Telephonics MCB-RT-1601 Color Weather and Search and Rescue Radar User Manual RDR 1600

Telephonics Corporation Color Weather and Search and Rescue Radar RDR 1600

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Pilot’s GuideRDR-1600

Color Weather and

Search and Rescue Radar

TM106101August 2001

Command Systems Division

TM106101(8/01)RDR-1600 Pilot’s Guide

TABLE OF CONTENTS

PARAGRAPHTITLE

PAGE

1.0 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

2.0SYSTEM CONFIGURATION . . . . . . . . . . . . . . . . . . .2

2.1ANTENNA AND RECEIVER-TRANSMITTER . . . . . . .3

2.2RADAR DISPLAY INDICATOR . . . . . . . . . . . . . . . . . .4

3.0 OPERATIONAL CONTROLS . . . . . . . . . . . . . . . . . . .5

3.1FUNCTION SELECTOR – CP-113K

CONTROL PANEL . . . . . . . . . . . . . . . . . . . . . . . . .5

3.2ANTENNA CONTROLS . . . . . . . . . . . . . . . . . . . . . . .6

3.3DISPLAY CONTROLS . . . . . . . . . . . . . . . . . . . . . . . .6

3.4PRIMARY MODE SELECTORS . . . . . . . . . . . . . . . . .6

3.5SECONDARY MODE SELECTOR AND GAIN

CONTROLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

3.6ALPHANUMERICS . . . . . . . . . . . . . . . . . . . . . . . . . .9

4.0PREFLIGHT (PFT) . . . . . . . . . . . . . . . . . . . . . . . . . .10

4.1PREFLIGHT WARNING . . . . . . . . . . . . . . . . . . . . . .10

5.0THEORY OF OPERATION . . . . . . . . . . . . . . . . . . . .11

5.1GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

5.2RADAR PRINCIPLES . . . . . . . . . . . . . . . . . . . . . . .12

5.3WEATHER RADAR PRINCIPLES . . . . . . . . . . . . . . .13

5.4RADAR REFLECTIVITY . . . . . . . . . . . . . . . . . . . . . .14

5.5WEATHER DISPLAY CALIBRATION . . . . . . . . . . . .15

5.6WEATHER ATTENUATION COMPENSATION . . . . .16

6.0WEATHER OPERATIONS . . . . . . . . . . . . . . . . . . . .18

6.1WEATHER MODE – WX . . . . . . . . . . . . . . . . . . . . .18

6.2WEATHER ALERT MODE – WXA . . . . . . . . . . . . . .19

6.3TARGET ALERT . . . . . . . . . . . . . . . . . . . . . . . . . . .19

6.4WEATHER MAPPING AND INTERPRETATION . . . .20

6.5OBSERVING WEATHER . . . . . . . . . . . . . . . . . . . . .20

6.5.1Thunderstorms and Turbulence . . . . . . . . . . . . . . . .21

6.5.2Tornadoes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

6.5.3Hail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

6.5.4Icing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

6.5.5Snow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

6.5.6Lightning and Static Discharges . . . . . . . . . . . . . . . .24

6.5.7Range Resolution . . . . . . . . . . . . . . . . . . . . . . . . . . .25

6.5.8Azimuth Resolution . . . . . . . . . . . . . . . . . . . . . . . . .25

6.5.9Indicator Resolution . . . . . . . . . . . . . . . . . . . . . . . . .26

6.5.10Short Range Displays . . . . . . . . . . . . . . . . . . . . . . . .27

6.6PATH PLANNING . . . . . . . . . . . . . . . . . . . . . . . . . . .28

6.6.1Path Planning Considerations . . . . . . . . . . . . . . . . . .28

TM106101(8/01)RDR-1600 Pilot’s Guide

iii

iiRDR-1600 Pilot’s GuideTM106101(8/01)

TABLE OF CONTENTS (CONT.)

PARAGRAPHTITLEPAGE

7.0SEARCH OPERATIONS . . . . . . . . . . . . . . . . . . . . .31

7.1GROUND MAPPING . . . . . . . . . . . . . . . . . . . . . . . .31

7.1.1Looking Angle . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32

7.1.2Other Aircraft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33

7.2SEARCH MODE . . . . . . . . . . . . . . . . . . . . . . . . . . .33

7.3DIFFERENCE BETWEEN WEATHER AND

SEARCH MODES . . . . . . . . . . . . . . . . . . . . . . . . .34

7.4SEARCH MODES COMPARED . . . . . . . . . . . . . . . .35

7.4.1Search 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35

7.4.2Search 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

7.4.3Search 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

8.0TILT MANAGEMENT . . . . . . . . . . . . . . . . . . . . . . . .37

8.1TILT CONTROL . . . . . . . . . . . . . . . . . . . . . . . . . . . .37

8.2TILT PERFORMANCE CHECK . . . . . . . . . . . . . . . .38

8.3EARLY DETECTION OF ENROUTE WEATHER . . .39

9.0ANTENNA STABILIZATION . . . . . . . . . . . . . . . . . .40

9.1LIMITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40

9.2ERRORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40

9.3COMPENSATION . . . . . . . . . . . . . . . . . . . . . . . . . .41

10.0BEACON MODES . . . . . . . . . . . . . . . . . . . . . . . . . .42

10.1BEACON FORMAT SELECTION . . . . . . . . . . . . . . .43

10.2DO-172 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43

11.0AC 90-80 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44

12.0MULTIPLE INDICATORS . . . . . . . . . . . . . . . . . . . . .45

13.0SYSTEM SPECIFICATIONS . . . . . . . . . . . . . . . . . .46

13.1RT-1601 RT UNIT . . . . . . . . . . . . . . . . . . . . . . . . . .46

13.2DA-1203A ANTENNA DRIVE ASSEMBLY . . . . . . . .46

13.3CP-113K CONTROL PANEL . . . . . . . . . . . . . . . . . .47

14.0ADVISORY CIRCULARS . . . . . . . . . . . . . . . . . . . . .48

APPENDIX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A-1

WARNING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A-3

CAUTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A-3

MAXIMUM PERMISSIBLE EXPOSURE

LEVEL (MPEL) . . . . . . . . . . . . . . . . . . . . . . . . . . .A-4

LIST OF ILLUSTRATIONS

FIGURETITLE

PAGE

2-1Typical System Block Diagram . . . . . . . . . . . . . . . . . .2

2.1-1Receiver-Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . .3

2.1-2DA-1203A Drive Assembly with AA4512A 12”

Flat Plate Antenna . . . . . . . . . . . . . . . . . . . . . . . . . .3

2.1-3CP-113K Control Panel . . . . . . . . . . . . . . . . . . . . . . . .3

2.2-1MFD Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

3.1-1CP-113K Control Panel . . . . . . . . . . . . . . . . . . . . . . . .5

3.2-1Tilt Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

3.4-1Primary Mode Selectors . . . . . . . . . . . . . . . . . . . . . . .7

3.5-1Secondary Mode Selector and Gain Controls . . . . . . .8

3.6-1MFD Screen Presentations . . . . . . . . . . . . . . . . . . . . .9

4.1-1Preflight Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

5.2-1Radar Transmit-Receive Timing . . . . . . . . . . . . . . . . .12

5.4-1Reflective Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

5.6-1STC Electronically Compensates for

Distance Attenuation . . . . . . . . . . . . . . . . . . . . . . . .16

6.1-1Typical Weather Display . . . . . . . . . . . . . . . . . . . . . . .18

6.3-1Weather Alert with Target Alert Display . . . . . . . . . . . .19

6.5-1Storm Components . . . . . . . . . . . . . . . . . . . . . . . . . . .20

6.5.3-1Finger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

6.5.3-2Hook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

6.5.3-3Scalloped Edge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

6.5.3-4U-Shaped . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

6.5.8-1Azimuth Resolution . . . . . . . . . . . . . . . . . . . . . . . . . . .25

6.5.10-1Short Range Display . . . . . . . . . . . . . . . . . . . . . . . . . .27

6.6.1-1Penetration of Weather . . . . . . . . . . . . . . . . . . . . . . . .28

6.6.1-2Minimizing Doglegging . . . . . . . . . . . . . . . . . . . . . . . .29

6.6.1-3“Blind Alley” or “Box Canyon” Situations . . . . . . . . . . .29

7.1-1Over Terrain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31

7.1-2Over Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31

7.1.1-1A Smaller Incident Angle . . . . . . . . . . . . . . . . . . . . . . .32

7.1.1-2Concentration of the Beam . . . . . . . . . . . . . . . . . . . . .32

7.3-1Wx and SRCH Buttons . . . . . . . . . . . . . . . . . . . . . . . .34

7.4.1-1Search 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35

7.4.2-1Search 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

7.4.3-1Search 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

Introduction

TM106101(8/01)RDR-1600 Pilot’s Guide

1.0INTRODUCTION

In the early days of aviation, pilots were more concerned with just staying

airborne than worrying about weather. Airplanes were for fun. Pilots flew

only short hops, on clear days, and could often see their destination. There

was little need for navigation equipment. If your compass was working and

your gas held out, you could probably make it home safely. Later, as flying

came of age, thunderstorms and their associated turbulence were more of

a problem. When the weather was good, aircraft utilization was high. But

when storms were prevalent, you might take the long way home.

Today, weather radar is as much at home in the cockpit as the compass.

Corporate aircraft operators, and private pilots, as well as the airlines have

adopted weather radar with full confidence in its usefulness and reliability.

Most commercial airborne weather radars available today also provide the

pilot with one or more ancillary modes of operation and system options that

make the radar more functional and increase its versatility.

Telephonics would like to welcome you to the growing family of Telephonics

Weather Radar System owners and operators.

The RDR-1600 Color Weather Radar System is the newest advancement

of this series of radars. The RDR-1600 series radars are the most popular,

advanced capability, multi-mode radars available from any manufacturer.

The RDR-1600 provides five primary modes of operation: three air-to-

surface search and detection modes, and two conventional weather avoid

ance modes. This lightweight digital X-band radar system provides a peak

power of 10 kW, and is primarily designed for fixed or rotary-wing aircraft

engaged in patrol, search and rescue missions, and for transporting

personnel and equipment to remote sites (e.g., off-shore oil rigs, etc.).

The system interfaces with multi-function electronic displays. The MFD is

referred to as an indicator in this manual. The RDR-1600 will also interface

with an Attitude Heading Reference System (AHRS). AHRS Pitch and Roll

data will be converted from digital ARINC 429 to analog pitch and roll data

that is used by the DA-1203A antenna drive unit for antenna stabilization.

The RDR-1600 also has the capability to receive and decode both standard

2-pulse beacon transponders and the DO-172 6-pulse transponders. This

system also provides two short ranges of 0.5 nm and 1.0 nm for search and

rescue.

This manual is designed to help you understand the RDR-1600 and its

operational procedures. Please read it carefully before operating the unit.

If you have any questions, please contact Telephonics (see back cover).

ivRDR-1600 Pilot’s GuideTM106101(8/01)

LIST OF ILLUSTRATIONS (CONT.)

FIGURETITLEPAGE

8.1-1Adjusting the Antenna Tilt . . . . . . . . . . . . . . . . . . . . . .37

8.2-1Altitude vs. Range . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

8.3-1Weather Target . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39

9.1-1Aircraft Pitching/Rolling ±30° . . . . . . . . . . . . . . . . . . . .40

10.1-1Standard Beacon . . . . . . . . . . . . . . . . . . . . . . . . . . . .43

10.2-1DO-172 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43

14-1Cross-Section of a Thunderstorm . . . . . . . . . . . . . . . .50

LIST OF TABLES

TABLETITLEPAGE

5.5-1Radar Display and Thunderstorm Levels

versus Rainfall Rates . . . . . . . . . . . . . . . . . . . . . . . .15

6.5.9-1Minimum Distinguishable Target Separation . . . . . . . .26

8.3-1Antenna Tilt Control Settings . . . . . . . . . . . . . . . . . . . .39

System Configuration (Cont.)

System Configuration

2RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide

2.0SYSTEM CONFIGURATION

Figure 2-1.Typical System Block Diagram

2.1ANTENNA AND RECEIVER-TRANSMITTER

The RT-1601 Receiver-Transmitter generates 10 KW pulses of X-band

energy. Reflected signals of weather, search and beacon modes received

by the antenna are amplified and sent to the radar display indicator.

The flat-panel antenna, which is available in diameters of 10, 12 or 18

inches scans 60 or 120 degrees. Swept by a motor-driven gear train, the

vertical component is positioned by the tilt control on the Radar Control

Panel (RCP or CP-113k). A stabilization system presents an upright radar

display while the aircraft is turning, climbing or descending.

Figure 2.1-1.Receiver-

TransmitterFigure 2.1-2.DA-1203A Drive

Assembly with AA4512A 12” Flat

Plate Antenna

Figure 2.1-3.CP-113K Control Panel

Operational Controls

System Configuration (Cont.)

4RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide

2.2RADAR DISPLAY INDICATOR

Figure 2.2-1.MFD Display

The MFD displays green, yellow and red moving maps of weather and

surface features.

The choice of two weather modes, three search modes and antenna scan

of 60 or 120 degrees is selected by the pilot. A target alert feature is active

in the weather alert mode, and a movable track cursor helps the pilot plan

his flight around severe weather. A beacon mode enables the display of

beacon locations and a code feature identifies the beacons. Beacon

Formatting allows for the display of either standard or DO-172 type

beacons. This information can be displayed in any of eight separate ranges.

Rainfall per hour Ground Return Color

0-1 mm No significant return Dark

1-4 mm Light Green

1-12 mm Medium Yellow

12 mm or more Heavy Red

3.0OPERATIONAL CONTROLS

3.1FUNCTION SELECTOR – CP-113K CONTROL PANEL

OFFRemoves system power.

STBYSystem is operationally ready; no display.

TEST

Displays a test pattern without transmitting, identified by

TEST and RT FAULT.

ONSystem transmits in normal operation.

60°

Directs the antenna to sector scan 60° about the boresight

of the aircraft. This position will work in weather, search

(map), and beacon modes.

Figure 3.1-1.CP-113K Control Panel

Operational Controls (Cont.)

6RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide

BCN

Pressing this button will select the two Beacon type

formats to be selected. Sequentially pressing the Beacon

button will select the following beacon modes:

Beacon Only Mode

Beacon A, Beacon B, Beacon A, Beacon B, . . .

Dual Mode (Beacon/Weather or Beacon/Search)

Beacon A, Beacon B, Beacon Off, Beacon Am . . .

Beacon Only Mode: If the starting mode of operation is

weather (or search), then pressing the beacon button will

place the system in Beacon/Weather (Search) mode. To

activate beacon only mode, press the weather (or search)

button to turn off weather (search) mode. To reactivate dual

mode, press either the weather or search buttons.

Beacon A – Standard 2-pulse beacon

Beacon B – DO-172 compatible beacon

Figure 3.4-1.Primary Mode Selectors

3.2ANTENNA CONTROLS

PULL STAB OFFThis switch is connected to the Tilt Control Knob. When

the Tilt Control Knob is pressed in, the stabilization

function is active. When this knob is pulled out, the

stabilization function is turned off.

TILTAdjusts antenna tilt angle.

Figure 3.2-1.Tilt Control

3.3DISPLAY CONTROLS

The MFD has a brightness control to adjust the brightness of the screen.

3.4PRIMARY MODE SELECTORS

(PUSH ON/PUSH OFF)

WxSelects weather mode, the primary mode of operation

(automatically selected at turn-on). Weather displayed and

Wx appear on screen. When pressed again, the weather

mode is removed. If no other mode button is active, the Wx

mode remains.

WxASelects weather alert mode causing red returns to flash if

the MFD is capable of performing this function. WxA

appears and Target Alert is enabled.

SRCHPressing this push button selects the three Search modes

in sequential cyclic manner (i.e., Search 1, Search 2,

Search 3, Search 1, Search 2, Search 3, etc.). Search

modes are as follows:

Search 1 – Sea clutter rejection. Active on the ten-mile

range or less.

Search 2 – Short range precision mapping. Active on the

ten-mile range or less.

Search 3 – Normal surface mapping.

Beacon mode is compatible with both weather mode and

Search mode.

Operational Controls (Cont.)

8RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide

3.6ALPHANUMERICS

Figure 3.6-1.MFD Screen Presentations

Note

+MFDs display of radar data will vary by manufacturer. Refer to the

MFD Pilot’s Guide for specific radar display.

3.5SECONDARY MODE SELECTOR AND GAIN CONTROLS

BCN GAINThe Beacon Gain is a rotary potentiometer that controls the

gain of the Beacon receiver.

SRCH GAINThe Search Gain is a rotary potentiometer that controls

the gain of the Search receiver.

CODEPressing this switch selects Beacon Codes in a sequential

cyclic fashion (i.e., Code 0, Code 1, Code 2, . . . Code 15

or Code 0, Code 1, Code 2, . . . Code 9) depending on

Beacon Mode selected. The selected code is annunciated

on the MFD.

When DO-172 Beacon (Beacon Mode B) is selected via

the BCN button, the total of sixteen codes (0-15) can be

selected by the Code switch. Selecting a Standard two-

pulse Beacon (Beacon Mode A) via the BCN button, the

total of ten codes (0-9) can be selected by the Code

button. The Code button is not active unless the Beacon

mode has been selected.

Figure 3.5-1.Secondary Mode Selector and Gain Controls

Theory of Operation

Preflight

10RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide

5.0THEORY OF OPERATION

5.1GENERAL

The primary use of this radar is to aid the pilot in avoiding thunderstorms

and associated turbulence. Since each operator normally develops unique

operational procedures for use of Weather Radar, the following information

is presented for use at the operator’s discretion.

Operational techniques with the RDR-1600 Series Weather Radars are not

different than with earlier generation radars. The proficient operator

manages his antenna tilt control to achieve the best possible knowledge of

storm height, size, and relative direction of movement.

4.0PREFLIGHT (PFT)

4.1PREFLIGHT WARNING

Test the system to verify proper operation before each flight. Rotate the

function selector from OFF to STBY. Allow system to warm up for about 100

seconds, then move the function selector to TEST. No display appears in

the STBY position and the radar does not transmit in either STBY or TEST.

The test pattern scans 120° and automatically selects the 80 mile range.

Look for distinct color bands and range marks in the order shown. Adjust

display brightness for a comfortable level. Checklist and flight log options

may be used at this time if installed.

WARNING

Do not turn the radar on within 25 feet of ground personnel or

containers holding flammable or explosive material. The radar

should never be operated during refueling.

When ready to use the radar, rotate the function selector to ON position.

Figure 4.1-1.Preflight Warnings

Note

+The design of the system is such that full operation is possible

approximately two minutes after turn-on. Therefore, the pilot may

choose to leave the function switch in OFF, rather than STBY, if no

significant weather is in the immediate area of the aircraft. The life

of the magnetron transmitting tube will be extended by leaving the

system “OFF” when possible. This, in turn, will reduce the cost of

maintenance.

Theory of Operation (Cont.)

12RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide

5.3WEATHER RADAR PRINCIPLES

Airborne weather avoidance radar, as its name implies, is for avoiding

severe weather – not for penetrating it. Whether to fly into an area of radar

echoes depends on echo intensity, spacing between the echoes, and the

capabilities of both pilot and aircraft. Remember that weather radar detects

only precipitation drops; it does not detect minute cloud droplets. Therefore,

the radar scope provides no assurance of avoiding instrument weather in

clouds and fog. Your indicator may be clear between intense echoes; this

clear area does not necessarily mean you can fly between the storms and

maintain visual sighting of them.

The geometry of the weather radar radiated beam precludes its use for

reliable proximity warning or anti-collision protection. The beam is charac

terized as a cone-shaped pencil beam. It is much like that of a flashlight or

spotlight beam. It would be an event of chance, not of certainty, that such a

beam would come upon another aircraft in flight.

WARNING

Weather radar is not practical as a pilot operable collision

avoidance system. Weather analysis and avoidance are the

primary functions of the radar system.

5.2RADAR PRINCIPLES

Radar is fundamentally a distance measuring system using the principle of

radio echoing. The term RADAR is an acronym for Radio Detecting And

Ranging. It is a method for locating targets by using radio waves. The trans-

mitter generates microwave energy in the form of pulses. These

pulses are then transferred to the antenna where they are focused into a

beam by the antenna. The radar beam is much like the beam of a flashlight.

The energy is focused and radiated by the antenna in such a way that it is

most intense in the center of the beam with decreasing intensity near the

edge. The same antenna is used for both transmitting and receiving. When

a pulse intercepts a target, the energy is reflected as an echo, or return

signal, back to the antenna. From the antenna, the returned signal is trans-

ferred to the receiver and processing circuits located in the receiver

transmitter unit. The echoes or returned signals are displayed on an

indicator.

Radio waves travel at the speed of 300 million meters per second and thus

yield nearly instantaneous information when echoing back. Radar ranging

is a two-way process that requires 12.36 micro-seconds for the radio wave

to travel out and back for each nautical mile of target range. As shown in

the distance illustration in Figure 5.2-1, it takes 123.6 micro-seconds for a

transmitted pulse of radar energy to travel out and back from an area of

precipitation 10 nautical miles away.

Figure 5.2-1.Radar Transmit-Receive Timing

Theory of Operation (Cont.)

14RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide

5.5WEATHER DISPLAY CALIBRATION

The MFD Radar display should be calibrated to show four levels of target

intensity: Black (level 0), Green (level one), Yellow (level two) and Red

(level three). The meaning of these levels is shown in the following chart as

is their approximate relationship to the Video Integrated Processor (VIP)

intensity levels used by the National Weather Service (NWS). These levels

are valid only when (1) the Wx or WxA modes are selected; (2) the dis

played returns are within the STC range of the radar (approximately 40

miles); (3) the returns are beam filling; and (4) there are no intervening

radar returns.

Table 5.5-1.Radar Display and Thunderstorm Levels

versus Rainfall Rates

Video Integrated Processor (VIP)

Categorizations

Rainfall Rate

Display

Level

mm/Hr. In./Hr Story

Category VIP

Level mm/Hr. In./Hr.

Remarks

(Red) 12 0.5 Strong 3 Greater

than 12 Greater

than 0.5 Severe turbulence,

possible lightning

(Yellow) 4-12 0.17-0.5 Moderate 2 2.5-12 0.1-0.5

Light to moderate

turbulence is

possible with

lightning

(Green 1-4 0.04-0.17 Weak 1 0.25-2.5 .01-0.1

Light to moderate

turbulence is

possible with

lightning

(Black) Less

than 1 Less than

0.04

5.4RADAR REFLECTIVITY

What target will reflect the radar’s pulses and thus be displayed on the

indicator?

Only precipitation (or objects more dense than water such as earth or solid

structures) will be detected by an X-band weather radar. Therefore,

weather radar does not detect clouds, thunderstorms or turbulence direct-

ly. Instead, it detects precipitation which may be associated with dangerous

thunderstorms and turbulence. The best radar reflectors are raindrops and

wet hail. The larger the raindrop, the better it reflects. Because large drops

in a small concentrated area are characteristic of a severe thunderstorm,

the radar displays the storm as a strong echo. Drop size is the most impor-

tant factor in high radar reflectivity. Generally, ice, dry snow and dry hail

have low reflective levels and often will not be displayed by the radar.

A cloud that contains only small raindrops, such a fog or drizzle, will not pro-

duce a measurable radar echo. But if the conditions should change and the

cloud begins to produce rain, it will be displayed on radar.

Figure 5.4-1.Reflective Levels

Theory of Operation (Cont.)

16RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide

Attenuation due to precipitation is far more intense and is less predictable

than attenuation due to distance. As the radar pulses pass through mois

ture, some radar energy is reflected, however, much of that energy is

absorbed. If the rain is very heavy or extends for many miles, the beam may

not reach completely through the area of precipitation. The weather radar

has no way of knowing if the beam has been fully attenuated or has

reached the far side of the precipitation area. If the beam has been fully

attenuated, the radar will display a “radar shadow” which appears as an end

to the precipitation when, in fact, the heavy rain may extend for many more

miles. In the worst case, precipitation attenuation may cause the area of

heaviest precipitation to be displayed as the thinnest area of heavy precip

itation. Or it may cause one cell containing heavy precipitation to totally

block or shadow a second heavy cell located behind the first cell and pre

vent it from being displayed on the radar.

CAUTION

Never fly into radar shadows and never believe that the full extent of

heavy rain is being seen on radar unless another cell or a ground

target can be seen beyond the heavy cell.

Proper use of the antenna tilt control can help detect radar shadows.

Attenuation can also be a problem when flying in a large area of general

rain. If the rain is moderate, the radar beam may only reach 20 or 30 miles

before it is fully attenuated. The pilot may fly along for many miles seeing

the same 20-30 miles of precipitation ahead on the radar when, actually, the

rain may extend for a great distance. In order to aid in reducing the effects

of precipitation attenuation, the RDR-1600 contains sophisticated weather

attenuation compensation circuitry. The Attenuation Compensation feature

is totally automatic and requires no pilot action to activate it. However, the

Compensation logic cannot operate until echoes are within the Sensitivity

Time Control range of approximately 40 miles. Whenever a level two

level (yellow) or level three (red) echo is displayed within the STC range,

the Compensation circuits cause the receiver gain to increase while the

antenna scans the sector containing heavy rain. The Compensation circuit

ry allows the radar beam to effectively look deeper into and through heavy

rain to search for possible storm cells beyond. While Attenuation

Compensation does not eliminate precipitation attenuation, it does allow the

radar to see through more rain at short ranges where every bit of weather

information possible is needed. If there is suspicion that the radar is atten

uating due to precipitation, exercise extreme caution and ask the ATC

Controller what they are showing. Often the ground-based ATC radar will

have a better overall picture of a large rain area and the pilot can compare

the controller’s information with his own radar picture to avoid the strongest

cells in a general area of rain.

5.6WEATHER ATTENUATION COMPENSATION

Attenuation is an extremely important phenomenon for the weather radar

operator to understand. When a radar pulse is transmitted into the

atmosphere, it is progressively absorbed and scattered so that it loses its

ability to return to the antenna. This attenuation or weakening of the radar

pulse is caused by two primary sources, distance and precipitation. The

RDR-1600 radars have several advanced features which significantly

reduce the affects of attenuation but no airborne weather radar can elimi-

nate them completely. It is therefore up to the operator to understand the

radar’s limitations in dealing with attenuation.

Attenuation because of distance is due to the fact that the radar energy

leaving the antenna is inversely proportional to the square of the distance.

For example, the reflected radar energy from a target 60 miles away will be

one fourth (if the target is beam filling) of the reflected energy from an

equivalent target 30 miles away. The displayed effect to the operator is that

as the storm is approached it will appear to be gaining in intensity. To com-

pensate for distance attenuation, both Sensitivity Timing Control (STC) and

Extended STC circuitry are employed. The RDR-1600 has an STC range of

approximately 40 nautical miles and within this range the radar will elec-

tronically compensate for the effects of distance attenuation with the net

effect that targets do not appear to grow larger as the distance decreases.

Outside the STC range the Extended STC circuitry increases the displayed

intensity to more accurately represent storm intensity. The Extended STC

will not, however, totally compensate for distance attenuation and,

therefore, targets in this range can be expected to grow as the distance

decreases until reaching the STC range.

Figure 5.6-1.STC Electronically Compensates for

Distance Attenuation

Weather Operations (Cont.)

Weather Operations

18RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide

6.2WEATHER ALERT MODE – WXA

In Weather Alert mode, WxA, you will see a standard weather presentation

displayed in Green, Yellow and Red, except that the red returns flash

between black and red to draw your attention to the heavier activity.

6.3TARGET ALERT

In Weather Alert Mode, WxA, the words TGT ALRT flash if red returns exist

within 25 miles beyond the displayed range.

Figure 6.3-1.Weather Alert with Target Alert Display

6.0WEATHER OPERATIONS

6.1WEATHER MODE – WX

The RDR-1600 will provide you with target information to a greater degree

than ever possible on previous generation weather radars. With a 240 nm

maximum display range, you will have plenty of time to plan weather avoid-

ance maneuvers.

Figure 6.1-1.Typical Weather Display

By pressing the “WX” button on the face of the indicator, you will see a stan-

dard weather presentation. Different levels of precipitation are displayed in

Green, Yellow and Red. Use the range up/down buttons to select the

desired full scale range distance to be displayed. See Paragraph 8.0 for

Weather Operations (Cont.)

20RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide

6.5.1Thunderstorms and Turbulence

The RDR-1600 weather radar can give you a clue to the presence of

turbulence. Areas of the display where the colors change rapidly over a

short distance represent steep rainfall gradients, which are usually associ

ated with severe turbulence.

Turbulence may be divided into two basic types:

(1) clear-air turbulence. It is not possible to detect clear-air turbulence

with this type of radar.

(2) turbulence associated with thunderstorms and precipitation. This

type is most common. Weather radar is most helpful to the pilot

with this type.

Weather guidance is now available from ground radar stations in some

areas. However, this system suffers in comparison with the airborne

weather radar when the weather is clearly visible on the pilot’s indicator,

instantly available for the pilot to act upon, considering his immediate

circumstances and future flight planning.

The strong up and down drafts in a thunderstorm create very large rain

drops which are usually displayed on a radar as level three.

The probability of turbulence in these strong vertical gusts is great. The

National Severe Storms Laboratory (NSSL) has found that the intensity

level of the precipitation reflection correlates with the degree of turbulence

found in a thunderstorm. The most severe turbulence in the storm,

however, may not be at the same place that gives the greatest radar reflec

tivity.

The rate of change in rainfall rate laterally within a storm is called the rain

gradient. This change will appear on the indicator as a change from green

to yellow to red. If the rainfall rate increases from level one to three in a

short distance, the rain gradient is steep and severe turbulence is often

present. Avoid any storm with a steep rain gradient by an extra margin and

especially avoid flying near the portion of the storm with the steepest

gradient.

6.4WEATHER MAPPING AND INTERPRETATION

This section contains general information on use of the radar for weather

interpretation. Review of this information will assist the pilot.

6.5OBSERVING WEATHER

A weather radar is only as good as the operator’s interpretation of the

echoes that are displayed on the radar indicator. The pilot must combine his

knowledge of how radar works and its limitations with such things as the

prevailing weather pattern, the geographic location, and his personal expe-

rience in order to make a sound interpretation of the displayed targets.

As a starting point, the operator should read FAA Advisory Circular number

00-24B, Subject: Thunderstorms. It is also highly recommended that the

operator take advantage of one of the commercially available weather radar

seminars.

Figure 6.5-1.Storm Components

Weather Operations (Cont.)

22RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide

6.5.3Hail

Hail usually has a film of water on its surface; consequently, a hailstone is

often reflected as a very large water particle. Because of the film and

because hail stones usually are larger than raindrops, thunderstorms with

large amounts of wet hail return stronger signals than those with rain.

Although wet hail is an excellent reflector of radar energy, some hail shafts

are extremely small (100 yards or less). These narrow shafts make poor

radar targets.

Hail shafts are usually identified with four different characteristics patterns:

(1) fingers and protrusions, (2) hooks, (3) scalloped edges on the cloud out

line and (4) U-shaped cloud edges 3 to 7 miles across.

These echoes appear quite suddenly and along any edge of the storm out

line. They also change in intensity and shape in a matter of seconds, and

for this reason careful monitoring of the display is essential. It must be

noted that weak or fuzzy projections are not normally associated with hail;

however, such echoes should be watched closely for signs of rapid intensi

fication.

The 40-mile operating range seems best and, with occasional up-tilt to

check for fresh hail from above, generally good results can be obtained.

Note

+It takes an experienced eye to identify “hooks” and “fingers” and

other radar echo characteristics which can indicate hail or torna-

does. However, the pilot can be sure that any echo with very

ragged edges or rapid changes in shape or intensity will contain

severe turbulence.

Figure 6.5.3-1.FingerFigure 6.5.3-2.Hook

Figure 6.5.3.3.Scalloped

EdgeFigure 6.5.3-4.U-Shaped

6.5.2Tornadoes

It is possible that conclusive methods of detecting tornadoes with airborne

radar may eventually be developed. However, evidence collected to date

indicates tornadoes may be detected if the following echoes are observed:

1. A hook-shaped pendant which may be 5 or more miles long and in the

general shape of the numeral 6 strongly suggests the presence of a

major tornado, especially if the pendant is a bright one and if it projects

from the southwest quadrant (northeast quadrant in the southern hemi-

sphere) of a major thunderstorm moving eastward. The pendant may be

lost in ground clutter when viewed on the indicator and in some cases

might not be much more than a blunt projection or scalloped edge of the

parent thunderstorm echo.

2. A crescent-shaped indentation on the side of a major thunderstorm echo

3 to 7 miles long is another possible identifier of an active or potential

tornado in the vicinity.

3. The best procedure is to make wider than usual detours around sharp-

edged thunderstorms and especially those which show projections or

crescent-shaped indentations.

Weather Operations (Cont.)

24RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide

6.5.7Range Resolution

The ability of the radar system to resolve closely spaced targets in range

depends on transmitter pulse width. In long range modes, the RDR-1600

can distinguish objects spaced as close as 0.19 nm (385 yds.) apart. In

Search 1 (SR1) and Search 2 (SR2) modes on ranges of 20 miles and

below, the resolution is improved to 0.04 nm (80 yds.).

6.5.8Azimuth Resolution

The ability of the radar to resolve adjacent targets in azimuth depends on

antenna beam width and range to the target. The diameter of the radiated

beam increases as it gets further from the antenna. Larger antennas have

narrower beam widths and, therefore, produce better ground mapping and

weather pictures.

Targets separated by a distance less than the beam diameter will merge

and appear on the indicator as one.

Figure 6.5.8-1.Azimuth Resolution

6.5.4Icing

There is reason to believe that the radar will be of assistance in locating

areas of heavy icing conditions. However, weather radar has not yet proved

its ability to distinguish between super-cooled water droplets and ice crys-

tals, since both are usually quite small. Needless to say, the operational

problem in each case would be different. In the first case icing would defi-

nitely exist but in the second case the pure crystals would offer no danger.

1.It should be remembered, however, that super-cooled water and ice

crystals can co-exist. In each case the radar echo would be small or

even nil due to the minute size of the free water particles. At this time, it

appears fairly certain that radar is not going to give warning of cloud icing

unless it happens to be involved with active precipitation at the time.

When precipitation is occurring, however, the areas of maximum ice

exposure should appear as sandy or grainy echoes.

2.An icing condition that the radar might possibly detect is the intermittent

moderate or heavy icing condition associated with unstable air lifted by

frontal action or orographic effects. In this situation, the cumulus cells

are hidden by surrounding cloud layers but could be spotted by radar.

This would be of assistance in avoiding the moderate-to-heavy icing

which occasionally occurs in cumulus clouds.

WARNING

Thunderstorm icing can be extremely hazardous.

6.5.5Snow

Dry snowfall has not been detected with any success on weather radar.

However, a characteristic sandy or grainy echo identifies the presence of

steady moderate-to-heavy wet snow. Such echoes are not readily obvious

and require a little study of the display before they can be seen.

6.5.6Lightning and Static Discharges

Lightning and static discharges could scatter the display momentarily.

However, the general presentation is unaffected and should return to

normal within 1 scan.

Weather Operations (Cont.)

26RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide

6.5.10Short Range Displays

The RDR-1600 allows the selection of full-scale ranges of 1.0 nm and

0.5 nm in Search Modes.

These unique short range selections are especially useful during

approaches and surveillance operations, because it keeps the target from

getting lost in the clutter at the vertex of the display.

When operating in either short range mode, certain features become

unavailable. They are: Moving Map with Waypoints, BeaconTrac and

Beacon Identification. All other modes are still accessible.

Figure 6.5.10-1.Short Range Display

In the weather mode, the RDR-1600 is unable to ascertain radar returns

from close in. On the short range displays, the RDR-1600 paints a red arc

in this range to depict the dead band area, as shown in Figure 6.5.10-1.

6.5.9Indicator Resolution

The resolution of the indicator depends on the number of display bits on the

screen. A typical screen matrix is composed of 256 bits horizontally by 256

bits vertically. The display resolution is equal to 1/256 times the display

range as shown in Table 6.5.9-1. The lower the range, the better the

resolution.

Table 6.5.9-1.Minimum Distinguishable Target Separation

Resolution

Range (nm) Miles Feet Meters

2.0 0.008 48 14.8

5.0 0.02 122 37.0

10.0 0.04 243 74.1

20.0 0.08 486 148.2

40.0 0.16 972 296.3

80.0 0.31 1884 574.1

Weather Operations (Cont.)

28RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide

Figure 6.6.1-3.“Blind Alley” or “Box Canyon” Situations

A “Blind Alley” or “Box Canyon” situation can be very dangerous when view

ing the short ranges. Periodically switch to longer range displays to

observe distant conditions. As shown above, the short-range returns show

an obvious corridor between two areas of heavy rainfall, but the long-range

setting shows a larger area of heavy rainfall.

Figure 6.6.1-2.Minimizing Doglegging

Cells beyond 75 miles are areas of substantial rainfall; do not wait for

red to appear. Plan and execute evasive action quickly to minimize

“doglegging.”

6.6PATH PLANNING

Remember to plan a deviation path early. Simply skirting the red portion of

a cell is not enough. Plan an avoidance path for all weather echoes which

appear beyond 100 miles since this indicates they are quite intense.

The most intense echoes are severe thunderstorms. Remember that hail

may fall several miles from the cloud, and hazardous turbulence may

extend as much as 20 miles from the storm. Avoid the most intense echoes

by at least 20 miles, that is, echoes should be separated by at least 40

miles before you fly between them. As echoes diminish in intensity, you can

reduce the distance by which you avoid them.

6.6.1Path Planning Considerations

•Avoid cells containing red areas by at least 20 miles.

•Do not deviate downwind unless absolutely necessary. Your chances of

encountering severe turbulence and damaging hail are greatly reduced

by selecting the upwind side of the storm.

•If looking for a corridor, remember corridors between two cells containing

red areas should be at least 40 miles wide from the outer fringes of the

radar echo.

Note

+Do not approach a storm cell containing red any closer than 20 nm.

Echoes should be separated by at least 40 nm before attempting

to fly between them.

Figure 6.6.1-1.Penetration of Weather

When a complete detour is impractical, penetration of weather patterns may

be required. Avoid adjacent cells by at least 20 miles.

Search Operations

Weather Operations (Cont.)

30RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide

7.0SEARCH OPERATIONS

7.1GROUND MAPPING

A secondary objective of the radar system is gathering and presentation of

terrain data. This data is represented in the form of a topographical map

that can be employed as a supplement to standard navigation procedures.

Target quality affects the indicator display in various situations. Use of the

SRCH gain control and TILT knob will often improve picture contrast so

specific ground targets are more readily recognizable.

Figure 7.1-1.Over Terrain

Illumination of terrain results in a “diffused” reflection of the beam. A portion

of this reflected energy is scattered back toward the antenna resulting in the

prominent display of land features as well as lakes, large rivers, shore lines

and ships.

Figure 7.1-2.Over Water

Calm water or water with swells does not provide good returns. The ener

gy is reflected in a forward scatter angle with inadequate portions being

returned. The resulting display is “no target”. Choppy water provides better

returns from the downwind side of the waves. The resulting display is a

target whose intensity will vary with the degree to choppiness.

Above all, remember: Never regard any thunderstorm as LIGHT, even when

radar observers report the echoes are of light intensity. Avoiding thunder-

storms is the best policy.

DON’Tattempt to preflight plan a course between closely

space echoes.

DON’Tland or take off in the face of a thunderstorm in the

projected flight path. A sudden wind shift or low level turbu-

lence could cause loss of control.

DON’Tattempt to fly under a thunderstorm even if you can see

through to the other side. Turbulence under the storm could be

severe.

DON’Ttry to navigate between thunderstorms that cover 6/10

or more of the display. Fly around the storm system by a wide

margin.

DON’Tfly without airborne radar into a cloud mass containing

scattered embedded thunderstorms. Scattered thunderstorms

not embedded usually can be circumnavigated.

DOavoid by at least 20 miles any thunderstorm identified as

severe or giving an intense radar echo. This is especially true

under the anvil of a large cumulonimbus.

DOclear the top of a known or suspected severe thunderstorm

by at least 10,000 feet altitude. This may exceed the altitude

capability of the aircraft.

DOremember that vivid and frequent lightning indicates a

severe thunderstorm.

DOregard as severe any thunderstorm with tops 35,000 feet

or higher whether the top is visually sighted or determined by

radar.

Search Operations (Cont.)

32RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide

7.1.2Other Aircraft

Tests show that only with extremely careful observation at relatively short

ranges can other aircraft be detected by this type of radar equipment. The

character of this echo is such that this type of radar system cannot be

considered adequate for this purpose.

7.2SEARCH MODE

An advantage of this radar system is the enhancement of short range

mapping capability. This facilitates locating specific targets on land or sea

and provides a navigational map as a supplement to standard navigation

procedures.

7.1.1Looking Angle

The incident angle at which the terrain is illuminated has a direct bearing on

the detectable range and the area of illumination. A large incident angle

gives the radar system a smaller detectable range of operation (due to a

minimized reflection of direct radar energy). However, the illuminated area

“A” is larger.

Figure 7.1.1-1.A Smaller Incident Angle

A smaller incident angle gives the radar a larger detectable range of oper-

ation because of an increase of direct radar energy reflected from the

target to the antenna. The area of illumination (“A”) is smaller.

Figure 7.1.1-2.Concentration of the Beam

Concentration of the beam energy on the small area of terrain increases the

magnitude of the echo intercepted by the antenna. The resulting detectable

range is therefore increased for mountainous terrain; the maximum

distance at which this terrain can be monitored is greater because of the

more direct reflection (or radar echo) produced. Illuminating the backslope

of hills stretches the area of coverage beyond the flat terrain coverage.

Search Operations (Cont.)

34RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide

7.4SEARCH MODES COMPARED

In the photographs below, the aircraft is flying southwest along the Florida

Keys. Florida’s marshy coast is on the right and the islands are in the cen

ter of the screen. Strong boat target returns are on the left. Tilt and search

gain are adjusted for optimum display. Note that in SRCH 3, the land

masses blend together while in SRCH 2 and SRCH 1, a small boat (arrow)

target can be extracted from heavy seas.

7.4.1Search 3

Conventional ground map mode. Beyond 10 mile range, SR1 and SR2 are

the same as SR3.

The radar’s long range mapping compatibility may be used to recognize

known, well defined targets such as mountains, lakes, rivers, or cities. Use

of gain and tilt controls will often improve picture quality.

Figure 7.4.1-1.Search 3

7.3DIFFERENCE BETWEEN WEATHER AND SEARCH MODES

In weather modes, the receiver gain is preset and cannot be changed by

the pilot. In the search modes, the pilot controls receiver gain with the

SRCH knob on the indicator front panel for best display resolution.

Additionally, in search modes on ranges below 10 miles, the transmitter

pulse is changed to enhance target resolution.

When operating in weather or search modes, both weather and ground

returns can appear on the screen at the same time.

Figure 7.3-1.Wx and SRCH Buttons

Tilt Management

Search Operations (Cont.)

36RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide

8.0TILT MANAGEMENT

8.1TILT CONTROL

One of the most important factors in improving your expertise in using your

radar is antenna tilt management. Control of the vertical movement of the

antenna, and hence the radar beam, is through the antenna tilt knob.

Proper antenna tilt management provides information of the storm’s

approximate size and relative direction of movement.

The correct procedure for weather avoidance is to aim the antenna directly

at the storm, not above it, or at the ground. The tilt control permits posi

tioning the antenna in small increments up or down, to keep the antenna

intersecting the storm area. Also, changes in pitch attitude can be com

pensated for by adjusting the antenna tilt.

Figure 8.1-1.Adjusting the Antenna Tilt

7.4.2Search 2

Short range precision mapping on ranges of 10 miles or less.

Figure 7.4.2-1.Search 2

7.4.3Search 1

Sea clutter rejection effect on ranges of 10 miles or less.

Figure 7.4.3-1.Search 1

Tilt Management (Cont.)

38RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide

8.3EARLY DETECTION OF ENROUTE WEATHER

To set the Antenna Tilt to optimize the radar’s ability to quickly identify

significant weather, follow these steps:

Select the Wx (Weather) or WxA (Weather Alert) mode of operation.

Adjust brightness control as desired.

2.Select the 40 or 80 nm range.

Adjust the Antenna Tilt control down until the entire display is filled with

ground returns.

Slowly work the Antenna Tilt up so that ground returns are painted on or

about the outer one third of the indicator area.

Watch the strongest returns seen on the display. if, as they are

approached, they become weaker and fade out after working back inside

the near limit of the general ground return pattern, they are probably

ground returns or insignificant weather. If they continue strong after

working down into the lower half of the indicator, you are approaching a

hazardous storm or storms, and should deviate immediately.

Examine the area behind strong targets. If radar shadows are detected,

you are approaching a hazardous storm or storms, and should deviate

immediately. Regardless of the aircraft’s altitude, if weather is being

detected, move the Antenna Tilt control up and down in small increments

until the return object is optimized. At that angle, the most active vertical

level of the storm is being displayed.

Antenna Tilt Angle

Altitude (ft) 10” 12” 18” Line-of-Sight

Range (SM)

5,000 +7.0° +6.0° +5.0° 87

10,000 6.0° 5.0° 4.0° 123

15,000 5.5° 4.0° 3.0° 150

20,000 4.5° 3.5° 2.5° 174

25,000 4.0° 3.0° 2.0° 194

30,000 3.5° 2.5° 1.5° 213

35,000 3.0° 2.0° 1.0° 230

40,000 2.5° 1.5° 0.5° 246

Figure 8.3-1.Weather Target

If target is shown at or beyond the line-of-sight range listed above, the

chances are good that it is a weather target.

Table 8.3-1.Antenna Tilt Control Settings

Note

+The TILT position in

Step 4 should be that

shown in the chart.

The exact setting will

depend upon the air-

craft’s pitch altitude

and the flatness of

the terrain.

8.2TILT PERFORMANCE CHECK

A good performance check of your radar system in flight is to lower the tilt

slowly and observe the maximum range of solid ground returns. As a rule

of thumb, this range in miles should approximate the square root of your

operational altitude.

Figure 8.2-1.Altitude vs. Range

For example, at 5,000 ft. the maximum displayed ground target range

should be about 70 nautical miles. You should perform this test on every

flight. Don’t wait until you’re penetrating severe weather to discover that

your system is not providing optimum performance.

If the radar is operating normally when you reach cruising altitude, select

the longest display range and lower the antenna tilt until ground targets are

displayed. Now, slowly raise the tilt until the ground returns disappear. This

will give you the optimum tilt setting for your cruise altitude. Each time a

new range is selected, however, the tilt control must be readjusted, down

for a shorter range, and up for a longer one.

Antenna Stabilization (Cont.)

Antenna Stabilization

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9.3COMPENSATION

There are some compensations the pilot can use for antenna stabilization

errors. When the system has been operating properly in level flight, the pilot

may be able to correct for ground return showing on one side and not the

other by tilting the antenna up until all ground returns are cleared. During

takeoff, the pilot can raise the antenna tilt to clear the ground returns

caused by gyro acceleration error, then as the airplane stops accelerating,

readjust the antenna tilt back toward level. Adjusting antenna tilt is also the

remedy for ground returns that appear because of gyro precession in a pro

longed turn. Good operating practices include:

•Adjust radar and obtain weather picture before takeoff

•Compensate antenna tilt for gyro precession

•Evaluate weather in the immediate sphere of operation

•Do not “over-scan” weather targets

•

During excessive aircraft maneuvers, recognize the limitations of

stabilization

9.0ANTENNA STABILIZATION

Airborne radar antennas are stabilized to preserve a normal cockpit display

when the aircraft is climbing, descending or turning. When the aircraft

departs from straight and level flight, the stabilization system automatically

adjusts the antenna position to compensate for the change. Both limits and

errors associated with antenna stabilization are important to the pilot.

9.1LIMITS

The limits of antenna stabilization are different for climbing or descending

and turning while climbing or descending. For straight ahead climbs and

descents, the limits are simply the mechanical stops at 30 degrees. When

turning, the tilt and bank angles determine the stabilization limits (the rule

of thumb is a total of 30 degrees) so moderate turns combined with mod-

erate climbs and descents will stay within limits.

Figure 9.1-1.Aircraft Pitching/Rolling ±30°

9.2ERRORS

There are two sources of stabilization errors: acceleration and drift.

Accelerations and decelerations cause the gyro to precess in pitch. The

pilot may not notice a small temporary discrepancy between the altitude

indicator and visible horizon, but on the radar screen the antenna pitch pre-

cession will appear as an exaggeration of the desired tilt. Drift errors

(appearing on the attitude indicators pitch and roll precession accumulate

in turns) disappear slowly after the aircraft returns to straight and level.

Gyro precession errors directly affect radar stabilization and the quality of

the return displayed on the screen.

Beacon Mode (Cont.)

Beacon Mode

42RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide

10.1BEACON FORMAT SELECTION

The RDR-1600 will always display all beacon signals on the screen as they

respond to the radar interrogation, regardless of the format selection.

To identify a particular beacon and place an identification number beside it,

you must first identify whether the beacon is the standard or DO-172

format. This is accomplished by observing the beacon responses.

If the beacon is of the standard format, there will always be only 2 “slash

es” on the display spaced 7 nm apart or more. The RDR-1600 can identify

any one of nine standard beacons in this mode.

Figure 10.1-1.Standard Beacon

10.2DO-172

A selected beacon utilizing the DO-172 format will have two framing “slash

es” which are positioned approximately 2 nm apart. Within these two

“frames” will be a combination of up to four slashes. Varying the combina

tions of the inner slashes makes it possible to identify any one of fifteen dif

ferent DO-172 beacon codes. This feature is especially beneficial when

operating in areas of multiple beacon activity.

Figure 10.2-1.DO-172

After the beacon type has been identified and the proper format selected,

the operator may now select the desired beacon number by pressing the

COURSE/CODE (CRS CODE) button the proper number of times.

10.0BEACON MODES

In the Beacon (BCN) mode, the RDR-1600 can interrogate, receive and dis-

play signals from fixed transponder beacons on all ranges. The beacon

itself is displayed as curved “slashes”, with the position of the beacon

located approximately in the center of the closest slash.

The RDR-1600 will also display the bearing and radar distance to any

selected beacon; this information is displayed in the lower left corner of the

indicator display.

For greater flexibility, the beacon mode may be operated alone or in com-

bination with the weather or search modes.

TM106101(8/01)RDR-1600 Pilot’s Guide

Multiple Indicators

44RDR-1600 Pilot’s GuideTM106101(8/01)

Course Bearing Cursor (Cont.)

12.0MULTIPLE INDICATORS

An additional MFD unit, is required for multiple indicator installations.

Since all controls for the radar system are located on the control panel, both

MFD observers will see the same display.

•Operating modes

•Search and beacon gain

•Antenna tilt angle

•Antenna scan angle

•Beacon code

All indicators independently control:

•Display range

•Desired brightness level

The RDR-1600 will perform dual scan operation when the range of indica

tor No. 1 (or 2) is greater than or equal to 20 nm and indicator No. 2 (or 1)

is less than or equal to 10 nm, and the mode of operation is either search

1 or search 2. In this situation, the short range will use a short transmitted

pulse, and the long range will use a long transmitted pulse. This is an

incompatible situation in that the transmitter cannot transmit both a long

and short pulse at the same time. In this situation, indicator No. 1 will be

updated on the right to left sweep of the antenna, and indicator No. 2 will

be updated on the left to right sweep of the antenna.

11.0AC 90-80

The FAA allows lower minimums in radar approaches to clusters of rigs,

when both the radar altimeter and “course bearing cursor” are operating

and are used as described in AC 90-80. For details on minimum approach

heights and distances, refer to FAA AC 90-80.

Note

+Advisory Circular AC 90-80, Approval of Offshore Standard

Approach Procedures. . .can be downloaded from www.faa.govin

Adobe Acrobat format.

Click on:

•Aviation Support and Regulation, then

•Guidance, Reference, Advisory, then

•Index of FAA Advisory Circulars (AC)

Go to the search engine at the bottom of the AC page and enter

the title in quotations to find the AC.

TM106101(8/01)RDR-1600 Pilot’s Guide

System Specifications (Cont.)

46RDR-1600 Pilot’s GuideTM106101(8/01)

System Specifications

13.3CP-113K CONTROL PANEL

Environmental Qualification:DO-160A Env. Cat.

F1A/PKS/XXXXXXABABA

Altitude:55,000 feet

Temperature:-20 degrees C. to +55 degrees C.

(-4 degrees F. to +131 degrees F.)

Cooling:

May be required as determined by ambient

temperature range in aircraft cockpit.

Mounting:Panel mounted, DZUS.

Weight:1.7 lbs. maximum (0.77 kg)

TSO:C63c

Overall Dimensions

Height:2.25 inches maximum (57.2 mm)

Width:5.75 inches maximum (146.0 mm)

Length:6.5 inches maximum (165.1 mm)

Input Power

Voltage+28 Vdc inputs per DO-160A

Category B. Two inputs available.

Power Draw Using2.5 watts maximum electrical power drain

+28 Vdc Lighting from +28 Vdc power bus plus 7.5 watts

Power Busmaximum lighting power drain from

+28 Vdc lighting bus.

Power Draw using 5 Vac,10 watts maximum electrical and lighting

400 Hz Lighting

input power drain from +28 Vdc power bus.

Power BusOne milliamp power drain from 5 Vac

lighting bus (reference).

13.0SYSTEM SPECIFICATIONS

13.1RT-1601 RT UNIT

Frequency:9375 MHz Xmit/Rec; 9310 MHz BCN REC

RF Power Output:10 KW Peak Power

PRF/Pulse Width:Short Range Search 1500 P.P.S./0.2 sec

Long Range Search and Beacon; 200 P.P.S./2.35 sec

Altitude:50,000 ft.

Temperature:-50°C to +55°C

Size:5”w x 6-1/4”h x 13-7/8”d (1/2 ATRI)

Weight:16 lbs. (7.26 kg)

TSO:C63c

13.2DA-1203A ANTENNA DRIVE ASSEMBLY

Reflector Size:10”, 12”, or 18” Flat Plate

Scan Angle:120° or 60°

Tilt Angle:±15°

Scan Rate:28°/sec

Stabilization Accuracy:±1°

Altitude:50,000 ft.

Temperature:-50°C to +55°C

Weight:10”, 0.88 lbs. (4 Kgs), 12”; 1.1 lbs. (0.498 Kgs), 18”; 2.2 lbs.

(1.0 Kgs)

Drive Assembly:6.5 lbs. (2.95 Kgs)

Counterbalanced Drive Assembly:9.5 lbs. (4.32 Kgs)

TSO:C63b

TM106101(8/01)RDR-1600 Pilot’s Guide

Advisory Circulars (Cont.)

48RDR-1600 Pilot’s GuideTM106101(8/01)

Advisory Circulars

AC 00-24B

1/20/83

b.Tornadoes.

(1)The most violent thunderstorms draw air into their cloud bases

with great vigor. If the incoming air has any initial rotating motion, it often

forms an extremely concentrated vortex from the surface well into the

cloud. Meteorologists have estimated that wind in such a vortex can

exceed 200 knots; pressure inside the vortex is quite low. The strong

winds gather dust and debris and the low pressure generates a funnel-

shaped cloud extending downward from the cumulonimbus base. If the

cloud does not reach the surface, it is a "funnel cloud"; if it touches a land

surface, it is a "tornado."

(2)Tornadoes occur with both isolated and squall line thunder-

storms. Reports for forecasts of tornadoes indicate that atmospheric con-

ditions are favorable for violent turbulence. An aircraft entering a tornado

vortex is almost certain to suffer structural damage. Since the vortex

extends well into the cloud, any pilot inadvertently caught on instruments

in a severe thunderstorm could encounter a hidden vortex.

(3)Families of tornadoes have been observed as appendages of

the main cloud extending several miles outward from the area of lightning

and precipitation. Thus, any cloud connected to a severe thunderstorm

carries a threat of violence.

c.Turbulence.

(1)

Potentially hazardous turbulence is present in all thunderstorms,

and a severe thunderstorm can destroy an aircraft. Strongest turbulence

within the cloud occurs with shear between updrafts and downdrafts.

Outside the cloud, shear turbulence has been encountered several thou-

sand feet above and 20 miles laterally from a severe storm. A low level

turbulent area is the shear zone associated with the gust front. Often, a

"roll cloud" on the leading edge of a storm marks the top of the eddies in

this shear and it signifies an extremely turbulent zone. Gust fronts often

move far ahead (up to 15 miles) of associated precipitation. The gust front

causes a rapid and sometimes drastic change in surface wind ahead of

an approaching storm. Advisory Circular 00-50A, "Low Level Wind Shear,"

explains in greater detail the hazards associated with gust fronts. Figure

A-1 shows a schematic cross section of a thunderstorm with areas out-

side the cloud where turbulence may be encountered.

(2)It is almost impossible to hold a constant altitude in a thunder-

storm, and maneuvering in an attempt to do so provides greatly increased

stress on the aircraft. It is understandable that the speed of the aircraft

determines the rate of turbulence encounters. Stresses are least if the air

craft is held in a constant attitude and allowed to "ride the waves." To

date, we have no sure way to pick "soft spots" in a thunderstorm.

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

Washington, D.C.

Subject: THUNDERSTORMSDate: 1/20/83AC No.: 00-24B

Initiated by: AFO-260Change:

1.PURPOSE. This advisory circular describes the hazards of thunder-

storms to aviation and offers guidance to help prevent accidents caused

by thunderstorms.

2,CANCELLATION. Advisory Circular 00-24A, dated June 23, 1978, is

canceled.

3.RELATED READING MATERIAL. Advisory Circulars 00-6A, Aviation

Weather, 00-45B, Aviation Weather Services, 00-50A, Low Level Wind

Shear.

4.GENERAL. We all know what a thunderstorm looks like. Much has

been written about the mechanics and life cycles of thunderstorms. They

have been studied for many years; and while much has been learned, the

studies continue because much is not known. Knowledge and weather

radar have modified our attitudes toward thunderstorms, but one rule con-

tinues to be true - any storm recognizable as a thunder-storm should be

considered hazardous until measurements have shown it to be safe. That

means safe for you and your aircraft. Almost any thunderstorm can spell

disaster for the wrong combination of aircraft and pilot.

5.HAZARDS. A thunderstorm packs just about every weather hazard

know to aviation into one vicious bundle. Although the hazards occur in

numerous combinations, let us look at the most hazardous combination of

thunderstorms, the squall line, then we will examine the hazards individu-

ally.

a.Squall Lines. A squall line is a narrow band of active thunder-

storms. Often it develops on or ahead of a cold front in moist, unstable air,

but it may develop in unstable air far removed from any front. The line

may be too long to detour easily and too wide and severe to penetrate. It

often contains steady-state thunderstorms and presents the single most

intense weather hazard to aircraft. It usually forms rapidly, generally

reaching maximum intensity during the late afternoon and the first few

hours of darkness.

TM106101(8/01)RDR-1600 Pilot’s Guide

Advisory Circulars (Cont.)

50RDR-1600 Pilot’s GuideTM106101(8/01)

Advisory Circulars (Cont.)

AC 00-24B

1/20/83

(2)As hailstones fall through air whose temperature is above 0°C,

they begin to melt and precipitation may reach the ground as either hail or

rain. Rain at the surface does not mean the absence of hail aloft. You

should anticipate possible hail with any thunderstorm, especially beneath

the anvil of a large cumulonimbus. Hailstones larger than one-half inch in

diameter can significantly damage an aircraft in a few seconds.

f.Low Ceiling and Visibility. Generally, visibility is near zero within a

thunderstorm cloud. Ceiling and visibility also may be restricted in precipi

tation and dust between the cloud base and the ground. The restrictions

create the same problem as all ceiling and visibility restrictions; but the

hazards are increased many fold when associated with the other thunder

storm hazards of turbulence, hail, and lightning which make precision

instrument flying virtually impossible.

g.Effect on Altimeters. Pressure usually falls rapidly with the ap-

proach of a thunderstorm, then rises sharply with the onset of the first

gust and arrival of the cold downdraft and heavy rain showers, falling

back to normal as the storm moves on. This cycle of pressure change

may occur in 15 minutes. If the pilot does not receive a corrected altimeter

setting, the altimeter may be more than 100 feet in error.

h.Lightning. A lightning strike can puncture the skin of an aircraft and

can damage communications and electronic navigational equipment.

Lightning has been suspected of igniting fuel vapors causing explosion;

however, serious accidents due to lightning strikes are extremely rare.

Nearby lightning can blind the pilot rendering him momentarily unable to

navigate either by instrument or by visual reference. Nearby lightning can

also induce permanent errors in the magnetic compass. Lightning dis-

charges, even distant ones, can disrupt radio communications on low and

medium frequencies. Though lightning intensity and frequency have no

simple relationship to other storm parameters, severe storms, as a rule,

have a high frequency of lightning.

i.Engine Water Ingestion.

(1)Turbine engines have a limit on the amount of water they can

ingest. Updrafts are present in many thunderstorms, particularly those in

the developing stages. If the updraft velocity in the thunderstorm

approaches or exceeds the terminal velocity of the falling raindrops, very

high concentrations of water may occur. It is possible that these concen-

trations can be in excess of the quantity of water turbine engines are

designed to ingest. Therefore, severe thunderstorms may contain areas of

high water concentration which could result in flame-out and/or structural

failure of one or more engines.

(2)At the present time, there is no known operational procedure

that can completely eliminate the possibility of engine damage/flameout

AC 00-24B1/20/83

d.Icing.

(1)Updrafts in a thunderstorm support abundant liquid water with

relatively large droplet sizes; and when carried above the freezing level,

the water becomes supercooled. When the temperature in the upward

current cools to about -15°C, much of the remaining water vapor subli-

mates as ice crystals; and above this level, at lower temperatures, the

amount of supercooled water decreases.

(2)Supercooled water freezes on impact with an aircraft. Clear

icing can occur at any altitude above the freezing level; but at high levels,

icing from smaller droplets may be rime or mixed rime and clear. The

abundance of large, supercooled water droplets makes clear icing very

rapid between 0°C and -15°C and encounters can be frequent in a cluster

of cells. Thunderstorm icing can be extremely hazardous.

Figure 14-1.Cross-Section of a Thunderstorm

e.Hail.

(1)Hail competes with turbulence as the greatest thunderstorm

hazard to aircraft. Supercooled drops above the freezing level begin to

freeze. Once a drop has frozen, other drops latch on and freeze to it, so

the hailstone grows - sometimes into a huge iceball. Large hail occurs

with severe thunderstorms with strong updrafts that have built to great

heights. Eventually, the hailstones fall, possible some distance from the

storm core. Hail may be encountered in clear air several miles from dark

thunderstorm clouds.

TM106101(8/01)RDR-1600 Pilot’s Guide

Advisory Circulars (Cont.)

52RDR-1600 Pilot’s GuideTM106101(8/01)

Advisory Circulars (Cont.)

AC 00-24B

1/20/83

radar echoes depends on echo intensity, spacing between the echoes,

and the capabilities of you and your aircraft. Remember that weather

radar detects only precipitation drops; it does not detect turbulence.

Therefore, the radar scope provides no assurance of avoiding turbulence.

The radar scope also does not provide assurance of avoiding instrument

weather from clouds and fog. Your scope may be clear between intense

echoes; this clear area does not necessarily mean you can fly between

the storms and maintain visual sighting of them.

f.Remember that while hail always gives a radar echo, it may fall

several miles from the nearest visible cloud and hazardous turbulence

may extend to as much as 20 miles from the echo edge. Avoid intense or

extreme level echoes by at least 20 miles; that is, such echoes should be

separated by at least 40 miles before you fly between them. With weaker

echoes you can reduce the distance by which you avoid them.

7.DO'S AND DON'TS OF THUNDERSTORM FLYING.

a.Above all, remember this: never regard any thunderstorm lightly

even when radar observers report the echoes are of light intensity.

Avoiding thunderstorms is the best policy. Following are some do's and

don'ts of thunderstorm avoidance:

(1)Don't land or takeoff in the face of an approaching thunder-

storm. A sudden gust front of low level turbulence could cause loss of

control.

(2)Don't attempt to fly under a thunderstorm even if you can see

through to the other side. Turbulence and wind shear under the storm

could be disastrous.

(3)Don't fly without airborne radar into a cloud mass containing

scattered embedded thunderstorms. Scattered thunderstorms not embed

ded usually can be visually circumnavigated.

(4)

Don't trust the visual appearance to be a reliable indicator of the

turbulence inside a thunderstorm.

(5)Do avoid by at least 20 miles any thunderstorm identified as

severe or giving an intense radar echo. This is especially true under the

anvil of a large cumulonimbus.

(6)Do circumnavigate the entire area if the area has 6/10 thunder-

storm coverage.

(7)Do remember that vivid and frequent lightning indicates the

probability of a severe thunderstorm.

(8)Do regard as extremely hazardous any thunderstorm with tops

35,000 feet or higher whether the top is visually sighted or determined by

radar.

AC 00-24B1/20/83

during massive water ingestion. Although the exact mechanism of these

water-induced engine stalls has not bee determined, it is felt that thrust

changes may have an adverse effect on engine stall margins in the pres-

ence of massive water ingestion.

(3)Avoidance of severe storm systems is the only measure as-

sured to be effective in preventing exposure to this type of multiple engine

damage/flameout. During an unavoidable encounter with severe storms

with extreme precipitation, the best known recommendation is to follow

the severe turbulence penetration procedure contained in the approved

airplane flight manual with special emphasis on avoiding thrust changes

unless excessive airspeed variations occur.

6.WEATHER RADAR.

a.Weather radar detects droplets of precipitation size. Strength of the

radar return (echo) depends on drop size and number. The greater the

number of drops, the stronger is the echo; and the larger the drops, the

stronger is the echo. Drop size determines echo intensity to a much

greater extent that does drop number. Hailstones usually are covered with

a film of water and, therefore, act as huge water droplets giving the

strongest of all echoes.

b.Numerous methods have been used in an attempt to categorize the

intensity of a thunderstorm. To standardize thunderstorm language

between weather radar operators and pilots, the use of Video Integrator

Processor (VIP) levels is being promoted.

c.The National Weather Service (NWS) radar observer is able to

objectively determine storm intensity levels with VIP equipment. These

radar echo intensity levels are on a scale of one to six. If the maximum

VIP Levels are 1 "weak" and 2 "moderate," then light to moderate tur-

bulence is possible with lightning. VIP Level 3 is "strong" and severe tur-

bulence is possible with lightning. VIP Level 4 is "very strong" and severe

turbulence is likely with lightning. VIP Level 5 is "intense" with severe tur-

bulence, lightning, hail likely, and organized surface wind gusts. VIP Level

6 is "extreme' with severe turbulence, lightning, large hail, extensive sur-

face wind gusts, and turbulence.

d.Thunderstorms build and dissipate rapidly. Therefore, do not

attempt to plan a course between echoes. The best use of ground radar

information is to isolate general areas and coverage of echoes. You must

avoid individual storms from in-flight observations either by visual sighting

or by airborne radar. It is better to avoid the whole thunderstorm area than

to detour around individual storms unless they are scattered.

e.Airborne weather avoidance radar is, as its name implies, for avoid-

ing severe weather - not for penetrating it. Whether to fly into an area of

TM106101(8/01)RDR-1600 Pilot’s Guide

Advisory Circulars (Cont.)

54RDR-1600 Pilot’s GuideTM106101(8/01)

Advisory Circulars (Cont.)

ADVISORY CIRCULARAC 20-68B

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration, Washington, D.C.

Recommended radiation safety precautions for ground operation of

airborne weather radar.

Initiated by: AFO-512

PURPOSE

This circular sets forth recommended radiation safety precautions to be

taken by personnel when operating airborne weather radar on the ground.

CANCELLATION

AC 20-68A, dated April 11, 1975, is canceled.

Telephonics MCB-RT-1601 Color Weather and Search and Rescue Radar User Manual RDR 1600

Telephonics Corporation Color Weather and Search and Rescue Radar RDR 1600

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