Honeywell Weather Radio 880 Users Manual PRIMUS Digital Radar System
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- TITLE
- FRONT MATTER
- Record of Revisions
- Record of Temporary Revisions
- List of Effective Pages
- Table of Contents
- List of Illustrations
- Figure 2-1. PRIMUS 880 Configurations
- Figure 2-2. Typical PRIMUS 880 Weather Radar Components
- Figure 3-1. Typical PRIMUS 880 Digital Weather Radar Display
- Figure 3-2. WI-880 Weather Radar Indicator Front Panel View
- Figure 3-3. WI-880 Weather Radar Indicator Display Screen Features
- Figure 3-4. WC-880 Weather Radar Controller Configurations
- Figure 3-5. WC-884 Weather Radar Controller
- Figure 4-1. Indicator Test Pattern 120°Scan (WX), With TEXT FAULT Enabled
- Figure 4-2. EFIS Test Pattern (Typical) 120° Scan Shown (WX)
- Figure 4-3. WI-880 Indicator Test Pattern With TEXT FAULT Enabled
- Figure 5-1. Positional Relationship of an Airplane and Storm Cells Ahead as Displayed on Indicator
- Figure 5-2. Antenna Beam Slicing Out Cross Section of Storm During Horizontal Scan
- Figure 5-3. Sea Returns
- Figure 5-4. Radar Beam Illumination High Altitude 12-Inch Radiator
- Figure 5-5. Radar Beam Illumination High Altitude 18-Inch Radiator
- Figure 5-6. Radar Beam Illumination Low Altitude 12-Inch Radiator
- Figure 5-7. Radar Beam Illumination Low Altitude 18-Inch Radiator
- Figure 5-8. Ideal Tilt Angle
- Figure 5-9. Earth’ s Curvature
- Figure 5-10. Convective Thunderstorms
- Figure 5-11. Unaltered Tilt
- Figure 5-12. Proper Tilt Technique
- Figure 5-13. Tilt Management With Heading Changes
- Figure 5-14. Fast Developing Thunderstorm
- Figure 5-15. Low Altitude Tilt Management
- Figure 5-16. Antenna Size and Impact on Tilt Management
- Figure 5-17. Rules of Thumb
- Figure 5-18. Manual Tilt at Low Altitudes
- Figure 5-19. Symmetrical Ground Returns
- Figure 5-20. Ground Return Indicating Misalignment (Upper Right)
- Figure 5-21. Ground Return Indicating Misalignment (Upper Left)
- Figure 5-22. Roll Stabilization Inoperative
- Figure 5-23. Roll Offset Adjustment Display - Initial
- Figure 5-24. Roll Offset Adjustment Display - Final
- Figure 5-25. Weather Radar Images
- Figure 5-26. Radar and Visual Cloud Mass
- Figure 5-27. Squall Line
- Figure 5-28. REACT ON and OFF Indications
- Figure 5-29. Probability of Turbulence Presence in a Weather Target
- Figure 5-30. Total Return Vector
- Figure 5-31. No Turbulence
- Figure 5-32. Turbulent
- Figure 5-33. Weather Display With Turbulence
- Figure 5-34. Turbulence Levels (From Airman’ s Information Manual)
- Figure 5-35. Hail Size Probability
- Figure 5-36. Rain Coming From Unseen Dry Hail
- Figure 5-37. Familiar Hailstorm Patterns
- Figure 5-38. Overshooting a Storm
- Figure 5-39. Short- and Long-Blind Alley
- Figure 5-40. Azimuth Resolution in Weather Modes
- Figure 5-41. Weather Display
- Figure 5-42. Typical Hook Pattern
- Figure 5-43. V-Notch Echo, Pendant Shape
- Figure 5-44. The Classic Pendant Shape
- Figure 5-45. Rain Gradients
- Figure 5-46. Crescent Shape
- Figure 5-47. Line Echo Wave Pattern (LEWP)
- Figure 5-48. Bow-Shaped Line of Thunderstorms
- Figure 5-49. Ground Mapping Display
- Figure 6-1. MPEL Boundary
- Figure 7-1. Fault Annunciation on Weather Indicator With TEXT FAULT Fields
- Figure 7-2. Fault Code on EFIS Weather Display With TEXT FAULTS Disabled
- Figure 7-3. Radar Indication With Text Fault Enabled (On Ground)
- Figure A-1. Schematic Cross Section of a Thunderstorm
- Figure B-1. EHSI Display Over KPHX Airport With the EGPWS Display
- Figure B-2. EGPWS Test Display
- List of Tables
- Table 2-1. Dual Control Mode Truth Table
- Table 2-2. PRIMUS 880 Weather Radar Equipment List
- Table 3-1. Rainfall Rate Color Coding
- Table 3-2. Target Alert Characteristics
- Table 3-3. Rainfall Rate Color Coding
- Table 3-4. WC-880 Controller Target Alert Characteristics
- Table 3-5. WC-884 Controller Target Alert Characteristics
- Table 3-6. Rainfall Rate Color Coding
- Table 4-1. PRIMUS 880 Power-Up Procedure
- Table 5-1. Approximate Tilt Setting for Minimal Ground Target Display 12-Inch Radiator
- Table 5-2. Approximate Tilt Setting for Minimal Ground Target Display 18-Inch Radiator
- Table 5-3. Approximate Tilt Setting for Minimal Ground Target Display 24-Inch Radiator
- Table 5-4. Pitch and Roll Trim Adjustments Criteria
- Table 5-5. Stabilization In Straight and Level Flight Check Procedure
- Table 5-6. Stabilization in Turns Check Procedure
- Table 5-7. In-flight Roll Offset Adjustment Procedure
- Table 5-8. Pitch Offset Adjustment Procedure
- Table 5-9. Roll Gain Adjustment
- Table 5-10. Pitch Gain Adjustment
- Table 5-11. Display Levels Related to VIP Levels (Typical)
- Table 5-12. Severe Weather Avoidance Procedures
- Table 5-13. TILT Setting for Maximal Ground Target Display (12-Inch Radiator)
- Table 5-14. TILT Setting for Maximal Ground Target Display (18-Inch Radiator)
- Table 7-1. Fault Data Fields
- Table 7-2. Text Faults
- Table 7-3. Pilot Messages
- Table B-1. EGPWS Obstacle Display Color Definitions
- List of Illustrations
- SECTIONS
- 1. INTRODUCTION
- 2. SYSTEM CONFIGURATIONS
- 3. OPERATING CONTROLS
- 4. NORMAL OPERATION
- 5. RADAR FACTS
- List of Figures - Section V
- Figure 5-1. Positional Relationship of an Airplane and Storm Cells Ahead as Displayed on Indicator
- Figure 5-2. Antenna Beam Slicing Out Cross Section of Storm During Horizontal Scan
- Figure 5-3. Sea Returns
- Figure 5-4. Radar Beam Illumination High Altitude 12-Inch Radiator
- Figure 5-5. Radar Beam Illumination High Altitude 18-Inch Radiator
- Figure 5-6. Radar Beam Illumination Low Altitude 12-Inch Radiator
- Figure 5-7. Radar Beam Illumination Low Altitude 18-Inch Radiator
- Figure 5-8. Ideal Tilt Angle
- Figure 5-9. Earth’ s Curvature
- Figure 5-10. Convective Thunderstorms
- Figure 5-11. Unaltered Tilt
- Figure 5-12. Proper Tilt Technique
- Figure 5-13. Tilt Management With Heading Changes
- Figure 5-14. Fast Developing Thunderstorm
- Figure 5-15. Low Altitude Tilt Management
- Figure 5-16. Antenna Size and Impact on Tilt Management
- Figure 5-17. Rules of Thumb
- Figure 5-18. Manual Tilt at Low Altitudes
- Figure 5-19. Symmetrical Ground Returns
- Figure 5-20. Ground Return Indicating Misalignment (Upper Right)
- Figure 5-21. Ground Return Indicating Misalignment (Upper Left)
- Figure 5-22. Roll Stabilization Inoperative
- Figure 5-23. Roll Offset Adjustment Display - Initial
- Figure 5-24. Roll Offset Adjustment Display - Final
- Figure 5-25. Weather Radar Images
- Figure 5-26. Radar and Visual Cloud Mass
- Figure 5-27. Squall Line
- Figure 5-28. REACT ON and OFF Indications
- Figure 5-29. Probability of Turbulence Presence in a Weather Target
- Figure 5-30. Total Return Vector
- Figure 5-31. No Turbulence
- Figure 5-32. Turbulent
- Figure 5-33. Weather Display With Turbulence
- Figure 5-34. Turbulence Levels (From Airman’ s Information Manual)
- Figure 5-35. Hail Size Probability
- Figure 5-36. Rain Coming From Unseen Dry Hail
- Figure 5-37. Familiar Hailstorm Patterns
- Figure 5-38. Overshooting a Storm
- Figure 5-39. Short- and Long-Blind Alley
- Figure 5-40. Azimuth Resolution in Weather Modes
- Figure 5-41. Weather Display
- Figure 5-42. Typical Hook Pattern
- Figure 5-43. V-Notch Echo, Pendant Shape
- Figure 5-44. The Classic Pendant Shape
- Figure 5-45. Rain Gradients
- Figure 5-46. Crescent Shape
- Figure 5-47. Line Echo Wave Pattern (LEWP)
- Figure 5-48. Bow-Shaped Line of Thunderstorms
- Figure 5-49. Ground Mapping Display
- List of Tables - Section V
- Table 5-1. Approximate Tilt Setting for Minimal Ground Target Display 12-Inch Radiator
- Table 5-2. Approximate Tilt Setting for Minimal Ground Target Display 18-Inch Radiator
- Table 5-3. Approximate Tilt Setting for Minimal Ground Target Display 24-Inch Radiator
- Table 5-4. Pitch and Roll Trim Adjustments Criteria
- Table 5-5. Stabilization In Straight and Level Flight Check Procedure
- Table 5-6. Stabilization in Turns Check Procedure
- Table 5-7. In-flight Roll Offset Adjustment Procedure
- Table 5-8. Pitch Offset Adjustment Procedure
- Table 5-9. Roll Gain Adjustment
- Table 5-10. Pitch Gain Adjustment
- Table 5-11. Display Levels Related to VIP Levels (Typical)
- Table 5-12. Severe Weather Avoidance Procedures
- Table 5-13. TILT Setting for Maximal Ground Target Display (12-Inch Radiator)
- Table 5-14. TILT Setting for Maximal Ground Target Display (18-Inch Radiator)
- Radar Operation
- Tilt Management
- Stabilization
- Pitch Offset Adjustment
- Roll Gain Adjustment
- Pitch Gain Adjustment
- Interpreting Weather Radar Images
- Weather Display Calibration
- Variable Gain Control
- Rain Echo Attenuation Compensation Technique (REACT)
- Radome
- Weather Avoidance
- Ground Mapping
- List of Figures - Section V
- 6. MAXIMUM PERMISSIBLE EXPOSURE LEVEL (MPEL)
- 7. IN-FLIGHT TROUBLESHOOTING
- 8. HONEYWELL PRODUCT SUPPORT
- 9. ABBREVIATIONS
- APPENDICES
- APPENDIX A. Federal Aviation Administration (FAA) Advisory Circulars
- List of Illustrations
- SUBJECT: RECOMMENDED RADIATION SAFETY PRECAUTIONS FOR GROUND OPERATION OF AIRBORNE WEATHER RADAR
- SUBJECT: THUNDERSTORMS
- Purpose
- Cancellation
- Related Reading Material
- General
- Hazards
- National Severe Storms Laboratory (NSSL) Thunderstorm Research
- Relationship Between Turbulence and Reflectivity
- Relationship Between Turbulence and Altitude
- Turbulence and Echo Intensity on NWS Radar (WSR-57)
- Turbulence in Relation to Distance from Storm Core
- Turbulence in Relation to Distance from Storm Edge
- Turbulence Above Storm Tops
- Turbulence Below Cloud Base
- Maximum Storm Tops
- Hail in Thunderstorms
- Visual Appearance of Storm and Associated Turbulence with Them
- Modification of Criteria When Severe Storms and Rapid Development Are Evident
- Extrapolation to Different Climbs
- Use of Airborne Radar
- APPENDIX B. Enhanced Ground--Proximity Warning System (EGPWS)
- APPENDIX A. Federal Aviation Administration (FAA) Advisory Circulars
- INDEX
Printed in U.S.A. Pub. No. A28--1146--102--03 September 1996
Revised January 2006
Honeywell International Inc.
Commercial Electronic Systems
5353 W. Bell Rd.
Glendale, Arizona 85308--3912
U.S.A.
(CAGE 55939)
PRIMUSr880 Digital Weather
Radar System
Pilot’s Guide
PRIMUS
r
880
Digital
W
eather
Radar
System
A28-1146-102-00 Table of Contents
TC-1
Table of Contents
Section Page
1. INTRODUCTION 1-1.............................
2. SYSTEM CONFIGURATIONS 2-1.................
3. OPERATING CONTROLS 3-1....................
WI-880 Weather Radar Indicator Operation 3-1......
WC-880 Weather Radar Controller Operation 3-11....
WC-884 Weather Radar Controller Operation 3-20....
Hidden Modes 3-26...............................
Forced Standby Override 3-26...................
Roll Offset 3-27................................
Roll Gain 3-27.................................
Pitch Offset 3-27...............................
Pitch Gain 3-28................................
4. NORMAL OPERATION 4-1.......................
Preliminary Control Settings 4-1...................
Standby 4-4..................................
Radar Mode -Weather 4-4....................
Radar Mode -Ground Mapping 4-6.............
Test Mode 4-6................................
5. RADAR FACTS 5-1..............................
Radar Operation 5-1.............................
Tilt Management 5-5.............................
Stabilization 5-18.................................
Dynamic Error 5-18............................
Accelerative Error 5-18.........................
Pitch and Roll Trim Adjustments 5-19.............
Stabilization Precheck 5-21.....................
Roll stabilization check 5-25........................
Pitch offset adjustment 5-28........................
Roll gain adjustment 5-29..........................
Pitch gain adjustment 5-30.........................
Interpreting Weather Radar Images 5-31.............
Weather Display Calibration 5-35...................
Variable Gain Control 5-37.........................
PRIMUS
r
880 Digital Weather Radar System
A28--1146--102--01
REV 1
Table of Contents
TC--2
Table of Contents (cont)
Section Page
5. RADAR FACTS (cont)
Rain Echo Attenuation Compensation Technique
(REACT) 5-37..................................
Shadowing 5-40...............................
Turbulence Probability 5-40.....................
Turbulence Detection Theory 5-42...............
Turbulence Detection Operation 5-45.............
Hail Size Probability 5-47.......................
Spotting Hail 5-48..............................
Azimuth Resolution 5-53........................
Radome 5-54....................................
Weather Avoidance 5-55...........................
Configurations of Individual Echoes (Northern
Hemisphere) 5-60............................
Line Configurations 5-65........................
Additional Hazards 5-68........................
Ground Mapping 5-69.............................
6. MAXIMUM PERMISSIBLE EXPOSURE LEVEL
(MPEL) 6-1....................................
7. IN--FLIGHT TROUBLESHOOTING 7--1.............
Test Mode With TEXT FAULTS Enabled 7-2.........
Fault Code and Text Fault Relationships 7-5.........
8. HONEYWELL PRODUCT SUPPORT 8-1..........
9. ABBREVIATIONS 9-1...........................
APPENDICES
A FEDERAL AVIATION ADMINISTRATION (FAA)
ADVISORY CIRCULARS A--1....................
Purpose A--1....................................
Cancellation A--1.................................
Related Reading Material A--1......................
Background A--2.................................
Precautions A--2.................................
PRIMUS
r
880 Digital Weather Radar System
A28--1146--102--01
REV 1
Table of Contents
TC--3
Table of Contents (cont)
A FEDERAL AVIATION ADMINISTRATION (FAA)
ADVISORY CIRCULARS (
CONT
)
SUBJECT: THUNDERSTORMS A--4...............
Purpose A--4..................................
Related Reading Material A--4...................
General A--4..................................
Hazards A--4..................................
National Severe Storms Laboratory (NSSL)
Thunderstorm Research A--11..................
B ENHANCED GROUND--PROXIMITY WARNING
SYSTEM (EGPWS) B--1.........................
System Operation B--1............................
EGPWS Controls B--1..........................
Related EGPWS System Operation B--3..........
EGPWS Operation B--3........................
EGPWS Display B--4..........................
EGPWS Test B--6.............................
INDEX Index--1.............................................
List of Illustrations
Figure Page
2--1 PRIMUS
R
880 Configurations 2-2..................
2--2 Typical PRIMUS
R
880 Weather Radar
Components 2-5...............................
3--1 Typical PRIMUS
R
880 Digital Weather Radar
Display 3-1....................................
3--2 WI--880 Weather Radar Indicator Front Panel
View 3-2......................................
3--3 WI--880 Weather Radar Indicator Display Screen
Features 3-3...................................
3--4 WC--880 Weather Radar Controller Configurations 3-11.
3--5 WC--884 Weather Radar Controller 3-20.............
4--1 Indicator Test Pattern 120°Scan (WX), With TEXT
FAULT Enabled 4-2............................
4--2 EFIS Test Pattern (Typical) 120°Scan Shown
(WX) 4-3......................................
4--3 WI--880 Indicator Test Pattern With TEXT FAULT
Enabled 4-4...................................
PRIMUS
r
880 Digital Weather Radar System
A28--1146--102--01
REV 1
Table of Contents
TC--4
Table of Contents (cont)
List of Illustrations
(
cont
)
Figure Page
5--1 Positional Relationship of an Airplane and Storm
Cells Ahead as Displayed on Indicator 5-2.........
5--2 Antenna Beam Slicing Out Cross Section of Storm
During Horizontal Scan 5-3......................
5--3 Sea Returns 5-4.................................
5--4 Radar Beam Illumination High Altitude
12--Inch Radiator 5-5...........................
5--5 Radar Beam Illumination High Altitude
18--Inch Radiator 5-5...........................
5--6 Radar Beam Illumination Low Altitude
12--Inch Radiator 5-6...........................
5--7 Radar Beam Illumination Low Altitude
18--Inch Radiator 5-6...........................
5--8 Ideal Tilt Angle 5-11...............................
5--9 Earth’s Curvature 5-11............................
5--10 Convective Thunderstorms 5-12....................
5--11 Unaltered Tilt 5-12................................
5--12 Proper Tilt Technique 5-13.........................
5--13 Tilt Management With Heading Changes 5-13........
5--14 Fast Developing Thunderstorm 5-14.................
5--15 Low Altitude Tilt Management 5-14..................
5--16 Antenna Size and Impact on Tilt Management 5-15....
5--17 Rules of Thumb 5-15..............................
5--18 Manual Tilt at Low Altitudes 5-17....................
5--19 Symmetrical Ground Returns 5-22..................
5--20 Ground Return Indicating Misalignment
(Upper Right) 5-22...............................
5--21 Ground Return Indicating Misalignment
(Upper Left) 5-23................................
5--22 Roll Stabilization Inoperative 5-24...................
5--23 Roll Offset Adjustment Display -- Initial 5-26..........
5--24 Roll Offset Adjustment Display -- Final 5-27..........
5--25 Weather Radar Images 5-31.......................
5--26 Radar and Visual Cloud Mass 5-33..................
5--27 Squall Line 5-34..................................
5--28 REACT ON and OFF Indications 5-39...............
5--29 Probability of Turbulence Presence in a Weather
Target 5-41.....................................
5--30 Total Return Vector 5-44...........................
5--31 No Turbulence 5-44...............................
PRIMUS
r
880 Digital Weather Radar System
A28--1146--102--01
REV 1
Table of Contents
TC--5
Table of Contents (cont)
List of Illustrations
(
cont
)
Figure Page
5--32 Turbulent 5-45....................................
5--33 Weather Display With Turbulence 5-45..............
5--34 Turbulence Levels (From Airman’s Information
Manual) 5-47...................................
5--35 Hail Size Probability 5-48..........................
5--36 Rain Coming From Unseen Dry Hail 5-49............
5--37 Familiar Hailstorm Patterns 5-50....................
5--38 Overshooting a Storm 5-51........................
5--39 Short-- and Long--Blind Alley 5-52...................
5--40 Azimuth Resolution in Weather Modes 5-53..........
5--41 Weather Display 5-55.............................
5--42 Typical Hook Pattern 5-61.........................
5--43 V--Notch Echo, Pendant Shape 5-62................
5--44 The Classic Pendant Shape 5-63...................
5--45 Rain Gradients 5-64...............................
5--46 Crescent Shape 5-65..............................
5--47 Line Echo Wave Pattern (LEWP) 5-66...............
5--48 Bow--Shaped Line of Thunderstorms 5-67............
5--49 Ground Mapping Display 5-69......................
6--1 MPEL Boundary 6-1.............................
7--1 Fault Annunciation on Weather Indicator With TEXT
FAULT Fields 7-3..............................
7--2 Fault Code on EFIS Weather Display With TEXT
FAULTS Disabled 7-4...........................
7--3 Radar Indication With Text Fault Enabled
(On Ground) 7-4...............................
A--1 Schematic Cross Section of a Thunderstorm A--6.....
B--1 EHSI Display Over KPHX Airport With the
EGPWS Display B--5............................
B--2 EGPWS Test Display B--6.........................
PRIMUS
r
880 Digital Weather Radar System
A28--1146--102--01
REV 1
Table of Contents
TC--6
Table of Contents (cont)
List of Tables
Table Page
2--1 Dual Control Mode Truth Table 2-3................
2--2 PRIMUS
R
880 Weather Radar Equipment List 2-4....
3--1 Rainfall Rate Color Coding 3-4...................
3--2 Target Alert Characteristics 3-7...................
3--3 Rainfall Rate Color Coding 3-13...................
3--4 WC--880 Controller Target Alert Characteristics 3-17...
3--5 WC--884 Controller Target Alert Characteristics 3-21...
3--6 Rainfall Rate Color Coding 3-24...................
4--1 PRIMUS
R
880 Power--Up Procedure 4-1..........
5--1 Approximate Tilt Setting for Minimal Ground Target
Display 12--Inch Radiator 5-8...................
5--2 Approximate Tilt Setting for Minimal Ground Target
Display 18--Inch Radiator 5-9...................
5--3 Approximate Tilt Setting for Minimal Ground Target
Display 24--Inch Radiator 5-10...................
5--4 Pitch and Roll Trim Adjustments Criteria 5-20........
5--5 Stabilization In Straight and Level Flight Check
Procedure 5-21................................
5--6 Stabilization in Turns Check Procedure 5-23........
5--7 In--flight Roll Offset Adjustment Procedure 5-25......
5--8 Pitch Offset Adjustment Procedure 5-28............
5--9 Roll Gain Adjustment 5-29........................
5--10 Pitch Gain Adjustment 5-30.......................
5--11 Display Levels Related to VIP Levels (Typical) 5-36..
5--12 Severe Weather Avoidance Procedures 5-60........
5--13 TILT Setting for Maximal Ground Target Display
12--Inch Radiator 5-70...........................
5--14 TILT Setting for Maximal Ground Target Display
18--Inch Radiator 5-71...........................
7--1 Fault Data Fields 7-3............................
7--2 Text Faults 7-5.................................
7--3 Pilot Messages 7-8.............................
B--1 EGPWS Obstacle Display Color Definitions B--4......
PRIMUS
r
880
Digital
W
eather
Radar
System
A28-1146-102-00 Introduction
1-1
1. Introduction
The PRIMUSR880 DigitalWeatherRadarSystemisalightweight,
X-band digitalradarwith alphanumerics designed forweatherdetection
(WX)and ground mapping (GMAP).
The primary purpose of the system is to detect storms along the
flightpath and give the pilot avisual indication in color of their rainfall
intensity and turbulence content. After proper evaluation, the pilot can
chart acourse to avoid these storm areas.
WARNING
THE SYSTEMPERFORMSTHEFUNCTIONSOF
WEATHER DETECTIONORGROUND MAPPING. ITSHOULD
NOTBEUSED NOR RELIED UPONFORPROXIMITY
WARNING OR ANTICOLLISIONPROTECTION.
In weather detection mode, storm intensity levels are displayed in
four bright colors contrasted against a deep black background.
Areas of very heavy rainfall appear in magenta, heavy rainfall in red,
less severe rainfall in yellow,moderate rainfall in green, and little or no
rainfall in black (background). Areas of detected turbulence appear in
soft white. The antenna sweep position indicator is ayellow bar.
Range marksand identifyingnumerics, displayedin contrastingcolors,
are provided to facilitate evaluation of storm cells.
Select the GMAP function to optimize system parameters to improve
resolution and enhance identification of small targets at short ranges.
The reflected signal from ground surfaces is displayed as magenta,
yellow,or cyan (most to least reflective).
NOTE: SectionV,RadarFacts,describesavarietyofradaroperating
topics. It is recommended that you read Section V,Radar
Facts, before learning the specific operational details of the
PRIMUSâ880 Digital Weather Radar System.
PRIMUS
r
880
Digital
W
eather
Radar
System
A28-1146-102-00
Introduction
1-2
Theradarindicatorisequippedwiththeuniversaldigitalinterface(UDI).
This feature expands the use of the radar indicator to display
information such as checklists, short and long range navigation
displays (when used with aHoneywell DATANAVsystem) and
electrical discharge data from Honeywell’sLSZ-850 Lightning Sensor
System (LSS).
NOTE: Refer to Honeywell Pub. 28-1146-54, LSZ-850 Lightning
Sensor System Pilot’sHandbook, for more information.
PRIMUS
r
880
Digital
W
eather
Radar
System
A28-1146-102-00 System Configurations
2-1
2. System Configurations
The PRIMUSâ880 Digital Weather Radar System can be operated in
many configurations to display weather or ground mappinginformation
on a radar indicator,electronic flight instrument system (EFIS) display,
multifunctiondisplay(MFD),oronacombinationofthesedisplays.The
various system configurations are summarized in the following
paragraphs and shown in figure 2-1.
NOTE: Other configurations are possible but not illustrated.
The stand-alone configuration consists of two units: receiver
transmitter antenna (RTA), and a dedicated radar indicator.In this
configuration,theradarindicatorcontainsallthecontrolstooperatethe
PRIMUSâ880 Digital Weather Radar System. Asingle or dual
HoneywellEFIScanbeaddedtothestand-aloneconfiguration.Insuch
acase the electronic horizontal situation indicator (EHSI) repeats the
data displayed on the radar indicator.System control remains with
the radar indicator.
The second system configuration uses an RTA, and single or dual
controllers. The single or dual EFIS is the radar display.Since there is
no radar indicator in this configuration, the radar system operating
controlsarelocatedonthecontroller.Withasinglecontroller,allcockpit
radar displays are identical.
The dual configuration gives the appearance of having two radar
systems on the aircraft. In the dual configuration, the pilot and copilot
each select independent radar mode, range, tilt, and gain settings for
display on their respective display.The dual configuration time shares
theRTA.Ontheright-to-leftantennascan, thesystemswitches tothe
mode, range, tilt, and gain selected by the left controller and updates
the left display.On the reverse antenna scan, the system switches to
the mode, range, tilt, and gain setting selected by the right controller
and updates the right display.Either controller can be slaved to the
other controller to show identical images on both sides of the cockpit.
NOTE: When WAIT,SECTOR SCAN, or FORCED STANDBY are
activated, the radar operates as if in single controller
configuration. This is an exception to the ability of each pilot
to independently select modes.
PRIMUS
r
880
Digital
W
eather
Radar
System
A28-1146-102-00
System Configurations
2-2
STAND-ALONE CONFIGURATION
SINGLE OR DUAL EFIS OPTION
RTA
WU-880 INDICATOR
WI-880
EFIS ONLYCONFIGURATION
RTA
WU-880 CONTROLLER
WC-880
SINGLE OR DUAL EFIS OPTIONAL
2ND CONTROLLER
EFIS /MFD CONFIGURATION
RTA
WU-880 CONTROLLER
WC-880
MFD AND
SINGLE OR DUAL EFIS
OPTIONAL
2ND CONTROLLER
AD-46690-R2@
TRB STAB TGT SECT
+
-
TILTSLVRADARGAIN
RCTWX
SBY GMAP
FP
TST
OFF
PULL
VAR
MAXMIN
PULL
ACT
TRB STAB TGT SECT
+
-
TILTSLVRADARGAIN
RCTWX
SBY GMAP
FP
TST
OFF
PULL
VAR
MAXMIN
PULL
ACT
TRB STAB TGT SECT
+
-
TILTSLVRADARGAIN
RCTWX
SBY GMAP
FP
TST
OFF
PULL
VAR
MAXMIN
PULL
ACT
TRB STAB TGT SECT
+
-
TILTSLVRADARGAIN
RCTWX
SBY GMAP
FP
TST
OFF
PULL
VAR
MAXMIN
PULL
ACT
PRIMUSâ880 Configurations
Figure 2-1
PRIMUS
r
880
Digital
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eather
Radar
System
A28-1146-102-00 System Configurations
2-3
The third system configuration is similar to the second except that a
Honeywell multifunction display (MFD) system is added. As before,
single ordual controllerscan beused. Whenasinglecontroller isused,
all displays show the same radar data. Dual controllers are used to
operate in the dual mode. The MFD can be slaved to either controller
toduplicatethedata displayedontheselectedside.Table2-1isatruth
table for dual control modes.
Left
Controller
Mode
Right
Controller
Mode Left Side
(NOTE 1) Right Side
(NOTE 1) RTA
Mode
OFF OFF OFF OFF OFF
OFF Standby ”SLV”
Standby Standby Standby
Standby OFF Standby ”SLV”
Standby Standby
OFF ON ”SLV”ON ON ON
ON OFF ON ”SLV”ON ON
Standby ON Standby/
2ON/2 ON
ON Standby ON/2 Standby/2 ON
ON ON ON/2 ON/2 ON
Standby Standby Standby Standby Standby
Dual Control Mode Truth Table
Table 2-1
PRIMUS
r
880 Digital Weather Radar System
A28--1146--102--03
REV 3
System Configurations
2-4
NOTES: 1. ON is used to indicate any selected radar mode.
2. “SLV” means that displayed data is controlled by
opposite side controller.
3. XXX/2 means that display is controlled by appropriate
on--side control for the antenna sweep direction
associated with that control. (/2 implies two controllers
are on.)
4. In standby, the RTA is centered in azimuth with 15_
upward tilt. Video data is suppressed. The transmitter
is inhibited.
5. The MFD, if used, can repeat either left-- or right--side
data, depending upon external switch selection.
Equipment covered in this guide is listed in table 2--2 and shown in
figure 2--2.
Model Unit Part No.
Cockpit Mounted Options
WI--880 Weather Radar Indicator 7007700--401/402/
403/404
WC--880 Weather Radar Controller 7008471--4XX
WC--884 Weather Radar Controller 7006921--815/816
Remote Mounted Equipment
WU--880 Receiver Transmitter Antenna 7021450--801
NOTE: Typically, either the indicator or one of the remote
controllers (one or two) is installed.
PRIMUS
R
880 Weather Radar Equipment List
Table 2--2
PRIMUS
r
880
Digital
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Radar
System
A28-1146-102-00 System Configurations
2-5/(2-6 blank)
WC-884 CONTROLLER
WC-880 CONTROLLERWI-880 INDICATOR
WU-880 RTA
AD-46691@
Typical PRIMUSâ880 Weather Radar Components
Figure 2-2
PRIMUS
r
880
Digital
W
eather
Radar
System
A28-1146-102-00 Operating Controls
3-1
3. Operating Controls
WI-880 WEATHER RADAR INDICATOR OPERATION
Allcontrolsusedtooperate thesystem displayshown infigure 3-1,are
located on the WI-880Weather Radar Indicator front panel. There are
three basic controllers that are described in this section, they are (in
order of description):
DWI-880 Weather Radar Indicator
DWC-880 Weather Radar Controller
DWC-884 Weather Radar Controller.
AZ
AUTO
TILT50
40
30
20
10
+1.0
21 3 4 T
Typical PRIMUSâ880 Digital
Weather Radar Display
Figure 3-1
The controls and display features of the WI-880 Weather Radar
Indicator are indexed and identified in figure 3-2.Brightness levels for
all legends and controls on the indicator are controlled by the dimming
bus for the aircraft panel.
PRIMUS
r
880
Digital
W
eather
Radar
System
A28-1146-102-00
Operating Controls
3-2
AD-46693-R1@
RCT
TGT
AZ
SCT
RANGE
GMAP
WX FP
TST
SBY
OFF
GAIN
MIN MAX
PULL
VAR
PULL
ACT
TILT+
-
BRT
STB
TRB 7
8
9
10
11
2
1
3
4
5
6
12
10
BRT
OFF CLR
TST
SBY LX
WI-880 Weather Radar Indicator Front Panel View
Figure 3-2
1Display Area
Seefigure3-3andtheassociatedtextwhichexplainsthealphanumeric
display.
PRIMUS
r
880
Digital
W
eather
Radar
System
A28-1146-102-00 Operating Controls
3-3
AD-46694-R2@
T
TGT
1234T
VAR!
1 2 3
VAR
1234T
VAR!
TARGET/TARGET ALERT:
ARM (GREEN)
ALERT(YELLOW INVERTED VIDEO)
TILTANGLE ALTITUDE
COMPENSATED
TILT(ACT)
ANNUNCIATION
RANGE RING
MARKERS
(120-DEGREE
SCAN SHOWN)
WX CALIBRATED GAIN
WX VARIABLE GAIN
GMAP CALIBRATED GAIN
GMAP VARIABLE GAIN
WX/T CALIBRATED GAIN
WX/T VAR
COLOR BAR:
MESSAGES ARE LISTED
IN PRIORITY ORDER.
NOTE:
STBY
FSBY
WAIT
TEST
WX
WX/T
FLTPLN
GMAP
MODE:
REACT:RCT
NOTE FAIL
STB A
WI-880 Weather Radar Indicator Display Screen Features
Figure 3-3
2Function Switch
Arotary switch used to select the following functions:
DOFF-This position turns offthe radar system.
DSBY (Standby) -This position places the radar system in standby,
aready state, with the antenna scan stopped, the transmitter
inhibited, and the display memory erased. STBY,in white, is shown
in the mode field.
If SBY is selected before the initial RTAwarmup period is complete
(approximately 90 seconds), the white WAIT legend is shown in
the mode field. When warmup is complete the system changes the
mode field to STBY.
DWX (Weather) -This position selects the WX mode of operation.
When WX is selected, the system is fully operational and all internal
parameters are set for enroute weather detection. The
alphanumerics are white and WX is shown in the mode field.
PRIMUS
r
880
Digital
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eather
Radar
System
A28-1146-102-00
Operating Controls
3-4
If WX is selected before the initial RTAwarmup period is over
(approximately 90 seconds), the white WAIT legend is displayed
in the mode field. In wait mode, the transmitter and antenna scan
are inhibited and the display memory is erased. When the warmup
is complete, the system automatically switches to the WX mode.
The system, in preset gain, is calibrated as listed in table 4-1.
Rainfall Rate Color
in/hr mm/hr
.04-.16 1-4Green
.16-.47 4-12 Yellow
.47-2 12-50 Red
>2>5 0Magenta
Rainfall Rate Color Coding
Table 3-1
DGMAP (Ground Mapping) -The GMAP position puts the radar
system in the ground mapping mode. The system is fully
operational and all parameters are set to enhance returns from
ground targets.
NOTE: REACT,TGT,orTURBmodesare notselectableinGMAP.
WARNING
WEATHER TYPE TARGETS ARE NOT CALIBRATED WHEN
THE RADAR IS IN THE GMAP MODE. BECAUSE OF THIS, DO
NOT USE THE GMAP MODE FOR WEATHER DETECTION.
As aconstant reminder that GMAP is selected, the alphanumerics
are changed to green, the GMAP legend is shown in the mode field,
and the color scheme is changed to cyan, yellow,and magenta.
Cyan represents the least reflective return, yellow is amoderate
return, and magenta is astrong return.
If GMAP is selected before the initial RTAwarmup period is
complete, the white WAIT legend is shown in the mode field. In wait
mode, the transmitter and antenna scan are inhibited and the
memory is erased. When the warmup period is complete, the
system automatically switches to the GMAP mode.
DFP(FlightPlan)-TheFPpositionputstheradarsystemintheflight
plan mode, which clears the screen of radar data so ancillary data
can be displayed. Examples of this data are:
PRIMUS
r
880 Digital Weather Radar System
A28--1146--102--03
REV 3 3-5
Operating Controls
DFP (Flight Plan) -- The FP position puts the radar system in the flight
plan mode, which clears the screen of radar data so ancillary data
can be displayed. Examples of this data are:
—Navigation displays
—Electrical discharge (lightning) data.
NOTE: In the FP mode, the radar RTA is put in standby, the
alphanumerics are changed to cyan, and the FLTPLN
legend is shown in the mode field.
The target (TGT) alert mode can be used in the FP mode. With
target alert on and the FP mode selected, the target alert armed
annunciation (green TGT) is displayed. The RTA searches for a
hazardous target from 5 to 55 miles and ±7.5°of the aircraft heading.
No radar targets are displayed. If a hazardous target is detected,
the target alert armed annunciation switches to the alert
annunciation (yellow TGT). This advises the pilot that a hazardous
target is in his flightpath and the WX mode should be selected to
view it.
NOTE: The TGT function is inoperative when a checklist is
displayed.
DTST (Test) -- The TST position selects the radar test mode. A
special test pattern is displayed to verify system operation. The
TEST legend is shown in the mode field. Refer to Section 4, Normal
Operations, for a description of the test pattern.
WARNING
UNLESS THE SYSTEM IS IN FORCED STANDBY, THE
TRANSMITTER IS ON AND RADIATING X--BAND
MICROWAVE ENERGY IN TEST MODE. REFER TO SECTION 6,
MAXIMUM PERMISSIBLE EXPOSURE LEVEL (MPEL), AND THE
APPENDIX, FEDERAL AVIATION ADMINISTRATION (FAA)
ADVISORY CIRCULARS, TO PREVENT POSSIBLE HUMAN BODY
DAMAGE.
FSBY (Forced Standby)
FSBY is an automatic, nonselectable radar mode. As an installation
option, the indicator can be wired to the weight--on--wheels (WOW)
squat switch. When wired, the RTA is in the FSBY mode when the
aircraft is on the ground. In FSBY mode, the transmitter and antenna
scan are both inhibited, the display memory is erased, and the FSBY
legend is displayed in the mode field. When in the FSBY mode,
pushing the STAB button 4 times within 3 seconds, restores normal
operation.
PRIMUS
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880
Digital
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System
A28-1146-102-00
Operating Controls
3-6
WARNING
FORCEDSTANDBYMODEMUSTBEVERIFIEDBYTHEOPERATOR
TOENSURE SAFETYFORGROUND PERSONNEL.
3TGT (Target)
The TGT button is an alternate-action switch that enables and
disablestheradartargetalertfeature.Targetalertis selectableinallbut
the 300-mile range. When selected, target alert monitors beyond the
selectedrangeand7.5°oneachsideoftheaircraftheading.If areturn
with target alert characteristics is detected in the monitored area, the
target alert legend changes from the green Tarmed condition to the
yellow TGT warning condition. (See the target alert characteristics in
table3-2for atarget description.)These annunciationsadvise thepilot
of potentially hazardous targets directly in front of the aircraft that are
outsidetheselectedrange.Whenayellowwarningisreceived,thepilot
should select longer ranges to view the questionable target. (Note that
target alert is inactive within the selected range.)
Selecting target alert forces the system to preset gain. Target alert can
be selected only in the WX or FP modes.
NOTE: In order to activate the target alert warning, the target must
have the depth and range characteristics described in table
3-2.
PRIMUS
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880
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3-7
Selected Range
(NM) Minimum Target
Depth (NM) Target Range
(NM)
5 5 5-55
10 5 10-60
25 5 25-75
50 5 50-100
100 5 100-150
200 5 200-250
300 N/A N/A
FP (Flight Plan) 5 5-55
Target Alert Characteristics
Table 3-2
4RCT (Rain Echo Attenuation Compensation Technique
(REACT))
The RCT switch is an alternate-action switch that enables and
disables REACT.
The REACT circuitry compensates for attenuation of the radar signal
as it passes through rainfall. The cyan field indicates areas where
further compensation is not possible. Any target detected within
the cyan field cannot be calibrated and should be considered
dangerous. All targets in the cyan field are displayed as fourth level
precipitation, magenta.
REACT is available in the WX mode only and selecting REACT forces
the system to preset gain. When engaged, the white RCT legend is
displayed in the REACT field.
NOTES: 1. REACT’Sthree main functions (attenuation
compensation, cyan field, and forcing targets to
magenta)areswitchedonandoffwiththeRCTswitch.
2. Refer to Section 5, Radar Facts, for adescription of
REACT.
5STB (Stabilization)
TheSTBbuttontogglespitchandrollstabilizationONandOFF.Itisalso
used with the STB adjust mode and to override forced standby.
The radar antenna is normally attitude stabilized. It automatically
compensates for roll and pitch maneuvers (refer to Section 5, Radar
Facts, for adescription of stabilization). The STB OFF annunciator is
displayed on the screen.
PRIMUS
r
880 Digital Weather Radar System
A28--1146--102--03
REV 3
Operating Controls
3-8
The radar antenna is normally attitude stabilized. It automatically
compensates for roll and pitch maneuvers (refer to Section 5, Radar
Facts, for a description of stabilization). The STB OFF annunciator is
displayed on the screen.
6 TRB (Turbulence)
The TRB switch is used to select the turbulence detection mode of
operation. The TRB mode can only be selected if the FUNCTION
switch is in the WX position and the selected range is 50 miles or less.
The weather/turbulence mode is annunciated in the mode field with the
WX/T legend. Areas of moderate or greater turbulence are shown in
soft white. The turbulence threshold is five meters per second.
WARNINGS
1. TURBULENCE CAN ONLY BE DETECTED WITHIN AREAS OF
RAINFALL. THE PRIMUS
R
880 DIGITAL WEATHER RADAR
SYSTEM CANNOT DETECT CLEAR AIR TURBULENCE.
2. UNDETECTED TURBULENCE CAN EXIST WITHIN ANY
STORM CELL. REFER TO SECTION 5, RADAR FACTS, OF THIS
GUIDE FOR ADDITIONAL INFORMATION.
Selecting the 100--, 200--, or 300--mile range turns off turbulence
detection. The /T is deleted from the mode annunciation. Subsequently
selecting ranges of 50 miles or less re--engages turbulence detection.
A description of the turbulence detection capabilities and limitations is
given in Section 5 , Radar Facts, of this guide.
7 RANGE
The RANGE buttons are two momentary--contact buttons used to
select the operating range of the radar. The range selections are from
5 to 300 NM full scale. In FP mode, additional ranges of 500 and 1000
NM are available. The up arrow selects increasing ranges, and the
down arrow selects decreasing ranges. Each of the five range rings on
the display has an associated marker that annunciates its range.
8 AZ (Azimuth)
The AZ button is an alternate--action switch that enables and disables
the electronic azimuth marks. When enabled, azimuth marks at 30_
intervals are displayed. The azimuth marks are the same color as the
other alphanumerics.
9 SCT (Scan Sector)
PRIMUS
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880
Digital
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Radar
System
A28-1146-102-00 Operating Controls
3-9
10 BRT (Brightness) or BRT/LSS (Lightning Sensor System)
The BRTknob is asingle-turncontrol thatadjusts thebrightness ofthe
display.Clockwise (cw) rotation increases display brightness and
counterclockwise (ccw) rotation decreases brightness.
An optional BRT/LSS four-position rotary switch selects the separate
LSZ-850 Lightning Sensor System (LSS) operating modes and the
brightnesscontrolonsomemodels.ItsLSScontrolswitchpositionsare
as follows:
DOFF -This position removes all power from the LSS.
DSBY (Standby) -This position inhibits the display of LSS data, but
the system accumulates data in this mode.
DLX (Lightning Sensor System) -In this position the LSS is fully
operational and data is being displayed on the indicator.
DCLR/TST(Clear/Test)-Inthispositionaccumulateddataiscleared
from the memory of the LSS. After 3seconds the test mode is
initiated in the LSS. Refer to the LSZ-850 Lightning Sensor System
Pilot’sHandbook, for adetailed description of LSS operation.
11 TILT
The TILTknob is arotary control that is used to select the tilt angle of
the antenna beam with relation to the horizon. CW rotation tilts beam
upward to +15_;ccw rotation tilts beam downward to -15_.
Adigital readout of the antenna tilt angle is displayed on the CRT,with
0.5_resolution.
DPULL ACT (Altitude Compensated Tilt) Function -When the
TILTcontrol knob is pulled out, the system engages the ACT.In ACT
the antenna tilt is automatically adjusted with regard to the selected
range and barometric altitude. The antenna tilt automatically
readjusts with changes in altitude and/or selected range. In ACT,the
tilt control can fine tune the autotilt setting by ±2°.
ACT is annunciated with an Afollowing the digital tilt readout. The
digital tilt readout always shows the commanded tilt of the antenna
regardless of the tilt command source (ACT command or manual tilt
command).
WARNINGS
1. TOAVOID FLYING UNDER OR OVER STORMS,
FREQUENTLYSELECT MANUAL TILT TOSCAN BOTH
ABOVE AND BELOW YOUR FLIGHT LEVEL.
2. ALWAYS USE MANUAL TILTFOR WEATHER ANALYSIS.
PRIMUS
r
880
Digital
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Radar
System
A28-1146-102-00
Operating Controls
3-10
12 GAIN
The GAIN knob is asingle-turnrotary control and push/pull switch that
is usedto controlthe receivergain. Pushin onthe GAINswitch toenter
the system into the preset calibrated gain mode. Calibrated gain is the
normalmodeandisused forweatheravoidance.Incalibratedgain,the
rotary portion of the GAIN control does nothing. In calibrated gain, the
colorbarlegendislabeled1,2,3,4inWXmodeor 1,2,3inGMAPmode.
Pull out on the GAIN switch to enter the system into the variable gain
mode with VAR displayed in the color bar.Variable gain is useful for
additional weather analysis and for ground mapping. In WX mode,
variable gain can increase receiver sensitivity over the calibrated level
to show very weak targets or it can be reduced below the calibrated
level to eliminate weak returns.
WARNING
HAZARDOUS TARGETS MAYBE ELIMINATED FROM THE DIS-
PLAYWITH LOW SETTINGS OF VARIABLE GAIN.
In the GMAP mode, variable gain is used to reduce the level of the
typically very strong returns from ground targets.
Minimum gain is with the control at its full ccw position. Gain increases
as the control is rotated cw from full ccw .At full cw position, the gain
is at maximum.
In variable gain, the color bar legend contains the variable gain (VAR)
annunciation. Selecting RCT or TGT forces the system into calibrated
gain.
PRIMUS
r
880
Digital
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Radar
System
A28-1146-102-00 Operating Controls
3-11
WC-880 WEATHER RADAR CONTROLLER
OPERATION
The controls and display features of the WC-880 Weather Radar
Controller are indexed andidentified infigure 3-4.Brightness levelsfor
all legend and controls on the indicator are controlled by the dimming
bus for the aircraft panel.
7 6 5 4 3
8 1 9 10 2
TRB STAB TGT SECT
+
-
TILT
PULL
ACT
CLR
TST
LXSBY
OFF
LSS
SLV
RADARGAIN
RCTWX
SBY GMAP
FP
TST
OFF
PULL
VAR
MAXMIN
AD-46695-R1@
OFF
7 6 5 4 3
8 1 9 2
TRB STAB TGT SECT
+
-
TILT
PULL
ACT
SLVRADARGAIN
RCTWX
SBY GMAP
FP
TST
OFF
PULL
VAR
MAXMIN
AD-46696-R1@
OFF
WC-880 Weather Radar Controller Configurations
Figure 3-4(cont)
PRIMUS
r
880
Digital
W
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Radar
System
A28-1146-102-00
Operating Controls
3-12
6 5 4 3
8 1 10 2
TRB STAB TGT SECT
+
-
TILT
CLR
TST
LXSBY
OFF
LSSSLVRADARGAIN
RCTWX
SBY GMAP
FP
TST
OFF
PULL
VAR
MAXMIN
AD-46697-R1@
PULL
ACT
WC-880 Weather Radar Controller Configurations
Figure 3-4
NOTES: 1. With acontroller without built-in range control, range
iscontrolled fromthe installedEFIS navigationdisplay
2. Controllers are available with and without the LSS
function.
3. Whenever single or dual radar controllers are used,
theradardataisdisplayedontheEFISand/or anMFD
or navigation display (ND).
PRIMUS
r
880
Digital
W
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Radar
System
A28-1146-102-00 Operating Controls
3-13
1RADAR
This rotary switch is used to select one of the following functions.
DOFF -This position turns the radar system off.
DSBY (Standby) -This position places the radar system in standby;
aready state, with the antenna scan stopped, the transmitter
inhibited, and the display memory erased. STBY is displayed on the
EFIS/MFD.
DWX (Weather) -This position selects the weather detection mode.
The system is fully operational and all internal parameters are set
for enroute weather detection.
If WX is selected before the initial RTAwarmup period is complete
(approximately 45 to 90 seconds), the WAIT legend is displayed on
the EFIS/MFD. In WAIT mode, the transmitter and antenna scan are
inhibited and the display memory is erased. When the warmup is
complete, the system automatically switches to the WX mode.
The system, in preset gain, is calibrated as described in table 3-3.
Rainfall Rate Color
in/hr mm/hr
.04-.16 1-4Green
.16-.47 4-12 Yellow
.47-2 12-50 Red
>2>5 0Magenta
Rainfall Rate Color Coding
Table 3-3
DRCT (Rain Echo Attenuation Compensation Technique) -This
switch position turns on RCT.
The REACT circuitry compensates for attenuation of the radar
signal as it passes through rainfall. The cyan field indicates areas
where further compensation is not possible. Any target detected
within the cyan field cannot be calibrated and should be considered
dangerous. All targets in the cyan field are displayed as 4th level
precipitation, magenta.
RCTisasubmode of the WXmode and selecting RCTforcesthe
systemto presetgain.When RCTis selected, the RCTlegend is
displayed on the EFIS/MFD.
PRIMUS
r
880
Digital
W
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System
A28-1146-102-00
Operating Controls
3-14
NOTES: 1. REACT’sthree functions (attenuation
compensation, cyan field, and forcing targets to
magenta) are switched on and offwith the RCT
switch.
2. Refer to Section 5, Radar Facts, for adescription
of REACT.
DGMAP (Ground Mapping) -The GMAP position puts the radar
system in the Ground Mapping mode. The system is fully
operational and all parameters are set to enhance returns from
ground targets.
NOTE: REACT,TGT,orTRBmodesare notselectableinGMAP.
WARNING
WEATHERTYPE TARGETSARENOTCALIBRATEDWHEN
THERADARISINTHEGMAPMODE.BECAUSEOF THIS,DONOT
USE THEGMAPMODEFORWEATHER DETECTION.
As aconstant reminder that GMAP is selected, the alphanumerics
are changed to green, the GMAP legend is displayed in the
mode field, and the color scheme is changed to cyan, yellow,and
magenta. Cyan represents the least reflective return, yellow is a
moderate return, and magenta is astrong return.
If GMAP is selected before the initial RTAwarmup period is
complete (approximately 45 to 90 seconds), the white WAIT legend
is displayed in the mode field. In wait mode, the transmitter and
antenna scan are inhibited and the memory is erased. When the
warmup period is complete, the system automatically switches to
the GMAP mode.
DFP(FlightPlan)-TheFPpositionputstheradarsystemintheflight
plan mode, which clears the screen of radar data so ancillary data
can be displayed. Examples of this data are:
-Navigation displays
-Electrical discharge (lightning) data.
NOTE: Inthe FPmode, the radarRTAisputinstandby, the
alphanumerics arechanged tocyan,and the FLTPLN
legend isdisplayed inthe mode field.
PRIMUS
r
880
Digital
W
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Radar
System
A28-1146-102-00 Operating Controls
3-15
The targetalertmode can be used inthe FPmode.Withtargetalert
on and the FPmode selected, the targetalertarmed annunciation
(green TGT)isdisplayed.The RTAsearchesfora hazardoustarget
from5to55milesand ±7.5 degreesofdead ahead.Noradar
targetsare displayed.Ifa hazardoustargetisdetected, the targetalert
armed annunciation switchestothe alertannunciation (amberTGT).
Thisadvisesthe pilot thata hazardoustargetisin hisflightpath and he
shouldselect the WXmode toviewit.
NOTE: When displaying checklist, the TGTfunction isinoperative.
DTST (Test) -The TST position selects the radar test mode. A
special test pattern is displayed to verify system operation. The
TEST legend is displayed in the mode field. Refer to Section 4,
Normal Operations, for adescription of the test pattern.
WARNING
UNLESS THESYSTEM ISIN FORCEDSTANDBY,THE TRANSMIT-
TER IS ON AND RADIATING X-BAND MICROWAVE ENERGY IN
TEST MODE. REFER TOSECTION 6, MAXIMUM PERMISSIBLE
EXPOSURE LEVEL (MPEL).
DFSBY (Forced Standby) -FSBY is an automatic, nonselectable
radar mode. As an installation option, the indicator can be wired
to the weight-on-wheels (WOW) squat switch. When wired, the
RTAis in the FSBY mode when the aircraft is on the ground. In FSBY
mode, the transmitter and antenna scan are both inhibited, the
display memory is erased, and the FSBY legend is displayed in the
mode field. When in the FSBY mode, pushing the STAB button 4
times in 3seconds restores normal operation.
The FSBY mode isasafetyfeaturethatinhibitsthe transmitteron the
ground to eliminatethe X-Band microwaveradiation hazard.Referto
Section 6,MaximumPermissibleExposure Level(MPEL).
WARNING
FORCED STANDBY MODE MUST BE VERIFIED BY THE OPERA-
TOR TOENSURE SAFETY FOR GROUND PERSONNEL.
Ininstallationswithtworadarcontrollers,itisonlynecessaryto override
forced standbyfromone controller.
If either controller is returned to standby mode while weight is on
wheels, the system returns to the forced standby mode.
PRIMUS
r
880
Digital
W
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Radar
System
A28-1146-102-00
Operating Controls
3-16
2TILT
The TILTswitch is arotary control that is used to select the tilt angle of
antenna beam with relation to the horizon. CW rotation tilts beam
upward 0_to 15_;ccw rotation tilts beam downward 0_to -15_.The
range between +5_and -5_is expanded for ease ofsetting. Adigital
readout of the antenna tilt angle is displayed on the EFIS.
DPULL ACT (Altitude Compensated Tilt) Function -When the
TILTcontrol knob is pulled out, the system engages the ACT
(option). In ACT ,the antenna tilt is automatically adjusted with
regard to the selected range and barometric altitude. The antenna
tilt automatically readjusts with changes in altitude and/or selected
range. In ACT,the tilt control can fine tune the tilt setting by ±2°.
ACT is annunciated with an Afollowing the digital tilt readout. The
digital tilt readout always shows the commanded tilt of the antenna
regardless of the tilt command source (ACT command or manual tilt
command).
WARNINGS
1. TOAVOID FLYING UNDER OR OVER STORMS,
FREQUENTLYSELECT MANUAL TILT TOSCAN BOTH
ABOVE AND BELOW YOUR FLIGHT LEVEL.
2. ALWAYS USE MANUAL TILTFOR WEATHER ANALYSIS.
3SECT (Scan Sector)
The SECT switch is an alternate-action button that is used to select
either the normal 12 looks/minute 120_scan or the faster update 24
looks/minute 60_sector scan.
4TGT (Target)
The TGT switch is an alternate-action, button that enables and
disablestheradartargetalertfeature.Targetalertis selectableinallbut
the 300 mile range. When selected, target alert monitors beyond the
selected range and 7.5_on each side of the aircraft heading. If areturn
withcertaincharacteristics isdetected inthe monitoredarea, thetarget
alert changes from the green armed condition to the yellow TGT
warning condition. This annunciation advises the pilot that apotentially
hazardoustargetliesdirectlyinfrontandoutsideoftheselected range.
When this warning is received, the pilot should select longer ranges to
view the questionable target. Note that target alert is inactive within the
selected range.
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Selecting target alert forces the system to preset gain. Target alert can
only be selected in the WX and FP modes.
In order to activate target alert, the target must have the depth and
range characteristics described in table 3-4:
Selected Range
(NM) Minimum Target
Depth (NM) Target Range
(NM)
5 5 5-55
10 5 10-60
25 5 25-75
50 5 50-100
100 5 100-150
200 5 200-250
300 N/A N/A
FP (Flight Plan) 5 5-55
WC-880 Controller Target Alert Characteristics
Table 3-4
5STB (Stabilization)
The STB button turns the pitch and roll stability ON and OFF. It is also
used with the STB adjust mode and to override forced standby.
NOTE: Some controllers annunciate OFF when stabilization is OFF.
6TRB (Turbulence Detection)
TRB is aswitch used to select the turbulence detection mode of
operation. The TRB mode can only be selected if the FUNCTION
switch is in the WX or RCT positions and theselected rangeis 50miles
or less. The weather/turbulence mode is annunciated in the mode field
withtheWX/Tlegend.Areasofatleastmoderateturbulenceareshown
in soft white. The turbulence threshold is five meters per second.
PRIMUS
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REV 3
Operating Controls
3-18
WARNINGS
1. TURBULENCE CAN ONLY BE DETECTED WITHIN AREAS OF
RAINFALL. THE PRIMUS
R
880 DIGITAL WEATHER RADAR
SYSTEM CANNOT DETECT CLEAR AIR TURBULENCE.
2. UNDETECTED TURBULENCE CAN EXIST WITHIN ANY
STORM CELL. REFER TO SECTION 5, RADAR FACTS, OF THIS
GUIDE FOR ADDITIONAL INFORMATION.
Selecting the 100, 200, or 300 mile range turns off the turbulence
detection. The /T is deleted from the mode annunciation and variable
gain is engaged if previously selected. Subsequent selection of ranges
of 50 miles or less re--engages turbulence detection.
A description of the turbulence detection capabilities and limitations of
this radar system is given in Section 5, Radar Facts, of this guide.
7 RANGE
The RANGE switches are two momentary contact buttons that are used
to select the operating range of the radar (and LSS if installed). The
system permits selection of ranges in WX mode from 5 to 300 NM full
scale. In the flight plan (FPLN) mode, additional ranges of 500 and
1000 miles are permitted. The up arrow selects increasing ranges,
while the down arrow selects decreasing ranges. One--half the
selected range is annunciated at the one--half scale range mark on the
EHSI.
NOTE: Some Integrated avionics systems incorporate radar range
with the map display range control on a MFD/ND display.
8GAIN
The GAIN is a single turn rotary control and push/pull switch that is used
to control the receiver gain. When the GAIN switch is pushed, the
system enters the preset, calibrated gain mode. Calibrated gain is the
normal mode and is used for weather avoidance. In calibrated gain, the
rotary portion of the GAIN control does nothing.
When the GAIN switch is pulled out, the system enters the variable
gain mode. Variable gain is useful for additional weather analysis and
for ground mapping. In WX mode, variable gain can increase receiver
sensitivity over the calibrated level to show weak targets or it can
be reduced below the calibrated level to eliminate weak returns.
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WARNING
LOW VARIABLE GAIN SETTINGS CAN ELIMINATE HAZARDOUS
TARGETS FROM THE DISPLAY.
In GMAP mode, variable gain is used to reduce the level of strong
returns from ground targets.
Minimum gain is attained with the control at its full ccw position. Gain
increases as the control is rotated in acw direction from full ccw at full
cw position, the gain is at maximum.
The VAR! legend annunciates variable gain. Selecting RCT or TGT
forces the system into calibrated gain.
9SLV(Slave)
The SLVannunciator is only used in dual controller installations. With
dual controllers, one controller can be slaved to the other by selecting
OFF on that controller only,with the RADAR mode switch. This slaved
condition is annunciated with the SLVannunciator.
In the slaved condition, both controllers must be offbefore the
radar system turns off.
10 LSS (Lightning Sensor System) (Option)
The LSS switch is an optional four-position rotary switch that selects
the LSS operating modes described below:
DOFF -In this position all power is removed from the LSS.
DSBY-InthispositionthedisplayofLSSdataisinhibited,buttheLSS
still accumulates data.
DLX -In this position the LSS is fully operational and it displays LSS
data on the indicator.
DCLR/TST -In this position, accumulated data is cleared from the
memory of the LSS. After 3seconds the test mode is initiated in the
LSS.
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WC-884 WEATHER RADAR CONTROLLER
OPERATION
The controls and display features of the WC-884 Weather Radar
Controller are indexed andidentified infigure 3-5.Brightness levelsfor
all legend and controls on the indicator are controlled by the dimming
bus for the aircraft panel.
Whenever single or dual radar controllers are used, the radar data is
displayed on the EFIS, MFD, or NAVdisplay.
BRT
GAIN MAXMIN
PULL VAR
OFF
STBY
TEST WX
GMAP
MODE
TGT TRBRCTSTAB
10
25 100
200
RANGE
50
300
FPLN
SLVTILT
PULL ACT
0
+
-
1 2 3 4 5
10 9 8 7 6 AD-46698-R2@
WC-884 Weather Radar Controller
Figure 3-5
1BRT (Brightness)
The BRTswitch is arotary control that is used to set the radar (raster)
brightness on the EFIS display.
2TGT (Target Alert)
The TGT switch is an alternate-action, button that enables and
disablestheradartargetalertfeature.Targetalertis selectableinallbut
the 300-mile range. When selected, target alert monitors beyond the
selected range and 7.5_on each side of the aircraft heading. If areturn
withcertaincharacteristics isdetected inthe monitoredarea, thetarget
alert changes from the green armed condition to the amber TGT
warning condition. (Refer to the target alert characteristics in table 3-5
foratargetdescription.)TheamberTGTalertsthepilotastopotentially
hazardous targets directly in front and outside of the selected range.
When the alert is given, the pilot should select longer ranges to view
the questionable target. Target alert is inactive within the selected
range.
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Selecting target alert forces the system into preset gain. Target alert
can be selected in the WX and FP modes.
Toactivate target alert, the target must have the depth and range
characteristics described in table 3-5:
Selected Range
(NM) Minimum Target
Depth (NM) Target Range
(NM)
10 5 10-60
25 5 25-75
50 5 50-100
100 5 100-150
200 5 200-250
300 N/A N/A
FP (Flight Plan) 5 5-55
WC-884 Controller Target Alert Characteristics
Table 3-5
3STB (Stabilization)
The STAB button is athat turns the pitch and roll stabilization ON and
OFF.
This radar is normally attitude stabilized. It automatically compensates
for roll and pitch maneuvers (refer to Section 5, Radar Facts, for a
description of stabilization). The amber STB annunciator appears
on thescreen.ItisalsousedwiththeSTBadjustmode,andtooverride
forced standby.
4RCT (Rain Echo Attenuation Compensation Technique)
SelectingRCTforcesthesystemtopresetgain.WhenRCT isselected,
the green REACT legend is displayed in the mode field. The RCT
circuitry compensates for attenuation of the radar signal as it passes
through rainfall. The cyan field indicates areas where further
compensationis not possible.Anytargetdetectedwithinthecyanfield
cannot be calibrated and should be considered dangerous. All targets
in the cyan field are displayed as fourth level precipitation, magenta.
NOTE: RefertoSection 5,RadarFacts, fora description ofREACT.
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REV 3
Operating Controls
3-22
5 TRB (Turbulence Detection)
TRB switch is used to select the turbulence detection mode of
operation. The TRB mode can only be selected if the MODE switch is
in the WX position and the selected range is 50 miles or less. The
weather/turbulence mode is annunciated in the mode field with the
green WX/T legend. Areas of at least moderate turbulence are shown
in soft white.
CAUTION
TURBULENCE CAN ONLY BE DETECTED WITHIN AREAS OF
RAINFALL. THE PRIMUS
R
880 DIGITAL WEATHER RADAR
SYSTEM DOES NOT DETECT CLEAR AIR TURBULENCE.
WARNING
UNDETECTED TURBULENCE CAN EXIST WITHIN ANY STORM
CELL. REFER TO SECTION 5, RADAR FACTS, OF THIS GUIDE
FOR ADDITIONAL INFORMATION.
Selecting the 100--, 200--, or 300--mile range turns off the turbulence
detection. The /T is deleted from the mode annunciation and variable
gain is engaged if previously selected. Subsequent selection of ranges
of 50 miles or less re--engages turbulence detection.
A description of the turbulence detection capabilities and limitations can
be found in Section 5, Radar Facts, of this guide.
6TILT
The TILT switch is a rotary control used to select tilt angle of antenna
beam with relation to the horizon. CW rotation tilts beam upward to
+15_; ccw rotation tilts beam downward to --15_.
A digital readout of the antenna tilt angle is displayed on the EFIS.
DPULL ACT (Altitude Compensated Tilt) Function -- When the
TILT control knob is pulled out, the system engages the ACT
(option). In ACT, the antenna tilt is automatically adjusted with
regard to the selected range and barometric altitude. The antenna
tilt automatically readjusts with changes in altitude and/or selected
range. In ACT, the tilt control can fine tune the tilt setting by ±2°.
ACT is annunciated with an Afollowing the digital tilt legend. The
digital tilt readout always shows the commanded tilt of the antenna
regardless of the tilt command source (ACT command or manual tilt
command).
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3-23
WARNINGS
1. TOAVOID FLYING UNDER OR OVER STORMS,
FREQUENTLYSELECT MANUAL TILT TOSCAN BOTH
ABOVE AND BELOW YOUR FLIGHT LEVEL.
2. ALWAYS USE MANUAL TILTFOR WEATHER ANALYSIS.
7RANGE
RANGE is arotary control used to select one of six ranges (10, 25, 50,
100,200,and300NM).Theseventhpositionoftherangeswitchisflight
plan mode. Selecting FPLNblanks theradar informationfrom theEFIS
display and the mode annunciation flashes if aradiating mode is
selected. The EFIS is set to arange determined by the installation.
Targetalertcan be used inthe FPLNmode.Withtargetalerton inthe
FPLNmode,thetargetalertarmedannunciation(greenTGT)isdisplayed.
The RTAbecomesactive and starts searching fora hazardoustarget
from5to55milesand±7.5_deadahead.Noradartargetsaredisplayed.
If a hazardoustargetisdetected, the targetalertarmed annunciation
switchestothe alertannunciation (amberTGT).Thisadvisoryindicates
thata hazardoustargetisinthe aircraft’sflightpath and the WXmode
shouldbeselected.
8SLV(Slave)
TheSLVannunciatorisadeadfrontannunciatorthatisonlyusedindual
controller installations. With dual controllers, one controller can be
slavedtotheotherbyselectingtheRADARmodeswitchtoOFFonthat
controller,only.This slaved condition is annunciated with the SLV
annunciator.
In the slaved condition both controllers must be offbefore the radar
system turns off.
9MODE
The MODE switch is arotary switch used to select one of the following
functions:
DOFF -In this position the radar system is turned off.
DSTBY -In this position the radar system is placed in standby; a
ready state, with the antenna scan stopped, the transmitter
inhibited, and the display memory erased. STBY,in green, is
displayed in the mode field.
If STBY is selected before the initial RTAwarmup period is complete
(approximately 45 -90 seconds), the flashing WAIT legend is
displayed in the mode field.
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When the warmup is complete, the system changes the mode field
from WAIT to STBY.
DTEST-This position selects the radar test mode. Atest pattern is
displayed to verify that system operates. The green TEST legend
is displayed in the mode field. Refer to Section 4, Normal
Operation, for adescription of the test pattern.
WARNING
UNLESS THESYSTEM ISIN FORCEDSTANDBY,THE TRANSMIT-
TER IS ON AND RADIATING X-BAND MICROWAVE ENERGY IN
TEST MODE. REFER TOSECTION 6, MAXIMUM PERMISSI-
BLE EXPOSURE LEVEL (MPEL).
DWX -In this position, the radar system is fully operational and all
internal parameters are set for enroute weather detection.
If WXis selected beforethe initialRTAwarmup period is complete,a
flashing WAITlegend isdisplayed. InWAITmode, the transmitter
and antenna scan areinhibited and the memoryiserased.When the
warmup is complete, the systemautomatically switchestothe WX
mode and a green WXisdisplayed inmode field.
The system, in preset gain, is calibrated given in table NO TAG.
Rainfall Rate Color
in/hr mm/hr
.04-.16 1-4Green
.16-.47 4-12 Yellow
.47-2 12-50 Red
>2>5 0Magenta
Rainfall Rate Color Coding
Table 3-6
DGMAP -Selecting GMAP places the radar system in the ground
mapping mode. The system is fully operational and all internal
parameters are set to enhance returns from ground targets. RCT
compensation is inactive.
WARNING
WEATHER TYPE TARGETS ARE NOT CALIBRATED WHEN
THE RADAR IS IN THE GMAP MODE. BECAUSE OF THIS, DO
NOT USE THE GMAP MODE FOR WEATHER DETECTION.
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When GMAP is selected, agreen GMAP legend is displayed and the
color scheme is changed to cyan, yellow,magenta. Cyan
represents the least reflective return, yellow is amoderate return,
and magenta is astrong return.
If GMAP is selected before the initial RTAwarmup period is
complete, aflashing WAIT legend is displayed. In WAIT mode, the
transmitter and antenna scan are inhibited and the memory is
erased. When the warmup is complete, the system automatically
switches to the GMAP mode.
WARNING
THESYSTEMPERFORMSONLYTHE FUNCTIONS OF WEATHER
DETECTION OR GROUND MAPPING. IT CANNOT BE RELIED
UPON FOR PROXIMITY WARNING OR ANTICOLLISION
PROTECTION.
DFSBY -Forced standby is an automatic, nonselectable radar
mode. As an installation option, the controllers can be wired to the
WOW squat switch. When wired, the RTAis in the forced standby
mode when the aircraft is on the ground. In the forced standby
mode, the transmitter and antenna scan are both inhibited, the
memory is erased, and the amber FSBY legend is displayed in the
mode field. When in the forced standby mode, pushing the STAB
button 4times in 3seconds, exits the mode.
FSBY mode is asafety feature that inhibits the transmitter on the
ground to eliminate the X-band microwave radiation hazard. Refer
to Section 6, Maximum Permissible Exposure Level (MPEL).
NOTE: In dual installations, overriding the forced standby using
the TGT button is done on only one controller.
WARNING
FORCEDSTANDBYMODEMUSTBEVERIFIEDBYTHEOPERATOR
TOENSURE SAFETYFORGROUND PERSONNEL.
10 GAIN
The GAIN is asingle-turn rotary control and push/pull switch that is
used to control the receiver gain. When the GAIN switch is pushed,the
system enters the preset, calibrated gain mode. Calibrated gain is the
normalmodeandisused forweatheravoidance.Incalibratedgain,the
rotary portion of the GAIN control does nothing.
WhentheGAINswitchispulledout,thesystementersthevariablegain
mode. Variable gain is useful for additional weather analysis and for
ground mapping. In WX mode, variable gain can increase receiver
sensitivity over the calibrated level to show weak targets or it can be
reduced below the calibrated level to eliminate weak returns.
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WARNING
WHEN LOW SETTINGS OF VARIABLE GAIN ARE USED,
HAZARDOUS TARGETS CAN BE ELIMINATED FROM
THE DISPLAY.
In the GMAP mode, variable gain is used to reduce the level of the
typically very strong returns from ground targets.
Minimum gain is with the control at its full ccw position. Gain increases
as the control is rotated in acw direction from full ccw.At the full cw
position, the gain is at maximum.
TheVARlegendannunciatesvariablegain.SelectingRCTorTGTforces
the systeminto presetgain.Presetgainisnotannunciated.
HIDDEN MODES
The PRIMUSâ880 has five hidden modes that are summarized as
follows:
DForced Standby (FSBY) Override
DRoll Offset
DRoll Gain (NOTE)
DPitch Offset (NOTE)
DPitch Gain (NOTE).
NOTE: Atthetimeofinstallation,theprogrammingstrapSTABTRIM
ENABLE,determinesiftherollandpitchgain,and pitchoffset
adjustment features are available. Consult the aircraft
installation information to determine the installed
configuration.
Forced Standby Override
DFunction -Forced standby places the radar in astandby mode
on the ground that prevents the radar from radiating and
therefore, exposing ground personnel to radiation exposure.
This mode is annunciated as FSBY (STBY on EFIS) in systems
where mode annunciations are made.
DEntry Method -Power up aircraft on the ground or land the
aircraft with the radar powered.
DExit Method -Push the STAB button 4times within 3seconds
on radar indicator or on controller.
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Roll Offset
DFunction -Roll offset permits exact compensation of the
antenna roll to eliminate the effects of small errors in the aircraft
radar installation. Constantly lopsided ground returns can be
eliminated. (Refer to Section 5, Radar Facts, table 5-5.)
DEntry Method -Using only one controller that is in the WX and
variable gain modes, select RCT OFF.Push STB 4times within
3seconds. Verify that VAR and RCT are not displayed.
DControl -The GAIN control is used to adjust the roll offset.
DExit Method -Push STAB (once) to continue with the next
adjustment.
Roll Gain
DFunction-Rollgaincorrectstheinstallationatbankanglesover
20°,for unsymmetrical radar displays.
DEntry Method -Selected by sequencing through the roll offset
and pitch offset menus with the STAB button. (Refer to Section
5, Radar Facts, table 5-9.)
DControl -Pull GAIN knob out and use it.
DExit Method -Push STAB (once) to continue with the next
adjustment.
Pitch Offset
DFunction -Adjusts the pitch attitude of the antenna to allow
radar returns, in straight and level flight, to conform to the radar
range rings.
DEntry Method -Selected by sequencing through the roll offset
menu with the STAB button. (Refer to Section 5, Radar Facts,
table 5-8.)
DControl -Pull the GAIN knob out and use it.
DExit Method -Push STAB (once) to continue with the next
adjustment.
Pitch Gain
DFunction -Adjuststhe gainif theradar displayis inpitch sothat
the contour lines track the range lines at higher pitch attitudes.
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DEntry Method -Selected by sequencing through the roll offset,
pitch offset, and roll gain menus with the STAB button. (Refer to
Section 5, Radar Facts, table 5-10.)
DControl -Pull the GAIN knob out and use it.
DExit Method -Push the GAIN knob in. Push STAB to exit and
save settings.
NOTES: 1. If installation is configured only for roll offset
adjustment, pushing the STB button saves and exits
after the roll offset adjustment is made.
2. Upon exiting, stabilization may be either OFF or ON
depending on how many times it was pushed during
the procedure. Be sure to set stabilization OFF or ON
as desired.
3. If uponentering theadjustment mode,no changesare
desired, keep the gain knob pushed in and repeatedly
push STAB until the mode is exited.
PRIMUS
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REV 3 4-1
Normal Operation
4. Normal Operation
PRELIMINARY CONTROL SETTINGS
Table 4--1 gives the proper power--up procedure for the PRIMUS
R
880
Digital Weather Radar System.
Step Procedure
1Verify that the system controls are in the positions
described below before powering up the radar system:
Mode control: Off
GAIN control: Preset Position
TILT control: +15
2Take the following precautions, if the radar system will be
operated in any mode other than standby or forced
standby while the aircraft is on the ground:
D
Direct nose of aircraft so that antenna scan sector is
free of large metallic objects such as hangars or
other aircraft for a minimum distance of 100 feet (30
meters), and tilt the antenna fully upwards.
D
Do not operate the radar system during aircraft
refueling or during refueling operations within 100
feet (30 meters).
D
Do not operate the radar if personnel are standing
too close to the 120_forward sector of aircraft.
(Refer to Section 6, Maximum Permissible
Exposure Level, in this guide.)
D
Operating personnel should be familiar with FAA AC
20--68B, which is reproduced in Appendix A of this
guide.
3If the system is being used with an EFIS display,
power--up by selecting the weather display on the
EHSI. Apply power to the radar system using either
the indicator or controller power controls.
4Select either Standby or Test mode.
PRIMUS
R
880 Power--Up Procedure
Table 4--1 (cont)
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A28-1146-102-00
Normal Operation
4-2
Step Procedure
5When power is first applied the radar is in WAIT for
approximately 90 seconds to allow the magnetron to
warm up. Power sequences ON-OFF-ONlasting less
than 3seconds result in a 6-second wait period.
NOTE: If forced standby is incorporated, it is necessary
to exit forced standby.
WARNING
OUTPUT POWER IS RADIATED IN TEST MODE.
6After the warm-up, select the Test mode and verify
that the test pattern is displayed as shown in figure
4-1. If the radar is being used with an EFIS, the test
pattern is similar to that shown in figures 4-2 and 4-3.
Verify that the yellow antenna position indicator (API)
is shown at the top of the display.
7Verify that the azimuth marks, target alert (TGT), and
sector scan controls are operational.
PRIMUSâ880 Power-Up Procedure
Table 4-1
Indicator Test Pattern 120_Scan (WX),
With TEXT FAULTEnabled
Figure 4-1
PRIMUS
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A28--1146--102--03
REV 3 4-3
Normal Operation
AD--46700--R2@
VOR1
VOR2
TEST
+11
HDG
319
25
15
DTRK
315
GSPD
MAG1
321
TGT FMS1
130 NM
V
260 KTS
50
GRAY
MAGENTA
BLUE
WX RANGE
ANNUNCIATOR
(WHITE)
P880 WX
MODE
ANNUNCIATIONS
RED
WX RANGE
RINGS
(WHITE)
TGT OR VAR ANNUNCIATOR
:
:
TGT:
VAR:
TEXT AREA
GREEN
ANTENNA
TILT
ANGLE
YELLOW
NOTES: 1.
2.
IF THE BITE DETECTS A FAULT IN TEST MODE, FAIL ”N” WILL BE SHOWN.
”N”ISAFAULTCODE
ANY FAULT CODE CAN ALSO BE DISPLAYED IN THE MAINTENANCE MODE.
IN THAT CASE, IT REPLACES THE ANTENNA TILT ANGLE.
TARGET ALERT
-- GREEN--SELECTED
-- AMBER TGT DETECTED
VARIABLE GAIN (AMBER)
NOTES: 1. Refer to the specific EFIS document for a detailed
description.
2. The example shown is for installations with TEXT
FAULT disabled.
EFIS Test Pattern (Typical) 120_Scan Shown (WX)
Figure 4--2
PRIMUS
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A28--1146--102--03
REV 3
Normal Operation
4-4
WI--880 Indicator Test Pattern With TEXT FAULT Enabled
Figure 4--3
Standby
When Standby is selected, and the radar is not in dual control mode
(refer to table 2--1, dual control mode truth table, for dual control
operation), the antenna is stowed in a tilt--up position and is neither
scanning nor transmitting.
Standby should be selected when the pilot wants to keep power applied
to the radar without transmitting.
Radar Mode -- Weather
For purposes of weather avoidance, pilots should familiarize
themselves with FAA Advisory Circular AC 00--24B (1--20--83).Subject:
“Thunderstorms.” The advisory circular is reproduced in Appendix A of
this guide.
To help the pilot categorize storms as described in the advisory circular
referenced above, the radar receiver gain is calibrated in the WX mode
with the GAIN control in the preset position. The radar is not calibrated
when variable gain is being used, but calibration is restored if RCT,
TRB, or target alert (TGT) is selected.
PRIMUS
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A28--1146--102--03
REV 3 4-5
Normal Operation
To aid in target interpretation, targets are displayed in various colors.
Each color represents a specific target intensity. The intensity levels
chosen are related to the National Weather Service (NWS) video
integrated processor (VIP) levels.
In the WX mode, the system displays five levels as black, green, yellow,
red, and magenta in increasing order of intensity.
If RCT is selected, the radar receiver adjusts the calibration
automatically to compensate for attenuation losses as the radar pulse
passes through weather targets on its way to illuminate other targets.
There is a maximum extent to which calibration can be adjusted. When
this maximum value is reached, REACT compensation ceases. At this
point, a cyan field is added to the display to indicate that no further
compensation is possible.
In the absence of intervening targets, the range at which the cyan field
starts is approximately 290°with a 12--inch antenna. For the 18-- and
24--inch antennas, the cyan field starts beyond 300 NM and therefore
will not be seen if there are no intervening targets.
The RCT feature includes attenuation compensation (Refer to Section
5, Radar Facts, of this guide for a description of attenuation
compensation.). Rainfall causes attenuation and attenuation
compensation modifies the color calibration to maintain calibration
regardless of the amount of attenuation. Modifying the color calibration
results in a change in the point where calibration can no longer keep the
radar system calibrated for red level targets. The heavier the rainfall,
the greater the attenuation and the shorter the range where XSTC runs
out of control. Therefore, the range at which the cyan
background starts varies depending on the amount of attenuation. The
greater the attenuation, the closer the start of the cyan field.
The radar’s calibration includes a nominal allowance for radome losses.
Excessive losses in the radome seriously affect radar calibration. One
possible means of verification are signal returns from known targets.
Honeywell recommends that the pilot report evidence of weak returns
to ensure that radome performance is maintained at a level that does
not affect radar calibration.
Target alert can be selected in any WX range. The target alert circuit
monitors for hazardous targets within 7.5_of the aircraft centerline.
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Normal Operation
4-6
Radar Mode -Ground Mapping
NOTE: Refer to Tilt Management in Section 5, Radar Facts, for
additional information on the use of tilt control.
Ground-mapping operation is selected by setting the controls
to GMAP.The TILTcontrol is turned down until ausable amount of
navigable terrain is displayed. The degree of down-tiltdepends on the
aircraft altitude and the selected range.
The receiver STC characteristicsare alteredto equalizeground-target
reflection versus range. As aresult, selecting preset GAIN generally
createsthedesiredmapping display.However,thepilotcancontrolthe
gain manually (by selecting manual gainand rotatingthe GAINcontrol)
to help achieve an optimum display.
With experience, the pilot can interpret the color display patterns that
indicate water regions, coast lines, hilly or mountainous regions, cities,
or even large structures. Agood learning method is to practice
ground-mapping duringflightsinclearvisibilitywheretheradardisplay
can be visually compared with the terrain.
TEST MODE
ThePRIMUSâ880DigitalWeatherRadarSystemhasaself-testmode
and a maintenance function.
In the self-test (TST) mode aspecial test pattern is displayed as
illustrated earlier in this section. The functions of this pattern are as
follows:
DColor Bands -Aseries of green/yellow/red/magenta/white bands,
indicate that the signal to color conversion circuits are operating
normally.
The maintenance function lets the pilot or the line maintenance
technician determine the major fault areas. The fault data can be
displayed in one of two ways (selected at the time of installation):
DTEXT FAULT-Aplain English text indicating the failure is placed
in the test band.
DFault code -Afault code is displayed, refer to the maintenance
manual for an explanation.
The indicator or EFIS display indicates afault as noted below.
DDedicated Radar Indicator -AFAIL annunciation is shown at the
top left corner of the test pattern. It indicates that the built-in test
equipment (BITE) circuitry is detecting amalfunction. The exact
nature of the malfunction can be seen by selecting TEST.(Refer to
Section 7, In-Flight Troubleshooting.)
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4-7/(4-8 blank)
DEFIS/MFD/ND -Faults are normally shown when test is selected.
NOTES: 1. Some weather failures on EFIS are annunciated
with an amber WX.
2. Some EFIS installations can power up with an
amber WX if weather radar is turned off.
3. If the fault code option is selected, they are shown
with the FAIL annunciation (e.g., FAIL 13).
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5-1
5. Radar Facts
RADAR OPERATION
The PRIMUSâ880 Digital Weather Radar works on an echo principle.
The radar sends out short bursts of electromagnetic energy that travel
through space as aradio wave. When the traveling wave of energy
strikes atarget, some of the energy reflects back to the radar receiver.
Electroniccircuitsmeasuretheelapsedtime betweenthetransmission
and the reception of the echo to determine the distance to the target
(range). Because the antenna beam is scanning right and left in
synchronism with the sectoring sweep on the indicator,the bearing of
the target is found, as shown in figure 5-1.
The indicator with the radar is called aplan-position indicator (PPI)
type. When an architect makes adrawing for ahouse, one of the views
he generally shows is aplan view,adiagram of the house as viewed
from above. The PPI aboard an airplane presents across sectional
picture of the storm as though viewed from above. In short, it is NOT
ahorizon view of the storm cells ahead but rather aMAP view.This
positional relationship of the airplane and the storm cells, as displayed
by the indicator,is shown in figure 5-1.
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Radar Facts
5-2
20
40 +0.6
60
80
100
WX
0
AIRCRAFT HEADING
AD-12055-R2@
Positional Relationship of an Airplane and
Storm Cells Ahead as Displayed on Indicator
Figure 5-1
The drawing is laid out to simulate the face of the indicator with the
semicircularrangemarks.Toderiveaclearerconceptofthepicturethat
the indicator presents, imagine that the storm is aloaf of sliced bread
standing on end. From apoint close to the surface of earth, it towers
toahigh-altitudesummit.Withoutupsetting theloaf ofbread, theradar
removes asingle slice from the middle of the loaf, and places this slice
flat upon the table. Looking at the slice of bread from directly above, a
cross section of the loaf can be seen in its broadest dimension. In the
same manner,the radar beam literally slices out ahorizontal cross
section of the storm and displays it as though the viewer was looking
PRIMUS
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5-3
atitfromabove,asshowninfigure5-2.Theheightofthe sliceselected
for display depends upon the altitude and also upon the upward or
downward TILTadjustment made to the antenna.
Antenna Beam Slicing Out Cross Section of Storm
During Horizontal Scan
Figure 5-2
Weather radar can occasionally detect other aircraft, but it is not
designed for this purpose and should never be considered a
collision-avoidancedevice. Nor is weather radar specifically designed
as anavigational aid, but it can be used for ground mapping by tilting
the antenna downward. Selecting the GMAP mode enhances returns
from ground targets.
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Radar Facts
5-4
When the antenna is tilted downward for ground mapping, two
phenomenamayoccurthatcanconfusethepilot.Thefirstiscalled”The
Great Plains Quadrant Effect” that is seen most often when flying over
the great plains of central United States. In this region, property lines
(fences), roads, houses, barns, and power lines tend to be laid out in
astringent north-south/east-west orientation. As aresult, radar
returns from these cardinal points of the compass tend to be more
intense than returns from other directions and the display shows these
returns as bright north/south/east/west spokes overlaying the ground
map.
The second phenomenon is associated with radar returns from water
surfaces (generally called sea clutter), as shown in figure 5-3. Calm
water reflects very low radar returns since it directs the radar pulses
onward instead of backward (i.e. the angle of incidence from mirrored
light shone on it at an angle). The same is true when viewing choppy
waterfromtheupwindside.Thedownwindsideofwaves,however,can
reflect astrong signal because of the steeper wave slope. Arelatively
bright patch of sea return, therefore, indicates the direction of surface
winds.
REFLECTION
CALM WATER OR WATER WITH
SWELLS DOES NOT PROVIDE
GOOD RETURN.
CHOPPY WATER PROVIDES
GOOD RETURN FROM
DOWNWIND SIDE OF WAVES
WIND DIRECTION AT
SURFACE OF WATER
PATCH
OF SEA
RETURNS
AD-12056-R2@
Sea Returns
Figure 5-3
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5-5
TILTMANAGEMENT
The pilot can use tilt management techniques to minimize ground
clutter when viewing weather targets.
Assume the aircraft is flying over relatively smooth terrain which is
equivalent to sea level in altitude. The pilot must make adjustments for
the effects of mountainous terrain.
The figures below help to visualize the relationship between tilt angle,
flight altitude, and selected range. Figures 5-4 and 5-5show the
distance above and below aircraft altitude that is illuminated by the
flat-plate radiator during level flight with 0_tilt. Figures 5-6 and 5-7
show arepresentative low altitude situation, with the antenna adjusted
for 2.8_up-tilt.
ELEVATION IN FEET
80,000
70,000
60,000
50,000
30,000
20,000
10,000
0025 50
RANGE NAUTICAL MILES 100
AD-35693@
CENTER OF RADAR BEAM
20,000 FT
20,000 FT
41,800 FT
41,800 FT
10,500 FT
10,500 FT
7.9
ZERO TILT
Radar Beam Illumination High Altitude
12-Inch Radiator
Figure 5-4
ELEVATION IN FEET
80,000
70,000
60,000
50,000
30,000
20,000
10,000
00 25 50
RANGE NAUTICAL MILES 100
AD-17717-R1@
CENTER OF RADAR BEAM
14,800 FT
14,800 FT
29,000 FT
29,000 FT
7,400 FT
7,400 FT
5.6
ZERO TILT
Radar Beam Illumination High Altitude
18-Inch Radiator
Figure 5-5
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Radar Facts
5-6
40,000
40
ELEVATION IN FEET
RANGE NAUTICAL MILES AD-17718-R1@
30,000
20,000
10,000
5,000
0302010 50 60 70 80
20,900 FT
20,900 FT
10,500 FT
1.15
7.9
4,200 FT
4,200 FT
ANTENNA ADJUSTED
FOR 2.8 UPTILT
10,500 FT
Radar Beam Illumination Low Altitude
12-Inch Radiator
Figure 5-6
0
RANGE NAUTICAL MILES AD-17719@
ELEVATION IN FEET
40,000
30,000
20,000
10,000
5,000
0 10 20 30 40 50 60 70 80
ANTENNA ADJUSTED
FOR 2.8 UPTILT
5.6 3,000 FT
3,000 FT
7,400 FT
7,400 FT 14,000 FT
14,000 FT
Radar Beam Illumination Low Altitude
18-Inch Radiator
Figure 5-7
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5-7
Tables 5-1 and 5-2give the approximate tilt settings at which ground
targets begin to be displayed on the image periphery for 12-and
18-inchradiators. The range at which ground targets can be observed
is affected by the curvature of the earth, the distance from the aircraft
to the horizon, and altitude above the ground. As the tilt control is
rotated downward, ground targets first appear on the display at less
than maximum range.
NOTE: Operation with a 24-inch radiator is similar.
Tofind the ideal tilt angle after the aircraft is airborne, adjust the TILT
control so that groundclutter does not interfere with viewing of weather
targets. Usually,this can be done by tiltingthe antennadownward in1_
incrementsuntilgroundtargetsbegintoappearatthedisplayperiphery.
Ground returns can be distinguished from strong storm cells by
watchingforclosergroundtargetswitheachsmalldownwardincrement
of tilt. The more the downward tilt, the closer the ground targets that
are displayed.
When ground targets are displayed, move the tilt angle upward in 1_
increments until the ground targets begin to disappear.Proper tilt
adjustmentisapilotjudgment,buttypicallythebest tiltangle lieswhere
ground targets are barely visible or just offthe radar image.
Tables 5-1 and 5-2give the approximate tilt settings required for
different altitudes and ranges. If the altitude changes or adifferent
range is selected, adjust the tilt control as required to minimize ground
returns.
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5-8
RANGE
SCALE
(NM)
ALTITUDE
(FEET)
25 50 100 200 300 LINE OF
SIGHT
(NM)
40,000
35,000
30,000
25,000
20,000
15,000
10,000
5,000
4,000
3,000
2,000
1,000 +3
-0
+2
+2
+3
+3 +3
+2+2
+2
+3
+3
+1 +2
0+1
-1+1
0+1
+10
+1-1
246
230
213
195
174
151
123
87
78
67
55
39
(LINE OF SIGHT LIMITED REGION)
(TILT LIMITED
REGION)
AD-29830-R2@
5 10
-2
-3
-4
-2
-4
-6
-8
-10
-12
+3
-6
-1
0
+1
+2
-11
+2
-5
-4
-2
0
Approximate Tilt Setting for Minimal Ground Target Display
12-Inch Radiator
Table 5-1
Tiltanglesshownareapproximate.Wherethe tiltangle isnot listed,the
operator must exercise good judgment.
NOTE: The line of sight distance is nominal. Atmospheric conditions
and terrain offset this value.
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5-9
RANGE
SCALE
(NM)
ALTITUDE
(FEET)
10 25 50 100 200 LINE OF
SIGHT
(NM)
40,000
35,000
30,000
25,000
20,000
15,000
10,000
5,000
4,000
3,000
2,000
1,000 -5-4
-13
-9
-8
-7
-6-5-4
-5
-5
-5
-5-6-8
-6
-6
-5
-10 -7-6
-11 -8-6
-12 -8
-7
-11 -8
-7-10
-9-13
246
230
213
195
174
151
123
87
78
67
55
39
(LINE OF SIGHT LIMITED REGION)
(TILT LIMITED
REGION)
AD-35710@
Approximate Tilt Setting for Minimal Ground Target Display
18-Inch Radiator
Table 5-2
Tiltanglesshownareapproximate.Wherethe tiltangle isnot listed,the
operator must exercise good judgment.
NOTE: The line of sight distance is nominal. Atmospheric conditions
and terrain offset this value.
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Radar Facts
5-10
0.5 1.0 2.5 5 10 25 50 100 200
40,000
35,000
30,000
25,000
20,000
15,000
10,000
5,000
4,000
3,000
2,000
1,000
500
246
230
213
195
174
151
123
87
78
67
55
39
27
Line of
Sight
(NM)
-2-3-6
-2
-2
-1
-1
0
00
-5
-4
-3
-2
-1
-7
-7
-3
-9
-6
-2
0
0
-2
+1
-4
-6
-8
-8
-3
-2
-1
0
+1
+1
+1
+1
+1
+1
+1
+1
0
0
-8
-6
-4
-2
Range
Scale
(NM)
Altitude
(Feet)
(TILTLIMITED
REGION)
(LINE OF SIGHT LIMITED REGION)
AD-50232@
Approximate Tilt Setting for Minimal Ground Target Display
24-Inch Radiator
Table 5-3
Tilt angles shown are approximate. Where the tilt angle is not listed,
the operator must exercise good judgement.
NOTE: The line of sight distance is nominal. Atmospheric
conditions and terrain offset this value.
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A28-1146-102-00 Radar Facts
5-11
Tilt management is often misunderstood. It is crucial to safe operation
of airborne weather radar. If radar tiltangles arenot properlymanaged,
weather targets can be missed or underestimated.
Theupperlevelsofconvectivestormsarethemostdangerousbecause
of the probability of violent windshears and large hail. But hail and
winshear are not very reflective because they lack reflective liquid
water.
The figures that follow show the relationship between flight situations
andthecorrecttiltangle.Thefirstdescribesahighaltitudesituation;the
second describes alow altitude situation.
DThe ideal tilt angle shows afew ground targets at the edge of the
display (see figure 5-8).
AD-35694@
GROUND
RETURN
Ideal Tilt Angle
Figure 5-8
DEarth’scurvature can be a factor if altitude is low enough, or if the
selected range is long enough, as shown in figure 5-9.
AD-35695@
GROUND
RETURN
Earth’sCurvature
Figure 5-9
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5-12
DConvective thunderstorms become much less reflective above the
freezing level. This reflectivity decreases gradually over the first
5000 to 10,000 feet above the freezing level, as shown in figure
5-10.
AD-35696@
FREEZING LEVEL
Convective Thunderstorms
Figure 5-10
The aircraft in figure 5-10 has aclear radar indication of the
thunderstorm, probably with ashadow in the ground returns behind
it.
DIf the tilt angle shown in figure 5-11 is not altered, the thunderstorm
appears to weaken as the aircraft approaches it.
AD-35697@
FREEZING LEVEL
Unaltered Tilt
Figure 5-11
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5-13
DProper tilt management demands that tilt be changed continually
when approaching hazardous weather so that ground targets are
not painted by the radar beam, as shown in figure 5-12.
AD-35698@
FREEZING
LEVEL
Proper Tilt Technique
Figure 5-12
DAfter heading changes in afoul weather situation, the pilot should
adjust the tilt to see whatwas broughtinto theaircraft’sflightpathby
the heading changes, as shown in figure 5-13.
AD-30429@
DISPLAYBEFORE
TURN
DISPLAYAFTER
TURN
THUNDERSTORM WAS OUT
OF DISPLAYBEFORE TURN
AND IS NOW UNDER BEAM
Tilt Management With Heading Changes
Figure 5-13
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Radar Facts
5-14
DUnder the right conditions, adangerous thunder bumper can
develop in 10 minutes, and can in fact spawn and mature under the
radar beam as the aircraft approaches it, as shown in figure 5-14.
If flying at 400 kt groundspeed, afast developing thunderstorm that
spawns67NMinfrontoftheaircraftcanbelargeenoughtodamage
the aircraft by the time it arrives at the storm.
AD-35699@
FREEZING
LEVEL
THUNDERST
ORM
MA
TURES
AS IT APPROACHES
Fast Developing Thunderstorm
Figure 5-14
DAt lowaltitude, thetilt shouldbe setas lowas possibleto getground
returns at the periphery only as shown in figure 5-15.
CORRECT WRONG
FREEZING
LEVEL
AD-35700@
Low Altitude Tilt Management
Figure 5-15
Excess up-tiltshould be avoided as it canilluminate weatherabove
the freezing level.
NOTE: The pilot should have freeze level information as apart of
the flight planning process.
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5-15
DThe antenna size used on the aircraft alters the best tilt settings by
about 1_.However,tilt management is the same for either size, as
shown in figure 5-16.
10-IN. ANTENNA
HAS 10 BEAM 12-IN. ANTENNA
HAS 7.9 BEAM
18-IN. ANTENNA
HAS 5.6 BEAM
24-IN. ANTENNA
HAS 4.2 BEAM
Antenna Size and Impact on Tilt Management
Figure 5-16
NOTE: A10-inch antenna is shown for illustration purposes only.
DSomeoftherulesofthumbare describedbelow andshown infigure
5-17.
-A1_look down angle looks down 100 ft per mile
-Bottom of beam is 1/2 beam width below tilt setting
-A12-inch antenna grazes the ground at 100 NM if set to 0_tilt
at 40,000 ft.
AD-35702@
TILT
BEAM WIDTH
Rules of Thumb
Figure 5-17
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5-16
ALTITUDE COMPENSATED TILT(ACT)
The PRIMUSâ880 Digital Weather Radar hasan ACTfeature thatcan
be selected by pulling out the tilt control knob. This feature is
annunciatedontheradardisplaybyaddinganAsuffixtothetiltreadout.
While in ACT or manual tilt the digital tilt readout always shows the
actual (true) tilt of the antenna.
In ACT,the antenna tilt is automatically adjusted with regard to the
selected range and the aircraft’sbarometric attitude. ACT adjusts the
tilt to show afew ground targets at the edge of the display.In ACT,the
ideal setting can be adjusted ±2° to accommodate terrain height or
pilot preferences.
NOTE: Since ACT uses air data computer barometric altitude to
adjust the tilt, operating near high altitude airports or even
highterraincanresultinalowerthandesiredtiltangle.Insuch
cases, use of the manual tilt is recommended.
Tocalculate the tilt angle, the weather radar uses the air data
computer’sbarometric altitude with reference to an assumed ground
levelof2000feetabovesealevel.Thisassumedgroundlevelis afactor
during low altitude flight, especially when flying in mountainous areas.
The ground targets that are usually at the edge of the display tend to
migrate to the middle of the display.This also happens when longer
ranges (200 NM to 300 NM) are selected and the altitude is such that
the earth’scurvature is afactor.
In ACT the range control can be used to sweep the beam along the
ground to look for storms at various ranges, as shown in figure 5-18.
ACT is best suited for high altitude operation while in the weather
surveillance mode; i.e., aircraft is in cruise and there is no weather
within 100 NM. The operator can then use the range control to
frequently sweep the beam down to avoid overflying any fast
developing storms.
Atloweraltitudes,manualtiltshouldbeusedtofrequentlysweepabove
andbelow theflight levelto avoidflying underor overstorms, asshown
in figure 5-18. Manual tilt should also be used exclusively when
analyzing weather.
NOTE: The radar system does not have enough information to be
able to tilt the beam into the wet, lower portions of cells by
itself.Theoperator mustmanage tiltdynamically ormanually
to locate and analyze weather.ACT simply adjusts the beam
to the earth’ssurface at the selected maximum range. Also,
it assumes that the surface is at 2000 feet above sea level.
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5-17
AD-35703@
25 50
100 NM
Manual Tilt at Low Altitudes
Figure 5-18
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Radar Facts
5-18
STABILIZATION
The purpose of the stabilization system is to hold the elevation of the
antenna beam relative to the earth’ssurface constant at all azimuths,
regardless of aircraft bank and pitch maneuvers. The stabilization
system uses the aircraft attitude source as a reference.
Several sources of error exist in any stabilization system.
Dynamic Error
Dynamic error is the basis of the stabilization system. Stabilization is
acorrective process. It logically follows that there must first be some
error to correct. In stabilization, this error is called dynamic. An
exampleofdynamicerroroccurswhenagustliftstherightwingandthe
pilot instinctively raises the right aileron and lowers the left. In this
action, the pilot detects achanging (dynamic) error in aircraft attitude
and corrects it.
Asthegustliftsthewing,theaircraftattitudesourcesends acontinuous
stream of attitude change information to stabilization circuits which, in
turn, control the motors that raise and lower the beam. In short, a
dynamic error in aircraftattitude (asseen bythe radar)is detected,and
the antenna attitude is corrected for it. Extremely small errors of less
than 1_can be detected and compensated. However,the point is
ultimately reached where dynamic error is too small to be detected.
Without detection, there is no compensation.
Accelerative Error
One of the most common forms of error seen in aradar-antenna
stabilization system results from forces of acceleration on the aircraft
equipped with avertical gyroscope. Acceleration forces result from
speeding up, slowing down, or turning. Radar stabilization
accuracy depends upon the aircraft vertical gyroscope. Therefore,
any gyroscopic errors accumulated through acceleration are
automatically imparted to the antenna stabilization system.
Avertical gyroscope contains agravity-sensitive element, a
heavily dampened pendulous device that enables the gyro to erect
itselftoearthgravityattherateofapproximately2_/min.Thependulous
device is unable to differentiate between earth gravity and an
acceleration force. It tends to rest at afalse-gravityposition where the
forces of gravity and acceleration are equal. As long as the
acceleration force persists, the gyroscope precesses toward a
false-gravity position at the rate of approximately 2_/min. The radar
follows the gyroscope into error at the same rate. When the
acceleration force ceases, the gyroscope precesses back to true
gravity erection at the same rate.
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5-19
Some vertical gyroscopes have provisions for deactivating the
roll-erection torque motor (whenever the airplane banks more
than approximately 6_)to reduce the effect of lateral
acceleration during turns. Tosome extent, stabilization error is
displayed in the radar image after any speed change and/or turn
condition. If the stabilization system seems to be in error because the
radar begins ground mapping on one side and not the other,or
because it appears that the tilt adjustment has slipped, verify
that aircrafthasbeeninnonturning,constant-speedflightlongenough
to allow the gyroscope to erect on true earth gravity.
When dynamic and acceleration errors are taken into account,
maintaining accuracy of 1/2 of 1_or less is not always possible. Adjust
the antenna tilt by visually observing the ground return. Then, slowly
tilt the antenna upward until terrain clutter no longer enters the display,
exceptattheextremeedges.Ifgrounddisplayisobserved ononeside
but not on the other,the stabilization system is somewhat in error,but
it is probably impossible to adjust it more accurately.
Pitch and Roll Trim Adjustments
The PRIMUSâ880 is delivered from the Honeywell factory or repair
facility adjusted for correct pitch and roll stabilization and should be
ready for use. However,due to the tolerances of some vertical
reference sources, you may elect tomake afinal adjustmentwhenever
the radar or vertical reference is replaced on the aircraft, or if
stabilization problems are observed in flight.
The four trim adjustments and their effects are summarized in table
5-4.
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Radar Facts
5-20
Trim Adjustment Flight Condition Effect On Ground
Return Display
(Over Level
Terrain)
Roll offset Straight and level Nonsymmetrical
display
Pitch offset Straight and level Ground displays do
not follow contour of
range arcs.
Roll gain Constant roll angle
>20°Nonsymmetrical
display
Pitch gain Constant pitch angle
>5°Ground displays do
not follow contour of
range arcs.
Generally,it is recommended to perform trim adjustments only if
noticeable effects are being observed.
Pitch and Roll Trim Adjustments Criteria
Table 5-4
NOTES: 1. Depending on the installation, not all of the
adjustments shown in table 5-4are available. If STAB
TRIM ENABLE programming strap is open, only the
roll offset adjustment is available. If STAB TRIM
ENABLE is grounded, all four adjustments are
available. Consult the installation configuration
information for details.
2. After any adjustment procedure is completed, monitor
the ground returns displayed by the radar during
several pitch and roll maneuvers. Verify that the
ground returns stay somewhat constant during
changes in aircraft orientations. If not, repeat the
adjustment procedure.
3. After the trim adjustment feature is selected, more
than one adjustment can be made. They are available
in the sequence shown in table 5-4, and can be done
in the sequence of first finishing one adjustment, then
proceedingtodothenextbypushingtheSTABbutton.
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Stabilization Precheck
Prior to performing any of the adjustment procedures, conduct the
precheck procedures listed in tables 5-5 and 5-6.
LEVEL FLIGHT STABILIZATION CHECK
Check stabilization in level flight using the procedure in table 5-5.
Step Procedure
1Trim the aircraft for straight and level flight in smooth,
clear air over level terrain.
2Select the 50-mile range.
3Rotate the tilt control upward until all ground returns
disappear.
4Rotate the tilt downward until ground returns just begin
to show.
5After several antenna sweeps, verify that ground
returns are equally displayed (figure 5-19). If returns
are only on one side of the radar screen or uneven
across the radar screen, amisalignment of the radar
antenna mounting is indicated. This problem can be
corrected by means of the roll offset function before
proceeding (figures 5-20 and 5-21).
6Refer to the roll offset adjustment procedure in table
5-7.
Stabilization In Straight and Level Flight Check Procedure
Table 5-5
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10
5
15
20
AD-17720-R1@
GMAP
Symmetrical Ground Returns
Figure 5-19
10
5
15
20
AD-17721-R1@
GMAP
Ground Return Indicating Misalignment (Upper Right)
Figure 5-20
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10
5
15
20
AD-17722-R1@
GMAP
Ground Return Indicating Misalignment (Upper Left)
Figure 5-21
ROLL STABILIZATION CHECK
Once proper operation is established in level flight, verify stabilization
in aturn using the procedure in table 5-6.
Step Procedure
1Place the aircraft in 20° roll to the right.
2Note the radar display.Itshould contain appreciably no
more returns than found during level flight. Figure 5-22
indicates that roll stabilization is inoperative.
3If returns display on the right side of radar indicator;
the radar system is understabilizing.
4Targets on the left side of the radar display indicate the
system is Overstabilizing. Refer to table 5-9for roll
gain adjustment.
NOTE: Proper radar operation in turns depends on the accuracy
and stability of the installed attitude source.
Stabilization in Turns Check Procedure
Table 5-6
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5-24
In prolonged turns, gyro precession can occur that is tracked by the
stabilization system and appears as undesirable ground targets on the
indicator.Forexample,a1°precessionerror(whichwouldprobablynot
be noticed on the gyro horizon) moves the antenna beam
approximately 10,500feet at apoint100 NMfrom theaircraft, Ifground
targets between 50 and 80 NM depending on aircraft altitude and the
actual setting of the tilt control.
10
5
15
20
AD-17723-R1@
GMAP
Roll Stabilization Inoperative
Figure 5-22
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5-25
ROLL STABILIZATION CHECK
You can make an in-flight adjustment when level flight stabilization
errors are detected. This procedure is done by either the WC-880 or
WC-884 Weather Radar Controller or the WI-880 Weather Radar
Indicator.During this procedure, described in table 5-7, the GAIN
control acts as roll offset control. After the procedure the GAIN control
reverts to acting as again control.
Step Procedure
1If two controllers are installed, one must be turned off.
If an indicator is used as the controller,the procedure
is the same as given below.
2Fly to an altitude of 10,000 feet above ground level
(AGL), or greater.
3Set range to 25 NM.
4Adjust the tilt down until asolid band of ground returns
are shown on the screen. Then adjust the tilt until the
green region of the ground returns start at about 20
NM.
5On the WC controller,select RCT OFF.
6Select STAB (STB) 4times within 3seconds. A
display with text instructions will be displayed. See
figure 5-23. The radar unit is in the roll offset
adjustment mode.
7Pull out the GAIN knob to make aroll offset
adjustment. See figure 5-24 for atypical display.The
offset range is from -2.0° to +2.0° and is adjustable by
the GAIN knob. The polarity of the GAIN knob is such
that clockwise rotation of the knob causes the antenna
to move down when scanning on the right side.
8While flying straight and level, adjust the GAIN knob
until ground clutter display is symmetrical.
9Push in the GAIN knob. When the GAIN knob is
pushed in, the display returns to the previous
message.
In-flight Roll Offset Adjustment Procedure
Table 5-7(cont)
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Step Procedure
10 Push the STAB (STB) button to go to the next menu
(pitch offset).
NOTE: Onceset,therollcompensationisstored in nonvolatile memory in
the RTA. It is remembered when the system is powered down.
In-flight Roll Offset Adjustment Procedure
Table 5-7
WX
Roll Offset Adjustment Display -Initial
Figure 5-23
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5-27
WX
Roll Offset Adjustment Display -Final
Figure 5-24
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5-28
PITCH OFFSET ADJUSTMENT
This in-flight adjustment in made in straight and level flight when the
ground returns do not follow the contours of the radar display range
arcs. The procedure is listed in table 5-8.
Step Procedure
1If two controllers are installed, one must be turned off.
If an indicator is used, the procedure is the same as
given below.
2Fly to an altitude of 10,000 feet AGL or greater.
3Set range to 25 NM.
4Adjust the tilt down until asolid band of ground returns
are shown on the screen. Then adjust the tilt until the
green region of the ground returns start at about 20
NM.
5Select RCT OFF.
6Select STAB (STB) 4times within 3seconds. The roll
offset display is shown.
7From the roll offset entry menu, push the STAB (STB)
button once more to bring up the pitch offset entry
menu.
8Tochange the pitch offset value, pull out the GAIN
knob and rotate it. The offset range is from -2.0° to
+2.0°.
9When flying straight and level, adjust so the contour of
the ground returns follow the contour of the range arcs
as closely as possible.
10 When change is completed, push in the GAIN knob.
The display returns to the previous message.
11 Push the STAB (STB) button to go to the next menu
(roll gain).
Pitch Offset Adjustment Procedure
Table 5-8
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ROLL GAIN ADJUSTMENT
This in-flightadjustment is made in abank when the ground returns do
not remain symmetrical during turns. The procedure is listed in table
5-9.
Step Procedure
1If two controllers are installed, one must be turned off.
If an indicator is used as the controller,the procedure
is the same as given below.
2Fly to an altitude of 10,000 feet AGL or greater.
3Set range to 25 NM.
4Adjust the tilt down until asolid band of ground returns
are shown on the screen. Then adjust the tilt until the
green region of the ground returns start at about 20
NM.
5On the WC controller,select variable gain (pull), WX,
and REACT OFF.VAR shows on the display
6Select STAB (STB) 4times within 3seconds. A
display with text instructions is shown.
7From the roll offset entry menu, push the STAB (STB)
button twice more to bring up the roll gain entry menu.
8Tochange the roll gain value, pull out the GAIN knob
and rotate it. The roll gain adjustment range is from 90
to 110%.
9While flying with asteady roll angle of 10 to 20°,adjust
for symmetrical display of ground returns.
10 When change is completed, push in the GAIN knob.
The display returns to the previous message.
11 Push the STAB (STB) button to go to the next menu
(pitch gain).
Roll Gain Adjustment
Table 5-9
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5-30
PITCH GAIN ADJUSTMENT
This in-flightadjustment is made in abank when the ground returns do
not follow the contours of the range arcs during turns. The procedure
is listed in table 5-10.
Step Procedure
1If two controllers are installed, one must be turned off.
If an indicator is used as the controller,the procedure
is the same as given below.
2Fly to an altitude of 10,000 feet AGL or greater.
3Set range to 25 NM.
4Adjust the tilt down until asolid band of ground returns
are shown on the screen. Then adjust the tilt until the
green region of the ground returns start at about 20
NM.
5On the WC controller,select variable gain (pull), WX
and REACT OFF.VAR shows on the display.
6Push STAB (STB) 4times within 3seconds. Adisplay
with text instruction is shown.
7From the roll offset entry menu, push the STAB (STB)
button 3more times to bring up the pitch gain entry
menu.
8Tochange the pitch gain value, pull out the GAIN knob
and rotate it. The pitch gain adjustment range is from
90 to 110%.
9While flying with asteady pitch angle of >5°,adjust so
the contour of the ground returns follow the contour of
the range arcs as closely as possible.
10 When change is completed, push in the GAIN knob.
The display returns to the previous message.
11 Push the STAB button to exit the mode and save the
value in nonvolatile memory.
Pitch Gain Adjustment
Table 5-10
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5-31
INTERPRETING WEATHER RADAR IMAGES
From aweather standpoint, hail and turbulence are the principal
obstacles to asafe and comfortable flight. Neither of these conditions
is directly visible on radar.The radar shows only the rainfall patterns
with which these conditions are associated.
The weather radar can see water best in its liquid form, as shown in
figure 5-25 (not water vapor; not ice crystals; not hail when small and
perfectly dry). It can see rain, wet snow,wet hail, and dry hail when its
diameter is about 8/10 of the radar wavelength or larger.(At X-band,
this means that dry hail becomes visible to the radar at about 1-in.
diameter.)
WET HAIL -GOOD
RAIN -GOOD
WET SNOW -GOOD
DRYHAIL -POOR
DRYSNOW -VERYPOOR
VAPOR
ICE CRYSTALS
SMALL DRYHAIL
AD-46704-R1@
REFLECTIVE LEVELS WILL NOT REFLECT
Weather Radar Images
Figure 5-25
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The following are some truths about weather and flying, as shown in
figure 5-26.
DTurbulence results when two air masses at different temperatures
and/or pressures meet.
DThis meeting can form athunderstorm.
DThe thunderstorm produces rain.
DThe radar displays rain (thus revealing the turbulence).
DInthe thunderstorm’s cumulus stage,echoesappearon the display
and growprogressivelylargerand sharper.The antenna can be tilted
up and downinsmall incrementstomaximizethe echo pattern.
DIn the thunderstorm’smature stage, radar echoes are sharp and
clear; hail occurs most frequently early in this stage.
DIn the thunderstorm’sdissipating stage, the rain area is largest and
shows best with aslight downward antenna tilt.
Radar can be used to look inside the precipitation area to spot zones
ofpresentanddevelopingturbulence.Someknowledgeofmeteorology
is required to identify these areas as being turbulent. The most
important fact is that the areas of maximum turbulence occur where
the most abrupt changes from light or no rain to heavy rain occur.The
term applied to this change in rate is rain gradient. The greater the
change in rainfall rate, the steeper the rain gradient. The steeper the
rain gradient, the greater the accompanying turbulence. More
important, however,is another fact: Storm cells are not static or stable,
but are in aconstant state of change. While asingle thunderstorm
seldomlasts morethananhour,asquallline,showninfigure 5-27can
contain many such storm cells developing and decaying over amuch
longer period. Asingle cell can start as acumulus cloud only 1mile in
diameter,rise to 15,000 ft, grow within 10 minutes to 5miles in
diameter and tower to an altitude of 60,000 feet or more. Therefore,
weather radar should not be used to take flash pictures of weather,but
to keep weather under continuous surveillance.
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RED LEVEL*
60 8040200 NAUTICAL MILES
RAINFALL RATE
AD-12057-R2@
Radar and Visual Cloud Mass
Figure 5-26
As masses of warm, moist air are hurled upward to meet the colder air
above, the moisture condenses and builds into raindrops heavy
enough to fall downward through the updraft. When this precipitation is
heavy enough, it can reverse the updraft. Between these downdrafts
(shafts of rain), updrafts continue at tremendous velocities. It is not
surprising, therefore, that the areas of maximum turbulence are near
these interfaces between updraft and downdraft. Keep these facts in
mind when tempted to crowd arain shaft or to fly over an
innocent-looking cumulus cloud.
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Tofind asafe and comfortable route through the precipitation area,
study the radar image of the squall line while closing in on the
thunderstorm area. In the example shown in figure 5-27, radar
observation shows that the rainfall is steadily diminishing on the left
whileitisveryheavyintwomaturecells(andincreasingrapidlyinathird
cell) to the right. The safest and most comfortable course liesto theleft
where the storm is decaying into alight rain. The growing cell on the
right should be given awide berth.
AD-12058-R1@BEST DETOUR
OUTLINE OF RAIN AREA VISIBLE TORADAR
DECAYING
CELLS
AREAS OF MAXIMUM TURBULENCE
MATURE CELLS
GROWING
CELLS
Squall Line
Figure 5-27
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WEATHER DISPLAYCALIBRATION
Groundbased radarobservers ofthe NationalWeather Service(NWS)
currently use video integrator processor (VIP) levels in reporting
thunderstorm intensity levels. Theseradar echointensity levels areon
ascale of one to six. Refer to Section 6of FAA Advisory Circular
AC-00-24Bfor additional details.
Toassistthepilotincategorizingstormsinaccordance withVIPlevels,
theindicatordisplaycolorsrepresentcalibratedrainfallratesinWXand
preset calibrated gain. The relationship between the 4-color
calibrations and the VIP levels is shown in table 5-11.
As covered in the RCT description, intervening attenuating rainfall
reduces the calibrated range and the radar can incorrectly depict the
true cell intensity.
The radar calibration includes anominal allowance for radome losses.
Excessive losses in the radome seriously affect radar calibration. One
possible means of verification is signal returns from known ground
targets. It is recommended that you report evidence of weak returns to
ensure that radome performance is maintained at alevelthat doesnot
affect radar calibration.
Totest for aperformance loss, note the distance at which the aircraft’s
base city,amountain, or ashoreline can be painted from agiven
altitude.When flyingin familiarsurroundings, verifythat landmarkscan
still be painted at the same distances.
Anylossinperformanceresultsinthesystemnotpainting thereference
target at the normal range.
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DISPLAY
LEVEL
RAINFALL
RATE
MM/HR
RAINFALL
RATE
IN./HR
4
(MAGENTA)
GREATER
THAN
50
GREATER
THAN
2
3
(RED)
2
(YELLOW)
12 -50 0.5 -2
4-12 0.17 -0.5
232 >300 >300
130 190 230
90 130 160
1
(GREEN) 1-40.04 -0.17
0
(BLACK) LESS THAN
1LESS THAN
0.04
55 80 100
---
MAXIMUM*
CALIBRATED
RANGE (NM)
12-IN
FLAT-PLATE
MAXIMUM*
CALIBRATED
RANGE (NM)
18-IN
FLAT-PLATE
MAXIMUM*
CALIBRATED
RANGE (NM)
24-IN
FLAT-PLATE
EXTREME 6
GREATER
THAN
125
(5)
INTENSE 550 -125
(2 -5)
VERY
STRONG 425 -50
(1 -2)
STRONG 312 -25
(0.5 -1)
MODERATE 22.5 -12
(0.1 -0.5)
WEAK 10.25 -2.5
(0.01 -0.1)
STORM
CATEGORY VIP
LEVEL RAINFALL
RATE-MM/HR
(IN./HR)
VIDEO INTEGRATED PROCESSOR
CATEGORIZATIONS
REFLECTIVITY 300 NM
THE THRESHOLD FOR THE VIP LEVELS CAN BE REALIZED WHEN THERE IS NO INTERVENING RADAR
SIGNAL ATTENUATION. WITH RCT SELECTED, RCT BLUE FIELD OCCURS WHEN THE MINIMUM RED
LEVEL DETECTED IS BELOW SYSTEM SENSITIVITY.
*
AD-17926-R5@
Display Levels Related to VIP Levels (Typical)
Table 5-11
NOTE: The radar is calibrated for convective weather.
Stratiform storms at or near thefreezing levelcan showhigh
reflectivity.Do not penetrate such targets.
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VARIABLE GAIN CONTROL
The PRIMUSâ880 Digital Weather Radar variable gain control is a
single turn rotary control and a push/pull switch that is used to control
theradar’sreceivergain.Withtheswitchpushedin,thesystemisinthe
preset, calibrated gain mode. In calibrated gain, therotary controldoes
nothing.
WhentheGAINswitchispulledout,thesystementersthevariablegain
mode. Variable gainis usefulfor additionalweather analysis.In theWX
mode,variablegaincanincreasereceiversensitivityover thecalibrated
level to show very weak targets or it can be reduced below the
calibrated level to eliminate weak returns.
WARNING
LOW VARIABLE GAIN SETTINGS CAN ELIMINATE HAZARDOUS
TARGETS.
RAIN ECHO ATTENUATION COMPENSATION
TECHNIQUE (REACT)
Honeywell’sREACT feature has three separate, butrelated functions.
DAttenuation Compensation -As the radar energy travelsthrough
rainfall, the raindrops reflect aportion ofthe energyback towardthe
airplane. This results in less energy being available to detect
raindrops at greater ranges. This process continues throughout the
depth of the storm, resulting in aphenomenon known as
attenuation. The amount of attenuation increases with an increase
inrainfallrateandwithan increaseinthe rangetraveledthroughthe
rainfall (i.e., heavy rain over alarge area results in high levels of
attenuation, while light rain over asmall area results in low levels of
attenuation).
Stormswithhighrainfallrates cantotally attenuate the radarenergy
makingitimpossibletoseeasecondcellhiddenbehindthefirstcell.
In some cases, attenuation can be so extreme that the total depth
of asingle cell cannot be shown.
Without some form of compensation, attenuation causes asingle
cell to appear to weaken as the depth of the cell increases.
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Honeywell hasincorporated attenuation compensation thatadjusts
the receivergain byan amountequaltothe amountofattenuation.
Thatis, the greaterthe amountofattenuation, the higherthe receiver
gain and thus, the moresensitivethe receiver.Attenuation
compensation continuously calibratesthe displayofweathertargets,
regardless of the amountofattenuation.
With attenuation compensation, weather target calibration is
maintained throughout the entire range of asingle cell. The
cell behind acell remains properly calibrated, making proper
calibration of weather targets at long ranges possible.
DCyan REACT Field -From the description of attenuation, it can be
seen that high levels of attenuation (caused by cells with heavy
rainfall) causes the attenuation compensation circuitry to increase
the receiver gain at afast rate.
Low levels of attenuation (caused by cells with low rainfall rates)
cause the receiver gain to increase at aslower rate.
The receiver gain is adjusted to maintain target calibration. Since
there is amaximum limit to receiver gain, strong targets (high
attenuation levels) cause the receiver to reach its maximum gain
value in ashort time/short range. Weak or no targets (low
attenuation levels) cause the receiver to reach its maximum gain
value in alonger time/longer range. Once the receiver reaches its
maximum gain value, weather targets can no longer be calibrated.
The point where red level weather target calibration is no longer
possible is highlighted by changing the background field from black
to cyan.
Any area of cyan background is an area where attenuation has
caused the receiver gain to reach its maximum value, so further
calibration of returns is not possible. Extreme caution is
recommended in any attempt to analyze weather in these
cyan areas. The radar cannot display an accurate picture of what
is in these cyan areas. Cyan areas should be avoided.
NOTE: If the radar is operated such that ground targets are
affecting REACT,they could cause REACT to provide
invalid indications.
Any target detected inside acyan area is automatically forced to a
magenta colorindicating maximumseverity.Figure5-28showsthe
same storm with REACT OFF and with REACT ON.
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With REACT Selected
REACT
REACT ON and OFF Indications
Figure 5-28
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5-40
Shadowing
An operating technique similartothe REACTblue fieldis shadowing.To
usethe shadowing technique, tilt the antenna down until ground isbeing
painted justinfrontof the stormcell(s).An area ofno ground returns
behind the stormcell hasthe appearance ofashadowbehind the cell.
This shadowarea indicatesthat the stormcell hastotallyattenuated the
radarenergyand the radarcannotshowanyadditionaltargets(WXor
ground)behind the cell.The cell thatproducesaradarshadowisavery
strong and dangerous cell.Itshould be avoided by20 miles.
WARNING
DO NOT FLYINTOTHE SHADOW BEHIND THE CELL.
Turbulence Probability
The graph of turbulence probability is shown in figure 5-29.This graph
shows the following:
DThere is a100% probability of light turbulence occurring in any area
of rain.
DAlevel one storm (all green) has virtually no chance of containing
severe or extreme turbulence but has between a5% and 20%
chance that moderate turbulence exists.
DAlevel two storm (one containing green and yellow returns) has
virtually no probability of extreme turbulence but has a20% to 40%
chance of moderate turbulence and up to a5% chance of severe
turbulence.
DAlevelthree storm(green, yellow,and redradar returns)has a40%
to 85% chance of moderate turbulence, a5% to 10% chance of
severe turbulence, and a slight chance of extreme turbulence.
DAlevel four storm (one with amagenta return) has moderate
turbulence, a10% to 50% chance ofsevere turbulence,and a slight
to 25% chance of extreme turbulence.
WARNING
THE AREAS OF TURBULENCE MAYNOT BE ASSOCIATED WITH
THE MAXIMUM RAINFALL AREAS. THE PROBABILITIES OF
TURBULENCE ARE STATED FOR THE ENTIRE STORM AREA,
NOT JUST THE HEAVY RAINFALL AREAS.
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Althoughpenetratingastormwithared(levelthree) coreappears tobe
an acceptable risk, it is not. At the lower end of the red zone, there is
nochanceofextremeturbulence,aslightchanceof severeturbulence,
and a 40% chance of moderate turbulence. However,the radar lumps
alloftherainfallratesbetween12mmto50mmperhourintoonegroup
-alevel three (red). Once the rainfall rate reaches the red threshold,
it masks any additional information about the rainfall rate until the
magenta threshold is reached. Ared return covers arange of
turbulence probabilities and the worst case must be assumed,
especiallysinceextreme,destructiveturbulenceisborninthe redzone.
Therefore, once the red threshold is reached, the risk in penetration
becomes totally unacceptable.
Likewise, once the magenta threshold is reached, it must be
assumed that more severe weather is being masked.
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
TURBULENCE PROBABILITY
LIGHT
LEVEL 1
GREEN LEVEL 2
YELLOW LEVEL 3
RED LEVEL 4
MAGENTA
(4 mm /Hr) (12 mm /Hr) (50 mm /Hr)
AD-15357-R2@
RAINFALL RATE
Probability of Turbulence Presence
in aWeather Target
Figure 5-29
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5-42
Turbulence Detection Theory
The PRIMUSâ880 Digital Weather Radar uses aturbulence detection
technique called Pulse Pair Processing (PPP). The PPP technique
used in the new PRIMUSâ880 Digital Weather Radar is adapted from
the proven technique used in the earlier PRIMUSâWeather Radars.
Intheturbulencedetectionmodeofoperation,thePRIMUSâ880Digital
Weather Radar transmits about 1400 pulses per second with apower
of 10 kW.The pulse pair processor compares the returns from
successive pulses to determine the presence of turbulence (i.e.,
the return from pulse one is compared to the return from pulse two,
pulse two’sreturn is compared to pulse three’s, and so on). Since the
processor is comparing the returns from two subsequent pulses (a
pair), it was given the name pulse pair processor.
Toperform the comparison, the radar first divides the selected range
into 128 equal parts with each part called arange bin. The radar
compares the return data in each range bin for the first pulse with the
return data in each range bin for the second pulse. For example, the
data returned from pulse one in range bin 34 is compared to the data
returned from pulse two in range bin 34. This process continues
throughout the entire area covered by the radar (all range bins) and a
turbulence decision is made for each range bin. When turbulence is
detected in any bin, the color of that bin is made white.
The return data being compared is the total return vector (TRV). TRV
is the vector sum of the return from each raindrop contained within the
range bin. In other words, the first pulse TRVof range bin 34 is
comparedtotheTRVforpulsetwoinrangebin 34.Atotalreturnvector
is shown in figure 5-30.
In the simplified example of figure 5-30, the range bin contains
five raindrops of equal size that are at slightly different ranges. The
amplitudesofthereturnsfromtheraindrops(vectorlength)areidentical
because all the drops are equal in size, but the phase (vector rotation)
of the individual returns varies because of the variation in the range of
the raindrops. The radar does not see the individual returns, rather it
sees the total return vector which is the vector sum of the returns from
all the individual raindrops. In reality,the range bin could contain
thousandsandthousandsofraindropswhichmeansthatalongerchain
of vectors are summed, but the result is still one total return vector.
PRIMUS
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5-43
With the very short time between radar pulses when in the turbulence
mode (one pulse every .0008 second), little or no turbulence results in
little or no change in the size or position of the raindrops. This results
in little or no change in the individual returns from each raindrop and a
commensurate little or no change in the total return vector.Therefore,
whenthereislittleornodifferencebetweentwosubsequenttotalreturn
vectors in the same range bin, there is little or no turbulence in that
range bin. This is illustrated by comparing figures 5-30 and 5-31.
If turbulenceispresentinthe precipitation, thereisasignificantchange in
the raindrop size and/orposition between the subsequentradarpulses.
Thisdifferenceresultsin a change inthe individualreturnvectorsfrom
eachraindrop and a commensuratechange inthe totalreturnvector.
Therefore,if thereisasignificantdifference between pairsof totalreturn
vectorsforthe samerange bin, thatbincontainsturbulence and is
displayed inwhite.Thisisillustrated bycomparing figures5-30 and 5-32.
The presence of turbulence is detected by comparing the amplitude of
subsequent total return vectors.
Tomeasureraindrop motion, the turbulence detection circuitrymeasures
the raindrop motion directlytoward and awayfromthe antenna.Raindrop
motionthatisperpendiculartothe antennadoesnotproduce anydoppler
effectand cannotbe measured bythe turbulence detection circuitry.For
thisreason, therecan be areasof turbulence notdetectable byradar,or
the displayed areasof turbulencecan change fromantenna scan to
antennascanastheturbulencethrowsthe raindropsinvariousdirections.
WARNING
AREAS OF TURBULENCE CAN NOT ALWAYS BE
DETECTED BY THE RADAR.
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5-44
Total Return Vector
Figure 5-30
AD-17726-R1@
No Turbulence
Figure 5-31
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5-45
AD-17727-R1@
TURBULENT
Turbulent
Figure 5-32
Turbulence Detection Operation
WiththeradarintheWXmodeandwith50milesorless rangeselected,
pushing the TRB switch turns onthe turbulencedetection mode.Areas
of detected turbulence are displayed in soft white, as shown in figure
5-33.Soft white is ahigh contrast shade of white that has aslight gray
appearance.
Weather Display With Turbulence
Figure 5-33
If anyrange greaterthan 50 milesis selected, turbulence detection turns
off and remainsoff until 50 milesorless isreselected.Similarly,ifany
mode otherthan WXis selected, turbulence detection turnsoff.
PRIMUS
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5-46
Mode annunciation for the turbulence detection mode is the /T legend
that is added to the WX annunciation. The resultant annunciation is
WX/T for weather and turbulence. The color bar legend on the
dedicated radar indicator includes aTwithin asoft white square
whenever turbulence detection is turned on. EFIS/MFD does not have
acolor bar legend.
The PRIMUSâ880 Digital Weather Radar measures the motion of
raindrops to determine areas of turbulence. The radar must detect
precipitation before it can detect turbulence. It cannot detect clear air
turbulence.
WARNING
THE PRIMUSâ880 DIGITALWEATHER RADAR CAN ONLYDETECT
TURBULENCEWITHINAREASOFPRECIPITATION.ITCANNOTDE-
TECTCLEAR AIRTURBULENCE.
Theturbulencedetectionthresholdismoderateturbulence.That is,any
area of raindrop motion that is detected as moderate, severe, or
extreme turbulence is displayed in white. Areas shown as turbulentare
at least moderate turbulence and can be severe, extreme, or
combinations of the three levels of turbulence. All three must be
avoided.
Turbulence is most accurately measured within ?30_of straight
ahead. Turbulence measurements outside this area experience
reducedaccuracy.Thereducedaccuracyresultsfromtheeffectsofthe
antenna scan angle and aircraft motion. Levels of turbulence are
described in the Airman’sInformation Manual and are shown in figure
5-34.
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5-47
INTENSITY AIRCRAFT REACTION REACTION INSIDE
AIRCRAFT
LIGHT
Turbulence that momentarily causes
slight, erratic changes in altitude and/or
attitude (pitch, roll, yaw).
Occupants may feel aslight
strain against seat belts or
shoulder straps. Unsecured
objects may be displaced
slightly.
MODERATE
Turbulence that is similar to light
turbulence but of greater intensity.
Changes in altitude and/or attitude
occur but the aircraft remains in
positive control at all times. It usually
causes variations in indicated
airspeed.
Occupants feel definite
strains against seat belts or
shoulder straps. Unsecured
objects are dislodged.
SEVERE
Turbulence that causes large abrupt
changes in altitude and/or attitude. It
usually causes large variations in
indicated airspeed. Aircraft may be
momentarily out of control.
Occupants are forced
violently against seat belts
or shoulder straps.
Unsecured objects are
tossed about.
Turbulence Levels
(From Airman’sInformation Manual)
Figure 5-34
Hail Size Probability
Whenevertheradarshowsaredormagentatarget,theentirestormcell
should be considered extremely hazardous and must not be
penetrated. Further support for this statement comes from the hail
probability graph shown in figure 5-35. The probability of destructive
hail starts at arainfall rate just above the red level three threshold.
Like precipitation, the red and magenta returns should be considered
as amask over more severe hail probabilities.
By now,it should be clear that the only safe way to operate in areas of
thunderstorm activity is to AVOID ALL CELLS THATHAVE RED OR
MAGENTARETURNS.
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5-48
RELATIVE FREQUENCY
60%
40%
20%
0%
80%
100%
1/2”HAIL
1/4”HAIL
3/4”AND LAGER HAIL
AD-15358-R1@
LEVEL 2
YELLOW LEVEL 3
RED LEVEL 4
MAGENTA
Hail Size Probability
Figure 5-35
Spotting Hail
As previously stated, dry hail is apoor reflector,and therefore
generatesdeceptivelyweakorabsentradarreturns.Whenflyingabove
thefreezinglevel,hailcanbeexpectedinregionsaboveandaroundwet
storm cells found at lower altitudes. The hail is carried up to the
tropopause by strong vertical winds inside the storm. In large storms,
these winds can easily exceed 200 kt, making them very dangerous.
Since the core of such astorm is very turbulent, but largely icy,the red
core on the radar display is weak or absent and highly mobile. The
stormcorecanbeexpectedtochangeshapeswitheachantennascan.
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5-49
On reaching the tropopause, the hail is ejected from thestorm andfalls
downward to apoint where it is sucked back into the storm. When the
hail falls below the freezing level, however,it begins to melt and form
athin surface layer of liquid detectable by radar.Aslight downward tilt
of the antenna toward the warmer air shows rain coming from unseen
dryhailthatisdirectlyintheflightpath,asshowninfigure5-36.Atlower
altitudes, the reverse is sometimes true; the radar may be scanning
below arapidly developing storm cell, from which the heavy rain
dropletshavenot hadtimetofallthroughtheupdraftstotheflightlevel.
Tilting the antenna up and down regularly produces the total weather
picture.
Using atilt setting that has the radar look into the area of maximum
reflectivity (5000 to 20,000 ft) gives the strongest radar picture.
However the tilt setting must not be left at this setting. Periodically,the
pilot should look up and down from this setting to see the total picture
of the weather in the flightpath.
Often, hailstorms generate weak but characteristic patterns like those
shown in figure 5-37. Fingers or hooks of cyclonic winds that radiate
from the main body of astorm usually contain hail. AUshaped pattern
is also (frequently) acolumn of dry hail that returns no signal but is
buriedinalargerareaofrainthatdoesreturnastrongsignal.Scalloped
edges on a pattern also indicate the presence of dry hail bordering
arain area. Finally,weak or fuzzy protuberances are not
always associated with hail, but should be watched closely; they
can change rapidly.
AD-12059-R1@
BEAM IN
DOWNWARD
TILTPOSITION
WET HAIL
AND RAIN
DRYHAIL
Rain Coming From Unseen Dry Hail
Figure 5-36
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5-50
U-SHAPEHOOKFINGER
AD-35713@
Familiar Hailstorm Patterns
Figure 5-37
The more that is learned about radar,the more the pilot is an
all-importantpart ofthe system.The properuse ofcontrols isessential
togatheringallpertinentweather data.The properinterpretation ofthat
data(thedisplayedpatterns)isequallyimportanttosafetyandcomfort.
This point is illustrated again in figure 5-38. When flying at higher
altitudes, astorm detected on the long-range setting can
disappear from the display as it is approached. The pilot should not be
fooledintobelievingthestormhasdissipatedastheaircraftapproaches
it. The possibility exists that the radiated energy is being directed from
the aircraft antenna above the storm as the aircraft gets closer. If this
is the case, the weather shows up again when the antenna is tilted
downward as little as 1_.Assuming that astorm has dissipated during
the approach can be quite dangerous; if this is not the case, the
turbulence above astorm can be as severe as that inside it.
PRIMUS
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5-51
OVERFLYING ASTORM
HAIL
AD-12061-R1@
Overshooting aStorm
Figure 5-38
Another example of the pilot’simportance in helping the radar serve its
safety/comfort purpose is shown in figure 5-39. This is the blind alley
or box canyon situation. Pilots can find themselves in this situation if
they habitually fly with the radar on the short range. The short-range
returns show an obvious corridor between two areas of heavy rainfall,
but the long-range setting shows the trap. Both the near and far
weather zones could be avoided by ashort-term course change of
about45_totheright.Alwaysswitchtolongrangebeforeenteringsuch
acorridor.
PRIMUS
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5-52
THE BLIND ALLEY
40
20
LONG RANGE
20
SHORTRANGE
AD-12062-R1@
Short-and Long-Blind Alley
Figure 5-39
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5-53
Azimuth Resolution
When two targets, such as storms, are closely adjacent at the
same range, the radar displays them as asingle target, as shown in
figure 5-38. However,as the aircraft approaches the targets, they
appear to separate. In the illustration, the airplane is far away from the
targets at position A.At this distance, the beam width is spreading. As
the beam scans across thetwo targets,there isno pointat whichbeam
energy is not reflected, either by one target or the other,because the
space between the targets is not wide enough to pass the beam width.
In target position B, the aircraft is closer to the same two targets; the
beam width is narrower,and the targets separate on the display.
100
60
40
20
INDICATOR DISPLAY A
50
30
20
10
INDICATOR DISPLAY B
A
AD-35705@
B
40
80
Azimuth Resolution in Weather Modes
Figure 5-40
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5-54
RADOME
Ice or water on the radome does not generally cause radar failure, but
it hampers operation. Theradome isconstructed ofmaterials thatpass
the radar energy with little attenuation. Ice or water increases the
attenuation making the radar appear to have less sensitivity.Ice can
cause refractive distortion, acondition characterized by loss of image
definition. If the ice should cause reverberant echoes within the
radome, the condition might be indicated by the appearance of
nonexisting targets.
The radome can also cause refractive distortion, which would make it
appear that the TILTcontrol was out of adjustment, or that bearing
indications were somewhat erroneous.
Aradomewithiceorwatertrappedwithinitswallscancausesignificant
attenuation and distortion of the radar signals. This type of attenuation
cannot be detected by the radar,even with REACT on, but it can, in
extreme cases, cause blind spots. If atarget changes significantly in
size, shape, or intensity as aircraft heading or attitude change, the
radome is probably the cause.
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5-55
WEATHER AVOIDANCE
Figure 5-41 illustrates atypical weather display in WX mode.
Recommended procedures when using the radar for weather
avoidance are given in table 5-12. The procedures are given in bold
face, explanations of the procedure follow in normal type face.
Weather Display
Figure 5-41
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5-56
Step Procedure
1Keep TGT alert enabled when using short ranges to
be alerted if anew storm cell develops in the
aircraft’sflightpath.
2Keep the gain in preset. The gain control should be
in preset except for brief periods when variable gain
is used for detailed analysis. Immediately after the
analysis, switch back to preset gain.
WARNING
DO NOTLEAVE THERADAR INVARIABLE GAIN.SIG-
NIFICANT WEATHER MAYNOT BE DISPLAYED.
3Any storm with reported tops at or greater than
20,000 feet must be avoided by 20 NM.
WARNING
DRYHAIL CAN BE PREVALENT ATHIGHER ALTI-
TUDES WITHIN, NEAR, OR ABOVE STORM CELLS,
AND SINCE ITS RADAR REFLECTIVITY IS
POOR, IT MAYNOT BE DETECTED.
4Use increased gain (rotate GAIN control to its
maximum cw position) when flying near storm tops.
This helps display the normally weaker returns that
could be associated with hail.
Severe Weather Avoidance Procedures
Table 5-12 (cont)
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5-57
Step Procedure
5When flying at high altitudes, tilt downward
frequently to avoid flying above storm tops.
Studiesbythe NationalSevereStormsLaboratory(NSSL)
ofOklahoma have determined that thunderstorms
extending to 60,000 ft showlittlevariation of turbulence
intensitywith altitude.
Ice crystals are poor reflectors. Rain water at the lower
altitudes produce astrong echo, however at higher
altitudes, the nonreflective ice produces aweek echo as
the antenna is tilted up. Therefore, though the intensity
of the echo diminishes with altitude, it does not mean
the severity of the turbulence has diminished.
NOTE: If the TILTcontrol is left in afixed position at
the higher flight levels, astorm detected at
long range can appear to become weaker
and actually disappear as it is approached.
This occurs because the storm cell which
was fully within the beam at 100 NM gradually
passes out of and under the radar beam.
6When flying at low altitudes rotate tilt upward
frequently to avoid flying under athunderstorm.
Thereis some evidencethatmaximumturbulence exists
atmiddle heightsinstorms(20,000 to 30,000 ft);however,
turbulence beneathastormisnot tobeminimized.
However, the loweraltitude maybe affected by strong
outflow windsand severeturbulencewherethunderstorms
are present. The sameturbulenceconsiderationsthat
applyto high altitude flightnearstormsapplytolow
altitude flight.
7Avoid all rapidly moving echoes by 20 miles.
Asingle thunderstorm echo, aline of echoes, or a
cluster of echoes moving 40 knots or more will often
contain severe weather.Although nearby,slower moving
echoes may contain more intense aviation hazards, all
rapidly moving echoes warrant close observation. Fast
moving, broken to solid line echoes are particularly
disruptive to aircraft operations.
8Avoid, the entire cell if any portion of the cell is red
or magenta by 20 NM.
The stronger the radar return, the greater the frequency
and severity of turbulence and hail.
Severe Weather Avoidance Procedures
Table 5-12 (cont)
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5-58
Step Procedure
9Avoid all rapidly growing storms by 20 miles.
When severestormsand rapid developmentare evident,
the intensityof the radar returnmayincrease bya huge
factorinamatterofminutes.Moreover, the summitof the
stormcellsmaygrowat7000 ft/min.The pilotcannot
expectaflightpaththrough suchafield ofstrong storms
separated by20 to 30 NMtobefree ofsevere
turbulence.
10 Avoid all storms showing erratic motion by 20
miles.
Thunderstormstend tomovewiththe average wind that
existsbetween the base and top of the cloud.Anymotion
differing fromthisis considered erraticand mayindicate
the stormis severe.There areseveralcausesoferratic
motion.Theymayactindividuallyorinconcert. Three of
the mostimportantcausesoferraticmotion are:
1. MoistureSource.Thunderstormstendtogrowtoward
alayer of very moist air (usually south or southeast in
theU.S.)inthelowest1500to5000ftabovetheearth’s
surface. Moist air generates most of the energy for the
storm’sgrowth and activity.Thus, athunderstorm may
tend to move with the average wind flow around it, but
also grow toward moisture. When the growth toward
moisture is rapid, the echo motion often appears
erratic. On at least one occasion, athunderstorm echo
moved in direct opposition to the average wind!
2. Disturbed Wind Flow.Sometimes thunderstorm
updrafts block winds near the thunderstorm and act
much like arock in ashallow river bed. This pillar of
updraft forces the winds outside the storm to flow
around the storm instead of carrying it along. This also
happens in wake eddiesthat oftenform downstreamof
the blocking updraft
10
(cont) 3. Interaction WithOtherStorms.Athunderstormthatis
located between anotherstormand itsmoisturesource
may causethe blocked stormto have erraticmotion.
Sometimesthe blocking ofmoistureiseffective enough
tocausethe thunderstormto dissipate.
Severe Weather Avoidance Procedures
Table 5-12 (cont)
PRIMUS
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5-59
Step Procedure
Three of the most common erratic motions are:
1. Right Turning Echo.This is the most frequently
observed erratic motion. Sometimes athunderstorm
echo traveling the same direction and speed asnearby
thunderstormechoes,slows,andturnstotherightofits
previousmotion.Theerraticmotionmaylastanhouror
more before it resumes its previous motion. The storm
should be considered severe while this erratic motion
is in progress.
2. Splitting Echoes.Sometimes alarge (20-mile or
larger diameter) echo splits into two echoes. The
southernmost echo often slows, turns to the right of its
previous motion, and becomes severe with large hail
and extreme turbulence.
If atornado develops, it is usually at the right rear
portionofthesouthernecho.Whenthestormweakens,
it usually resumes its original direction of movement.
The northern echo moves left of the mean wind,
increases speed and often produces large hail and
extreme turbulence.
3. Merging Echoes.Merging echoes sometimes
become severe, but often the circulation of the
merging cells interfere with each other preventing
intensification. The greatest likelihood of aviation
hazards is at the right rear section of the echo.
Severe Weather Avoidance Procedures
Table 5-12 (cont)
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5-60
Step Procedure
11 Never continue flight towards or into aradar
shadow or the blue REACT field.
WARNING
STORMS SITUATED BEHIND INTERVENING RAIN-
FALL MAYBE MORE SEVERE THAN DEPICTED ON
THE DISPLAY.
If the radar signal can penetrate astorm, the target
displayed seems to cast ashadow with no visible
returns. This indicates that the storm contains agreat
amount of rain, that attenuates the signal and prevents
the radar from seeing beyond the cell under observation.
The REACT blue field shows areas where attenuation
could be hiding severe weather.Both the shadow and
the blue field are to be avoided by 20 miles. Keep the
REACT blue field turned on. The blue field will form
fingers that point towards the stronger cells.
Severe Weather Avoidance Procedures
Table 5-12
Configurations of Individual Echoes (Northern
Hemisphere)
Sometimes alarge echo will develop configurations which are
associated with particularly severe aviation hazards. Several of these
are discussed below.
AVOID HOOK ECHOES BY 20 MILES
The hook is probably the best known echo associated with severe
weather.Itis an appendage of athunderstorm echo and usually only
appears on weather radars. Figure 5-42 shows ahook echo.
PRIMUS
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5-61
N
AD-15560-R1@
Typical Hook Pattern
Figure 5-42
The hooks are located at the right rear side of the thunderstorm echo’s
direction of movement (usually the southwest quadrant).
The hook is not the tornado echo! Asmall scale low pressure area is
centered at the right rear side of the thunderstorm echo near its edge.
The low usually ranges from about 3to 10 miles in diameter.
Precipitation is drawn around the low’scyclonic circulation to form the
characteristic hook shape. Tornadoes form within the low near hook.
AccordingtostatisticsfromtheNSSL,almost60percentofallobserved
hookechoeshavetornadoesassociatedwiththem.Atornadoisalways
suspected when ahook echo is seen.
Ahook can form with no tornadoes and vice versa. However,when a
bona fide hook is observed on a weather radar,moderate or greater
turbulence,strongshifting surfacewinds, andhail areoften nearbyand
aircraft should avoid them.
PRIMUS
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5-62
There are many patterns on radar that resemble hook echoes but are
not associated with severe weather.Severe weather hook echoes last
at least 5minutes and are less than 25 miles in diameter.The favored
location for hook echoes is to the right rear of alarge and strong cell,
however,in rare cases tornadoes occur with hooks in other parts of the
cell.
AVOID V-NOTCH BY 20 MILES
Alarge isolated echo will sometimes have the configuration that is
shown in figure 5-43. This echo is called V-notch or flying eagle
although some imagination may be needed by the reader to see
the eagle. V-notch echoes are formed by the wind pattern at the
leading edge (left front) of the echo. Thunderstorm echoes with
V-notches are often severe, containing strong gusty winds, hail,
or funnelclouds,butnotallV-notchesindicatesevere weather.Again,
severe weather is most likely at Sin figure 5-43.
N
v
secho movement
AD-15561-R1@
V-Notch Echo, Pendant Shape
Figure 5-43
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5-63
AVOID PENDANT BY 20 MILES
The pendant shape shown in figure 5-44, represents one of the
most severe storms -the supercell. One study concluded that, in
supercells:
DThe average maximum size of hail is over 2inches (5.3 cm)
DThe average width of the hail swath is over 12.5 miles (20.2 km)
DSixty percent produce funnel clouds or tornadoes.
The classic pendant shape echo is shown in figure 5-44. Note the
general pendant shape, the hook, and the steep rain gradient. This
storm is extremely dangerous and must be avoided.
STORM MOTION
N
AD-35706@
The Classic Pendant Shape
Figure 5-44
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5-64
AVOID STEEP RAIN GRADIENTS BY 20 MILES
Figure 5-45 shows steep rain gradients. Refer to the paragraph,
Interpreting Weather Radar Images, this section, for adetailed
explanation of weather images.
Rain Gradients
Figure 5-45
AVOID ALL CRESCENT SHAPED ECHOES BY 20 MILES
Acrescent shaped echo, shown in figure 5-46, with its tips pointing
away from the aircraft indicates astorm cell that has attenuated the
radar energy to the point where the entire storm cell is not displayed.
This is especially true if the trailing edge is very crisp and well defined
with what appears to be a steep rain gradient.
When REACT is selected, the area behind the steep rain gradient fills
in with cyan.
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5-65
10 20 30
40
50
AD-22161-R1@
Crescent Shape
Figure 5-46
Line Configurations
AVOID THUNDERSTORM ECHOES ATTHE SOUTH END OF A
LINE OR ATABREAK IN ALINE BY 20 MILES
The echo at the south end of aline ofechoes isoften severeand sotoo
is the storm on the north side of abreak in line. Breaks frequently fill in
and are particularly hazardous for this reason. Breaks should be
avoided unless they are 40 miles wide. This is usually enough room to
avoid thunderstorm hazards.
Theabovetwolocationsfavorseverethunderstormformation sincethese
stormshaveless competition forlowlevelmoisturethan othersnearby.
PRIMUS
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5-66
AVOID LINE ECHO WAVE PATTERNS (LEWP) BY 20 MILES
One portion of aline may accelerate and cause the line to
assume awave-like configuration. Figure 5-47 is an example of an
LEWP.The most severe weather is likely at S.LEWPs form solid or
nearly solid lines that are dangerous to aircraft operations and
disruptive to normal air traffic flow.
N
AD-15562-R1@
S
Line Echo Wave Pattern (LEWP)
Figure 5-47
The Sindicates the location of the greatest hazards to aviation. The
nextgreatest probabilityis anywherealong theadvancing (usuallyeast
or southeast) edge of the line.
PRIMUS
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5-67
AVOID BOW-SHAPED LINE OF ECHOES BY 20 MILES
Sometimes afast moving, broken to solid thunderstorm line will
become bow-shapedas shown in figure5-48.Severeweather ismost
likely along the bulge and at the north end, but severe weather can
occur at any point along the line. Bow-shaped lines are particularly
disruptive to aircraft operations because they are broken to solid and
may accelerate to speeds in excess of 70 knots within an hour.
NVIP 1
VIP 3
VIP 5
S
100 mi
AD-15563-R1@
Bow-Shaped Line of Thunderstorms
Figure 5-48
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5-68
Additional Hazards
TURBULENCE VERSUS DISTANCE FROM STORM CORE
The stronger the return, the further the turbulence will be encountered
from the storm core at any altitude. Severe turbulence is often found in
the tenuous anvil cloud 15 to 20 miles downwind from asevere storm
core.Moreover,thestormcloudis onlythevisibleportionofaturbulent
system whose up and down drafts often extend outside of the storm
proper.
TURBULENCE VERSUS DISTANCE FROM STORM EDGE
Severe clear-airturbulence can occur near astorm, most oftenon the
downwind side. Tornadoes are located in avariety of positions with
respect to associated echoes, but many of the most intense and
enduringoccurontheup-relative-windside.The airrisinginatornado
can contribute to adownwind area of strong echoes, while the tornado
itself may or may not return an echo. Echo hooks and appendages,
though useful indexes of tornadoes, are not infallible guides.
Theappearanceofahookwarnsthepilottostayaway,butjustbecause
the tornado cannot be seen is no assurance that there is no tornado
present.
Expect severe turbulence up to 20 NM away from severe storms; this
turbulence often has awell-defined radar echo boundary.This
distance decreases somewhat with weaker storms that display
less well-defined echo boundaries.
The last section of this manual contains several advisory circulars. It is
recommended that the pilot become familiar with them.
PRIMUS
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A28-1146-102-00 Radar Facts
5-69
GROUND MAPPING
Ground mapping operation is selected with the GMAP button An
example of ground map display is shown in figure 5-49.Turn the TILT
control down until the desired amount of terrain is displayed. The
degreeofdown-tiltwilldependuponthetype ofterrain,aircraftaltitude,
and selected range. Tables 5-13and 5-5show tilt settings for maximal
ground target display at selected ranges.
Ground Mapping Display
Figure 5-49
Forthe lowranges(5,10,25,and 50 NM), the transmitterpulsewidthis
narrowed and the receiverbandwidthiswidened to enhancethe
identification ofsmall targets. In addition, the receiverSTCcharacteristics
are altered to betterequalize ground targetreflections versusrange.As
aresult, the presetgain position isgenerallyused to displaythe desired
map.The pilotcan manuallydecreasethe gainto eliminate unwanted
clutter.
PRIMUS
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Digital
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A28-1146-102-00
Radar Facts
5-70
RANGE
SCALE
(NM)
ALTITUDE
(FEET)
10 25 50 100 200 LINE OF
SIGHT
(NM)
40,000
35,000
30,000
25,000
20,000
15,000
10,000
5,000
4,000
3,000
2,000
1,000 -5-4
-13
-9
-8
-7
-6-5-4
-5
-5
-5
-5-6-8
-6
-6
-5
-10 -7-6
-11 -8-6
-12 -8
-7
-11 -8
-7-10
-9-13
246
230
213
195
174
151
123
87
78
67
55
39
(LINE OF SIGHT LIMITED REGION)
(TILT LIMITED
REGION)
AD-35710@
TILTSetting for Maximal Ground Target Display
12-Inch Radiator
Table 5-13
NOTE: The line ofsightdistanceisnominal.Atmospheric conditions
and terrainwill offset this value.
PRIMUS
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A28-1146-102-00 Radar Facts
5-71/(5-72 blank)
RANGE
SCALE
(MILES)
ALTITUDE
(FEET)
5 10 25 50 100 200 LINE OF
SIGHT
(MILES)
40,000
35,000
30,000
25,000
20,000
15,000
10,000
5,000
4,000
3,000
2,000
1,000 +1 +2 +2
-1
-3
-5
-7
-12
-7
-2
-1
0
+1 +2 +2
+2
+2
+1
+10-1
0
+1
+1
-3-1+1
-5-1 0
-13 -5-2-1
0
0
0
-11 -4-1
-1-9-3
-2-7
246
230
213
195
174
151
123
87
78
67
55
39
(LINE OF
SIGHT LIMITED REGION)
(TILT LIMITED
REGION)
AD-35711@
TILTSetting for Maximal Ground Target Display
18-Inch Radiator
Table 5-14
NOTES: 1. The line ofsightdistanceisnominal.Atmospheric
conditionsand terrainwill offset this value.
2. Tilt management for 24-inch radiator installation
operates in asimilar manner.
PRIMUS
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A28--1146--102--03
REV 3 6-1/(6-2 blank)
Maximum Permissible Exposure Level (MPEL)
6. Maximum Permissible Exposure
Level (MPEL)
Heating and radiation effects of weather radar can be hazardous to life.
Personnel should remain at a distance greater than Rfrom the radiating
antenna in order to be outside of the envelope in which radiation
exposure levels equal or exceed 10 mW/cm
2
, the limit recommended
in FAA Advisory Circular AC No. 20--68B, August 8, 1980, Subject:
Recommended Radiation Safety Precautions for Ground Operation of
Airborne Weather Radar. The radius, R, to the maximum permissible
exposure level boundary is calculated for the radar system on the basis
of radiator diameter, rated peak--power output, and duty cycle. The
greater of the distances calculated for either the far--field or near--field
is based on the recommendations outlined in AC No. 20--68B. The
advisory circular is reproduced without Appendix 1 in Appendix A of this
guide.
The American National Standards Institute (ANSI), in their document
ANSI C95.1--1982, recommends an exposure level of no more than
5mW/cm
2
.
Honeywell recommends that operators follow the 5 mW/cm
2
standard.
Figure 6--1 shows MPEL for both exposure levels.
MPEL Boundary
Figure 6--1
PRIMUS
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Digital
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System
A28-1146-102-00 In-Flight Troubleshooting
7-1
7. In-Flight Troubleshooting
The PRIMUSÒ880 Digital Weather Radar System can provide
troubleshooting information on one of two formats:
DFault codes
DText faults.
The selection is made at the time of installation. This section describes
access and use of this information.
If the fault codes option is selected, they are shown in place of the tilt
angle.ThetextfaultoptionprovidesEnglishtextintheradartestpattern
areas.
Critical functions in the receiver transmitter antenna (RTA) are
continuously monitored. Each fault condition has acorresponding
2-digitfault code (FC). Additionally,afault name, apilot message, and
aline maintenance message are associated with each fault condition.
Faults can be accessed on the ground, or while airborne. The following
conditions indicate that fault information is being displayed:
DDisplay,indicator,or RTAmalfunction
DFAIL annunciation on weather indicator or EFIS display.
If the feature TEXT FAULTS is enabled, the radar test pattern area will
display plan English text fault information. If it is not enabled, only the
fault code is shown (one at atime) on the indicator or EFIS display.
PRIMUS
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A28-1146-102-00
In-Flight Troubleshooting
7-2
NOTES: 1. FC installations with aradar indicator can display
stored faults for the current power-on cycle and nine
previous cycles. Installations with radar displayed on
the electronic flight instrument system (EFIS) do not
display stored faults.
2. In FC installation, that use aradar indicator,when the
storage memory is full, the indicator fault storage
deletes theoldest power-onfault codesto makeroom
for the newest.
3. In EFIS installations, some weather failures are only
annunciated with an amber WX.
4. In EFIS installations, with TEXT FAULTS enabled,the
fault codes are also presented as part of the FAIL
annunciation (e.g., FAIL 13).
Test Mode With TEXT FAULTS Enabled
Upon entering test mode, the most recent fault is displayed, cycling to
the oldest fault in the eligible list of faults. Upon reaching the last fault
an END OF LIST message is displayed. Torecycle through the list
again, exit and re-enter TEST mode.
PRIMUS
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880
Digital
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Radar
System
A28-1146-102-00 In-Flight Troubleshooting
7-3
Table 7-1describes the six fault data fields that are displayed in figure
7-1.
Field No. Description
1Pilot Message
2Line Maintenance Message
3Fault Code/Power-on Code
4Fault Name
5Transmit ON/OFF
6Strap Code
NOTES: 1. If airborne, only fault fields 1, 2, and 3 are
displayed.
2. Airborne, only the current faults are displayed.
3. Strap codes indicate the installation configuration
that was done at the time of installation. Refer to
the System Description and Installation manual for
further explanation.
Fault Data Fields
Table 7-1
Thelast32faultsfromthelast10power-oncyclesarecycledeverytwo
antenna sweeps (approximately 8seconds).
0.0 100
60
40
20
RCT/T
WEATHER INDICATOR
1 2 3 4
AD-46709@
PILOT
MESSAGE
FIELD
FAULTCODE/
POWER ON
COUNT
TRANSMIT
ON/OFF
FAULT
DISPLAY
MESSAGE
DIVIDER
LINE
MAINTENANCE
MESSAGE
FAULT
NAME
STRAP
CODE
Fault Annunciation on Weather Indicator With TEXT FAULT
Fields
Figure 7-1
PRIMUS
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880
Digital
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A28-1146-102-00
In-Flight Troubleshooting
7-4
Figure 7-2shows the fault codes displayed on EFIS with text faults
disabled.
AD-35708-R1@
VOR1
VOR2
FAIL
22
HDG
319 25
15
DTRK
315
GSPD
MAG1 321 TGT FMS1
130 NM
V
260 KTS
50
Fault Code on EFIS Weather Display
With TEXT FAULTS Disabled
Figure 7-2
Radar Indication With Text Fault Enabled (On Ground)
Figure 7-3
PRIMUS
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Digital
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A28-1146-102-00 In-Flight Troubleshooting
7-5
Fault Code and Text Fault Relationships
Table 7-2lists the relationship between:
DFault codes (FC)
DPilot/Maintenance Messages
DFault Name/type/description/cross reference (XREF).
FC XREF FAULTDESCRIPTION FAULTNAME PILOT
MSG LINE
MAINT FAULTTYPE
4808 Startup Code CRC
4809 IOP Code CRC
01 4810 DSP Code CRC FLASH CRC RADAR
FAIL PULL
RTAPOWER ON
4904 Config Table CRC
4905 FPGA Firmware CRC
4846 2V ADC Reference CONTINUOUS
4903 IOP Ready IOP RADAR
FAIL PULL
RTA
02 4908 Int ARINC 429
Loopback POWER ON
4910 Spurious ARINC
Interrupt IOP RADAR
FAIL PULL
RTACONTINUOUS
4913 ARINC 429 In Coupling IOP RADAR
FAIL PULL
RTAPOWER ON
4806 EEPROM Timer CRC FLASH CRC POWER ON
03 4811 EEPROM POC RADAR
FAIL PULL
RTAPOWER ON
4842 Stab Trim CRC EEPROM REDO
STAB
TRIM
REDO
STAB
TRIM POWER ON
4912 Calibration CRC IOP RADAR
FAIL PULL
RTA
4812 IOP Mailbox
04 4818 DSP Mailbox MAILBOX RAM RADAR
FAIL PULL
RTAPOWER ON
4813 Timing FPGA RAM
4814 Timing FPGA REG
05 4815 IO FPGA RAM FPGA RADAR
FAIL PULL
RTAPOWER ON
Text Faults
Table 7-2(cont)
PRIMUS
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Digital
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A28-1146-102-00
In-Flight Troubleshooting
7-6
FC FAULTTYPELINE
MAINT
PILOT
MSG
FAULTNAMEFAULTDESCRIPTIONXREF
4828 FPGA Download
4906 IO FPGA REG
06 4847 STC Monitor STC DAC RADAR
FAIL PULL
RTAPOWER ON
07 4830 HVPS Monitor HVPS MON RADAR
FAIL PULL
RTACONTINUOUS
4816 DSP RAM
4817 DSP Video RAM POWER ON
4855 DSP Watchdog CONTINUOUS
10 4900 Mailbox Miscompare DSP RADAR
FAIL PULL
RTA
4901 DSP Holda Asserted POWER ON
4902 DSP Holda not
Asserted
4825 Filament Monitor
11 4827 Severe Magnetron MAGNETRON RADAR
FAIL PULL
RTALATCHED
4829 PFN Trim Monitor HVPS MON CONTINUOUS
12 4831 Pulse Width PULSE WIDTH RADAR
UNCAL PULL
RTACONTINUOUS
13 4832 Elevation Error EL POSITION TILT
UNCAL CHK
RADOME
/RTA
CONTINUOUS
14 4833 Azimuth Error AZ POSITION AZIMUTH
UNCAL CHK
RADOME
/RTA
CONTINUOUS
15 4836 Over Temp OVER-TEMP RADAR
CAUTION PULL
RTACONTINUOUS
16 4837 Xmitter Power XMTR POWER RADAR
UNCAL PULL
RTACONTINUOUS
4839 No SCI Control
20 4911 No ARINC 429 Control NO CNTL IN CHK
CNTL
SRC
CHK
CNTL
SRC
PROBE
4840 AGC Limiting PICTURE
UNCAL CONTINUOUS
21 4927 AGC Rx DAC Monitor AGC RADAR
FAIL
PULL
RTAPOWER ON
4928 AGC Tx DAC Monitor
Text Faults
Table 7-2(cont)
PRIMUS
r
880
Digital
W
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Radar
System
A28-1146-102-00 In-Flight Troubleshooting
7-7
FC FAULTTYPELINE
MAINT
PILOT
MSG
FAULTNAMEFAULTDESCRIPTIONXREF
22 4841 Selftest OSC Failure RCVR
SELF-TEST PICTURE
UNCAL PULL
RTACONTIUOUS
4843 Multiple AFC Unlocks SPOKING
LIKELYCONTINUOUS
24 4845 AFC Sweeping AFC PULL
RTA
4929 AFC DAC Monitor
4930 AFC Trim DAC Monitor RADAR
FAIL POWER ON
27 4848 AHRS/IRS Source HS 429 STAB
UNCAL CHK ATT
SRC INSTALLATION
30 4849 DADC Source LS 429 TURB
UNCAL CHK ADC INSTALLATION
33 4852 Analog Stab Ref STAB REF STAB
UNCAL CHK ATT
SRC INSTALLATION
34 4853 Scan Switch Off SCAN SWITCH SCAN
SWITCH CHK
SWITCH INSTALLATION
35 4854 Xmit Switch Off XMIT SWITCH XMIT
SWITCH CHK
SWITCH INSTALLATION
4914 Invalid
altitude/airspeed/stab
strapping INVALID
STRAPS RADAR
UNCAL CHK
STRAPS
36 4915 Invalid controller source
strapping POWER ON
4916 Config1 database
version/size mismatch IOP RADAR
FAIL PULL
RTA
Text Faults
Table 7-2
PRIMUS
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Digital
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System
A28-1146-102-00
In-Flight Troubleshooting
7-8
Table 7-3describes the pilot messages.
Pilot MSG Description
RADAR FAIL The radar is currently inoperable and should not be
relied upon. It will need to be replaced or repaired at
the next opportunity.
RADAR CAUTION Afailure has been detected that can compromise the
calibration accuracy of the radar.Information from the
radar should be used only for advisory purposes such
as ground mapping for navigation.
PICTURE UNCAL The radar functions are ok, but receiver calibration is
degraded. Color level calibration should be assumed
to be incorrect.
Have the RTAchecked at the next opportunity.
TILTUNCAL An error in the antenna position system has been
detected. The displayed tilt angle setting could be
incorrect. This may also cause ground spoking.
Have the RTAchecked at the next opportunity.
TURB UNCAL Aproblem has been detected with the turbulence
detection hardware. Assume turbulence display to be
inaccurate. Nonturbulence modes should be
functioning properly.
Have the RTAchecked at the next opportunity.
SPOKING LIKELY A problem has been detected which may cause
spoking to occur.
Have the system checked at the next opportunity.
STAB UNCAL An error in the antenna positioning system has been
detected. Groundspoking, or excessive ground
returns during roll maneuvers may occur.This may be
due either to the RTAor the source of pitch and roll
information to the RTA.
NO AUTOTILTNo altitude information is available to make the
altitude compensated tilt calculation. Otherwise, the
unit may be operated as normal. Have system
(including altitude source) checked at the next
opportunity.
SCAN SWITCH The SCAN SWITCH located on the RTAis off,
disabling the antenna scan. Check at the next
opportunity.
XMIT SWITCH The XMIT switch located on the RTAis off, disabling
the transmitter.Check at the next opportunity.
Pilot Messages
Table 7-3
PRIMUS
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880 Digital Weather Radar System
A28--1146--102--03
REV 3 8-1
Honeywell Product Support
8. Honeywell Product Support
The Honeywell SPEX
R
program for corporate operators provides an
extensive exchange and rental service that complements a worldwide
network of support centers. An inventory of more than 9,000 spare
components assures that the Honeywell equipped aircraft will be
returned to service promptly and economically. This service is available
both during and after warranty.
The aircraft owner/operator is required to ensure that units provided
through this program have been approved in accordance with their
specific maintenance requirements.
All articles are returned to Reconditioned Specifications limits when
they are processed through a Honeywell repair facility. All articles are
inspected by quality control personnel to verify proper workmanship
and conformity to Type Design and to certify that the article meets all
controlling documentation. Reconditioned Specification criteria are on
file at Honeywell facilities and are available for review. All exchange
units are updated with the latest performance reliability MODs on an
attrition basis while in the repair cycle.
For more information regarding the SPEX program, including
maintenance, pricing, warranty, support, and access to an electronic
copy of the Exchange/Rental Program for Corporate Operators, Pub.
No. A65--8200--001, you can go to the Honeywell web site at:
http://www.avionicsservices.com/home.jsp
PRIMUS
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A28--1146--102--03
REV 3
Honeywell Product Support
8-2
CUSTOMER SUPPORT
Honeywell Aerospace Online Technical Publications
Web Site
Go to the Honeywell Online Technical Publications Web site at
https://pubs.cas.honeywell.com/ to:
DDownload or view publications online
DOrder a publication
DTell Honeywell of a possible data error in a publication.
Customer Response Center (CRC)
If you do not have access to the Honeywell Online Technical
Publications Web site, send an e--mail message or a fax, or speak to
a person at the CRC:
DE--mail: cas--publications--distribution@honeywell.com
DFax: 1--602--822--7272
DPhone: 1--877--484--2979 (USA)
DPhone: 1--602--436--0272 (International).
Also, the CRC is available if you need to:
DIdentify a change of address, telephone number, or e--mail address
DMake sure that you get the next revision of this guide.
PRIMUS
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880 Digital Weather Radar System
A28--1146--102--03
REV 3 9-1
Abbreviations
9. Abbreviations
Acronyms and abbreviations used in this guide are defined as follows:
ABBREVIATION EQUIVALENT
AC Advisory Circular
ACT Altitude Compensated Tilt
ADC Air Data Computer
AFC Automatic Flight Control
AGC Automatic Gain Control
AGL Above Ground Level
AHRS Attitude Heading Reference System
ANLG Analog
ANSI American National Standards Institute
API Antenna Position Indicator
ATT Attitude
AZ Azimuth
BITE Built--in Test Equipment
BRT Brightness
ccw Counterclockwise
CHK Check
CLR Clear
CNTL Control
CONFIG Configuration
CRC Cyclic Redundancy Check
CRT Cathode Ray Tube
cw Clockwise
DADC Digital Air Data Computer
DSP Display
EFIS Electronic Flight Instrument System
EGPWS Enhanced Ground--Proximity Warning System
EHSI Electronic Horizontal Situation Indicator
EL Elevation
FAA Federal Aviation Administration
FC Fault Code
PRIMUS
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A28--1146--102--01
REV 1
Abbreviations
9-2
FLTPLN, FP,
FPLN
Flight Plan
FMS Flight Management System
FPGA Field--Programmable Gate Array
FSBY Forced Standby
ft Feet
GCR Ground Clutter Reduction
GMAP Ground Mapping
GPS Global Positioning System
hr hour
HVPS High Voltage Power Supply
INHIB Inhibit
IO Input/Output
IOP Inoperative
IN Inch
IRS Inertial Reference System
kt, kts Knot(s)
LEWP Line Echo Wave Pattern
LSS, LX Lightning Sensor System
MFD Multifunction Display
mm millimeter
MON Monitor
MPEL Maximum Permissible Exposure Level
NAV Navigation
ND Navigation Display
NM Nautical Miles
NSSL National Severe Storms Laboratory
NWS National Weather Service
OSC Oscillator
PPI Plan--Position Indicator
PPP Pulse Pair Processing
PRIMUS
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880 Digital Weather Radar System
A28--1146--102--01
REV 1 9-3/(9-4 blank)
Abbreviations
RCT, REACT Rain Echo Attenuation Compensation Technique
RCVR Receiver
RTA Receiver Transmitter Antenna
SBY,STBY Standby
SCI Serial Control Interface
SCT, SECT Scan Sector
SECT Sector Scan
SLV Slave
SPEX Spares Exchange
SRC Source
STAB Stabilization
STC Sensitivity Timing Control
TCAS Traffic Alert and Crew Alerting System
TERR Terrain
TGT Target
TRB Turbulence
TRV Total Return Vector
TST Test
TURB Turbulence
UDI Universal Digital Interface
UNCAL Uncalibration
VAR Variable, Variance
VIP Video Integrated Processor
WOW Weight--on--Wheels
WX Weather
XMIT, XMTR Transmitter
XSTC Extended Sensitivity Timing Control
PRIMUS
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880
Digital
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Radar
System
A28-1146-102-00 Federal Aviation Administration (FAA) Advisory Circulars
A-1
Appendix A
Federal Aviation Administration
(FAA) Advisory Circulars
NOTE: This section contains aword-for-word transcription of the
contents of the following FAA advisory circulars:
DAC 20-68B
DAC 00-24B.
SUBJECT:RECOMMENDED RADIATION SAFETY
PRECAUTIONSFOR GROUND
OPERATION OFAIRBORNEWEATHER
RADAR
Purpose
Thiscircularsetsforthrecommendedradiationsafetyprecautionstobe
taken by personnel when operating airborne weather radar on the
ground.
Cancellation
AC 20-66A, dated April 11, 1975, is cancelled.
Related Reading Material
Barnes and Taylor,radiation Hazards and Protection (London: George
Newnes Limited, 1963), p. 211.
U.S. Department of Health, Education and Welfare, Public Health
Service, Consumer Protection and Environmental Health Service,
”Environmental health microwaves, ultraviolet radiation, and radiation
from lasers and television receivers -An Annotated Bibliography,”FS
2.300: RH-35, Washington, U.S. Government Printing Office, pp
56-57.
Mumford, W.W., ”Some technical aspects of microwave radiation
hazards,”Proceedings of the IRE, Washington, U.S. Government
Printing Office, February 1961, pp 427-447.
PRIMUS
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Digital
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Radar
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A28-1146-102-00
Federal Aviation Administration (FAA) Advisory Circulars
A-2
Background
Dangers from ground operation of airborne weather radar include the
possibilityofhumanbodydamageandignitionofcombustiblematerials
by radiated energy.Low tolerance parts of the body include the eyes
and the testis.
Precautions
Management and supervisory personnel should establish procedures
for advising personnel of dangers from operating airborne weather
radars on the ground. Precautionary signs should be displayed in
affected areas to alert personnel of ground testing.
GENERAL
DAirborne weather radar should be operated on the ground only by
qualified personnel.
DInstalled airborne radar should not be operated while other aircraft
isinthehangarorotherenclosureunlesstheradartransmitterisnot
operating, or the energy is directed toward an absorption shield
which dissipates the radio frequency energy.Otherwise, radiation
within the enclosure can be reflected throughout the area.
BODY DAMAGE
Toprevent possible human body damage, the following precautions
should be taken:
DPersonnelshouldneverstandnearbyandinfrontofaradarantenna
whichistransmitting. Whentheantennaisnotscanning,thedanger
increases.
DArecommended safe distance from operating airborne weather
radars should be established. Asafe distance can be determined
by using the equations in Appendix 1or the graphs of figures 1 and
2. This criterion is now accepted by many industrial organizations
and is based on limiting exposure of humans to an average power
density not greater than 10 milliwatts per square centimeter.
DPersonnelshouldbeadvisedtoavoidtheendof anopenwaveguide
unless the radar is turned off.
DPersonnel should be advised to avoid looking into awaveguide, or
into the open end of acoaxial connector or line connector to aradar
transmitter output, as severe eye damage may result.
PRIMUS
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Radar
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A28-1146-102-00 Federal Aviation Administration (FAA) Advisory Circulars
A-3
DPersonnel should be advised that when high power radar
transmitters are operated out of their protective cases, X-raysmay
be emitted. Stray X-rays may emanate from the glass envelope
type pulser,oscillator,clipper,or rectifier tubes, as well as
magnetrons.
COMBUSTIBLE MATERIALS
Toprevent possible fuel ignition, an insulated airborne weather radar
should not be operated while an aircraft is being refueled or defueled.
M.C. Beard
Director of Airworthiness.
PRIMUS
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Digital
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Radar
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A28-1146-102-00
Federal Aviation Administration (FAA) Advisory Circulars
A-4
SUBJECT:THUNDERSTORMS
Purpose
This advisory circular describes the hazards of thunderstorms to
aviation and offers guidance to help prevent accidents caused by
thunderstorms.
Cancellation
Advisory Circular 00-24A, dated
June 23, 1978, is cancelled.
Related Reading Material
Advisory Circulars, 00-6A, Aviation Weather,090-45B, Aviation
Weather Services, 00-50A, Low Level Wind Shear.
General
Weall know what athunderstorm looks like. Much has been written
aboutthemechanicsandlifecyclesofthunderstorms. Theyhavebeen
studied for many years; and while much has been learned, the studies
continue because much is not known. Knowledge and weather radar
have modified attitudes toward thunderstorms, but one rule continues
to be true -any storm recognizable as athunderstorm 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.
Hazards
Athunderstorm packs just about every weather hazard known to
aviation into one vicious bundle. Although the hazards occur in
numerouscombinations,letuslookatthemosthazardouscombination
of thunderstorm, the squall line, then we will examine the hazards
individually.
SQUALL LINES
Asqualllineisanarrowbandofactivethunderstorms. Oftenitdevelops
on or ahead of acold 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.
PRIMUS
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Digital
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A28-1146-102-00 Federal Aviation Administration (FAA) Advisory Circulars
A-5
TORNADOES
DThe most violent thunderstorms draw into their cloud bases with
greatvigor. Iftheincoming airhas any initial rotatingmotion, itoften
forms an extremely concentrated vortex from the surface well into
thecloud. Meteorologists haveestimated thatwind insuch avortex
can exceed 200 knots; pressure inside the vortex is quite low.The
strongwindsgatherdustanddebrisandthelowpressuregenerates
afunnelshapedcloudextendingdownwardfrom thecumulonimbus
base. If the cloud does not reach the surface, it is afunnel cloud;
if it touches the land surface, it is atornado.
DTornadoes occur with both isolated and squall line thunderstorms.
Reports for forecasts of tornadoes indicate that atmospheric
conditions are favorable for violent turbulence. An aircraft entering
atornadovortexisalmostcertaintosufferstructuraldamage. Since
the vortex extends wellinto thecloud, anypilot inadvertentlycaught
on instruments in asevere thunderstorm, could encounter ahidden
vortex.
DFamilies 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 asevere
thunderstorm carries athreat of violence.
TURBULENCE
DPotentially hazardous turbulence is present in all thunderstorms,
and a severe thunderstorm can destroy an aircraft. Strongest
turbulence within the cloud occurs with shear between updraftsand
downdrafts. Outside the cloud, shear turbulence has been
encountered several thousand feet above and 20 miles laterally
from asevere thunderstorm. Alow level turbulent area is the shear
zoneassociatedwiththegustfront. Often,arollcloudontheleading
edge of astorm marks the top of the eddies in this shear and it
signifies an extremely turbulent zone. Gust fronts move far ahead
(up to 15 miles) of associated precipitation. The gust front causes
arapid 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. Figure1showsaschematiccross sectionof athunderstorm
withareasoutsidethecloudwhereturbulencemaybeencountered.
DIt is almost impossible to hold aconstant altitude in athunderstorm,
and maneuvering in an attempt todo soproduces greatlyincreased
stress on the aircraft. It is understandable that the speed of the
aircraft determines the rate of turbulence encounters. Stresses are
least if the aircraft is held in aconstant attitude and allowed to ride
the waves. Todate, we have no sure way to pick soft spots in a
thunderstorm.
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ICING
DUpdrafts in athunderstorm support abundant liquid water with
relatively large droplet sizes; and when carried above the freezing
level, the water becomes supercooled. When temperature in the
upward current cools to about -15_C, much of the remaining water
vapor sublimates as ice crystals; and above this level, at lower
temperatures, the amount of supercooled water decreases.
DSupercooled water freezes on impact with an aircraft. Clear icing
can occur at any altitude above the freezinglevel; butat highlevels,
icingfromsmallerdropletsmayberimeormixedwithrimeandclear.
The abundance of large, supercooled droplets makes clear icing
very rapid between O_Cand -15 _Cand encounters can be
frequent in acluster of cells. Thunderstorm icing can be extremely
hazardous.
NAUTICAL MILES
0 5 10 15
WAKE
WAKE
GUST FRONT
MOTION OF STORM
WARM AIR INFLOW
COLD AIR OUTFLOW
AD-37561@
DRY AIR
INFLOW
COLD
AIR
OUTFLOW
WARM AIR
INFLOW
Schematic Cross Section of aThunderstorm
Figure A-1
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HAIL
DHail competes with turbulenceas thegreatest thunderstormhazard
to aircraft. Supercooled drops above the freezing level begin to
freeze. Once adrop has frozen, other drops latch on and freeze to
it,sothehailstonegrows-sometimesintoahugeiceball. Largehail
occurs with severe thunderstorms with strong updrafts that have
built to great heights. Eventually,the hailstones fall, possibly some
distance from the storm core. Hail may be encountered in clear air
several miles from dark thunderstorm clouds.
DAshailstonesfallthroughairwhosetemperatureisabove0_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 hailaloft.
You should anticipate possible hail with any thunderstorm,
especially beneath the anvil of alarge cumulonimbus. Hailstones
larger than one-half inch in diameter can significantly damage an
aircraft in afew seconds.
LOW CEILING AND VISIBILITY
Generally,visibility is near zero within athunderstorm cloud. Ceiling
and visibility may also be restricted in precipitation 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
increasedmanyfoldwhenassociatedwithother thunderstormhazards
ofturbulence,hail,andlightningwhichmakeprecisioninstrumentflying
virtually impossible.
EFFECT ON ALTIMETERS
Pressureusuallyfallsrapidlywiththeapproachofathunderstorm,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 acorrected altimeter setting, the altimeter
may be more than 100 feet in error.
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LIGHTNING
Alightning strike can puncture the skin of an aircraft and can damage
communication 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 by instrument or by visual reference. Nearby lightning can
also induce permanent errors in the magnetic compass. Lightning
discharges, even distant ones, can disrupt radio communications on
lowandmediumfrequencies. Thoughlightningintensityandfrequency
have no simple relationship to other storm parameters, severe storms,
as arule, have ahigh frequency of lightning.
WEATHER RADAR
Weather radar detects droplets of precipitation size. Strength of the
radar return (echo) depends on drop size and number.The greaterthe
number of drops, the stronger is the echo, and the larger the drops, the
stronger is the echo. Drop size determines echo intensity to amuch
greater extent than does drop number.Hailstones usually are covered
withafilmofwaterand, therefore,act ashuge waterdroplets givingthe
strongest of all echoes.
Numerous methods have been used in an attempt to categorize the
intensity of athunderstorm. Tostandardize thunderstorm language
betweenweatherradaroperatorsandpilots,theuseofVideoIntegrator
Processor (VIP) levels is being promoted.
The National Weather Service (NWS) radar observer is able to
objectivelydeterminestormintensitylevelswithVIPequipment. 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
turbulence is possible with lightning. VIP Level 3is strong and severe
turbulence is possible with lightning. VIP Level 4is very strong and
severe turbulence is likely with lightning. VIP Level 5is intense with
severe turbulence, lightning, hail likely,and organized surface wind
gusts. VIP Level 6is extreme with severe turbulence, lightning, large
hail, extensive wind gusts, and turbulence.
Thunderstormsbuild and dissipaterapidly.Therefore,do notattempt to
planacourse between echoes.The bestuse ofground radarinformation
istoisolate generalareasand coverage ofechoes.You mustavoid
individualstormsfromin-flightobservationseitherby visualsighting orby
airborne radar. It isbetterto avoidthe wholethunderstormarea than to
detouraround individualstormsunless theyarescattered.
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Airborne weather avoidance radar is, as its name implies, 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 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 avoidance
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 does not mean you can fly.
Remember that while hail always gives aradar echo, it may fall several
miles from the nearest cloud and hazardous turbulence may extend to
asmuchas20milesfromtheechoedge. Avoidintenseorextremelevel
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.
DO’SAND DON’TS OF THUNDERSTORM FLYING
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’sand don’ts
of thunderstorm avoidance:
DDon’tland ortake off inthe face ofan approaching thunderstorm.A
sudden gust frontoflowlevelturbulencecouldcauseloss ofcontrol.
DDon’tattempt to fly under athunderstorm even if you can see
through to the other side. Turbulence and wind shear under the
storm could be disastrous.
DDon’tfly without airborne radar into acloud mass containing
scattered embedded thunderstorms. Scattered thunderstorms not
embedded, usually can be visually circumnavigated.
DDon’ttrust the visual appearance to be a reliable indicator of the
turbulence inside athunderstorm.
DDoavoid,byatleast20miles,anythunderstormidentifiedassevere
or giving an intense radar echo. This is especially true under the
anvil of alarge cumulonimbus.
DDo circumnavigate the entire area if the area has 6/1 thunderstorm
coverage.
DDo remember that vivid and frequent lightning indicates the
probability of asevere thunderstorm.
DDo regard as extremely hazardous, any thunderstorm with tops
35,000 feet or higher,whether the top is visually sighted or
determined by radar.
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If you cannot avoid penetrating athunderstorm, the following are some
do’sBEFORE entering the storm.
DTighten your safety belt, put on your shoulder harness if you have
one, and secure all loose objects.
DPlan and hold your course to take you through the storm in a
minimum time.
DToavoidthemostcriticalicing,establishapenetrationaltitudebelow
the freezing level or above the level of -15 _C.
DVerify that pitot heat is on and turn on carburetor heat or jet engine
anti-ice. Icing can be rapid at any altitude and cause almost
instantaneous power failure and/or loss of airspeed indication.
DEstablish power settings for turbulence penetration airspeed
recommended in your aircraft manual.
DTurn up cockpit lights to highest intensity to lessen temporary
blindness from lightning.
DIf using automatic pilot, disengage altitude hold mode and speed
hold mode. The automatic altitude and airspeed controls will
increasemaneuversof theaircraft thusincreasing structuralstress.
DIf using airborne radar,tilt the antenna up and down occasionally.
This will permit you to detect other thunderstormactivity ataltitudes
other than the one being flown.
Following are some do’sand don’ts during thunderstorm penetration.
DDokeepyoureyesonyourinstruments. Lookingoutsidethecockpit
can increase danger of temporary blindness from lightning.
DDon’tchange power settings; maintain settings for the
recommended turbulence penetration airspeed.
DDo maintain constant attitude; let the aircraft ride the waves.
Maneuversin tryingto maintainconstant altitudeincrease stresson
the aircraft.
DDon’tturn back once you are in athunderstorm. Astraight course
through the storm most likely will get you out of the hazards most
quickly.In addition, turning maneuvers increase stress on the
aircraft.
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National Severe Storms Laboratory (NSSL)
Thunderstorm Research
The NSSL has, since 1964, been the focal point of our thunderstorm
research. In-flightconditions obtained from thunderstorm penetration
by controlled, especially equipped high performance aircraft are
compared by the NSSL with National Weather Service (NWS) type
ground-based radar and with newly developed doppler radar.The
following comments are based on NSSL’sinterpretation of information
and experience from this research.
RELATIONSHIP BETWEEN TURBULENCE AND REFLECTIVITY
Weather radar reflects precipitation such as rain and hail, turbulence.
It has been found, however,that the intensity level of the precipitation
reflection does correlate with the degree of turbulence in a
thunderstorm. The most severe turbulence is not necessarily found at
the same place that gives the greatest radar reflection.
RELATIONSHIP BETWEEN TURBULENCE AND ALTITUDE
TheNSSLstudiesofthunderstormsextendingto60,000feetshowlittle
variation of turbulence intensity with altitude.
TURBULENCEAND ECHOINTENSITYON NWSRADAR (WSR-57)
The frequency and severityof turbulenceincreaseswithradar reflectivity,
ameasure of the intensityofechoesfromstormtargetsatastandard
range.Derived gustvelocitiesexceeding2,100 feetperminute(classified
as severeturbulence)arecommonlyencountered inlevel3storms. In
level2storms,gustsofintensitybetween 1,200and 2,100feetperminute
(classified asmoderateturbulence)are encountered approximatelyonce
foreach 10 nauticalmilesof thunderstormflight.
TURBULENCEIN RELATIONTODISTANCEFROMSTORMCORE
NSSL dataindicatesthat the frequency and severityof turbulence
encountersdecreaseslowlywith distancefromstormcores.Significantly,
the dataindicatesthatwithin 20 milesfromthe centerofseverestorm
cores,moderatetosevereturbulenceisencountered atanyaltitudeabout
one-fifth asoften asinthe coresofLevel3 orgreaterthunderstorms.
Further,thedataindicatesthatmoderateturbulenceisencounteredatany
altitude up to10milesfromthe centeroflevel2thunderstorms.SEVERE
TURBULENCEISOFTENFOUND INTENUOUS ANVILCLOUDS15
TO20 MILES DOWNWIND FROMSEVERE STORMCORES.Our
findingsagree withmeteorologicalreasoning thatTHE STORMCLOUD
ISONLYTHE VISIBLE PORTIONOFATURBULENTSYSTEM
WHOSE UPDRAFTS AND DOWN-DRAFTSOFTENEXTEND
OUTSIDEOF THE STORMPROPER.
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TURBULENCE IN RELATION TODISTANCE FROM THE STORM
EDGE
THECLEARAIRONTHEINFLOWSIDEOFA STORMIS A PLACE
WHERE SEVERETURBULENCEOCCURS.At theedge ofacloud,the
mixingofcloudyandclearairoftenproducesstrongtemperaturegradients
associatedwithrapidvariationofverticalvelocity.Tornadoactivityisfound
inawide range ofspacialrelationshipstothe strong echoeswithwhich
theyarecommonlyassociated,butmanyofthemostintenseandenduring
tornadoesoccuron the southtowestedgesofseverestorms.The
tornado itselfisoften associated with onlyaweakecho.Echo hooks and
appendagesareusefulqualitativeindicatorsoftornadooccurrencebutare
bynomeansinfallibleguides.Severeturbulenceshouldbeanticipatedup
to 20 milesfromthe radaredge ofseverestorms; these often have a
well-defined radarecho boundary.The distance decreasesto
approximately10 mileswithweakerstormswhichmay sometimeshave
indefiniteradarecho boundaries.THEREFORE,AIRBORNERADARIS
A PARTICULARLYUSEFULAIDFORPILOTSINMAINTAININGA
SAFEDISTANCEFROMSEVERE STORMS.
TURBULENCE ABOVE STORM TOPS
Flight data shows arelationship between turbulence above storm tops
and the airspeed of upper tropospheric winds. WHEN THE WINDSAT
STORM TOP EXCEED 100 KNOTS, THERE ARE TIMES WHEN
SIGNIFICANT TURBULENCE MAY BE EXPERIENCED AS MUCH
AS 10,000 FEET ABOVE THE CLOUD TOPS. THIS VALUE MAY BE
DECREASED 1,000 FEET FOR EACH 10-KNOT REDUCTION OF
WIND SPEED. This is especially important for clouds whose height
exceeds the height of the tropopause. It should be noted that flight
above severe thunderstorms is an academic consideration for today’s
civil aircraft in most cases, since these storms usually extend up to
40,000 feet and above.
TURBULENCE BELOW CLOUD BASE
While there is little evidence that maximum turbulence exists at middle
heights in storms (FL 200-300), turbulence beneath astorm is not to
be minimized. This is especially true when the relative humidity is low
in any air layer between the surface and 15,000 feet. Then the lower
altitudes may be characterized by strong outflowing winds and severe
turbulence where thunderstorms are present. Therefore, THE SAME
TURBULENCE CONSIDERATIONS WHICH APPLYTOFLIGHT AT
HIGH ALTITUDES NEAR STORMS APPLYTOLOW LEVELS AS
WELL.
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MAXIMUM STORM TOPS
Photographic data indicates that the maximum height attained by
thunderstormcloudsisapproximately63,000feet. Suchverytallstorm
tops have not been explored by direct means, but meteorological
judgments indicate the probable existence of large hail and strong
vertical drafts to within afew thousand feet of the top of these isolated
stratosphere-penetrating storms. THEREFORE, IT APPEARS
IMPORTANT TOAVOID SUCH VERYTALL STORMS ATALL
ALTITUDES.
HAIL IN THUNDERSTORMS
The occurrence ofHAILISMUCH MORECLEARLYIDENTIFIEDWITH
THEINTENSITYOFECHOES THANISTURBULENCE.AVOIDANCE
OFMODERATE AND SEVERE STORMS SHOULDALWAYS BE
ASSOCIATEDWITHTHE AVOIDANCEOFDAMAGINGHAIL.
VISUAL APPEARANCE OF STORM AND ASSOCIATED
TURBULENCE WITH THEM
On numerous occasions, flight at NSSL have indicated that NO
USEFUL CORRELATION EXISTS BETWEEN THE EXTERNAL
VISUAL APPEARANCE OF THUNDERSTORMS AND THE
TURBULENCE AND HAIL WITHIN THEM.
MODIFICATION OF CRITERIA WHEN SEVERE STORMS AND
RAPID DEVELOPMENT ARE EVIDENT
During severe storm situations, radar echo intensities may grow by a
factor of ten each minute, and cloud tops by 7,000 feet per minute.
THEREFORE, NO FLIGHT PATH THROUGH AFIELD OF STRONG
OR VERYSTRONG STORMS SEPARATED BY 20-30 MILES OR
LESS MAYBECONSIDERED TOREMAIN FREE FROM SEVERE
TURBULENCE.
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EXTRAPOLATION TODIFFERENT CLIMBS
General comment: Severe storms are associated with an atmospheric
stratification marked by large values of moisture in low levels, relative
dryness in middle levels, and strong wind shear. It is well known that
this stratification of moisture permits excessive magnitudes of
convective instability to exist for an indefinite period until rapid
overturning of air is triggered by asuitable disturbance. Regions of the
atmosphere which are either very dry or very moist throughout
substantial depths cannot harbor great convective instability.Rather,
amore nearly neutral thermal stratification is maintained, partially
through aprocess of regular atmospheric overturning.
DDesert Areas -In desert areas, storms should be avoided on the
same basis as described in the above paragraphs. Whilenonstorm
turbulencemay,ingeneral,beexpectedmorefrequentlyoverdesert
areas during daylight hours than elsewhere, THE SAME
TURBULENCE CONSIDERATIONS PREVAIL IN THE VICINITY
OF THUNDERSTORMS.
DTropical-HumidClimates -When the atmosphereismoistand only
slightlyunstablethough a greatdepth,strong radarechoesmaybe
received fromtowering cloudswhich do notcontainverticalvelocities
asstrongasthosefromstormsovertheU.S.plains.Thenitisamatter
of the pilotbeing informed withrespect tothe generalatmospheric
conditionsaccompanying storms, foritiswell knownthat
PRACTICALLY ALL GEOGRAPHICAREAS HAVING
THUNDERSTORMS AREOCCASIONALLY VISITEDBY SEVERE
ONES.
USE OF AIRBORNE RADAR
Airborne radar is avaluable tool; HOWEVER, ITS USE IS
PRINCIPALLY AS AN INDICATOR OF STORM LOCATIONS FOR
AVOIDANCE PURPOSES WHILE ENROUTE.
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Appendix B
Enhanced Ground--Proximity
Warning System (EGPWS)
The Mark VII EGPWS combines information from aircraft navigation
equipment (i.e., flight management system (FMS), inertial reference
system (IRS), global positioning system (GPS), radio altimeter) with a
stored terrain database that alerts the pilot to potentially dangerous
ground proximity.
In addition to the verbal alert, the EGPWS can display the terrain data
on the weather radar indicator. Depending on the installation, the pilot
pushes a button to display the terrain, or the terrain data is automatically
displayed when a Terrain Alert occurs.
SYSTEM OPERATION
To display the EGPWS, the weather system can be in any mode except
OFF. When the EGPWS is active, the indicator range up and down
arrows control the EGPWS display range. The AZ button on the
indicator is also active and the azimuth lines can be displayed or
removed.
The other radar controls do not change the terrain display, but if they
are used while the EGPWS is displayed, they control the radar receiver
transmitter antenna (RTA), and the effect is displayed when the system
returns to the radar display.
EGPWS Controls
The typical EGPWS installation has remotely mounted push button
controls and status annunciators that are related to the display on the
radar indicator. The paragraphs below give a functional description of
the recommended controls.
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B--2
Use or disclosure of the information on this page is subject to the restrictions on the title page of this document.
PUSH BUTTON CONTROLS
The following remotely mounted push buttons control the EGPWS
display:
DINHIB (Inhibit) Button -- When active, the push on/push off INHIB
button prevents terrain data from being displayed on the radar
indicator. When the button is active, the INHIB annunciator lights.
DON (Terrain) Button -- When active, the push on/push off ON button
displays terrain on the radar indicator.
ANNUNCIATORS
The following annunciators are displayed on the radar indicator to
indicate EGPWS operation:
DFAIL -- The FAIL annunciator indicates that the EGPWS has failed.
DINHIB -- The INHIB annunciator indicates that the INHIB push
button has been pushed and is active. When INHIB is annunciated,
EGPWS is not displayed on the radar indicator, and the aural
annunciators do not sound.
NOTE: The FAIL and INHIB annunciators are often incorporated
into the INHIB push button.
DTERR (Terrain) -- The TERR annunciator indicates that the
annunciator lamp power is on. It does not indicate the operational
status of the system.
DON -- The ON annunciator indicates that the radar indicator is
displaying terrain. This ON push button lamp is lit if the ON push
button has been pushed and is active, or if an actual Terrain Alert
is indicated by the EGPWS system and the terrain is automatically
displayed.
NOTE: The TERR and ON annunciators are often incorporated
into the ON push button.
Some installation may not contain all of these controls and
annunciators, or they may have different names. Most EGPWS
installations have additional controls and/or annunciators (i.e., TEST).
Refer to the appropriate publication for details.
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Related EGPWS System Operation
Some installations may have a DATA--NAV (navigation display, and/or
checklist), lightning sensor system (LSS), and/or traffic alert and crew
alerting system (TCAS) that already share the radar indicator’s display
by way of the Universal Digital Interface (UDI) connector. These
systems have priority for access to the radar display screen. These
systems data may be overlaid on the EGPWS display, or they may
simply override the EGPWS display.
EGPWS Operation
The EGPWS system may vary, depending on the installed controls and
software level of the EGPWS computer.
In some installations, the EGPWS display on the radar indicator is
manually operated. It is only displayed if the pilot pushes the ON button,
and it is removed if the pilot pushes the ON button a second time.
In some installations, the EGPWS display has a pop--up mode in which
the terrain display is automatically displayed when the EGPWS system
detects a terrain alert situation.
The pilot can remove the ground display from the radar indicator, or
prevent the EGPWS system from displaying ground on the radar
indicator by pushing the INHIB button.
The ↑and ↓range buttons on the radar indicator control the range of
the ground display. The radar indicator AZ button is active, and can
display or remove azimuth buttons. The other radar controls do not
change the ground display, but if they are used while EGPWS is
displayed, they control the radar RTA and the effects of any changes
are seen when the radar image is re--displayed.
For additional information, refer to the appropriate EGPWS operating
manual.
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EGPWS Display
The EGPWS displays is shown as variable dot patterns in green,
yellow,orred. The density and color is a function of how close the
terrain is relative to the aircraft altitude above ground level (AGL), refer
to table B--1. Terrain/obstacle alerts are shown by painting the
threatening terrain as solid or red. Terrain that is more than 2000 feet
below the aircraft is not displayed. Areas where terrain data is not
available are shown in magenta.
Elevation of Terrain in Feet
AGL Color
2000 or more above the aircraft High density red
1000 -- 2000 above the aircraft High density yellow dot pattern
0--1000 above the aircraft Medium Density yellow Dot
Pattern
0--1000 below the aircraft Medium density green dot
pattern
1000 -- 2000 below the aircraft Low density green dot pattern
2000 or more below the aircraft black
Unknown terrain Magenta
NOTE: Caution terrain (60 second warning) is displayed as solid yellow. Warning
obstacle (30 second warning) is displayed as solid red.
EGPWS Obstacle Display Color Definitions
Table B--1
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Figure B--1 shows the EGPWS over KPHX airport at 2000 feet mean
sea level heading north. The terrain shows the mountains to the north
of Phoenix.
AD--62964@
EHSI Display Over KPHX Airport
With the EGPWS Display
Figure B--1
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B--6
EGPWS Test
When the EGPWS is selected for display, it can be tested. Push the
remote mounted EGPWS TEST button to display the test format shown
in figure B--2.
AD--63056@
EGPWS Test Display
Figure B--2
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Index
Index--1
Index
A
Abbreviations, 9-1
Accelerative error, 5-18
Altitude compensated tilt, 5-16
C
Categorizing storms, 5-35
D
Dynamic error, 5-18
E
Enhanced ground--proximity
warning system (EGPWS), B--1
annunciators, B--2
FAIL, B--2
INHIB, B--2
ON, B--2
TERR, B--2
displays, B--4
obstacle display color
definitions, B--4
EGPWS test, B--6
push buttons controls, B--2
INHIB button, B--2
ON (terrain) button, B--2
system operation, B--1
controls, B--1
EGPWS operation, B--3
related EGPWS system
operation, B--3
F
Federal Aviation Administration
(FAA) Advisory Circulars
recommended radiation safety
precautions for ground
operation of airborne weather
radar, A--1
background, A--2
cancellation, A--1
precautions, A--2
purpose, A--1
related reading material, A--1
thunderstorms, A--4
general, A--4
hazards, A--4
national severe storms
laboratory (NSSL) thunder--
storm research, A--11
purpose, A--4
related reading material, A--4
H
Hidden modes, 3-26
forced standby
entry method, 3-27
exit method, 3-27
function, 3-26
roll offset, 3-26, 3-27, 3-28
entry method, 3-27
exit method, 3-27
function, 3-27
use, 3-27
Honeywell product support, 8-1
24--hour exchange/rental support
centers, 8-2
customer support centers, 8-2
North America, 8-2
Rest of the world, 8-3
publication ordering information,
8-4
PRIMUS
r
880 Digital Weather Radar System
A28--1146--102--01
REV 1
Index
Index--2
Index (cont)
I
In--flight troubleshooting, fault
access
fault data fields, 7-3
pilot messages, 7-5
test mode with TEXT FAULTS
enabled, 7-2
text faults, 7-5
Interpreting weather radar images,
5-31
N
National severe storms laboratory
(NSSL) thunderstorm
research, A--11
extrapolation to different climbs,
A--14
hail in thunderstorms, A--13
maximum storm tops, A--13
modification of criteria when
severe storms and rapid
development are evident, A--13
relationship between turbulence
and altitude, A--11
relationship between turbulence
and reflectivity, A--11
turbulence above storm tops,
A--12
turbulence and echo intensity on
NWS radar (WSR--57), A--11
turbulence below cloud base,
A--12
turbulence in relation to distance
from the storm edge, A--12
turbulence in relation to distance
from storm core, A--11
use of airborne radar, A--14
visual appearance of storm and
associated turbulence with
them, A--13
Normal operation
preliminary control settings, 4-1
power--up procedure, 4-1
radar mode ---- ground
mapping, 4-6
radar mode ---- weather, 4-4
standby, 4-4
test mode, 4-6
color bands, 4-7
dedicated radar indicator, 4-7
fault code, 4--7
EFIS/MFD/ND, 4-7
noise band, 4-6
target alert block, 4-6
text fault, 4--6
O
Operating controls
hidden modes, 3-26
roll offset, 3-26, 3-27, 3-28
WC--884 Weather radar controller
operation, 3-20
BRT (brightness), 3-20
controller target alert
characteristics, 3-21
gain, 3-25
mode, 3-23
range, 3-23
RCT (rain echo attenuation
compensation technique),
3-21
SLV (slave), 3-23
STAB (stabilization), 3-21
TGT (target alert), 3-20
TILT, 3-22
TRB (turbulence detection),
3-21
Weather radar controller
operation, 3-11
controller target alert
characteristics, 3-17
gain, 3-18
LSS (lightning sensor system)
(option), 3-19
radar, 3-13
PRIMUS
r
880 Digital Weather Radar System
A28--1146--102--01
REV 1
Index
Index--3
Index (cont)
range, 3-18
SECT (scan sector), 3-16
SLV (slave), 3-19
STB (stabilization), 3-17
TGT (target), 3-16
Tilt, 3-16
TRB (turbulence detection),
3-17
WI--880 Weather radar indicator
operation, 3-1
AZ (azimuth), 3-8
BRT (brightness) or BRT/LSS
(lightning sensor system),
3-9
display area, 3-2
function switch, 3-3
gain, 3-10
range, 3-8
RCT (rain echo attenuation
compensation technique),
3-7
SCT (scan sector), 3-8
STAB (stabilization), 3-7
target alert characteristics,
3-7
TGT (target), 3-6
tilt, 3-9
TRB (turbulence), 3-8
P
Pitch and roll trim adjustments, 5-19
Preliminary control settings, 4-1
Radar mode ---- ground mapping,
4-6
power--up procedure, 4-1
radar mode ---- weather, 4-4
standby, 4-4
Procedures
in--flight roll offset adjustment
procedure, 5-26
pitch gain adjustment, 5-30
pitch offset adjustment
procedure, 5-28
PRIMUSR880 power--up
procedure, 4-2
roll gain adjustment, 5-29
severe weather avoidance
procedures, 5-60
stabilization in straight and level
flight check procedure, 5-21
stabilization in turns check
procedure, 5-23
R
Radar facts
additional comments, 5-68
turbulence versus distance
from storm core, 5-68
turbulence versus distance
from storm edge, 5-68
configurations of individual
echoes (Northern Hemisphere),
5-60
avoid all crescent shaped
echoes by 20 miles, 5-64
avoid hook echoes by 20
miles, 5-60
avoid pendant by 20 miles,
5-63
avoid steep rain gradients by
20 miles, 5-64
avoid V--notch by 20 miles,
5-62
ground mapping, 5-69
interpreting weather radar
images, 5-31
line configurations, 5-65
avoid bow--shaped line of
echoes by 20 miles, 5-67
avoid line echo wave patterns
(LEWP) by 20 miles, 5-66
avoid thunderstorm echoes at
the south end of a line or at
abreakinalineby20
miles, 5-65
radar operation, 5-1
radome, 5-54
PRIMUS
r
880 Digital Weather Radar System
A28--1146--102--01
REV 1
Index
Index--4
Index (cont)
Radar facts (cont)
rain echo attenuation
compensation technique
(REACT), 5-37
azimuth resolution, 5-53
hail size probability, 5-47
shadowing, 5-40
spotting hail, 5-48
turbulence detection
operation, 5-45
turbulence detection theory,
5-42
turbulence probability, 5-40
stabilization, 5-18
accelerative error, 5-18
dynamic error, 5-18
tilt management, 5-5
variable gain control, 5-37
weather avoidance, 5-55
severe weather avoidance
procedures, 5-60
weather display calibration, 5-35
Radar Images, 5-31
Radar operation, 5-1
Radiation Safety Precautions, A--1
Radome, 5-54
Rain echo attenuation
compensation technique
(REACT), 5-37
Recommended radiation safety
precautions for ground operation
of airborne weather radar, A--1
background, A--2
cancellation, A--1
precautions, A--2
body damage, A--2
combustible materials, A--3
general, A--2
purpose, A--1
related reading material, A--1
S
Shadowing, 5-40
Stabilization, 5-18
pitch gain adjustment, 5-30
pitch offset adjustment, 5-28
roll gain adjustment, 5-29
roll stabilization check, 5-23, 5-25
variable gain control, 5-37
Stabilization precheck, 5-21
System configurations, 2-1, 2-2
T
Test mode, 4-6
color bands, 4-7
dedicated radar indicator, 4-7
fault code, 4--7
EFIS/MFD/ND, 4-7
noise band, 4-6
target alert block, 4-6
text fault, 4--6
Thunderstorms, A--4
effect on altimeters, A--7
extrapolation to different climbs,
A--14
general, A--4
hail, A--7
hail in, A--13
hazards of, A--4
effect on altimeters, A--7
hail, A--7
do’s and don’ts of
thunderstorm flying, A--9
icing, A--6
lightning, A--8
low ceiling and visibility, A--7
schematic cross section of a
thunderstorm, A--6
squall lines, A--4
tornadoes, A--5
turbulence, A--5
weather radar, A--8
icing, A--6
lightning, A--8
low ceiling and visibility, A--7
maximum storm tops, A--13
PRIMUS
r
880 Digital Weather Radar System
A28--1146--102--01
REV 1
Index
Index--5
Index (cont)
National severe storms laboratory
(NSSL) thunderstorm research,
A--11
extrapolation to different
climbs, A--14
hail in thunderstorms, A--13
maximum storm tops, A--13
modification of criteria when
severe storms and rapid
development are evident,
A--13
relationship between
turbulence and altitude,
A--11
relationship between
turbulence and reflectivity,
A--11
turbulence above storm tops,
A--12
turbulence and echo intensity
on NWS radar (WSR--57),
A--11
turbulence below cloud base,
A--12
turbulence in relation to
distance from the storm
edge, A--12
turbulence in relation to
distance from storm core,
A--11
use of airborne radar, A--14
visual appearance of storm
and associated turbulence
with them, A--13
purpose, A--4
related reading material, A--4
squall line, A--4
thunderstorm flying, A--9
thunderstorm research, A--11
tornadoes, A--5
turbulence, A--5
above storm tops, A--12
and altitude, A--11
and echo intensity on NWS
radar, A--11
in relation to distance from
storm core, A--11
and reflectivity, A--11
below cloud base, A--12
in relation to distance from the
storm edge, A--12
visual appearance, A--13
Tilt management, 5-5
V
Variable gain control, 5-37
W
WC--884 Weather radar controller
operation, 3-20
mode, 3-23
FSBY, 3-25
GMAP, 3-24
OFF, 3-23
Rainfall rate color coding,
3-24
STBY, 3-23
WX, 3-24
tilt, 3-22
PULL ACT (altitude
compensated tilt) function,
3-22
Weather avoidance, 5-55
Weather display calibration, 5-35
Weather radar controller operation,
3-11
LSS (lightning sensor system)
(option), 3-19
CLR/TST, 3-19
LX, 3-19
Off, 3-19
SBY, 3-19
radar, 3-13
FP (flight plan), 3-14
FSBY (forced standby), 3-15
GMAP (ground mapping),
3-14
PRIMUS
r
880 Digital Weather Radar System
A28--1146--102--01
REV 1
Index
Index--6
Index (cont)
Weather radar controller operation
(cont)
OFF, 3-13
Rainfall rate color coding,
3-13
RCT (rain Echo attenuation
compensation technique),
3-13
SBY (standby), 3-13
TST (test), 3-15
WX (weather), 3-13
tilt, 3-16
PULL ACT (altitude
compensated tilt) function,
3-16
WI--880 Weather radar indicator
operation, 3-1
BRT (brightness) or BRT/LSS
(lightning sensor system), 3-9
CLR/TST (clear/test), 3-9
LX (lightning sensor system),
3-9
OFF, 3-9
SBY (standby) , 3-9
function switch, 3-3
FP (flight plan), 3-5
FSBY (forced standby), 3-5
GMAP (ground mapping), 3-4
OFF, 3-3
rainfall rate color coding, 3-4
SBY (standby), 3-3
TST (test), 3-5
WX (weather), 3-3
tilt, 3-9
PULL ACT (altitude
compensated tilt) function,
3-9
