamental instrument skills

Basic ﬂ ight maneuvers

Instrument approach (demonstrated)

Postﬂ ight procedures

Lesson 3—Flight instruments and human

factors

Ground Training

Human factors

Flight instruments and systems

Aircraft systems

Navigation instruments and systems

Flight Training

Aircraft and instrument preﬂ ight inspection

Radio communications

Checklist procedures

Attitude instrument ﬂ ying

Fundamental instrument skills

Basic ﬂ ight maneuvers

Spatial disorientation demonstration

Navigation systems

Postﬂ ight procedures

Lesson 4—Attitude instrument ﬂ ying

Ground Training

Human factors

Flight instruments and systems

B-2

Aircraft systems

Navigation instruments and systems

Attitude instrument ﬂ ying

Fundamental instrument skills

Basic ﬂ ight maneuvers

Flight Training

Aircraft and instrument preﬂ ight inspection

Checklist procedures

Radio communications

Attitude instrument ﬂ ying

Fundamental instrument skills

Basic ﬂ ight maneuvers

Spatial disorientation

Navigation

Postﬂ ight procedures

Lesson 5—Aerodynamic factors and

basic ﬂ ight maneuvers

Ground Training

Basic aerodynamic factors

Basic instrument ﬂ ight patterns

Emergency procedures

Flight Training

Aircraft and instrument preﬂ ight inspection

Checklist procedures

Radio communications

Basic instrument ﬂ ight patterns

Emergency procedures

Navigation

Postﬂ ight procedures

Lesson 6—Partial panel operations

Ground Training

ATC system

Flight instruments

Partial panel operations

Flight Training

Aircraft and instrument preﬂ ight inspection

Checklist procedures

Radio communications

Basic instrument ﬂ ight patterns

Emergency procedures

Partial panel practice

Navigation

Postﬂ ight procedures

Lesson 7—Recovery from unusual

attitudes

Ground Training

Attitude instrument ﬂ ying

ATC system

NAS overview

Flight Training

Preﬂ ight

Aircraft and instrument preﬂ ight inspection

Checklist procedures

Radio communications

Instrument takeoff

Navigation

Partial panel practice

Recovery from unusual attitudes

Postﬂ ight procedures

Lesson 8—Navigation systems

Ground Training

ATC clearances

Departure procedures

IFR en route charts

Flight Training

Aircraft and instrument preﬂ ight inspection

Checklist procedures

Radio communications

Intercepting and tracking

Holding

Postﬂ ight procedures

Lesson 9—Review and practice

Ground Training

Aerodynamic factors

Flight instruments and systems

Attitude instrument ﬂ ying

Navigation systems

NAS

ATC

Emergency procedures

Flight Training

Aircraft and instrument preﬂ ight inspection

Checklist procedures

Radio communications

Review and practice as determined by the ﬂ ight instructor

B-3

Instrument takeoff

Radio communications

Navigation systems

Emergency procedures

Postﬂ ight procedures

Lessons 10 through 19—Orientation,

intercepting, tracking, and holding using

each navigation system installed in the

aircraft

Ground Training

Preﬂ ight planning

Navigation systems

NAS

ATC

Emergencies

Flight Training

Aircraft and instrument preﬂ ight inspection

Checklist procedures

Radio communications

Departure procedures

En route navigation

Terminal operations

Partial panel operation

Instrument approach

Missed approach

Approach to a landing

Postﬂ ight procedures

Lessons 20 and 21—Cross-country

ﬂ ights

Ground Training

Preﬂ ight planning

Aircraft performance

Navigation systems

NAS

ATC

Emergencies

Flight Training

Emergency procedures

Partial panel operation

Aircraft and instrument preﬂ ight inspection

Checklist procedures

Radio communications

Departure procedures

En route navigation

Terminal operations

Instrument approach

Missed approach

Approach to a landing

Postﬂ ight procedures

Lessons 22 and 23—Review and practice

Ground Training

Human factors

Aerodynamic factors

Flight instruments and systems

Attitude instrument ﬂ ying

Basic ﬂ ight maneuvers

Navigation systems

NAS

ATC

Emergency operations

Flight Training

Aircraft and instrument preﬂ ight inspection

Checklist procedures

Radio communications

Review and practice as determined by the ﬂ ight instructor

Instrument takeoff

Partial panel operations

Unusual attitude recoveries

Radio communications

Navigation systems

Emergency procedures

Postﬂ ight procedures

Lessons 24 and subsequent—Practical

test preparation

Ground Training

Title 14 of the Code of Federal Regulations (14 CFR) parts

61, 71, 91, 95, and 97

Instrument Flying Handbook

Practical test standards

Administrative requirements

Equipment requirements

Applicant’s requirements

Flight Training

Review and practice until the student can consistently

perform all required tasks in accordance with the appropriate

practical test standards.

NOTE: It is the recommending instructor’s responsibility to

ensure that the applicant meets 14 CFR part 61 requirements

and is prepared for the practical test, including: training,

knowledge, experience, and the appropriate instructor

endorsements.

G-1

Absolute accuracy. The ability to determine present position

in space independently, and is most often used by pilots.

Absolute altitude. The actual distance between an aircraft

and the terrain over which it is ﬂ ying.

Absolute pressure. Pressure measured from the reference

of zero pressure, or a vacuum.

A.C. Alternating current.

Acceleration error. A magnetic compass error apparent when

the aircraft accelerates while ﬂ ying on an easterly or westerly

heading, causing the compass card to rotate toward North.

Accelerometer. A part of an inertial navigation system

(INS) that accurately measures the force of acceleration in

one direction.

ADF. See automatic direction ﬁ nder.

ADI. See attitude director indicator.

ADM. See aeronautical decision-making.

ADS–B. See automatic dependent surveillance–broadcast.

Adverse yaw. A ﬂ ight condition at the beginning of a turn in

which the nose of the aircraft starts to move in the direction

opposite the direction the turn is being made, caused by the

induced drag produced by the downward-deﬂ ected aileron

holding back the wing as it begins to rise.

Aeronautical decision-making (ADM). A systematic

approach to the mental process used by pilots to consistently

determine the best course of action in response to a given

set of circumstances.

A/FD. See Airport/Facility Directory.

Glossary

Agonic line. An irregular imaginary line across the surface of

the Earth along which the magnetic and geographic poles are in

alignment, and along which there is no magnetic variation.

Aircraft approach category. A performance grouping of

aircraft based on a speed of 1.3 times the stall speed in the

landing conﬁ guration at maximum gross landing weight.

Air data computer (ADC). An aircraft computer that

receives and processes pitot pressure, static pressure, and

temperature to calculate very precise altitude, indicated

airspeed, true airspeed, and air temperature.

AIRMET. Inﬂ ight weather advisory issued as an amendment

to the area forecast, concerning weather phenomena of

operational interest to all aircraft and that is potentially

hazardous to aircraft with limited capability due to lack of

equipment, instrumentation, or pilot qualiﬁ cations.

Airport diagram. The section of an instrument approach

procedure chart that shows a detailed diagram of the

airport. This diagram includes surface features and airport

conﬁ guration information.

Airport/Facility Directory (A/FD). An FAA publication

containing information on all airports, communications,

and NAVAIDs.

Airport surface detection equipment (ASDE). Radar

equipment specifically designed to detect all principal

features and trafﬁ c on the surface of an airport, presenting the

entire image on the control tower console; used to augment

visual observation by tower personnel of aircraft and/or

vehicular movements on runways and taxiways.

Airport surveillance radar (ASR). Approach control

radar used to detect and display an aircraft’s position in the

terminal area.

G-2

Airport surveillance radar approach. An instrument

approach in which ATC issues instructions for pilot

compliance based on aircraft position in relation to the ﬁ nal

approach course and the distance from the end of the runway

as displayed on the controller’s radar scope.

Air route surveillance radar (ARSR). Air route trafﬁ c

control center (ARTCC) radar used primarily to detect

and display an aircraft’s position while en route between

terminal areas.

Air route traffic control center (ARTCC). Provides ATC

service to aircraft operating on IFR flight plans within

controlled airspace and principally during the en route phase

of ﬂ ight.

Airspeed indicator. A differential pressure gauge that

measures the dynamic pressure of the air through which the

aircraft is flying. Displays the craft’s airspeed, typically in

knots, to the pilot.

Air traffic control radar beacon system (ATCRBS).

Sometimes called secondary surveillance radar (SSR), which

utilizes a transponder in the aircraft. The ground equipment is

an interrogating unit, in which the beacon antenna is mounted

so it rotates with the surveillance antenna. The interrogating

unit transmits a coded pulse sequence that actuates the aircraft

transponder. The transponder answers the coded sequence by

transmitting a preselected coded sequence back to the ground

equipment, providing a strong return signal and positive

aircraft identification, as well as other special data.

Airway. An airway is based on a centerline that extends from

one navigation aid or intersection to another navigation aid

(or through several navigation aids or intersections); used

to establish a known route for en route procedures between

terminal areas.

Alert area. An area in which there is a high volume of pilot

training or an unusual type of aeronautical activity.

Almanac data. Information the global positioning system

(GPS) receiver can obtain from one satellite which describes

the approximate orbital positioning of all satellites in the

constellation. This information is necessary for the GPS

receiver to know what satellites to look for in the sky at a

given time.

ALS. See approach lighting system.

Alternate airport. An airport designated in an IFR ﬂ ight

plan, providing a suitable destination if a landing at the

intended airport becomes inadvisable.

Alternate static source valve. A valve in the instrument static

air system that supplies reference air pressure to the altimeter,

airspeed indicator, and vertical speed indicator if the normal

static pickup should become clogged or iced over.

Altimeter setting. Station pressure (the barometric pressure

at the location the reading is taken) which has been corrected

for the height of the station above sea level.

AME. See aviation medical examiner.

Amendment status. The circulation date and revision

number of an instrument approach procedure, printed above

the procedure identiﬁ cation.

Ammeter. An instrument installed in series with an electrical

load used to measure the amount of current ﬂ owing through

the load.

Aneroid. The sensitive component in an altimeter or

barometer that measures the absolute pressure of the air.

It is a sealed, ﬂ at capsule made of thin disks of corrugated

metal soldered together and evacuated by pumping all of

the air out of it.

Aneroid barometer. An instrument that measures the

absolute pressure of the atmosphere by balancing the weight

of the air above it against the spring action of the aneroid.

Angle of attack. The acute angle formed between the

chord line of an airfoil and the direction of the air striking

the airfoil.

Anti-ice. Preventing the accumulation of ice on an aircraft

structure via a system designed for that purpose.

Approach lighting system (ALS). Provides lights that will

penetrate the atmosphere far enough from touchdown to give

directional, distance, and glide path information for safe

transition from instrument to visual ﬂ ight.

Area chart. Part of the low-altitude en route chart series,

this chart furnishes terminal data at a larger scale for

congested areas.

Area navigation (RNAV). Allows a pilot to ﬂ y a selected

course to a predetermined point without the need to overﬂ y

ground-based navigation facilities, by using waypoints.

ARSR. See air route surveillance radar.

ARTCC. See air route trafﬁ c control center.

G-3

ASDE. See airport surface detection equipment.

ASOS. See automated surface observing station.

ASR. See airport surveillance radar.

ATC. Air Trafﬁ c Control.

ATCRBS. See air traffic control radar beacon system.

ATIS. See automatic terminal information service.

Atmospheric propagation delay. A bending of the

electromagnetic (EM) wave from the satellite that creates

an error in the GPS system.

Attitude and heading reference systems (AHRS). System

composed of three-axis sensors that provide heading, attitude,

and yaw information for aircraft. AHRS are designed to

replace traditional mechanical gyroscopic flight instruments

and provide superior reliability and accuracy.

Attitude director indicator (ADI). An aircraft attitude

indicator that incorporates ﬂ ight command bars to provide

pitch and roll commands.

Attitude indicator. The foundation for all instrument ﬂ ight,

this instrument reﬂ ects the airplane’s attitude in relation to

the horizon.

Attitude instrument flying. Controlling the aircraft by

reference to the instruments rather than by outside visual

cues.

Autokinesis. Nighttime visual illusion that a stationary light

is moving, which becomes apparent after several seconds of

staring at the light.

Automated Weather Observing System (AWOS).

Automated weather reporting system consisting of various

sensors, a processor, a computer-generated voice subsystem,

and a transmitter to broadcast weather data.

Automated Surface Observing Station (ASOS). Weather

reporting system which provides surface observations every

minute via digitized voice broadcasts and printed reports.

Automatic dependent surveillance–broadcast (ADS-B). A

device used in aircraft that repeatedly broadcasts a message

that includes position (such as latitude, longitude, and

altitude), velocity, and possibly other information.

Automatic direction finder (ADF). Electronic navigation

equipment that operates in the low- and medium-frequency

bands. Used in conjunction with the ground-based

nondirectional beacon (NDB), the instrument displays the

number of degrees clockwise from the nose of the aircraft

to the station being received.

Automatic terminal information service (ATIS). The

continuous broadcast of recorded non-control information in

selected terminal areas. Its purpose is to improve controller

effectiveness and relieve frequency congestion by automating

repetitive transmission of essential but routine information.

Aviation medical examiner (AME). A physician with

training in aviation medicine designated by the Civil

Aerospace Medical Institute (CAMI).

AWOS. See automated weather observing system.

Azimuth card. A card that may be set, gyroscopically

controlled, or driven by a remote compass.

Back course (BC). The reciprocal of the localizer course

for an ILS. When ﬂ ying a back-course approach, an aircraft

approaches the instrument runway from the end at which the

localizer antennas are installed.

Baro-aiding. A method of augmenting the GPS integrity

solution by using a non-satellite input source. To ensure that

baro-aiding is available, the current altimeter setting must

be entered as described in the operating manual.

Barometric scale. A scale on the dial of an altimeter to which

the pilot sets the barometric pressure level from which the

altitude shown by the pointers is measured.

BC. See back course.

Block altitude. A block of altitudes assigned by ATC to

allow altitude deviations; for example, “Maintain block

altitude 9 to 11 thousand.”

Cage. The black markings on the ball instrument indicating

its neutral position.

Calibrated. The instrument indication compared with a

standard value to determine the accuracy of the instrument.

Calibrated oriﬁ ce. A hole of speciﬁ c diameter used to delay

the pressure change in the case of a vertical speed indicator.

G-4

Calibrated airspeed. The speed at which the aircraft

is moving through the air, found by correcting IAS for

instrument and position errors.

CAS. Calibrated airspeed.

CDI. Course deviation indicator.

Changeover point (COP). A point along the route or

airway segment between two adjacent navigation facilities

or waypoints where changeover in navigation guidance

should occur.

Circling approach. A maneuver initiated by the pilot to

align the aircraft with a runway for landing when a straight-

in landing from an instrument approach is not possible or is

not desirable.

Class A airspace. Airspace from 18,000 feet MSL up to and

including FL 600, including the airspace overlying the waters

within 12 NM of the coast of the 48 contiguous states and

Alaska; and designated international airspace beyond 12 NM

of the coast of the 48 contiguous states and Alaska within areas

of domestic radio navigational signal or ATC radar coverage,

and within which domestic procedures are applied.

Class B airspace. Airspace from the surface to 10,000 feet

MSL surrounding the nation’s busiest airports in terms of

IFR operations or passenger numbers. The conﬁ guration of

each Class B airspace is individually tailored and consists

of a surface area and two or more layers, and is designed to

contain all published instrument procedures once an aircraft

enters the airspace. For all aircraft, an ATC clearance is

required to operate in the area, and aircraft so cleared receive

separation services within the airspace.

Class C airspace. Airspace from the surface to 4,000 feet

above the airport elevation (charted in MSL) surrounding

those airports having an operational control tower, serviced

by radar approach control, and having a certain number of IFR

operations or passenger numbers. Although the conﬁ guration

of each Class C airspace area is individually tailored, the

airspace usually consists of a 5 NM radius core surface area

that extends from the surface up to 4,000 feet above the airport

elevation, and a 10 NM radius shelf area that extends from

1,200 feet to 4,000 feet above the airport elevation.

Class D airspace. Airspace from the surface to 2,500 feet

above the airport elevation (charted in MSL) surrounding

those airports that have an operational control tower. The

conﬁ guration of each Class D airspace area is individually

tailored, and when instrument procedures are published, the

airspace is normally designed to contain the procedures.

Class E airspace. Airspace that is not Class A, Class B, Class

C, or Class D, and is controlled airspace.

Class G airspace. Airspace that is uncontrolled, except

when associated with a temporary control tower, and has

not been designated as Class A, Class B, Class C, Class D,

or Class E airspace.

Clean configuration. A conﬁ guration in which all ﬂ ight

control surfaces have been placed to create minimum drag.

In most aircraft this means ﬂ aps and gear retracted.

Clearance. ATC permission for an aircraft to proceed under

speciﬁ ed trafﬁ c conditions within controlled airspace, for the

purpose of providing separation between known aircraft.

Clearance delivery. Control tower position responsible for

transmitting departure clearances to IFR ﬂ ights.

Clearance limit. The ﬁ x, point, or location to which an

aircraft is cleared when issued an air trafﬁ c clearance.

Clearance on request. An IFR clearance not yet received

after ﬁ ling a ﬂ ight plan.

Clearance void time. Used by ATC, the time at which the

departure clearance is automatically canceled if takeoff has

not been made. The pilot must obtain a new clearance or

cancel the IFR ﬂ ight plan if not off by the speciﬁ ed time.

Clear ice. Glossy, clear, or translucent ice formed by the

relatively slow freezing of large, supercooled water droplets.

Compass course. A true course corrected for variation and

deviation errors.

Compass locator. A low-power, low- or medium-frequency

(L/MF) radio beacon installed at the site of the outer or middle

marker of an ILS.

Compass rose. A small circle graduated in 360° increments,

printed on navigational charts to show the amount of

compass variation at different locations, or on instruments

to indicate direction.

Computer navigation fix. A point used to define a

navigation track for an airborne computer system such as

GPS or FMS.

Concentric rings. Dashed-line circles depicted in the plan

view of IAP charts, outside of the reference circle, that show

en route and feeder facilities.

G-5

Cone of confusion. A cone-shaped volume of airspace

directly above a VOR station where no signal is received,

causing the CDI to ﬂ uctuate.

Control and performance. A method of attitude instrument

ﬂ ying in which one instrument is used for making attitude

changes, and the other instruments are used to monitor the

progress of the change.

Control display unit. A display interfaced with the master

computer, providing the pilot with a single control point

for all navigations systems, thereby reducing the number of

required flight deck panels.

Controlled airspace. An airspace of deﬁ ned dimensions

within which ATC service is provided to IFR and VFR ﬂ ights

in accordance with the airspace classiﬁ cation. It includes

Class A, Class B, Class C, Class D, and Class E airspace.

Control pressures. The amount of physical exertion on the

control column necessary to achieve the desired attitude.

Convective weather. Unstable, rising air found in

cumiliform clouds.

Convective SIGMET. Weather advisory concerning

convective weather signiﬁ cant to the safety of all aircraft,

including thunderstorms, hail, and tornadoes.

Coordinated flight. Flight with a minimum disturbance of

the forces maintaining equilibrium, established via effective

control use.

COP. See changeover point.

Coriolis illusion. The illusion of rotation or movement in an

entirely different axis, caused by an abrupt head movement,

while in a prolonged constant rate turn that has ceased

stimulating the brain’s motion sensing system.

Crew resource management (CRM). The effective

use of all available resources—human, hardware, and

information.

Critical areas. Areas where disturbances to the ILS localizer

and glide slope courses may occur when surface vehicles or

aircraft operate near the localizer or glide slope antennas.

CRM. See crew resource management.

Cross-check. The ﬁ rst fundamental skill of instrument ﬂ ight,

also known as “scan,” the continuous and logical observation

of instruments for attitude and performance information.

Cruise clearance. An ATC clearance issued to allow a

pilot to conduct ﬂ ight at any altitude from the minimum

IFR altitude up to and including the altitude speciﬁ ed in the

clearance. Also authorizes a pilot to proceed to and make an

approach at the destination airport.

Current induction. An electrical current being induced into,

or generated in, any conductor that is crossed by lines of ﬂ ux

from any magnet.

DA. See decision altitude.

D.C. Direct current.

Dark adaptation. Physical and chemical adjustments of the

eye that make vision possible in relative darkness.

Deceleration error. A magnetic compass error that occurs

when the aircraft decelerates while ﬂ ying on an easterly

or westerly heading, causing the compass card to rotate

toward South.

Decision altitude (DA). A speciﬁ ed altitude in the precision

approach, charted in feet MSL, at which a missed approach

must be initiated if the required visual reference to continue

the approach has not been established.

Decision height (DH). A speciﬁ ed altitude in the precision

approach, charted in height above threshold elevation,

at which a decision must be made either to continue the

approach or to execute a missed approach.

Deice. The act of removing ice accumulation from an

aircraft structure.

Density altitude. Pressure altitude corrected for nonstandard

temperature. Density altitude is used in computing the

performance of an aircraft and its engines.

Departure procedure (DP). Preplanned IFR ATC departure,

published for pilot use, in textual and graphic format.

Deviation. A magnetic compass error caused by local

magnetic ﬁ elds within the aircraft. Deviation error is different

on each heading.

DGPS. Differential global positioning system.

DH. See decision height.

G-6

Differential Global Positioning System (DGPS). A system

that improves the accuracy of Global Navigation Satellite

Systems (GNSS) by measuring changes in variables to

provide satellite positioning corrections.

Direct indication. The true and instantaneous reﬂ ection of

aircraft pitch-and-bank attitude by the miniature aircraft,

relative to the horizon bar of the attitude indicator.

Direct User Access Terminal System (DUATS). A system

that provides current FAA weather and ﬂ ight plan ﬁ ling

services to certiﬁ ed civil pilots, via personal computer,

modem, or telephone access to the system. Pilots can request

speciﬁ c types of weather brieﬁ ngs and other pertinent data

for planned ﬂ ights.

Distance circle. See reference circle.

Distance measuring equipment (DME). A pulse-type

electronic navigation system that shows the pilot, by an

instrument-panel indication, the number of nautical miles

between the aircraft and a ground station or waypoint.

DME. See distance measuring equipment.

DME arc. A ﬂ ight track that is a constant distance from the

station or waypoint.

DOD. Department of Defense.

Doghouse. A turn-and-slip indicator dial mark in the shape

of a doghouse.

Domestic Reduced Vertical Separation Minimum

(DRVSM). Additional ﬂ ight levels between FL 290 and FL

410 to provide operational, trafﬁ c, and airspace efﬁ ciency.

Double gimbal. A type of mount used for the gyro in an

attitude instrument. The axes of the two gimbals are at right

angles to the spin axis of the gyro, allowing free motion in

two planes around the gyro.

DP. See departure procedure.

Drag. The net aerodynamic force parallel to the relative

wind, usually the sum of two components: induced drag

and parasite drag.

Drag curve. The curve created when plotting induced drag

and parasite drag.

DUATS. See direct user access terminal system.

Duplex. Transmitting on one frequency and receiving on a

separate frequency.

Eddy currents. Current induced in a metal cup or disc when

it is crossed by lines of ﬂ ux from a moving magnet.

EFAS. See En Route Flight Advisory Service.

EFC. See expect-further-clearance.

Electronic flight display (EFD). For the purpose of

standardization, any flight instrument display that uses

LCD or other image-producing system (Cathode Ray Tube

[CRT], etc.)

Elevator illusion. The sensation of being in a climb or

descent, caused by the kind of abrupt vertical accelerations

that result from up- or downdrafts.

Emergency. A distress or urgent condition.

Emphasis error. The result of giving too much attention

to a particular instrument during the cross-check, instead of

relying on a combination of instruments necessary for attitude

and performance information.

EM wave. Electromagnetic wave.

Encoding altimeter. A special type of pressure altimeter

used to send a signal to the air trafﬁ c controller on the ground,

showing the pressure altitude the aircraft is ﬂ ying.

En route facilities ring. Depicted in the plan view of IAP

charts, a circle which designates NAVAIDs, ﬁ xes, and

intersections that are part of the en route low altitude airway

structure.

En Route Flight Advisory Service (EFAS). An en route

weather-only AFSS service.

En route high-altitude charts. Aeronautical charts for en

route instrument navigation at or above 18,000 feet MSL.

En route low-altitude charts. Aeronautical charts for en

route IFR navigation below 18,000 feet MSL.

Equivalent airspeed. Airspeed equivalent to CAS in

standard atmosphere at sea level. As the airspeed and pressure

altitude increase, the CAS becomes higher than it should be,

and a correction for compression must be subtracted from

the CAS.

G-7

Expect-further-clearance (EFC). The time a pilot can

expect to receive clearance beyond a clearance limit.

FAA. Federal Aviation Administration.

FAF. See ﬁ nal approach ﬁ x.

False horizon. Inaccurate visual information for aligning the

aircraft, caused by various natural and geometric formations

that disorient the pilot from the actual horizon.

Federal airways. Class E airspace areas that extend upward

from 1,200 feet to, but not including, 18,000 feet MSL, unless

otherwise speciﬁ ed.

Feeder facilities. Used by ATC to direct aircraft to

intervening ﬁ xes between the en route structure and the

initial approach ﬁ x.

Final approach. Part of an instrument approach

procedure in which alignment and descent for landing are

accomplished.

Final approach fix (FAF). The ﬁ x from which the IFR

ﬁ nal approach to an airport is executed, and which identiﬁ es

the beginning of the ﬁ nal approach segment. An FAF is

designated on government charts by a Maltese cross symbol

for nonprecision approaches, and a lightning bolt symbol for

precision approaches.

Fixating. Staring at a single instrument, thereby interrupting

the cross-check process.

FL. See ﬂ ight level.

Flight configurations. Adjusting the aircraft control surfaces

(including ﬂ aps and landing gear) in a manner that will

achieve a speciﬁ ed attitude.

Flight director indicator (FDI). One of the major components

of a flight director system, it provides steering commands that

the pilot (or the autopilot, if coupled) follows.

Flight level (FL). A measure of altitude (in hundreds of feet)

used by aircraft ﬂ ying above 18,000 feet with the altimeter

set at 29.92" Hg.

Flight management system (FMS). Provides pilot and crew

with highly accurate and automatic long-range navigation

capability, blending available inputs from long- and short-

range sensors.

Flight path. The line, course, or track along which an aircraft

is ﬂ ying or is intended to be ﬂ own.

Flight patterns. Basic maneuvers, ﬂ own by reference to the

instruments rather than outside visual cues, for the purpose

of practicing basic attitude ﬂ ying. The patterns simulate

maneuvers encountered on instrument ﬂ ights such as holding

patterns, procedure turns, and approaches.

Flight strips. Paper strips containing instrument flight

information, used by ATC when processing ﬂ ight plans.

FMS. See ﬂ ight management system.

Form drag. The drag created because of the shape of a

component or the aircraft.

Fundamental skills. Pilot skills of instrument cross-check,

instrument interpretation, and aircraft control.

Glide slope (GS). Part of the ILS that projects a radio beam

upward at an angle of approximately 3° from the approach

end of an instrument runway. The glide slope provides

vertical guidance to aircraft on the ﬁ nal approach course for

the aircraft to follow when making an ILS approach along

the localizer path.

Glide slope intercept altitude. The minimum altitude of an

intermediate approach segment prescribed for a precision

approach that ensures obstacle clearance.

Global landing system (GLS). An instrument approach with

lateral and vertical guidance with integrity limits (similar to

barometric vertical navigation (BRO VNAV).

Global navigation satellite systems (GNSS). Satellite

navigation systems that provide autonomous geo-spatial

positioning with global coverage. It allows small electronic

receivers to determine their location (longitude, latitude, and

altitude) to within a few meters using time signals transmitted

along a line of sight by radio from satellites.

GNSS. See global navigation satellite systems.

Global positioning system (GPS). Navigation system

that uses satellite rather than ground-based transmitters for

location information.

G-8

Goniometer. As used in radio frequency (RF) antenna

systems, a direction-sensing device consisting of two ﬁ xed

loops of wire oriented 90° from each other, which separately

sense received signal strength and send those signals to two

rotors (also oriented 90°) in the sealed direction-indicating

instrument. The rotors are attached to the direction-indicating

needle of the instrument and rotated by a small motor until

minimum magnetic ﬁ eld is sensed near the rotors.

GPS. See global positioning system.

GPS Approach Overlay Program. An authorization for

pilots to use GPS avionics under IFR for ﬂ ying designated

existing nonprecision instrument approach procedures, with

the exception of LOC, LDA, and SDF procedures.

Graveyard spiral. The illusion of the cessation of a turn

while still in a prolonged, coordinated, constant rate turn,

which can lead a disoriented pilot to a loss of control of the

aircraft.

Great circle route. The shortest distance across the surface

of a sphere (the Earth) between two points on the surface.

Ground proximity warning system (GPWS). A system

designed to determine an aircraft’s clearance above the Earth

and provides limited predictability about aircraft position

relative to rising terrain.

Groundspeed. Speed over the ground, either closing speed to

the station or waypoint, or speed over the ground in whatever

direction the aircraft is going at the moment, depending upon

the navigation system used.

GS. See glide slope.

GWPS. See ground proximity warning system.

HAA. See height above airport.

HAL. See height above landing.

HAT. See height above touchdown elevation.

Hazardous attitudes. Five aeronautical decision-making

attitudes that may contribute to poor pilot judgment:

antiauthority, impulsivity, invulnerability, machismo, and

resignation.

Hazardous Inflight Weather Advisory Service (HIWAS).

Service providing recorded weather forecasts broadcast to

airborne pilots over selected VORs.

Head-up display (HUD). A special type of ﬂ ight viewing

screen that allows the pilot to watch the ﬂ ight instruments

and other data while looking through the windshield of the

aircraft for other trafﬁ c, the approach lights, or the runway.

Height above airport (HAA). The height of the MDA above

the published airport elevation.

Height above landing (HAL). The height above a designated

helicopter landing area used for helicopter instrument

approach procedures.

Height above touchdown elevation (HAT). The DA/DH or

MDA above the highest runway elevation in the touchdown

zone (ﬁ rst 3,000 feet of the runway).

HF. High frequency.

Hg. Abbreviation for mercury, from the Latin

hydrargyrum.

HIWAS. See Hazardous Inflight Weather Advisory

Service.

Holding. A predetermined maneuver that keeps aircraft

within a speciﬁ ed airspace while awaiting further clearance

from ATC.

Holding pattern. A racetrack pattern, involving two turns

and two legs, used to keep an aircraft within a prescribed

airspace with respect to a geographic ﬁ x. A standard pattern

uses right turns; nonstandard patterns use left turns.

Homing. Flying the aircraft on any heading required to keep

the needle pointing to the 0° relative bearing position.

Horizontal situation indicator (HSI). A ﬂ ight navigation

instrument that combines the heading indicator with a CDI,

in order to provide the pilot with better situational awareness

of location with respect to the courseline.

HSI. See horizontal situation indicator.

HUD. See head-up display.

Human factors. A multidisciplinary ﬁ eld encompassing the

behavioral and social sciences, engineering, and physiology,

to consider the variables that influence individual and

crew performance for the purpose of optimizing human

performance and reducing errors.

G-9

Hypoxia. A state of oxygen deﬁ ciency in the body sufﬁ cient

to impair functions of the brain and other organs.

IAF. See initial approach ﬁ x.

IAP. See instrument approach procedures.

IAS. See indicated airspeed.

ICAO. See International Civil Aviation Organization.

Ident. Air Traffic Control request for a pilot to push

the button on the transponder to identify return on the

controller’s scope.

IFR. See instrument ﬂ ight rules.

ILS. See instrument landing system.

ILS categories. Categories of instrument approach

procedures allowed at airports equipped with the following

types of instrument landing systems:

ILS Category I: Provides for approach to a height

above touchdown of not less than 200 feet, and with

runway visual range of not less than 1,800 feet.

ILS Category II: Provides for approach to a height

above touchdown of not less than 100 feet and with

runway visual range of not less than 1,200 feet.

ILS Category IIIA: Provides for approach without

a decision height minimum and with runway visual

range of not less than 700 feet.

ILS Category IIIB: Provides for approach without

a decision height minimum and with runway visual

range of not less than 150 feet.

ILS Category IIIC: Provides for approach without a

decision height minimum and without runway visual

range minimum.

IMC. See instrument meteorological conditions.

Indicated airspeed (IAS). Shown on the dial of the

instrument airspeed indicator on an aircraft. Directly related

to calibrated airspeed (CAS), IAS includes instrument errors

and position error.

Indirect indication. A reﬂ ection of aircraft pitch-and-bank

attitude by the instruments other than the attitude indicator.

Induced drag. Drag caused by the same factors that produce

lift; its amount varies inversely with airspeed. As airspeed

decreases, the angle of attack must increase, in turn increasing

induced drag.

Induction icing. A type of ice in the induction system that

reduces the amount of air available for combustion. The most

commonly found induction icing is carburetor icing.

Inertial navigation system (INS). A computer-based

navigation system that tracks the movement of an aircraft

via signals produced by onboard accelerometers. The initial

location of the aircraft is entered into the computer, and all

subsequent movement of the aircraft is sensed and used to

keep the position updated. An INS does not require any inputs

from outside signals.

Initial approach fix (IAF). The ﬁ x depicted on IAP charts

where the instrument approach procedure (IAP) begins unless

otherwise authorized by ATC.

Inoperative components. Higher minimums are prescribed

when the specified visual aids are not functioning; this

information is listed in the Inoperative Components Table found

in the United States Terminal Procedures Publications.

INS. See inertial navigation system.

Instantaneous vertical speed indicator (IVSI). Assists in

interpretation by instantaneously indicating the rate of climb

or descent at a given moment with little or no lag as displayed

in a vertical speed indicator (VSI).

Instrument approach procedures (IAP). A series of

predetermined maneuvers for the orderly transfer of an

aircraft under IFR from the beginning of the initial approach

to a landing or to a point from which a landing may be

made visually.

Instrument flight rules (IFR). Rules and regulations

established by the Federal Aviation Administration to govern

ﬂ ight under conditions in which ﬂ ight by outside visual

reference is not safe. IFR ﬂ ight depends upon ﬂ ying by

reference to instruments in the ﬂ ight deck, and navigation is

accomplished by reference to electronic signals.

Instrument landing system (ILS). An electronic system

that provides both horizontal and vertical guidance to a

speciﬁ c runway, used to execute a precision instrument

approach procedure.

Instrument meteorological conditions (IMC).

Meteorological conditions expressed in terms of visibility,

distance from clouds, and ceiling less than the minimums

speciﬁ ed for visual meteorological conditions, requiring

operations to be conducted under IFR.

G-10

Instrument takeoff. Using the instruments rather than

outside visual cues to maintain runway heading and execute

a safe takeoff.

Interference drag. Drag generated by the collision of

airstreams creating eddy currents, turbulence, or restrictions

to smooth flow.

International Civil Aviation Organization (ICAO). The

United Nations agency for developing the principles and

techniques of international air navigation, and fostering planning

and development of international civil air transport.

International standard atmosphere (IAS). A model of

standard variation of pressure and temperature.

Inversion illusion. The feeling that the aircraft is tumbling

backwards, caused by an abrupt change from climb to straight-

and-level ﬂ ight while in situations lacking visual reference.

Inverter. A solid-state electronic device that converts D.C.

into A.C. current of the proper voltage and frequency to

operate A.C. gyro instruments.

Isogonic lines. Lines drawn across aeronautical charts to

connect points having the same magnetic variation.

IVSI. See instantaneous vertical speed indicator.

Jet route. A route designated to serve ﬂ ight operations from

18,000 feet MSL up to and including FL 450.

Jet stream. A high-velocity narrow stream of winds, usually

found near the upper limit of the troposphere, which ﬂ ows

generally from west to east.

KIAS. Knots indicated airspeed.

Kollsman window. A barometric scale window of a

sensitive altimeter used to adjust the altitude for the

altimeter setting.

LAAS. See local area augmentation system.

Lag. The delay that occurs before an instrument needle attains

a stable indication.

Land as soon as possible. ATC instruction to pilot. Land

without delay at the nearest suitable area, such as an open

ﬁ eld, at which a safe approach and landing is assured.

Land as soon as practical. ATC instruction to pilot. The

landing site and duration of ﬂ ight are at the discretion of the

pilot. Extended ﬂ ight beyond the nearest approved landing

area is not recommended.

Land immediately. ATC instruction to pilot. The urgency

of the landing is paramount. The primary consideration is

to ensure the survival of the occupants. Landing in trees,

water, or other unsafe areas should be considered only as

a last resort.

LDA. See localizer-type directional aid.

Lead radial. The radial at which the turn from the DME arc

to the inbound course is started.

Leans, the. A physical sensation caused by an abrupt

correction of a banked attitude entered too slowly to

stimulate the motion sensing system in the inner ear. The

abrupt correction can create the illusion of banking in the

opposite direction.

Lift. A component of the total aerodynamic force on an airfoil

and acts perpendicular to the relative wind.

Lines of flux. Invisible lines of magnetic force passing

between the poles of a magnet.

L/MF. See low or medium frequency.

LMM. See locator middle marker.

Load factor. The ratio of a speciﬁ ed load to the total weight

of the aircraft. The speciﬁ ed load is expressed in terms of

any of the following: aerodynamic forces, inertial forces, or

ground or water reactions.

Loadmeter. A type of ammeter installed between the generator

output and the main bus in an aircraft electrical system.

LOC. See localizer.

Local area augmentation system (LAAS). A differential

global positioning system (DGPS) that improves the accuracy

of the system by determining position error from the GPS

satellites, then transmitting the error, or corrective factors,

to the airborne GPS receiver.

G-11

Localizer (LOC). The portion of an ILS that gives left/right

guidance information down the centerline of the instrument

runway for ﬁ nal approach.

Localizer-type directional aid (LDA). A NAVAID used

for nonprecision instrument approaches with utility and

accuracy comparable to a localizer but which is not a part

of a complete ILS and is not aligned with the runway. Some

LDAs are equipped with a glide slope.

Locator middle marker (LMM). Nondirectional radio

beacon (NDB) compass locator, collocated with a middle

marker (MM).

Locator outer marker (LOM). NDB compass locator,

collocated with an outer marker (OM).

LOM. See locator outer marker.

Long range navigation (LORAN). An electronic

navigational system by which hyperbolic lines of position

are determined by measuring the difference in the time of

reception of synchronized pulse signals from two ﬁ xed

transmitters. LORAN A operates in the 1750 to 1950 kHz

frequency band. LORAN C and D operate in the 100 to 110

kHz frequency band.

LORAN. See long range navigation.

Low or medium frequency. A frequency range between

190–535 kHz with the medium frequency above 300

kHz. Generally associated with nondirectional beacons

transmitting a continuous carrier with either a 400 or 1,020

Hz modulation.

Lubber line. The reference line used in a magnetic compass

or heading indicator.

MAA. See maximum authorized altitude.

Mach number. The ratio of the true airspeed of the aircraft

to the speed of sound in the same atmospheric conditions,

named in honor of Ernst Mach, late 19th century physicist.

Mach meter. The instrument that displays the ratio of the

speed of sound to the true airspeed an aircraft is flying.

Magnetic bearing (MB). The direction to or from a radio

transmitting station measured relative to magnetic north.

Magnetic heading (MH). The direction an aircraft is pointed

with respect to magnetic north.

Mandatory altitude. An altitude depicted on an instrument

approach chart with the altitude value both underscored and

overscored. Aircraft are required to maintain altitude at the

depicted value.

Mandatory block altitude. An altitude depicted on an

instrument approach chart with two underscored and

overscored altitude values between which aircraft are

required to maintain altitude.

MAP. See missed approach point.

Margin identification. The top and bottom areas on an

instrument approach chart that depict information about

the procedure, including airport location and procedure

identiﬁ cation.

Marker beacon. A low-powered transmitter that directs its

signal upward in a small, fan-shaped pattern. Used along the

ﬂ ight path when approaching an airport for landing, marker

beacons indicate both aurally and visually when the aircraft

is directly over the facility.

Maximum altitude. An altitude depicted on an instrument

approach chart with overscored altitude value at which or

below aircraft are required to maintain altitude.

Maximum authorized altitude (MAA). A published altitude

representing the maximum usable altitude or ﬂ ight level for

an airspace structure or route segment.

MB. See magnetic bearing.

MCA. See minimum crossing altitude.

MDA. See minimum descent altitude.

MEA. See minimum en route altitude.

Mean sea level. The average height of the surface of the

sea at a particular location for all stages of the tide over a

19-year period.

MFD. See multi-function display.

MH. See magnetic heading.

MHz. Megahertz.

G-12

Microwave landing system (MLS). A precision instrument

approach system operating in the microwave spectrum which

normally consists of an azimuth station, elevation station,

and precision distance measuring equipment.

Mileage breakdown. A ﬁ x indicating a course change

that appears on the chart as an “x” at a break between two

segments of a federal airway.

Military operations area (MOA). Airspace established for

the purpose of separating certain military training activities

from IFR trafﬁ c.

Military training route (MTR). Airspace of deﬁ ned vertical

and lateral dimensions established for the conduct of military

training at airspeeds in excess of 250 knots indicated airspeed

(KIAS).

Minimum altitude. An altitude depicted on an instrument

approach chart with the altitude value underscored. Aircraft are

required to maintain altitude at or above the depicted value.

Minimum crossing altitude (MCA). The lowest allowed

altitude at certain ﬁ xes an aircraft must cross when proceeding

in the direction of a higher minimum en route altitude

(MEA).

Minimum descent altitude (MDA). The lowest altitude (in

feet MSL) to which descent is authorized on ﬁ nal approach,

or during circle-to-land maneuvering in execution of a

nonprecision approach.

Minimum en route altitude (MEA). The lowest published

altitude between radio fixes that ensures acceptable

navigational signal coverage and meets obstacle clearance

requirements between those ﬁ xes.

Minimum obstruction clearance altitude (MOCA). The

lowest published altitude in effect between radio ﬁ xes on VOR

airways, off-airway routes, or route segments, which meets

obstacle clearance requirements for the entire route segment

and which ensures acceptable navigational signal coverage

only within 25 statute (22 nautical) miles of a VOR.

Minimum reception altitude (MRA). The lowest altitude

at which an airway intersection can be determined.

Minimum safe altitude (MSA). The minimum altitude

depicted on approach charts which provides at least 1,000 feet

of obstacle clearance for emergency use within a speciﬁ ed

distance from the listed navigation facility.

Minimum vectoring altitude (MVA). An IFR altitude lower

than the minimum en route altitude (MEA) that provides

terrain and obstacle clearance.

Minimums section. The area on an IAP chart that displays the

lowest altitude and visibility requirements for the approach.

Missed approach. A maneuver conducted by a pilot when an

instrument approach cannot be completed to a landing.

Missed approach point (MAP). A point prescribed in each

instrument approach at which a missed approach procedure

shall be executed if the required visual reference has not

been established.

Mixed ice. A mixture of clear ice and rime ice.

MLS. See microwave landing system.

MM. Middle marker.

MOA. See military operations area.

MOCA. See minimum obstruction clearance altitude.

Mode C. Altitude reporting transponder mode.

MRA. See minimum reception altitude.

MSA. See minimum safe altitude.

MSL. See mean sea level.

MTR. See military training route.

Multi-function display (MFD). Small screen (CRT or LCD)

in an aircraft that can be used to display information to the

pilot in numerous configurable ways. Often an MFD will be

used in concert with a Primary Flight Display.

MVA. See minimum vectoring altitude.

NACG. See National Aeronautical Charting Group.

NAS. See National Airspace System.

National Airspace System (NAS). The common network of

United States airspace—air navigation facilities, equipment

and services, airports or landing areas; aeronautical charts,

information and services; rules, regulations and procedures,

technical information; and manpower and material.

G-13

National Aeronautical Charting Group (NACG). A

Federal agency operating under the FAA, responsible for

publishing charts such as the terminal procedures and en

route charts.

National Route Program (NRP). A set of rules and

procedures designed to increase the ﬂ exibility of user ﬂ ight

planning within published guidelines.

National Security Area (NSA). Areas consisting of airspace of

deﬁ ned vertical and lateral dimensions established at locations

where there is a requirement for increased security and safety

of ground facilities. Pilots are requested to voluntarily avoid

ﬂ ying through the depicted NSA. When it is necessary to

provide a greater level of security and safety, ﬂ ight in NSAs

may be temporarily prohibited. Regulatory prohibitions are

disseminated via NOTAMs.

National Transportation Safety Board (NTSB). A United

States Government independent organization responsible for

investigations of accidents involving aviation, highways,

waterways, pipelines, and railroads in the United States.

NTSB is charged by congress to investigate every civil

aviation accident in the United States.

NAVAID. Naviagtional aid.

NAV/COM. Navigation and communication radio.

NDB. See nondirectional radio beacon.

NM. Nautical mile.

NOAA. National Oceanic and Atmospheric Administration.

No-gyro approach. A radar approach that may be used in

case of a malfunctioning gyro-compass or directional gyro.

Instead of providing the pilot with headings to be ﬂ own,

the controller observes the radar track and issues control

instructions “turn right/left” or “stop turn,” as appropriate.

Nondirectional radio beacon (NDB). A ground-based radio

transmitter that transmits radio energy in all directions.

Nonprecision approach. A standard instrument approach

procedure in which only horizontal guidance is provided.

No procedure turn (NoPT). Term used with the appropriate

course and altitude to denote that the procedure turn is not

required.

NoPT. See no procedure turn.

Notice to Airmen (NOTAM). A notice filed with an aviation

authority to alert aircraft pilots of any hazards en route or at

a specific location. The authority in turn provides means of

disseminating relevant NOTAMs to pilots.

NRP. See National Route Program.

NSA. See National Security Area.

NTSB. See National Transportation Safety Board.

NWS. National Weather Service.

Obstacle departure procedures (ODP). Obstacle clearance

protection provided to aircraft in instrument meteorological

conditions (IMC).

ODP. See obstacle departure procedures.

OM. Outer marker.

Omission error. The failure to anticipate significant

instrument indications following attitude changes; for

example, concentrating on pitch control while forgetting

about heading or roll information, resulting in erratic control

of heading and bank.

Optical illusion. A misleading visual image. For the

purpose of this handbook, the term refers to the brain’s

misinterpretation of features on the ground associated

with landing, which causes a pilot to misread the spatial

relationships between the aircraft and the runway.

Orientation. Awareness of the position of the aircraft and

of oneself in relation to a speciﬁ c reference point.

Otolith organ. An inner ear organ that detects linear

acceleration and gravity orientation.

Outer marker. A marker beacon at or near the glide slope

intercept altitude of an ILS approach. It is normally located

four to seven miles from the runway threshold on the

extended centerline of the runway.

Overcontrolling. Using more movement in the control

column than is necessary to achieve the desired pitch-and

bank condition.

Overpower. To use more power than required for the purpose

of achieving a faster rate of airspeed change.

G-14

P-static. See precipitation static.

PAPI. See precision approach path indicator.

PAR. See precision approach radar.

Parasite drag. Drag caused by the friction of air moving

over the aircraft structure; its amount varies directly with

the airspeed.

PFD. See primary flight display.

PIC. See pilot-in-command.

Pilot-in-command (PIC). The pilot responsible for the

operation and safety of an aircraft.

Pilot report (PIREP). Report of meteorological phenomena

encountered by aircraft.

Pilot’s Operating Handbook/Airplane Flight Manual

(POH/AFM). FAA-approved documents published by the

airframe manufacturer that list the operating conditions for

a particular model of aircraft.

PIREP. See pilot report.

Pitot pressure. Ram air pressure used to measure airspeed.

Pitot-static head. A combination pickup used to sample pitot

pressure and static air pressure.

Plan view. The overhead view of an approach procedure on

an instrument approach chart. The plan view depicts the routes

that guide the pilot from the en route segments to the IAF.

POH/AFM. See Pilot’s Operating Handbook/Airplane

Flight Manual.

Point-in-space approach. A type of helicopter instrument

approach procedure to a missed approach point more than

2,600 feet from an associated helicopter landing area.

Position error. Error in the indication of the altimeter, ASI,

and VSI caused by the air at the static system entrance not

being absolutely still.

Position report. A report over a known location as

transmitted by an aircraft to ATC.

Precession. The characteristic of a gyroscope that causes an

applied force to be felt, not at the point of application, but

90° from that point in the direction of rotation.

Precipitation static (P-static). A form of radio interference

caused by rain, snow, or dust particles hitting the antenna and

inducing a small radio-frequency voltage into it.

Precision approach. A standard instrument approach

procedure in which both vertical and horizontal guidance

is provided.

Precision approach path indicator (PAPI). A system of

lights similar to the VASI, but consisting of one row of lights

in two- or four-light systems. A pilot on the correct glide slope

will see two white lights and two red lights. See VASI.

Precision approach radar (PAR). A type of radar used

at an airport to guide an aircraft through the ﬁ nal stages of

landing, providing horizontal and vertical guidance. The

radar operator directs the pilot to change heading or adjust

the descent rate to keep the aircraft on a path that allows it

to touch down at the correct spot on the runway.

Precision runway monitor (PRM). System allows

simultaneous, independent Instrument Flight Rules (IFR)

approaches at airports with closely spaced parallel runways.

Preferred IFR routes. Routes established in the major

terminal and en route environments to increase system

efﬁ ciency and capacity. IFR clearances are issued based on

these routes, listed in the A/FD except when severe weather

avoidance procedures or other factors dictate otherwise.

Pressure altitude. Altitude above the standard 29.92" Hg

plane.

Prevailing visibility. The greatest horizontal visibility

equaled or exceeded throughout at least half the horizon

circle (which is not necessarily continuous).

Primary and supporting. A method of attitude instrument

ﬂ ying using the instrument that provides the most direct

indication of attitude and performance.

Primary flight display (PFD). A display that provides

increased situational awareness to the pilot by replacing the

traditional six instruments used for instrument flight with

an easy-to-scan display that provides the horizon, airspeed,

altitude, vertical speed, trend, trim, rate of turn among other

key relevant indications.

PRM. See precision runway monitor.

Procedure turn. A maneuver prescribed when it is necessary

to reverse direction to establish an aircraft on the intermediate

approach segment or ﬁ nal approach course.

G-15

Profile view. Side view of an IAP chart illustrating the vertical

approach path altitudes, headings, distances, and ﬁ xes.

Prohibited area. Designated airspace within which ﬂ ight of

aircraft is prohibited.

Propeller/rotor modulation error. Certain propeller RPM

settings or helicopter rotor speeds can cause the VOR course

deviation indicator (CDI) to ﬂ uctuate as much as ±6°. Slight

changes to the RPM setting will normally smooth out this

roughness.

Rabbit, the. High-intensity ﬂ asher system installed at many

large airports. The ﬂ ashers consist of a series of brilliant

blue-white bursts of light ﬂ ashing in sequence along the

approach lights, giving the effect of a ball of light traveling

towards the runway.

Radar. Radio Detection And Ranging.

Radar approach. The controller provides vectors while

monitoring the progress of the ﬂ ight with radar, guiding

the pilot through the descent to the airport/heliport or to a

speciﬁ c runway.

Radials. The courses oriented from a station.

Radio or radar altimeter. An electronic altimeter that

determines the height of an aircraft above the terrain by

measuring the time needed for a pulse of radio-frequency

energy to travel from the aircraft to the ground and return.

Radio frequency (RF). A term that refers to alternating

current (AC) having characteristics such that, if the current is

input to antenna, an electromagnetic (EM) field is generated

suitable for wireless broadcasting and/or communications.

Radio magnetic indicator (RMI). An electronic navigation

instrument that combines a magnetic compass with an ADF

or VOR. The card of the RMI acts as a gyro-stabilized

magnetic compass, and shows the magnetic heading the

aircraft is ﬂ ying.

Radio wave. An electromagnetic wave (EM wave) with

frequency characteristics useful for radio transmission.

RAIM. See receiver autonomous integrity monitoring.

Random RNAV routes. Direct routes, based on area

navigation capability, between waypoints deﬁ ned in terms

of latitude/longitude coordinates, degree-distance ﬁ xes, or

offsets from established routes/airways at a speciﬁ ed distance

and direction.

Ranging signals. Transmitted from the GPS satellite, these

allow the aircraft’s receiver to determine range (distance)

from each satellite.

RB. See relative bearing.

RBI. See relative bearing indicator.

RCO. See remote communications outlet.

Receiver autonomous integrity monitoring (RAIM).

A system used to verify the usability of the received GPS

signals and warns the pilot of any malfunction in the

navigation system. This system is required for IFR-certiﬁ ed

GPS units.

Recommended altitude. An altitude depicted on an

instrument approach chart with the altitude value neither

underscored nor overscored. The depicted value is an

advisory value.

Receiver-transmitter (RT). A system that receives and

transmits a signal and an indicator.

Reduced vertical separation minimum (RVSM). Reduces

the vertical separation between flight level (FL) 290–410

from 2,000 feet to 1,000 feet and makes six additional FLs

available for operation. Also see DRVSM.

Reference circle (also, distance circle). The circle depicted

in the plan view of an IAP chart that typically has a 10 NM

radius, within which chart the elements are drawn to scale.

Regions of command. The “regions of normal and reversed

command” refers to the relationship between speed and the

power required to maintain or change that speed in ﬂ ight.

REIL. See runway end identiﬁ er lights.

Relative bearing (RB). The angular difference between the

aircraft heading and the direction to the station, measured

clockwise from the nose of the aircraft.

Relative bearing indicator (RBI). Also known as the ﬁ xed-

card ADF, zero is always indicated at the top of the instrument

and the needle indicates the relative bearing to the station.

Relative wind. Direction of the airﬂ ow produced by an object

moving through the air. The relative wind for an airplane in

ﬂ ight ﬂ ows in a direction parallel with and opposite to the

direction of ﬂ ight; therefore, the actual ﬂ ight path of the

airplane determines the direction of the relative wind.

G-16

Remote communications outlet (RCO). An unmanned

communications facility that is remotely controlled by air

trafﬁ c personnel.

Required navigation performance (RNP). A specified level

of accuracy defined by a lateral area of confined airspace in

which an RNP-certified aircraft operates.

Restricted area. Airspace designated under 14 CFR part

73 within which the ﬂ ight of aircraft, while not wholly

prohibited, is subject to restriction.

Reverse sensing. The VOR needle appearing to indicate the

reverse of normal operation.

RF. Radio frequency.

Rhodopsin. The photosensitive pigments that initiate the

visual response in the rods of the eye.

Rigidity. The characteristic of a gyroscope that prevents its

axis of rotation tilting as the Earth rotates.

Rime ice. Rough, milky, opaque ice formed by the

instantaneous freezing of small supercooled water droplets.

Risk. The future impact of a hazard that is not eliminated

or controlled.

RMI. See radio magnetic indicator.

RNAV. See area navigation.

RNP. See required navigation performance.

Runway end identifier lights (REIL). A pair of synchronized

ﬂ ashing lights, located laterally on each side of the runway

threshold, providing rapid and positive identiﬁ cation of the

approach end of a runway.

Runway visibility value (RVV). The visibility determined

for a particular runway by a transmissometer.

Runway visual range (RVR). The instrumentally derived

horizontal distance a pilot should be able to see down the

runway from the approach end, based on either the sighting

of high-intensity runway lights, or the visual contrast of

other objects.

RVR. See runway visual range.

RVV. See runway visibility value.

SA. See selective availability.

St. Elmo’s Fire. A corona discharge which lights up the aircraft

surface areas where maximum static discharge occurs.

Satellite ephemeris data. Data broadcast by the GPS

satellite containing very accurate orbital data for that

satellite, atmospheric propagation data, and satellite clock

error data.

Scan. The ﬁ rst fundamental skill of instrument ﬂ ight, also

known as “cross-check;” the continuous and logical observation

of instruments for attitude and performance information.

SDF. See simpliﬁ ed directional facility.

Selective availability (SA). A satellite technology permitting

the Department of Defense (DOD) to create, in the interest

of national security, a signiﬁ cant clock and ephemeris error

in the satellites, resulting in a navigation error.

Semicircular canal. An inner ear organ that detects angular

acceleration of the body.

Sensitive altimeter. A form of multipointer pneumatic

altimeter with an adjustable barometric scale that allows the

reference pressure to be set to any desired level.

SIDS. See standard instrument departure procedures.

SIGMET. The acronym for Signiﬁ cant Meteorological

information. A weather advisory issued concerning weather

signiﬁ cant to the safety of all aircraft.

Signal-to-noise ratio. An indication of signal strength

received compared to background noise, which is a measure

of how adequate the received signal is.

Simplex. Transmission and reception on the same

frequency.

Simplified directional facility (SDF). A NAVAID used

for nonprecision instrument approaches. The ﬁ nal approach

course is similar to that of an ILS localizer; however, the

SDF course may be offset from the runway, generally not

more than 3°, and the course may be wider than the localizer,

resulting in a lower degree of accuracy.

Single-pilot resource management (SRM). The ability for

crew or pilot to manage all resources effectively to ensure

the outcome of the flight is successful.

G-17

Situational awareness. Pilot knowledge of where the aircraft

is in regard to location, air trafﬁ c control, weather, regulations,

aircraft status, and other factors that may affect ﬂ ight.

Skidding turn. An uncoordinated turn in which the rate of

turn is too great for the angle of bank, pulling the aircraft to

the outside of the turn.

Skin friction drag. Drag generated between air molecules

and the solid surface of the aircraft.

Slant range. The horizontal distance from the aircraft antenna

to the ground station, due to line-of-sight transmission of the

DME signal.

Slaved compass. A system whereby the heading gyro is

“slaved to,” or continuously corrected to bring its direction

readings into agreement with a remotely located magnetic

direction sensing device (usually this is a ﬂ ux valve or ﬂ ux

gate compass).

Slipping turn. An uncoordinated turn in which the aircraft

is banked too much for the rate of turn, so the horizontal lift

component is greater than the centrifugal force, pulling the

aircraft toward the inside of the turn.

Small airplane. An airplane of 12,500 pounds or less

maximum certiﬁ cated takeoff weight.

Somatogravic illusion. The misperception of being

in a nose-up or nose-down attitude, caused by a rapid

acceleration or deceleration while in ﬂ ight situations that

lack visual reference.

Spatial disorientation. The state of confusion due to

misleading information being sent to the brain from various

sensory organs, resulting in a lack of awareness of the aircraft

position in relation to a speciﬁ c reference point.

Special use airspace. Airspace in which ﬂ ight activities are

subject to restrictions that can create limitations on the mixed

use of airspace. Consists of prohibited, restricted, warning,

military operations, and alert areas.

SRM. See single-pilot resource management.

SSR. See secondary surveillance radar.

SSV. See standard service volume.

Standard holding pattern. A holding pattern in which all

turns are made to the right.

Standard instrument departure procedures (SIDS).

Published procedures to expedite clearance delivery and to

facilitate transition between takeoff and en route operations.

Standard rate turn. A turn in which an aircraft changes its

direction at a rate of 3° per second (360° in 2 minutes) for

low- or medium-speed aircraft. For high-speed aircraft, the

standard rate turn is 1-1/2° per second (360° in 4 minutes).

Standard service volume (SSV). Deﬁ nes the limits of the

volume of airspace which the VOR serves.

Standard terminal arrival route (STAR). A preplanned

IFR ATC arrival procedure published for pilot use in graphic

and/or textual form.

STAR. See standard terminal arrival route.

Static longitudinal stability. The aerodynamic pitching

moments required to return the aircraft to the equilibrium

angle of attack.

Static pressure. Pressure of air that is still, or not moving,

measured perpendicular to the surface of the aircraft.

Steep turns. In instrument ﬂ ight, any turn greater than standard

rate; in visual ﬂ ight, anything greater than a 45° bank.

Stepdown fix. The point after which additional descent is

permitted within a segment of an IAP.

Strapdown system. An INS in which the accelerometers

and gyros are permanently “strapped down” or aligned with

the three axes of the aircraft.

Stress. The body’s response to demands placed upon it.

Structural icing. The accumulation of ice on the exterior

of the aircraft.

Suction relief valve. A relief valve in an instrument vacuum

system required to maintain the correct low pressure inside

the instrument case for the proper operation of the gyros.

Synchro. A device used to transmit indications of angular

movement or position from one location to another.

Synthetic vision. A realistic display depiction of the aircraft

in relation to terrain and flight path.

G-18

TAA. See terminal arrival area.

TACAN. See tactical air navigation.

Tactical air navigation (TACAN). An electronic navigation

system used by military aircraft, providing both distance and

direction information.

TAWS. See terrain awareness and warning system.

TCAS. See traffic alert collision avoidance system.

TCH. See threshold crossing height.

TDZE. See touchdown zone elevation.

TEC. See Tower En Route Control.

Technique. The manner in which procedures are executed.

Temporary flight restriction (TFR). Restriction to ﬂ ight

imposed in order to:

1. Protect persons and property in the air or on the

surface from an existing or imminent ﬂ ight associated

hazard;

2. Provide a safe environment for the operation of

disaster relief aircraft;

3. Prevent an unsafe congestion of sightseeing aircraft

above an incident;

4. Protect the President, Vice President, or other public

ﬁ gures; and,

5. Provide a safe environment for space agency

operations.

Pilots are expected to check appropriate NOTAMs during

ﬂ ight planning when conducting ﬂ ight in an area where a

temporary ﬂ ight restriction is in effect.

Tension. Maintaining an excessively strong grip on the control

column, usually resulting in an overcontrolled situation.

Terminal Instrument Approach Procedure (TERP).

Prescribes standardized methods for use in designing

instrument flight procedures.

Terminal arrival area (TAA). A procedure to provide a

new transition method for arriving aircraft equipped with

FMS and/or GPS navigational equipment. The TAA contains

a “T” structure that normally provides a NoPT for aircraft

using the approach.

TERP. See terminal instrument approach procedure.

Terrain Awareness and Warning System (TAWS). A

timed-based system that provides information concerning

potential hazards with fixed objects by using GPS positioning

and a database of terrain and obstructions to provide true

predictability of the upcoming terrain and obstacles.

TFR. See temporary ﬂ ight restriction.

Threshold crossing height (TCH). The theoretical height

above the runway threshold at which the aircraft’s glide

slope antenna would be if the aircraft maintains the trajectory

established by the mean ILS glide slope or MLS glide path.

Thrust (aerodynamic force). The forward aerodynamic

force produced by a propeller, fan, or turbojet engine as it

forces a mass of air to the rear, behind the aircraft.

Time and speed table. A table depicted on an instrument

approach procedure chart that identiﬁ es the distance from the

FAF to the MAP, and provides the time required to transit

that distance based on various groundspeeds.

Timed turn. A turn in which the clock and the turn

coordinator are used to change heading a deﬁ nite number of

degrees in a given time.

TIS. See traffic information service.

Title 14 of the Code of Federal Regulations (14 CFR).

The federal aviation regulations governing the operation of

aircraft, airways, and airmen.

Touchdown zone elevation (TDZE). The highest elevation

in the first 3,000 feet of the landing surface, TDZE is

indicated on the instrument approach procedure chart when

straight-in landing minimums are authorized.

Tower En Route Control (TEC). The control of IFR en route

trafﬁ c within delegated airspace between two or more adjacent

approach control facilities, designed to expedite trafﬁ c and

reduce control and pilot communication requirements.

TPP. See United States Terminal Procedures Publication.

Tracking. Flying a heading that will maintain the desired track

to or from the station regardless of crosswind conditions.

Traffic Alert Collision Avoidance System (TCAS).

An airborne system developed by the FAA that operates

independently from the ground-based Air Traffic Control

system. Designed to increase flight deck awareness of

proximate aircraft and to serve as a “last line of defense” for

the prevention of mid-air collisions.

G-19

Traffic information service (TIS). A ground-based service

providing information to the flight deck via data link using

the S-mode transponder and altitude encoder to improve the

safety and efficiency of “see and avoid” flight through an

automatic display that informs the pilot of nearby traffic.

Transcribed Weather Broadcast (TWEB). Meteorological

and aeronautical data recorded on tapes and broadcast over

selected NAVAIDs. Generally, the broadcast contains route-

oriented data with specially prepared NWS forecasts, inﬂ ight

advisories, and winds aloft. It also includes selected current

information such as weather reports (METAR/SPECI),

NOTAMs, and special notices.

Transponder. The airborne portion of the ATC radar

beacon system.

Transponder code. One of 4,096 four-digit discrete codes

ATC assigns to distinguish between aircraft.

Trend. Immediate indication of the direction of aircraft

movement, as shown on instruments.

Trim. Adjusting the aerodynamic forces on the control

surfaces so that the aircraft maintains the set attitude without

any control input.

TWEB. See Transcribed Weather Broadcast.

True airspeed. Actual airspeed, determined by applying a

correction for pressure altitude and temperature to the CAS.

UHF. See ultra-high frequency.

Ultra-high frequency (UHF). The range of electromagnetic

frequencies between 962 MHz and 1213 MHz.

Uncaging. Unlocking the gimbals of a gyroscopic instrument,

making it susceptible to damage by abrupt ﬂ ight maneuvers

or rough handling.

Underpower. Using less power than required for the purpose

of achieving a faster rate of airspeed change.

United States Terminal Procedures Publication (TPP).

Booklets published in regional format by the NACO that

include DPs, STARs, IAPs, and other information pertinent

to IFR ﬂ ight.

Unusual attitude. An unintentional, unanticipated, or

extreme aircraft attitude.

User-defined waypoints. Waypoint location and other data

which may be input by the user, this is the only GPS database

information that may be altered (edited) by the user.

Variation. Compass error caused by the difference in

the physical locations of the magnetic north pole and the

geographic north pole.

VASI. See visual approach slope indicator.

VDP. See visual descent point.

Vectoring. Navigational guidance by assigning headings.

Venturi tube. A specially shaped tube attached to the outside

of an aircraft to produce suction to allow proper operation

of gyro instruments.

Vertical speed indicator (VSI). A rate-of-pressure change

instrument that gives an indication of any deviation from a

constant pressure level.

Very-high frequency (VHF). A band of radio frequencies

falling between 30 and 300 MHz.

Very-high frequency omnidirectional range (VOR).

Electronic navigation equipment in which the ﬂ ight deck

instrument identiﬁ es the radial or line from the VOR station,

measured in degrees clockwise from magnetic north, along

which the aircraft is located.

Vestibule. The central cavity of the bony labyrinth of the ear,

or the parts of the membranous labyrinth that it contains.

VFR. See visual ﬂ ight rules.

VFR-on-top. ATC authorization for an IFR aircraft to operate

in VFR conditions at any appropriate VFR altitude.

VFR over-the-top. A VFR operation in which an aircraft

operates in VFR conditions on top of an undercast.

Victor airways. Airways based on a centerline that extends

from one VOR or VORTAC navigation aid or intersection,

to another navigation aid (or through several navigation aids

or intersections); used to establish a known route for en route

procedures between terminal areas.

G-20

Visual approach slope indicator (VASI). A visual aid of

lights arranged to provide descent guidance information

during the approach to the runway. A pilot on the correct

glide slope will see red lights over white lights.

Visual descent point (VDP). A deﬁ ned point on the ﬁ nal

approach course of a nonprecision straight-in approach

procedure from which normal descent from the MDA to the

runway touchdown point may be commenced, provided the

runway environment is clearly visible to the pilot.

Visual flight rules (VFR). Flight rules adopted by the

FAA governing aircraft ﬂ ight using visual references. VFR

operations specify the amount of ceiling and the visibility the

pilot must have in order to operate according to these rules.

When the weather conditions are such that the pilot can not

operate according to VFR, he or she must use instrument

ﬂ ight rules (IFR).

Visual meteorological conditions (VMC). Meteorological

conditions expressed in terms of visibility, distance from

cloud, and ceiling meeting or exceeding the minimums

speciﬁ ed for VFR.

VMC. See visual meteorological conditions.

VOR. See very-high frequency omnidirectional range.

VORTAC. A facility consisting of two components, VOR

and TACAN, which provides three individual services: VOR

azimuth, TACAN azimuth, and TACAN distance (DME) at

one site.

VOR test facility (VOT). A ground facility which emits a

test signal to check VOR receiver accuracy. Some VOTs are

available to the user while airborne, while others are limited

to ground use only.

VOT. See VOR test facility.

VSI. See vertical speed indicator.

WAAS. See wide area augmentation system.

Warning area. An area containing hazards to any aircraft

not participating in the activities being conducted in the

area. Warning areas may contain intensive military training,

gunnery exercises, or special weapons testing.

Waypoint. A designated geographical location used for route

deﬁ nition or progress-reporting purposes and is deﬁ ned in

terms of latitude/longitude coordinates.

WCA. See wind correction angle.

Weather and radar processor (WARP). A device that

provides real-time, accurate, predictive and strategic weather

information presented in an integrated manner in the National

Airspace System (NAS).

Weight. The force exerted by an aircraft from the pull of

gravity.

Wide area augmentation system (WAAS). A differential

global positioning system (DGPS) that improves the accuracy

of the system by determining position error from the GPS

satellites, then transmitting the error, or corrective factors,

to the airborne GPS receiver.

Wind correction angle (WCA). The angle between the

desired track and the heading of the aircraft necessary to

keep the aircraft tracking over the desired track.

Work. A measurement of force used to produce movement.

Zone of confusion. Volume of space above the station where

a lack of adequate navigation signal directly above the VOR

station causes the needle to deviate.

I-1

above ground level .............................3-31, 7-44, 8-2, 9-10

absolute accuracy .........................................................7-25

acceleration in cruise ﬂ ight ..........................................2-10

acute fatigue .............................................. 1-11, 1-12, 1-13

additional reports .........................................................10-7

adjust ............................................................................4-20

advanced technologies .................................................7-26

advanced technology systems ......................................3-28

adverse yaw ........................................................ 2-11, 2-12

aeronautical decision-making (ADM) 1-1, 1-12, 1-15, 1-17

aeronautical information manual (AIM) .............. 9-4, 10-2

agonic line ....................................................................3-12

air data computer (ADC) .............................................3-22

air route surveillance radar (ARSR) .................... 7-49, 9-7

air route trafﬁ c control center (ARTC) 7-50, 9-4, 9-7, 10-2

air trafﬁ c control (ATC) .............................. 1-15, 9-1, 11-1

inﬂ ight weather avoidance assistance ......................9-11

radar weather displays ..............................................9-11

air trafﬁ c control radar beacon system (ATCRBS) ......7-49

air trafﬁ c control towers .................................................9-5

aircraft approach categories .........................................8-23

aircraft control ................................................................6-3

aircraft system malfunctions ........................................11-3

airplane trim ...................................................................4-8

airport diagram .............................................................8-27

airport information .........................................................8-6

airport sketch ................................................................8-27

airport surface detection equipment (ASDE) ..... 7-49, 7-50

airport surveillance radar (ASR) .......................... 7-49, 9-7

Airport/Facility Directory (A/FD) .......1-9, 7-10, 8-6, 10-2

airspace classiﬁ cation .....................................................8-1

class A through G .......................................................8-2

airspeed color codes .....................................................3-10

airspeed

indicated .....................................................................3-9

indicator ..............................................4-6, 5-5, 5-37, 6-5

calibrated ....................................................................3-9

equivalent ...................................................................3-9

true .............................................................................. 3-9

Index

airspeed changes

common errors ..........................................................6-10

airspeed indicators .................................... 4-26, 5-29, 5-61

maximum allowable airspeed ...................................3-10

alcohol .......................................................................... 1-12

alternate airport ............................................................8-27

alternator/generator failure ...........................................11-5

altimeter ............................................................... 5-36, 6-4

amendment status .........................................................8-12

analog pictorial displays ..............................................3-22

anti-ice ..........................................................................2-12

approach lighting systems (ALS ..................................7-40

approach to stall ...........................................................5-26

altimeter

errors ...........................................................................3-4

cold weather ...............................................................3-5

enhancements (encoding) ...........................................3-7

analog instrument failure .............................................11-6

angle of attack ........................................................ 2-2, 2-6

approach azimuth guidance ..........................................7-45

approach control advances ...........................................9-12

approach control facility ..............................................9-12

approach to airport

without an operating control tower ........................10-14

with control tower, no approach control ................10-14

with control tower and approach control ................10-14

approaches ..................................................................10-12

missed ..................................................................... 10-21

parallel runways ..................................................... 10-20

radar ........................................................................ 10-17

timed, from a holding ﬁ x ........................................10-18

area navigation (RNAV) ..............................................7-19

arrival .........................................................................10-33

atmosphere .....................................................................2-4

layers of the atmosphere .............................................2-5

attitude and heading reference system (AHRS) ...........3-22

attitude director indicator (ADI) ..................................3-23

I-2

attitude

indicator ....... 4-4, 4-5, 4-7, 5-2, 5-6, 5-34, 5-37, 6-3, 6-5

control .........................................................................4-3

instrument ﬂ ying ....................................... 4-1, 4-21, 6-1

autokinesis ......................................................................1-7

automated ﬂ ight service stations (AFSS) .......................9-4

automated radar terminal systems (ARTS) ....................9-7

automated surface observing station (ASOS) ..............8-10

automated terminal information service (ATIS) ..........10-8

automated weather observing station (AWOS) ...........8-10

automatic dependent surveillance-broadcast (ADS-B) 3-28

automatic direction ﬁ nder (ADF) ................ 3-16, 7-3, 10-7

function of ..................................................................7-4

operational errors ........................................................7-8

automatic terminal information service (ATIS) . 1-15, 8-16

automatic weather observing system (AWOS) ..............7-3

autopilot systems ..........................................................3-24

autorotations .................................................................6-17

common errors ....................................................6-17

azimuth card ...................................................................7-4

back courses (BC) ........................................................7-39

bank control .......................... 4-4, 4-7, 4-20, 5-6, 5-37, 6-5

baro-aiding ...................................................................7-28

barometric vertical navigation (BARO VNAV) ..........8-32

basic aerodynamics (review of) .....................................2-2

relative wind ...............................................................2-2

angle of attack ............................................................2-2

basic instrument ﬂ ight patterns .......................... 5-30, 5-61

basic radio principles .....................................................7-2

blockage considerations .................................................3-2

indications of pitot tube blockage ..............................3-3

indications from static port blockage .........................3-3

effects of ﬂ ight conditions ..........................................3-3

calibrated .............................................................. 5-2, 6-14

calibrated oriﬁ ce .............................................................3-8

center approach/departure control ..................................9-7

certiﬁ ed checkpoints ....................................................7-16

changeover points (COPs) ...........................................8-10

changing technology ....................................................6-18

charted IFR altitudes ......................................................8-6

chronic fatigue .............................................................1-13

circling approaches ....................................................10-20

circling approach pattern ..............................................5-32

class D airspace ...................................................... 8-2, 9-6

clean conﬁ guration .......................................................5-11

clear ice ............................................................ 2-13, 10-24

clearances ..................................................................... 10-3

separations ................................................................10-4

clearance delivery ........................................................10-4

clearance on request .......................................................9-6

clearance void time ........................................................9-5

climbing

while accelerating .......................................................1-8

while turning ..............................................................1-8

climbs ................................................................. 2-10, 5-14

common errors

ﬁ xation ......................................................................4-27

omission ...................................................................4-28

emphasis ...................................................................4-28

communication equipment .............................................9-2

communication facilities ................................................9-4

communication procedures ............................................9-4

communication/navigation system malfunction ..........11-8

compass

course .......................................................................3-13

locator ............................................................. 7-28, 7-40

turns ....................................................... 5-21, 5-53, 6-15

compass rose ...................................................... 3-12, 5-25

computer navigation ﬁ x ...............................................8-10

concentric rings ............................................................8-18

conducting an IFR ﬂ ight ............................................10-27

constant airspeed climb

from cruise airspeed .................................................5-46

from established airspeed .........................................5-47

constant rate climbs ......................................................5-47

control

characteristics .............................................................2-7

and performance .........................................................4-2

instruments ....................................................... 4-2, 4-18

sequence ...................................................................9-13

control display unit (CDU) ..........................................3-26

control pressures ............................................................5-3

coordinated ............................................................. 5-6, 6-5

coordination of rudder and aileron controls .................2-11

coriolis illusion...............................................................1-6

course interception .......................................................7-14

course reversal elements

plan view ..................................................................8-20

proﬁ le view ...............................................................8-20

crew resource management (CRM) .............................1-14

critical areas ...................................................................7-2

cross-check ........................................................... 4-3, 4-20

common errors ..........................................................4-11

cruise clearance ............................................................10-4

current induction ..........................................................3-15

I-3

dark adaptation ...............................................................1-3

DECIDE model ............................................................1-17

decision height (DH) ................................. 3-31, 7-50, 8-21

deice .............................................................................2-13

density altitude ...............................................................2-5

departure ....................................................................10-31

departure procedures (DPs) ................7-1, 7-33, 8-12, 10-5

instrument ................................................................. 7-33

departures

airports without an operating control tower .............10-7

radar controlled ........................................................10-5

descents .............................................................. 5-16, 5-49

deviation .......................................................................3-12

differential global positioning systems (DGPS) ..........7-34

direct indication ............................................ 5-2, 5-34, 6-3

directional ....................................................................7-42

distance circle ...............................................................8-18

distance measuring equipment (DME) ................ 7-16, 8-7

arc .............................................................................7-17

components ...............................................................7-17

errors .........................................................................7-19

function of ................................................................7-17

diving

or rolling beyond the vertical plane ............................1-8

while turning ..............................................................1-8

DOD ............................................................................. 3-22

doghouse ......................................................................3-21

domestic reduced vertical

separation minimum (DRVSM) ...........................3-7

double gimbal ...............................................................3-18

drag ................................................................................2-3

drag curves .....................................................................2-6

dry air vacuum pump ...................................................3-17

duplex .............................................................................9-2

dynamic pressure type instruments ................................3-8

ears .................................................................................1-4

otolith organs .................................................. 1-4, 1-5

semicircular canals .................................................1-4

eddy currents ........................................................ 2-3, 3-14

electrical systems .........................................................3-18

electronic ﬂ ight display (EFD) .......................................4-1

electronic ﬂ ight instrument systems .............................3-27

elevator illusion ..............................................................1-6

emergencies ..................................................................6-16

en route ............................................................. 10-7, 10-32

en route ﬂ ight advisory service (EFAS) .........................9-4

en route high-altitude charts ...........................................8-6

en route procedures ......................................................10-7

encoding altimeter ..........................................................3-7

entry .................................................5-14, 5-46, 5-49, 6-10

equipment .....................................................................1-14

eyes ................................................................................1-2

false horizon ...................................................................1-7

fatigue ..........................................................................1-12

featureless terrain illusion ..............................................1-9

federal airways ...............................................................8-4

feeder facilities .............................................................8-18

feet per minute (fpm) .....................................................4-6

ﬁ ling in ﬂ ight ...............................................................10-2

ﬁ nal approach ﬁ x (FAF) ...............................................7-23

ﬁ nal approach waypoint (FAWP) ................................7-32

ﬂ ight director indicator (FDI) ......................................3-23

ﬂ ight instruments .......................................... 2-16, 3-1, 6-2

ﬂ ight levels (FL) ............................................................3-7

ﬂ ight management systems (FMS) ..............................3-25

function of ................................................................7-48

ﬂ ight patterns ...............................................................5-30

ﬂ ight planning information, sources ............................10-2

ﬂ ight strips .....................................................................9-5

ﬂ ight support systems ..................................................3-22

ﬂ ight path ............................................................... 2-2, 2-6

four step process used to change attitude .....................4-20

ﬂ ux gate compass .........................................................3-14

ﬂ ying experience ........................................................10-22

fog ...................................................................... 1-9, 10-24

form drag ........................................................................2-4

four forces ......................................................................2-2

fundamental skills

of attitude instrument ﬂ ying .....................................4-24

instrument cross-check .............................................4-10

instrument ﬂ ight .........................................................6-2

glide slope ....................................................................7-39

glide slope intercept altitude ......................................10-20

global landing system (GLS) .......................................8-32

global navigation satellite system (GNSS) ..................7-26

global positioning system (GPS) ....................... 3-27, 7-27

components ...............................................................7-27

errors .........................................................................7-33

familiarization ..........................................................7-34

function of ................................................................7-28

instrument approaches ..............................................7-31

nearest airport function .............................................11-9

substitution ...............................................................7-28

graveyard spiral ..............................................................1-6

ground lighting illusions ................................................1-9

I-4

ground proximity warning system (GPWS) ................3-34

ground speed ................................................................7-19

ground wave ...................................................................7-2

gyroscopic systems, power sources .............................3-16

pneumatic systems ....................................................3-16

vacuum pump systems .............................................3-17

gyroscopic instruments

attitude indicator .......................................................3-18

hazard identiﬁ cation .....................................................1-13

hazardous attitudes .......................................................1-18

and antidotes .............................................................1-18

Hazardous Inﬂ ight Weather Advisory Service

(HIWAS) ...................................................................... 8-10

haze ................................................................................1-9

head up display (HUD) ...................................... 3-34, 7-49

heading ............................................................... 5-13, 5-44

heading indicators ........................ 3-19, 4-7, 5-7, 5-38, 6-6

height above airport (HAA) .........................................8-27

height above landing (HAL) ........................................8-27

height above threshold elevation (HAT) ......................8-27

helicopter trim ..............................................................4-10

holding .........................................................................10-9

DME .......................................................................10-13

instructions .............................................................10-10

patterns .......................................................................7-1

procedures ..............................................................10-10

homing ...........................................................................7-5

horizontal situation indicator (HSI) ................... 3-22, 5-38

human

factors .........................................................................1-1

resources ................................................................... 1-14

IAP minimums ...........................................................10-21

ICAO cold temperature error table ................................3-6

ICAO Standard Atmosphere ..........................................2-5

icing ..............................................................................2-12

types of .....................................................................2-13

identifying intersections .................................................8-7

IFR en route and terminal operations ...........................7-28

IFR en route charts .........................................................8-6

IFR ﬂ ight plan ..............................................................10-2

canceling ...................................................................10-3

IFR Flight using GPS ...................................................7-30

illusions leading to spatial disorientation .......................1-5

IMSAFE Checklist .......................................................1-13

indirect indication ........................................... 5-3, 5-6, 6-4

induced drag ...................................................................2-3

induction icing .............................................................2-13

inertia navigation systems (INS) ..................................7-36

components ...............................................................7-37

errors .........................................................................7-37

initial approach ﬁ x (IAF) .......................... 7-23, 8-16, 8-18

inoperative components ...............................................8-27

instantaneous vertical speed indicator (IVSI) ........ 3-8, 4-6

instrument

approach capabilities ................................................7-36

approach systems ......................................................7-37

cross-check .............................................. 4-10, 4-24, 6-2

instrument approach procedures (IAPs) ...... 7-17, 8-2, 8-12

instrument approach procedures, compliance with ....10-12

instrument approaches

to civil airports .......................................................10-13

radar monitoring of .................................................10-18

instrument ﬂ ight .............................................................6-2

instrument ﬂ ight rules (IFR) ................................ 3-1, 10-1

instrument interpretation ................................................6-3

instrument landing systems (ILS) ................................7-37

components ...............................................................7-39

errors .........................................................................7-44

function .....................................................................7-42

instrument takeoffs .................................... 5-29, 5-60, 6-17

common errors ....................................... 5-29, 5-61, 6-18

instrument weather ﬂ ying ..........................................10-22

integrated ﬂ ight control system ....................................3-24

intercepting lead radials ...............................................7-19

interference drag ............................................................2-3

international civil aviation organization (ICAO) ... 2-5, 8-1

international standard atmosphere (ISA) .......................2-5

inversion illusion ............................................................1-6

inverted-V cross-check ................................................4-11

inverter .........................................................................3-18

isogonic lines ...............................................................3-12

jet routes .........................................................................8-5

Kollsman window .................................................. 3-4, 9-3

lag ........................................................................... 5-5, 6-5

land as soon as possible ...............................................6-17

land as soon as practical ...............................................6-17

land immediately ..........................................................6-17

landing ........................................................................10-22

landing minimums .......................................................8-23

large airplanes ..............................................................2-10

Law of Inertia .................................................................2-9

I-5

Law of Momentum ........................................................2-4

Law of Reaction .............................................................2-4

layers of the atmosphere ................................................2-5

lead radial .....................................................................7-19

leans, the ........................................................................1-5

learning methods

control and performance ................................... 4-2, 4-17

primary and supporting ..............................................4-2

letters of agreement (LOA) ..........................................9-14

leveling off .......................................5-16, 5-17, 5-48, 5-50

lift ........................................................................... 2-2, 2-6

lines of magnetic ﬂ ux ...................................................3-11

load factor ....................................................................2-11

local area augmentation system (LAAS) ........... 7-36, 8-32

localizer (LOC) ............................................................7-39

localizer type directional aid (LDA) ............................7-45

long range navigation (LORAN) ......................... 7-3, 7-24

components ...............................................................7-25

errors .........................................................................7-26

function of ................................................................7-26

loss of alternator/generator for electronic ﬂ ight

instrumentation ............................................................11-5

lubber line ....................................................................3-11

mach number ................................................................3-10

machmeters ..................................................................3-10

magnetic compass, basic aviation ................................3-11

induced errors ...........................................................3-12

magnetic bearing (MB) ..................................................7-3

magnetic heading (MH) .................................................7-3

magnetism ....................................................................3-10

margin identiﬁ cation ....................................................8-12

marker beacons ......................................... 7-37, 7-40, 7-44

maximum authorized altitude (MAA) ...........................8-7

mean sea level (MSL) ..................................................10-9

medical factors .............................................................1-12

acute fatigue..............................................................1-12

alcohol ......................................................................1-12

chronic fatigue ..........................................................1-13

fatigue ....................................................................... 1-12

microwave landing system (MLS) ...............................7-45

middle markers (MMs) ................................................7-39

mileage breakdown ......................................................8-10

military operations areas (MOAs) .................................8-4

military training routes (MTRs) .....................................8-4

minimum crossing altitude (MCA) ................................8-7

minimum descent altitude (MDA) ..................... 7-32, 8-21

minimum en route altitude (MEA) ................................8-6

minimum obstruction clearance altitude (MOCA) ........8-6

minimum reception altitude (MRA) ..............................8-6

minimum safe altitude (MSA) ........................... 8-16, 8-18

minimum vectoring altitudes (MVAs) ...........................9-6

minimums section ........................................................8-23

missed approach point (MAP) .....................................7-23

missed approach procedure ..........................................8-23

missed approach waypoint (MAHWP) ........................7-32

mixed ice ......................................................................2-14

Mode C...........................................................................3-7

altitude reporting ........................................................9-3

models for practicing ADM

perceive, process, perform .......................................1-17

DECIDE model, the .................................................1-17

monopulse secondary surveillance radar (MSSR) .......9-12

multi-function display (MFD) ................. 3-27, 3-28, 11-12

navigating page groups ...........................................11-10

nearest airports, using .............................................11-10

National Aeronautical Charting Group (NACG) ...........8-2

National Airspace System (NAS) .......................... 8-1, 9-1

National Security Areas (NSA) .....................................8-4

National Transportation Safety Board (NTSB .............2-16

nautical miles (NM) .....................................................7-17

navigation/communication (NAV/COM) equipment .........

................................................................................ 9-2, 9-3

navigation features .........................................................8-7

navigation instruments ......................................... 4-2, 4-19

nearest airport page group ..........................................11-10

nearest airports page soft keys ...................................11-10

nerves .............................................................................1-5

new technologies ..........................................................8-10

Newton’s First Law of Motion Law of Inertia ...............2-4

Newton’s Second Law of Motion Law of Momentum ..2-4

Newton’s Third Law of Motion Law of Reaction .........2-4

no-gyro approach .......................................................10-18

nondirectional beacon (NDB) ................................ 7-3, 8-7

nonprecision approach ...................................................9-7

nonstandard pressure on an altimeter .............................3-6

normal command ...........................................................2-7

North American Route Program (NRP) .........................8-6

nose high attitudes ........................................................5-27

nose low attitudes .........................................................5-28

notices to airmen (NOTAM) ................................ 7-10, 8-4

obstical clearance surface ............................................7-32

obstacle departure procedures (ODP) ..........................8-12

off-route obstruction clearance altitude (OROCA .........8-6

operating on the main battery ......................................11-5

operational errors .........................................................7-45

optical illusions ..............................................................1-9

I-6

featureless terrain illusion ..........................................1-9

fog ...............................................................................1-9

ground lighting illusions .............................................1-9

haze .............................................................................1-9

how to prevent landing errors due to optical illusions ....

....................................................................................1-9

runway width illusion .................................................1-9

runway and terrain slopes illusion ..............................1-9

water refraction ..........................................................1-9

orientation ......................................................................1-2

oscillation error ............................................................3-14

otolith organs ......................................................... 1-4, 1-5

outer markers (OMs) ....................................................7-39

outside air temperature (OAT) .....................................11-2

overcontrolling ................................................ 4-7, 5-4, 6-3

overpower ......................................................................5-9

parasite drag ...................................................................2-3

partial panel ﬂ ight ........................................................5-36

performance instruments ...................................... 4-2, 4-19

physiological and psychological factors ......................1-11

pilot brieﬁ ng .................................................................8-12

Pilot’s Operating Handbook/Airplane Flight

Manual (POH/AFM) ......................................................3-3

pilot/static instruments ...................................................3-3

pilot/static systems .........................................................3-2

failure .......................................................................11-7

pitch control ............................ 4-4, 4-20-21, 5-2, 5-34, 6-3

pitch/power relationship .................................................2-6

pitot pressure ..................................................................3-2

pitot-static head ..............................................................3-2

plan view ......................................................................8-16

course reversal elements ...........................................8-20

planning the descent and approach ..............................10-8

preﬂ ight ........................................................................10-2

proﬁ le view ..................................................................8-21

pneumatic systems .......................................................3-16

failure .......................................................................11-7

POH/AFM .................................................................... 10-2

position

error ............................................................................3-3

reports ....................................................................... 10-7

postural considerations ...................................................1-7

power ................................................2-10, 5-13, 5-25, 5-45

control ....................................... 4-4, 4-8, 4-21, 5-8, 5-39

settings .............................................................. 5-9, 5-39

precession .....................................................................3-16

error .................................................................... 5-7, 6-6

precipitation static (P-static) ........................................11-3

precision approach .......................................................7-37

precision approach path indicator (PAPI) ....................1-10

precision approach radar (PAR) ....................... 7-49, 10-17

precision runway monitor (PRM) ................................9-12

RADAR ....................................................................9-12

beneﬁ ts .....................................................................9-12

preferred IFR routes .......................................................8-5

pressure

altitude ................................................................ 2-5, 9-3

density ........................................................................2-5

indicating systems ....................................................3-18

preventing landing errors due to optical illusions ..........1-9

primary

bank ..........................................................................4-23

pitch ..........................................................................4-22

power ........................................................................4-23

yaw ...........................................................................4-23

primary and supporting method ........................... 4-4, 4-21

primary ﬂ ight display (PFD) ........................................3-27

additional information for speciﬁ c airport ............. 11-11

nearest airports, using .............................................11-10

procedure turn .................................................... 7-32, 8-20

holding in lieu of ......................................................8-20

standard 45° ..............................................................5-30

80/260 ....................................................................... 5-31

proﬁ le view ..................................................................8-21

propeller icing ..............................................................2-16

propeller/rotor modulation error ....................................7-2

racetrack pattern ...........................................................5-30

radar ..............................................................................9-3

limitations ................................................................. 7-50

transponders ...............................................................9-3

radar controlled departures ..........................................10-5

radar navigation (ground based) ..................................7-49

functions of ...............................................................7-49

radials ........................................................................... 7-10

radio altimeter ..............................................................3-30

radio frequency (RF .....................................................7-16

radio magnetic indicator (RMI) ........................... 3-15, 7-4

radio wave ......................................................................7-2

radius of turn ................................................................2-11

rate of turns ..................................................................2-10

receiver autonomous integrity monitoring (RAIM) .....7-28

receiver-transmitter (RT) .............................................3-31

rectangular cross-check ................................................4-11

reduced vertical separation minimum (RVSM) .............3-7

reference circle .............................................................8-18

I-7

regions of command .......................................................2-7

normal command ........................................................2-7

reversed command ......................................................2-8

relative bearing (RB) ......................................................7-3

relative wind ........................................................... 2-2, 2-4

remote communications outlet (RCO) .........................8-10

remote indicating compass ...........................................3-15

repeatable accuracy ......................................................7-25

required navigation performance .................................7-46

required navigation instrument system inspection .......3-34

reversal of motion ..........................................................1-8

RNAV instrument approach charts ..............................8-32

reversed command .........................................................2-8

reverse sensing .............................................................7-12

rhodopsin........................................................................1-2

rigidity .......................................................................... 3-16

rime ice .........................................................................2-13

risk................................................................................1-13

risk analysis ..................................................................1-13

RNAV (See area navigation) runway width

illusion ................................................................. 1-9, 1-10

and terrain slopes illusion ................................. 1-9, 1-10

runway end identiﬁ er lights (REIL) .............................7-40

runway visual range (RVR) ............................. 8-27, 10-22

runway visual value (RVV) .......................................10-22

safety systems ..............................................................3-30

scanning techniques .....................................................4-24

selected radial cross-check ................................. 4-11, 4-24

selective availability (SA) ............................................7-33

semicircular canals .........................................................1-4

sensitive altimeter ..........................................................3-3

principle of operation .................................................3-3

sensory systems for orientation ......................................1-2

servo failure .................................................................6-17

side-step maneuver .....................................................10-20

simplex ........................................................................... 9-2

simpliﬁ ed directional facility (SDF) ............................7-45

single-pilot resource management (SRM) ...................1-14

situational awareness ....................................... 1-14, 11-11

skin friction drag ............................................................2-3

sky wave .........................................................................7-2

slip/skid indicator .........................................................5-39

slow-speed ﬂ ight ............................................................2-8

small airplanes ...............................................................2-9

somatogravic illusion .....................................................1-6

space wave .....................................................................7-2

spatial disorientation ......................................................1-2

coping with spatial disorientation ..............................1-8

demonstration of spatial disorientation ......................1-7

special use airspace ........................................................8-2

speed stability .................................................................2-7

St. Elmo’s Fire ..................................................... 7-3, 11-3

stall warning systems ...................................................2-16

standard entry procedures ..........................................10-11

standard holding pattern

no wind .....................................................................10-9

with wind ..................................................................10-9

standard instrument departure procedures (SID) .........10-5

standard rate of turn .................................. 2-11, 5-19, 5-51

establishing ............................................................... 5-51

common errors ..........................................................5-51

standard terminal arrival routes (STAR) ............ 8-12, 10-9

standby battery .............................................................11-6

static longitudinal stability .............................................2-8

static pressure .................................................................3-2

steep turns .......................................................... 5-22, 5-53

stepdown ﬁ xes ..............................................................8-21

straight-and-level ﬂ ight ........................4-22, 5-2, 5-34, 6-3

airspeed changes ............................................. 5-11, 5-40

common errors ............................................................6-7

power control during ..................................................6-7

straight climbs and descents ............................... 5-14, 5-46

common errors ....................................... 5-17, 5-50, 6-13

stress .............................................................................1-11

structural icing ................................................ 2-13, 10-24

suction relief valve .......................................................3-17

synchro ......................................................................... 3-15

synthetic vision ............................................................3-27

system status ................................................................7-33

systems preﬂ ight procedures

before engine start ....................................................3-36

after engine start .......................................................3-37

taxiing and takeoff ....................................................3-37

engine shut down ......................................................3-37

tactical air navigation (TACAN) .................. 7-8, 8-7, 10-7

tailplane stall symptoms ...............................................2-16

task management ..........................................................1-15

teardrop

patterns .....................................................................5-31

procedure ..................................................................8-21

techniques ......................................................................5-1

for electrical usage ......................................... 11-5, 11-6

master battery switch ................................................11-5

operating on the main battery ......................... 11-5, 11-6

temporary ﬂ ight restrictions (TFRs) ..............................8-4

tension ................................................................ 4-10, 4-13

terminal arrival area (TAA) .........................................8-18

terminal instrument approach procedures (TERPs) .....8-12

I-8

Terminal Procedures Publications (TPP) .....................8-12

terminal radar approach control (TRACON) .................9-6

terrain alerting systems ................................................3-34

terrain awareness and warning systems (TAWS) ........3-34

threshold crossing height (TCH) ..................................8-32

thrust ......................................................2-2, 2-3, 2-6, 2-10

thunderstorm encounter, inadvertent ...........................11-2

thunderstorms ................................................... 9-11, 10-25

tilting to right or left .......................................................1-8

time factors .................................................................10-12

time and speed table .....................................................8-27

timed turns ................................................ 5-21, 5-53, 6-13

Title 14 of the Code of Federal Regulations

(14 CFR) ..................1-12, 3-2, 7-16, 8-4, 8-11, 10-2, 11-8

touch down zone elevation (TDZE) .............................8-27

Tower En Route Control (TEC) ............................. 8-6, 9-7

tracking ..........................................................................7-5

to and from the station ..............................................7-14

Traditional navigation systems ......................................7-3

trafﬁ c

advisory systems ......................................................3-31

alert systems .............................................................3-31

alert and collision avoidance system (TCAS) ..........3-31

avoidance ................................................................ 11-14

avoidance systems ....................................................3-31

information system (TIS) .........................................3-31

transcribed weather broadcast (TWEB) .......................8-10

transponder .....................................................................9-3

codes ........................................................................... 9-3

trend indicators .............................................................4-26

trim ................. 2-8, 4-8, 4-10, 4-20, 5-12, 5-13, 5-26, 5-45

control ............................................................... 4-8, 5-43

turbulence ...................................................................10-23

turn indicator ........................................................ 3-20, 6-7

turn rate indicator .........................................................5-38

turn-and-slip indicator .......................................... 3-20, 5-8

turns..................................................2-10, 5-19, 5-51, 6-13

change of airspeed .......................................... 5-24, 6-14

climbing and descending ................................ 5-24, 6-15

common errors ................................................ 5-25, 6-15

compass ................................................. 5-21, 5-53, 6-15

coordinator ................................................ 3-21, 4-8, 5-7

to predetermined headings .................... 5-20, 5-52, 6-13

radius of ....................................................................2-11

rate of ........................................................................2-10

standard rate .......................................... 2-11, 5-19, 5-51

steep .......................................................................... 5-22

timed ...................................................... 5-21, 5-53, 6-13

turn-and-slip indicator ................................... 3-20, 4-8, 5-8

types of icing ................................................................2-13

types of NAVAIDS ........................................................8-7

ultra high frequency (UHF) ...........................................7-3

uncaging ....................................................................... 5-29

underpower ..................................................................5-39

unforecast adverse weather ..........................................11-2

unusual attitude .................................................. 5-26, 6-16

common errors ....................................... 5-28, 5-58, 6-16

recognizing ...............................................................5-27

recovery from ................................................. 5-26, 5-55

vacuum pump systems .................................................3-17

variation .......................................................................3-12

vectoring ........................................................................9-6

venturi tubes .................................................................3-16

vertical card magnetic compass ...................................3-14

vertical speed indicator (VSI) ..................3-8, 4-5, 5-4, 6-5

very high frequency (VHF) ............................................9-2

very high frequency omni-directional

range (VOR) ...................................................................7-8

accuracy .................................................................... 7-16

function of ................................................................7-12

operational errors ......................................................7-14

receiver accuracy check ...........................................7-16

vestibular ......................................................... 1-2, 1-4, 1-5

vestibular illusions .........................................................1-5

VFR Over-The-Top ...................................................10-27

VFR-On-Top .............................................................. 10-26

Victor airways ................................................................8-4

visual approach slope indicator (VASI) .......................7-41

visual descent point (VDP) ..........................................8-21

visual ﬂ ight rules (VFR) ........................2-1, 3-1, 4-16, 6-1

visual illusions ...............................................................1-7

visual meteorological conditions

(VMC) ................................................1-3, 7-31, 7-34, 9-14

volcanic ash ................................................................10-24

VOR/DME RNAV .......................................................7-23

components ...............................................................7-23

errors .........................................................................7-24

function of ................................................................7-23

VOR test facility (VOT) ..............................................7-16

VMC (See visual meteorological conditions)

water refraction ..............................................................1-9

waypoint .........................................................................7-8

weather and radar processor (WARP) .........................9-11

weather avoidance assistance .......................................9-11

weather conditions .....................................................10-22

weather information and communication features .......8-10

I-9

weight ..................................................................... 2-2, 2-3

wet type vacuum pump ................................................3-17

wide area augmentation system (WAAS) ....................7-34

windshields ........................................................ 2-16, 2-17

wing, the .........................................................................2-2

wind correction angle (WCA) ........................................7-5

wind shear ..................................................................10-25

work .............................................................................2-10

zone of confusion .........................................................7-12

Instrument Flying Handbook.indb FAA_Instrument Handbook_2007 FAA Handbook 2007

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