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

Telephonics Corporation Color Weather and Search and Rescue Radar RDR 1600

manual

Pilot’s GuideRDR-1600Color Weather andSearch and Rescue RadarTM106101August 2001Command Systems DivisionTM106101(8/01)RDR-1600 Pilot’s GuideiTABLE OF CONTENTSPARAGRAPHTITLEPAGE1.0 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . .12.0SYSTEM CONFIGURATION . . . . . . . . . . . . . . . . . . .22.1ANTENNA AND RECEIVER-TRANSMITTER . . . . . . .32.2RADAR DISPLAY INDICATOR . . . . . . . . . . . . . . . . . .43.0 OPERATIONAL CONTROLS . . . . . . . . . . . . . . . . . . .53.1FUNCTION SELECTOR – CP-113KCONTROL PANEL . . . . . . . . . . . . . . . . . . . . . . . . .53.2ANTENNA CONTROLS . . . . . . . . . . . . . . . . . . . . . . .63.3DISPLAY CONTROLS . . . . . . . . . . . . . . . . . . . . . . . .63.4PRIMARY MODE SELECTORS . . . . . . . . . . . . . . . . .63.5SECONDARY MODE SELECTOR AND GAINCONTROLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83.6ALPHANUMERICS . . . . . . . . . . . . . . . . . . . . . . . . . .94.0PREFLIGHT (PFT) . . . . . . . . . . . . . . . . . . . . . . . . . .104.1PREFLIGHT WARNING . . . . . . . . . . . . . . . . . . . . . .105.0THEORY OF OPERATION . . . . . . . . . . . . . . . . . . . .115.1GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .115.2RADAR PRINCIPLES . . . . . . . . . . . . . . . . . . . . . . .125.3WEATHER RADAR PRINCIPLES . . . . . . . . . . . . . . .135.4RADAR REFLECTIVITY . . . . . . . . . . . . . . . . . . . . . .145.5WEATHER DISPLAY CALIBRATION . . . . . . . . . . . .155.6WEATHER ATTENUATION COMPENSATION . . . . .166.0WEATHER OPERATIONS . . . . . . . . . . . . . . . . . . . .186.1WEATHER MODE – WX . . . . . . . . . . . . . . . . . . . . .186.2WEATHER ALERT MODE – WXA . . . . . . . . . . . . . .196.3TARGET ALERT . . . . . . . . . . . . . . . . . . . . . . . . . . .196.4WEATHER MAPPING AND INTERPRETATION . . . .206.5OBSERVING WEATHER . . . . . . . . . . . . . . . . . . . . .206.5.1Thunderstorms and Turbulence . . . . . . . . . . . . . . . .216.5.2Tornadoes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .226.5.3Hail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .236.5.4Icing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .246.5.5Snow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .246.5.6Lightning and Static Discharges . . . . . . . . . . . . . . . .246.5.7Range Resolution . . . . . . . . . . . . . . . . . . . . . . . . . . .256.5.8Azimuth Resolution . . . . . . . . . . . . . . . . . . . . . . . . .256.5.9Indicator Resolution . . . . . . . . . . . . . . . . . . . . . . . . .266.5.10Short Range Displays . . . . . . . . . . . . . . . . . . . . . . . .276.6PATH PLANNING . . . . . . . . . . . . . . . . . . . . . . . . . . .286.6.1Path Planning Considerations . . . . . . . . . . . . . . . . . .28
TM106101(8/01)RDR-1600 Pilot’s GuideiiiiiRDR-1600 Pilot’s GuideTM106101(8/01)TABLE OF CONTENTS (CONT.)PARAGRAPHTITLEPAGE7.0SEARCH OPERATIONS . . . . . . . . . . . . . . . . . . . . .317.1GROUND MAPPING . . . . . . . . . . . . . . . . . . . . . . . .317.1.1Looking Angle . . . . . . . . . . . . . . . . . . . . . . . . . . . . .327.1.2Other Aircraft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .337.2SEARCH MODE . . . . . . . . . . . . . . . . . . . . . . . . . . .337.3DIFFERENCE BETWEEN WEATHER AND SEARCH MODES . . . . . . . . . . . . . . . . . . . . . . . . .347.4SEARCH MODES COMPARED . . . . . . . . . . . . . . . .357.4.1Search 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .357.4.2Search 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .367.4.3Search 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .368.0TILT MANAGEMENT . . . . . . . . . . . . . . . . . . . . . . . .378.1TILT CONTROL . . . . . . . . . . . . . . . . . . . . . . . . . . . .378.2TILT PERFORMANCE CHECK . . . . . . . . . . . . . . . .388.3EARLY DETECTION OF ENROUTE WEATHER . . .399.0ANTENNA STABILIZATION . . . . . . . . . . . . . . . . . .409.1LIMITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .409.2ERRORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .409.3COMPENSATION . . . . . . . . . . . . . . . . . . . . . . . . . .4110.0BEACON MODES . . . . . . . . . . . . . . . . . . . . . . . . . .4210.1BEACON FORMAT SELECTION . . . . . . . . . . . . . . .4310.2DO-172 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4311.0AC 90-80 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4412.0MULTIPLE INDICATORS . . . . . . . . . . . . . . . . . . . . .4513.0SYSTEM SPECIFICATIONS . . . . . . . . . . . . . . . . . .4613.1RT-1601 RT UNIT . . . . . . . . . . . . . . . . . . . . . . . . . .4613.2DA-1203A ANTENNA DRIVE ASSEMBLY . . . . . . . .4613.3CP-113K CONTROL PANEL . . . . . . . . . . . . . . . . . .4714.0ADVISORY CIRCULARS . . . . . . . . . . . . . . . . . . . . .48APPENDIX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A-1WARNING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A-3CAUTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A-3MAXIMUM PERMISSIBLE EXPOSURE LEVEL (MPEL) . . . . . . . . . . . . . . . . . . . . . . . . . . .A-4LIST OF ILLUSTRATIONSFIGURETITLEPAGE2-1Typical System Block Diagram . . . . . . . . . . . . . . . . . .22.1-1Receiver-Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . .32.1-2DA-1203A Drive Assembly with AA4512A 12” Flat Plate Antenna . . . . . . . . . . . . . . . . . . . . . . . . . .32.1-3CP-113K Control Panel . . . . . . . . . . . . . . . . . . . . . . . .32.2-1MFD Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43.1-1CP-113K Control Panel . . . . . . . . . . . . . . . . . . . . . . . .53.2-1Tilt Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .63.4-1Primary Mode Selectors . . . . . . . . . . . . . . . . . . . . . . .73.5-1Secondary Mode Selector and Gain Controls . . . . . . .83.6-1MFD Screen Presentations . . . . . . . . . . . . . . . . . . . . .94.1-1Preflight Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . .105.2-1Radar Transmit-Receive Timing . . . . . . . . . . . . . . . . .125.4-1Reflective Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . .145.6-1STC Electronically Compensates for Distance Attenuation . . . . . . . . . . . . . . . . . . . . . . . .166.1-1Typical Weather Display . . . . . . . . . . . . . . . . . . . . . . .186.3-1Weather Alert with Target Alert Display . . . . . . . . . . . .196.5-1Storm Components . . . . . . . . . . . . . . . . . . . . . . . . . . .206.5.3-1Finger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .236.5.3-2Hook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .236.5.3-3Scalloped Edge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .236.5.3-4U-Shaped . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .236.5.8-1Azimuth Resolution . . . . . . . . . . . . . . . . . . . . . . . . . . .256.5.10-1Short Range Display . . . . . . . . . . . . . . . . . . . . . . . . . .276.6.1-1Penetration of Weather . . . . . . . . . . . . . . . . . . . . . . . .286.6.1-2Minimizing Doglegging . . . . . . . . . . . . . . . . . . . . . . . .296.6.1-3“Blind Alley” or “Box Canyon” Situations . . . . . . . . . . .297.1-1Over Terrain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .317.1-2Over Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .317.1.1-1A Smaller Incident Angle . . . . . . . . . . . . . . . . . . . . . . .327.1.1-2Concentration of the Beam . . . . . . . . . . . . . . . . . . . . .327.3-1Wx and SRCH Buttons . . . . . . . . . . . . . . . . . . . . . . . .347.4.1-1Search 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .357.4.2-1Search 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .367.4.3-1Search 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36
IntroductionTM106101(8/01)RDR-1600 Pilot’s Guide11.0INTRODUCTIONIn the early days of aviation, pilots were more concerned with just stayingairborne than worrying about weather. Airplanes were for fun. Pilots flewonly short hops, on clear days, and could often see their destination. Therewas little need for navigation equipment. If your compass was working andyour gas held out, you could probably make it home safely. Later, as flyingcame of age, thunderstorms and their associated turbulence were more ofa problem. When the weather was good, aircraft utilization was high. Butwhen storms were prevalent, you might take the long way home.Today, weather radar is as much at home in the cockpit as the compass.Corporate aircraft operators, and private pilots, as well as the airlines haveadopted weather radar with full confidence in its usefulness and reliability.Most commercial airborne weather radars available today also provide thepilot with one or more ancillary modes of operation and system options thatmake the radar more functional and increase its versatility.Telephonics would like to welcome you to the growing family of TelephonicsWeather Radar System owners and operators.The RDR-1600 Color Weather Radar System is the newest advancementof this series of radars. The RDR-1600 series radars are the most popular,advanced capability, multi-mode radars available from any manufacturer.The RDR-1600 provides five primary modes of operation: three air-to-surface search and detection modes, and two conventional weather avoid-ance modes. This lightweight digital X-band radar system provides a peakpower of 10 kW, and is primarily designed for fixed or rotary-wing aircraftengaged in patrol, search and rescue missions, and for transporting personnel and equipment to remote sites (e.g., off-shore oil rigs, etc.).The system interfaces with multi-function electronic displays. The MFD isreferred to as an indicator in this manual. The RDR-1600 will also interfacewith an Attitude Heading Reference System (AHRS). AHRS Pitch and Rolldata will be converted from digital ARINC 429 to analog pitch and roll datathat is used by the DA-1203A antenna drive unit for antenna stabilization.The RDR-1600 also has the capability to receive and decode both standard2-pulse beacon transponders and the DO-172 6-pulse transponders. Thissystem also provides two short ranges of 0.5 nm and 1.0 nm for search andrescue.This manual is designed to help you understand the RDR-1600 and itsoperational procedures. Please read it carefully before operating the unit. If you have any questions, please contact Telephonics (see back cover).ivRDR-1600 Pilot’s GuideTM106101(8/01)LIST OF ILLUSTRATIONS (CONT.)FIGURETITLEPAGE8.1-1Adjusting the Antenna Tilt . . . . . . . . . . . . . . . . . . . . . .378.2-1Altitude vs. Range . . . . . . . . . . . . . . . . . . . . . . . . . . . .388.3-1Weather Target . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .399.1-1Aircraft Pitching/Rolling ±30° . . . . . . . . . . . . . . . . . . . .4010.1-1Standard Beacon . . . . . . . . . . . . . . . . . . . . . . . . . . . .4310.2-1DO-172 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4314-1Cross-Section of a Thunderstorm . . . . . . . . . . . . . . . .50LIST OF TABLESTABLETITLEPAGE5.5-1Radar Display and Thunderstorm Levelsversus Rainfall Rates . . . . . . . . . . . . . . . . . . . . . . . .156.5.9-1Minimum Distinguishable Target Separation . . . . . . . .268.3-1Antenna Tilt Control Settings . . . . . . . . . . . . . . . . . . . .39
System Configuration (Cont.)System Configuration2RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide32.0SYSTEM CONFIGURATIONFigure 2-1.Typical System Block Diagram2.1ANTENNA AND RECEIVER-TRANSMITTERThe RT-1601 Receiver-Transmitter generates 10 KW pulses of X-bandenergy. Reflected signals of weather, search and beacon modes receivedby the antenna are amplified and sent to the radar display indicator.The flat-panel antenna, which is available in diameters of 10, 12 or 18 inches scans 60 or 120 degrees. Swept by a motor-driven gear train, thevertical component is positioned by the tilt control on the Radar ControlPanel (RCP or CP-113k). A stabilization system presents an upright radardisplay while the aircraft is turning, climbing or descending.Figure 2.1-1.Receiver-TransmitterFigure 2.1-2.DA-1203A DriveAssembly with AA4512A 12” FlatPlate AntennaFigure 2.1-3.CP-113K Control Panel
Operational ControlsSystem Configuration (Cont.)4RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide52.2RADAR DISPLAY INDICATORFigure 2.2-1.MFD DisplayThe MFD displays green, yellow and red moving maps of weather and surface features.The choice of two weather modes, three search modes and antenna scanof 60 or 120 degrees is selected by the pilot. A target alert feature is activein the weather alert mode, and a movable track cursor helps the pilot planhis flight around severe weather. A beacon mode enables the display ofbeacon locations and a code feature identifies the beacons. BeaconFormatting allows for the display of either standard or DO-172 type beacons. This information can be displayed in any of eight separate ranges.Rainfall per hour Ground Return Color 0-1 mm No significant return Dark 1-4 mm Light Green 1-12 mm Medium Yellow 12 mm or more Heavy Red 3.0OPERATIONAL CONTROLS3.1FUNCTION SELECTOR – CP-113K CONTROL PANELOFFRemoves system power.STBYSystem is operationally ready; no display.TESTDisplays a test pattern without transmitting, identified byTEST and RT FAULT.ONSystem transmits in normal operation.60°Directs the antenna to sector scan 60° about the boresightof the aircraft. This position will work in weather, search(map), and beacon modes.Figure 3.1-1.CP-113K Control Panel
Operational Controls (Cont.)Operational Controls (Cont.)6RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide7BCNPressing this button will select the two Beacon type formats to be selected. Sequentially pressing the Beaconbutton will select the following beacon modes:Beacon Only ModeBeacon A, Beacon B, Beacon A, Beacon B, . . .Dual Mode (Beacon/Weather or Beacon/Search)Beacon A, Beacon B, Beacon Off, Beacon Am . . .Beacon Only Mode: If the starting mode of operation isweather (or search), then pressing the beacon button willplace the system in Beacon/Weather (Search) mode. Toactivate beacon only mode, press the weather (or search)button to turn off weather (search) mode. To reactivate dualmode, press either the weather or search buttons.Beacon A – Standard 2-pulse beaconBeacon B – DO-172 compatible beaconFigure 3.4-1.Primary Mode Selectors3.2ANTENNA CONTROLSPULL STAB OFFThis switch is connected to the Tilt Control Knob. Whenthe Tilt Control Knob is pressed in, the stabilizationfunction is active. When this knob is pulled out, the stabilization function is turned off.TILTAdjusts antenna tilt angle.Figure 3.2-1.Tilt Control3.3DISPLAY CONTROLSThe MFD has a brightness control to adjust the brightness of the screen.3.4PRIMARY MODE SELECTORS(PUSH ON/PUSH OFF)WxSelects weather mode, the primary mode of operation(automatically selected at turn-on). Weather displayed andWx appear on screen. When pressed again, the weathermode is removed. If no other mode button is active, the Wxmode remains.WxASelects weather alert mode causing red returns to flash ifthe MFD is capable of performing this function. WxAappears and Target Alert is enabled.SRCHPressing this push button selects the three Search modesin sequential cyclic manner (i.e., Search 1, Search 2,Search 3, Search 1, Search 2, Search 3, etc.). Searchmodes are as follows:Search 1 – Sea clutter rejection. Active on the ten-milerange or less.Search 2 – Short range precision mapping. Active on theten-mile range or less.Search 3 – Normal surface mapping.Beacon mode is compatible with both weather mode andSearch mode.
Operational Controls (Cont.)Operational Controls (Cont.)8RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide93.6ALPHANUMERICSFigure 3.6-1.MFD Screen PresentationsNote+MFDs display of radar data will vary by manufacturer. Refer to theMFD Pilot’s Guide for specific radar display.3.5SECONDARY MODE SELECTOR AND GAIN CONTROLSBCN GAINThe Beacon Gain is a rotary potentiometer that controls thegain of the Beacon receiver.SRCH GAINThe Search Gain is a rotary potentiometer that controlsthe gain of the Search receiver.CODEPressing this switch selects Beacon Codes in a sequentialcyclic fashion (i.e., Code 0, Code 1, Code 2, . . . Code 15or Code 0, Code 1, Code 2, . . . Code 9) depending onBeacon Mode selected. The selected code is annunciatedon the MFD.When DO-172 Beacon (Beacon Mode B) is selected viathe BCN button, the total of sixteen codes (0-15) can beselected by the Code switch. Selecting a Standard two-pulse Beacon (Beacon Mode A) via the BCN button, thetotal of ten codes (0-9) can be selected by the Code button. The Code button is not active unless the Beaconmode has been selected.Figure 3.5-1.Secondary Mode Selector and Gain Controls
Theory of OperationPreflight10RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide115.0THEORY OF OPERATION5.1GENERALThe primary use of this radar is to aid the pilot in avoiding thunderstormsand associated turbulence. Since each operator normally develops uniqueoperational procedures for use of Weather Radar, the following informationis presented for use at the operator’s discretion.Operational techniques with the RDR-1600 Series Weather Radars are notdifferent than with earlier generation radars. The proficient operator manages his antenna tilt control to achieve the best possible knowledge ofstorm height, size, and relative direction of movement.4.0PREFLIGHT (PFT)4.1PREFLIGHT WARNINGTest the system to verify proper operation before each flight. Rotate thefunction selector from OFF to STBY. Allow system to warm up for about 100seconds, then move the function selector to TEST. No display appears inthe STBY position and the radar does not transmit in either STBY or TEST.The test pattern scans 120° and automatically selects the 80 mile range.Look for distinct color bands and range marks in the order shown. Adjustdisplay brightness for a comfortable level. Checklist and flight log optionsmay be used at this time if installed.WARNINGDo not turn the radar on within 25 feet of ground personnel orcontainers holding flammable or explosive material. The radarshould never be operated during refueling.When ready to use the radar, rotate the function selector to ON position.Figure 4.1-1.Preflight WarningsNote+The design of the system is such that full operation is possibleapproximately two minutes after turn-on. Therefore, the pilot maychoose to leave the function switch in OFF, rather than STBY, if nosignificant weather is in the immediate area of the aircraft. The lifeof the magnetron transmitting tube will be extended by leaving thesystem “OFF” when possible. This, in turn, will reduce the cost ofmaintenance.
Theory of Operation (Cont.)Theory of Operation (Cont.)12RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide135.3WEATHER RADAR PRINCIPLESAirborne weather avoidance radar, as its name implies, is for avoidingsevere weather – not for penetrating it. Whether to fly into an area of radarechoes depends on echo intensity, spacing between the echoes, and thecapabilities of both pilot and aircraft. Remember that weather radar detectsonly precipitation drops; it does not detect minute cloud droplets. Therefore,the radar scope provides no assurance of avoiding instrument weather inclouds and fog. Your indicator may be clear between intense echoes; thisclear area does not necessarily mean you can fly between the storms andmaintain visual sighting of them.The geometry of the weather radar radiated beam precludes its use for reliable proximity warning or anti-collision protection. The beam is charac-terized as a cone-shaped pencil beam. It is much like that of a flashlight orspotlight beam. It would be an event of chance, not of certainty, that such abeam would come upon another aircraft in flight.WARNINGWeather radar is not practical as a pilot operable collisionavoidance system. Weather analysis and avoidance are the primary functions of the radar system.5.2RADAR PRINCIPLESRadar is fundamentally a distance measuring system using the principle ofradio echoing. The term RADAR is an acronym for Radio Detecting AndRanging. It is a method for locating targets by using radio waves. The trans-mitter generates microwave energy in the form of pulses. These pulses are then transferred to the antenna where they are focused into abeam by the antenna. The radar beam is much like the beam of a flashlight.The energy is focused and radiated by the antenna in such a way that it ismost intense in the center of the beam with decreasing intensity near theedge. The same antenna is used for both transmitting and receiving. Whena pulse intercepts a target, the energy is reflected as an echo, or return signal, back to the antenna. From the antenna, the returned signal is trans-ferred to the receiver and processing circuits located in the receiver transmitter unit. The echoes or returned signals are displayed on an indicator.Radio waves travel at the speed of 300 million meters per second and thusyield nearly instantaneous information when echoing back. Radar rangingis a two-way process that requires 12.36 micro-seconds for the radio waveto travel out and back for each nautical mile of target range. As shown inthe distance illustration in Figure 5.2-1, it takes 123.6 micro-seconds for atransmitted pulse of radar energy to travel out and back from an area of precipitation 10 nautical miles away.Figure 5.2-1.Radar Transmit-Receive Timing
Theory of Operation (Cont.)Theory of Operation (Cont.)14RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide155.5WEATHER DISPLAY CALIBRATIONThe MFD Radar display should be calibrated to show four levels of target intensity: Black (level 0), Green (level one), Yellow (level two) and Red(level three). The meaning of these levels is shown in the following chart asis their approximate relationship to the Video Integrated Processor (VIP)intensity levels used by the National Weather Service (NWS). These levelsare valid only when (1) the Wx or WxA modes are selected; (2) the dis-played returns are within the STC range of the radar (approximately 40miles); (3) the returns are beam filling; and (4) there are no interveningradar returns.Table 5.5-1.Radar Display and Thunderstorm Levels versus Rainfall RatesVideo Integrated Processor (VIP) Categorizations Rainfall Rate Rainfall Rate Display Level mm/Hr. In./Hr Story Category VIP Level mm/Hr. In./Hr. Remarks 3 (Red) 12 0.5 Strong 3 Greater than 12 Greater than 0.5 Severe turbulence, possible lightning 2 (Yellow) 4-12 0.17-0.5 Moderate 2 2.5-12 0.1-0.5 Light to moderate turbulence is possible with lightning 1 (Green 1-4 0.04-0.17 Weak 1 0.25-2.5 .01-0.1 Light to moderate turbulence is possible with lightning 0 (Black) Less than 1 Less than 0.04 5.4RADAR REFLECTIVITYWhat target will reflect the radar’s pulses and thus be displayed on theindicator?Only precipitation (or objects more dense than water such as earth or solidstructures) will be detected by an X-band weather radar. Therefore, weather radar does not detect clouds, thunderstorms or turbulence direct-ly. Instead, it detects precipitation which may be associated with dangerousthunderstorms and turbulence. The best radar reflectors are raindrops andwet hail. The larger the raindrop, the better it reflects. Because large dropsin a small concentrated area are characteristic of a severe thunderstorm,the radar displays the storm as a strong echo. Drop size is the most impor-tant factor in high radar reflectivity. Generally, ice, dry snow and dry hailhave low reflective levels and often will not be displayed by the radar.A cloud that contains only small raindrops, such a fog or drizzle, will not pro-duce a measurable radar echo. But if the conditions should change and thecloud begins to produce rain, it will be displayed on radar.Figure 5.4-1.Reflective Levels
Theory of Operation (Cont.)Theory of Operation (Cont.)16RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide17Attenuation due to precipitation is far more intense and is less predictablethan attenuation due to distance. As the radar pulses pass through mois-ture, some radar energy is reflected, however, much of that energy isabsorbed. If the rain is very heavy or extends for many miles, the beam maynot reach completely through the area of precipitation. The weather radarhas no way of knowing if the beam has been fully attenuated or hasreached the far side of the precipitation area. If the beam has been fullyattenuated, the radar will display a “radar shadow” which appears as an endto the precipitation when, in fact, the heavy rain may extend for many moremiles. In the worst case, precipitation attenuation may cause the area ofheaviest precipitation to be displayed as the thinnest area of heavy precip-itation. Or it may cause one cell containing heavy precipitation to totallyblock or shadow a second heavy cell located behind the first cell and pre-vent it from being displayed on the radar. CAUTIONNever fly into radar shadows and never believe that the full extent ofheavy rain is being seen on radar unless another cell or a ground target can be seen beyond the heavy cell. Proper use of the antenna tilt control can help detect radar shadows.Attenuation can also be a problem when flying in a large area of generalrain. If the rain is moderate, the radar beam may only reach 20 or 30 milesbefore it is fully attenuated. The pilot may fly along for many miles seeingthe same 20-30 miles of precipitation ahead on the radar when, actually, therain may extend for a great distance. In order to aid in reducing the effectsof precipitation attenuation, the RDR-1600 contains sophisticated weatherattenuation compensation circuitry. The Attenuation Compensation featureis totally automatic and requires no pilot action to activate it. However, theCompensation logic cannot operate until echoes are within the SensitivityTime Control range of approximately 40 miles. Whenever a level two level (yellow) or level three (red) echo is displayed within the STC range,the Compensation circuits cause the receiver gain to increase while the antenna scans the sector containing heavy rain. The Compensation circuit-ry allows the radar beam to effectively look deeper into and through heavyrain to search for possible storm cells beyond. While AttenuationCompensation does not eliminate precipitation attenuation, it does allow theradar to see through more rain at short ranges where every bit of weatherinformation possible is needed. If there is suspicion that the radar is atten-uating due to precipitation, exercise extreme caution and ask the ATCController what they are showing. Often the ground-based ATC radar willhave a better overall picture of a large rain area and the pilot can comparethe controller’s information with his own radar picture to avoid the strongestcells in a general area of rain.5.6WEATHER ATTENUATION COMPENSATIONAttenuation is an extremely important phenomenon for the weather radaroperator to understand. When a radar pulse is transmitted into the atmosphere, it is progressively absorbed and scattered so that it loses itsability to return to the antenna. This attenuation or weakening of the radarpulse is caused by two primary sources, distance and precipitation. TheRDR-1600 radars have several advanced features which significantlyreduce the affects of attenuation but no airborne weather radar can elimi-nate them completely. It is therefore up to the operator to understand theradar’s limitations in dealing with attenuation.Attenuation because of distance is due to the fact that the radar energyleaving the antenna is inversely proportional to the square of the distance.For example, the reflected radar energy from a target 60 miles away will beone fourth (if the target is beam filling) of the reflected energy from anequivalent target 30 miles away. The displayed effect to the operator is thatas the storm is approached it will appear to be gaining in intensity. To com-pensate for distance attenuation, both Sensitivity Timing Control (STC) andExtended STC circuitry are employed. The RDR-1600 has an STC range ofapproximately 40 nautical miles and within this range the radar will elec-tronically compensate for the effects of distance attenuation with the neteffect that targets do not appear to grow larger as the distance decreases.Outside the STC range the Extended STC circuitry increases the displayedintensity to more accurately represent storm intensity. The Extended STCwill not, however, totally compensate for distance attenuation and, therefore, targets in this range can be expected to grow as the distancedecreases until reaching the STC range.Figure 5.6-1.STC Electronically Compensates for Distance Attenuation
Weather Operations (Cont.)Weather Operations18RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide196.2WEATHER ALERT MODE – WXAIn Weather Alert mode, WxA, you will see a standard weather presentationdisplayed in Green, Yellow and Red, except that the red returns flashbetween black and red to draw your attention to the heavier activity.6.3TARGET ALERTIn Weather Alert Mode, WxA, the words TGT ALRT flash if red returns existwithin 25 miles beyond the displayed range.Figure 6.3-1.Weather Alert with Target Alert Display6.0WEATHER OPERATIONS6.1WEATHER MODE – WXThe RDR-1600 will provide you with target information to a greater degreethan ever possible on previous generation weather radars. With a 240 nmmaximum display range, you will have plenty of time to plan weather avoid-ance maneuvers.Figure 6.1-1.Typical Weather DisplayBy pressing the “WX” button on the face of the indicator, you will see a stan-dard weather presentation. Different levels of precipitation are displayed inGreen, Yellow and Red. Use the range up/down buttons to select thedesired full scale range distance to be displayed. See Paragraph 8.0 for
Weather Operations (Cont.)Weather Operations (Cont.)20RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide216.5.1Thunderstorms and TurbulenceThe RDR-1600 weather radar can give you a clue to the presence of turbulence. Areas of the display where the colors change rapidly over ashort distance represent steep rainfall gradients, which are usually associ-ated with severe turbulence.Turbulence may be divided into two basic types: (1) clear-air turbulence. It is not possible to detect clear-air turbulencewith this type of radar.(2) turbulence associated with thunderstorms and precipitation. Thistype is most common. Weather radar is most helpful to the pilotwith this type.Weather guidance is now available from ground radar stations in someareas. However, this system suffers in comparison with the airborne weather radar when the weather is clearly visible on the pilot’s indicator,instantly available for the pilot to act upon, considering his immediate circumstances and future flight planning.The strong up and down drafts in a thunderstorm create very large rain-drops which are usually displayed on a radar as level three.The probability of turbulence in these strong vertical gusts is great. TheNational Severe Storms Laboratory (NSSL) has found that the intensitylevel of the precipitation reflection correlates with the degree of turbulencefound in a thunderstorm. The most severe turbulence in the storm, however, may not be at the same place that gives the greatest radar reflec-tivity.The rate of change in rainfall rate laterally within a storm is called the raingradient. This change will appear on the indicator as a change from greento yellow to red. If the rainfall rate increases from level one to three in ashort distance, the rain gradient is steep and severe turbulence is oftenpresent. Avoid any storm with a steep rain gradient by an extra margin andespecially avoid flying near the portion of the storm with the steepest gradient.6.4WEATHER MAPPING AND INTERPRETATIONThis section contains general information on use of the radar for weatherinterpretation. Review of this information will assist the pilot.6.5OBSERVING WEATHERA weather radar is only as good as the operator’s interpretation of theechoes that are displayed on the radar indicator. The pilot must combine hisknowledge of how radar works and its limitations with such things as theprevailing weather pattern, the geographic location, and his personal expe-rience in order to make a sound interpretation of the displayed targets.As a starting point, the operator should read FAA Advisory Circular number00-24B, Subject: Thunderstorms. It is also highly recommended that theoperator take advantage of one of the commercially available weather radarseminars.Figure 6.5-1.Storm Components
Weather Operations (Cont.)Weather Operations (Cont.)22RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide236.5.3HailHail usually has a film of water on its surface; consequently, a hailstone isoften reflected as a very large water particle. Because of the film andbecause hail stones usually are larger than raindrops, thunderstorms withlarge amounts of wet hail return stronger signals than those with rain.Although wet hail is an excellent reflector of radar energy, some hail shaftsare extremely small (100 yards or less). These narrow shafts make poorradar targets.Hail shafts are usually identified with four different characteristics patterns:(1) fingers and protrusions, (2) hooks, (3) scalloped edges on the cloud out-line and (4) U-shaped cloud edges 3 to 7 miles across.These echoes appear quite suddenly and along any edge of the storm out-line. They also change in intensity and shape in a matter of seconds, andfor this reason careful monitoring of the display is essential. It must benoted that weak or fuzzy projections are not normally associated with hail;however, such echoes should be watched closely for signs of rapid intensi-fication.The 40-mile operating range seems best and, with occasional up-tilt tocheck for fresh hail from above, generally good results can be obtained.Note+It takes an experienced eye to identify “hooks” and “fingers” andother radar echo characteristics which can indicate hail or torna-does. However, the pilot can be sure that any echo with veryragged edges or rapid changes in shape or intensity will containsevere turbulence.Figure 6.5.3-1.FingerFigure 6.5.3-2.HookFigure 6.5.3.3.ScallopedEdgeFigure 6.5.3-4.U-Shaped6.5.2TornadoesIt is possible that conclusive methods of detecting tornadoes with airborneradar may eventually be developed. However, evidence collected to dateindicates tornadoes may be detected if the following echoes are observed:1. A hook-shaped pendant which may be 5 or more miles long and in thegeneral shape of the numeral 6 strongly suggests the presence of amajor tornado, especially if the pendant is a bright one and if it projectsfrom the southwest quadrant (northeast quadrant in the southern hemi-sphere) of a major thunderstorm moving eastward. The pendant may belost in ground clutter when viewed on the indicator and in some casesmight not be much more than a blunt projection or scalloped edge of theparent thunderstorm echo.2. A crescent-shaped indentation on the side of a major thunderstorm echo3 to 7 miles long is another possible identifier of an active or potentialtornado in the vicinity.3. The best procedure is to make wider than usual detours around sharp-edged thunderstorms and especially those which show projections orcrescent-shaped indentations.
Weather Operations (Cont.)Weather Operations (Cont.)24RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide256.5.7Range ResolutionThe ability of the radar system to resolve closely spaced targets in rangedepends on transmitter pulse width. In long range modes, the RDR-1600can distinguish objects spaced as close as 0.19 nm (385 yds.) apart. InSearch 1 (SR1) and Search 2 (SR2) modes on ranges of 20 miles andbelow, the resolution is improved to 0.04 nm (80 yds.).6.5.8Azimuth ResolutionThe ability of the radar to resolve adjacent targets in azimuth depends onantenna beam width and range to the target. The diameter of the radiatedbeam increases as it gets further from the antenna. Larger antennas havenarrower beam widths and, therefore, produce better ground mapping andweather pictures.Targets separated by a distance less than the beam diameter will mergeand appear on the indicator as one.Figure 6.5.8-1.Azimuth Resolution6.5.4IcingThere is reason to believe that the radar will be of assistance in locatingareas of heavy icing conditions. However, weather radar has not yet provedits ability to distinguish between super-cooled water droplets and ice crys-tals, since both are usually quite small. Needless to say, the operationalproblem in each case would be different. In the first case icing would defi-nitely exist but in the second case the pure crystals would offer no danger.1.It should be remembered, however, that super-cooled water and icecrystals can co-exist. In each case the radar echo would be small oreven nil due to the minute size of the free water particles. At this time, itappears fairly certain that radar is not going to give warning of cloud icingunless it happens to be involved with active precipitation at the time.When precipitation is occurring, however, the areas of maximum iceexposure should appear as sandy or grainy echoes.2.An icing condition that the radar might possibly detect is the intermittentmoderate or heavy icing condition associated with unstable air lifted byfrontal action or orographic effects. In this situation, the cumulus cellsare hidden by surrounding cloud layers but could be spotted by radar.This would be of assistance in avoiding the moderate-to-heavy icingwhich occasionally occurs in cumulus clouds.WARNINGThunderstorm icing can be extremely hazardous.6.5.5SnowDry snowfall has not been detected with any success on weather radar.However, a characteristic sandy or grainy echo identifies the presence ofsteady moderate-to-heavy wet snow. Such echoes are not readily obviousand require a little study of the display before they can be seen.6.5.6Lightning and Static DischargesLightning and static discharges could scatter the display momentarily.However, the general presentation is unaffected and should return to normal within 1 scan.
Weather Operations (Cont.)Weather Operations (Cont.)26RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide276.5.10Short Range DisplaysThe RDR-1600 allows the selection of full-scale ranges of 1.0 nm and 0.5 nm in Search Modes. These unique short range selections are especially useful during approaches and surveillance operations, because it keeps the target fromgetting lost in the clutter at the vertex of the display.When operating in either short range mode, certain features becomeunavailable. They are: Moving Map with Waypoints, BeaconTrac andBeacon Identification. All other modes are still accessible.Figure 6.5.10-1.Short Range DisplayIn the weather mode, the RDR-1600 is unable to ascertain radar returnsfrom close in. On the short range displays, the RDR-1600 paints a red arcin this range to depict the dead band area, as shown in Figure 6.5.10-1.6.5.9Indicator ResolutionThe resolution of the indicator depends on the number of display bits on thescreen. A typical screen matrix is composed of 256 bits horizontally by 256bits vertically. The display resolution is equal to 1/256 times the displayrange as shown in Table 6.5.9-1. The lower the range, the better the resolution.Table 6.5.9-1.Minimum Distinguishable Target Separation Resolution Range (nm) Miles Feet Meters 2.0 0.008 48 14.8 5.0 0.02 122 37.0 10.0 0.04 243 74.1 20.0 0.08 486 148.2 40.0 0.16 972 296.3 80.0 0.31 1884 574.1
Weather Operations (Cont.)Weather Operations (Cont.)28RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide29Figure 6.6.1-3.“Blind Alley” or “Box Canyon” SituationsA “Blind Alley” or “Box Canyon” situation can be very dangerous when view-ing the short ranges. Periodically switch to longer range displays toobserve distant conditions. As shown above, the short-range returns showan obvious corridor between two areas of heavy rainfall, but the long-rangesetting shows a larger area of heavy rainfall.Figure 6.6.1-2.Minimizing DogleggingCells beyond 75 miles are areas of substantial rainfall; do not wait for red to appear. Plan and execute evasive action quickly to minimize “doglegging.”6.6PATH PLANNINGRemember to plan a deviation path early. Simply skirting the red portion ofa cell is not enough. Plan an avoidance path for all weather echoes whichappear beyond 100 miles since this indicates they are quite intense.The most intense echoes are severe thunderstorms. Remember that hailmay fall several miles from the cloud, and hazardous turbulence mayextend as much as 20 miles from the storm. Avoid the most intense echoesby at least 20 miles, that is, echoes should be separated by at least 40miles before you fly between them. As echoes diminish in intensity, you canreduce the distance by which you avoid them.6.6.1Path Planning Considerations•Avoid cells containing red areas by at least 20 miles.•Do not deviate downwind unless absolutely necessary. Your chances ofencountering severe turbulence and damaging hail are greatly reducedby selecting the upwind side of the storm.•If looking for a corridor, remember corridors between two cells containingred areas should be at least 40 miles wide from the outer fringes of theradar echo.Note+Do not approach a storm cell containing red any closer than 20 nm.Echoes should be separated by at least 40 nm before attemptingto fly between them.Figure 6.6.1-1.Penetration of WeatherWhen a complete detour is impractical, penetration of weather patterns maybe required. Avoid adjacent cells by at least 20 miles.
Search OperationsWeather Operations (Cont.)30RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide317.0SEARCH OPERATIONS7.1GROUND MAPPINGA secondary objective of the radar system is gathering and presentation ofterrain data. This data is represented in the form of a topographical mapthat can be employed as a supplement to standard navigation procedures.Target quality affects the indicator display in various situations. Use of theSRCH gain control and TILT knob will often improve picture contrast sospecific ground targets are more readily recognizable.Figure 7.1-1.Over TerrainIllumination of terrain results in a “diffused” reflection of the beam. A portionof this reflected energy is scattered back toward the antenna resulting in theprominent display of land features as well as lakes, large rivers, shore linesand ships.Figure 7.1-2.Over WaterCalm water or water with swells does not provide good returns. The ener-gy is reflected in a forward scatter angle with inadequate portions beingreturned. The resulting display is “no target”. Choppy water provides betterreturns from the downwind side of the waves. The resulting display is a target whose intensity will vary with the degree to choppiness.Above all, remember: Never regard any thunderstorm as LIGHT, even whenradar observers report the echoes are of light intensity. Avoiding thunder-storms is the best policy.DON’Tattempt to preflight plan a course between closelyspace echoes.DON’Tland or take off in the face of a thunderstorm in the projected flight path. A sudden wind shift or low level turbu-lence could cause loss of control.DON’Tattempt to fly under a thunderstorm even if you can seethrough to the other side. Turbulence under the storm could besevere.DON’Ttry to navigate between thunderstorms that cover 6/10or more of the display. Fly around the storm system by a widemargin.DON’Tfly without airborne radar into a cloud mass containingscattered embedded thunderstorms. Scattered thunderstormsnot embedded usually can be circumnavigated.DOavoid by at least 20 miles any thunderstorm identified assevere or giving an intense radar echo. This is especially trueunder the anvil of a large cumulonimbus.DOclear the top of a known or suspected severe thunderstormby at least 10,000 feet altitude. This may exceed the altitudecapability of the aircraft.DOremember that vivid and frequent lightning indicates asevere thunderstorm.DOregard as severe any thunderstorm with tops 35,000 feetor higher whether the top is visually sighted or determined byradar.
Search Operations (Cont.)Search Operations (Cont.)32RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide337.1.2Other AircraftTests show that only with extremely careful observation at relatively shortranges can other aircraft be detected by this type of radar equipment. Thecharacter of this echo is such that this type of radar system cannot be considered adequate for this purpose.7.2SEARCH MODEAn advantage of this radar system is the enhancement of short range mapping capability. This facilitates locating specific targets on land or seaand provides a navigational map as a supplement to standard navigationprocedures.7.1.1Looking AngleThe incident angle at which the terrain is illuminated has a direct bearing onthe detectable range and the area of illumination. A large incident anglegives the radar system a smaller detectable range of operation (due to aminimized reflection of direct radar energy). However, the illuminated area“A” is larger.Figure 7.1.1-1.A Smaller Incident AngleA smaller incident angle gives the radar a larger detectable range of oper-ation because of an increase of direct radar energy reflected from the target to the antenna. The area of illumination (“A”) is smaller.Figure 7.1.1-2.Concentration of the BeamConcentration of the beam energy on the small area of terrain increases themagnitude of the echo intercepted by the antenna. The resulting detectablerange is therefore increased for mountainous terrain; the maximum distance at which this terrain can be monitored is greater because of themore direct reflection (or radar echo) produced. Illuminating the backslopeof hills stretches the area of coverage beyond the flat terrain coverage.
Search Operations (Cont.)Search Operations (Cont.)34RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide357.4SEARCH MODES COMPAREDIn the photographs below, the aircraft is flying southwest along the FloridaKeys. Florida’s marshy coast is on the right and the islands are in the cen-ter of the screen. Strong boat target returns are on the left. Tilt and searchgain are adjusted for optimum display. Note that in SRCH 3, the land masses blend together while in SRCH 2 and SRCH 1, a small boat (arrow)target can be extracted from heavy seas.7.4.1Search 3Conventional ground map mode. Beyond 10 mile range, SR1 and SR2 arethe same as SR3.The radar’s long range mapping compatibility may be used to recognizeknown, well defined targets such as mountains, lakes, rivers, or cities. Useof gain and tilt controls will often improve picture quality.Figure 7.4.1-1.Search 37.3DIFFERENCE BETWEEN WEATHER AND SEARCH MODESIn weather modes, the receiver gain is preset and cannot be changed bythe pilot. In the search modes, the pilot controls receiver gain with theSRCH knob on the indicator front panel for best display resolution.Additionally, in search modes on ranges below 10 miles, the transmitterpulse is changed to enhance target resolution.When operating in weather or search modes, both weather and groundreturns can appear on the screen at the same time.Figure 7.3-1.Wx and SRCH Buttons
Tilt ManagementSearch Operations (Cont.)36RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide378.0TILT MANAGEMENT8.1TILT CONTROLOne of the most important factors in improving your expertise in using yourradar is antenna tilt management. Control of the vertical movement of theantenna, and hence the radar beam, is through the antenna tilt knob.Proper antenna tilt management provides information of the storm’sapproximate size and relative direction of movement.The correct procedure for weather avoidance is to aim the antenna directlyat the storm, not above it, or at the ground. The tilt control permits posi-tioning the antenna in small increments up or down, to keep the antennaintersecting the storm area. Also, changes in pitch attitude can be com-pensated for by adjusting the antenna tilt.Figure 8.1-1.Adjusting the Antenna Tilt7.4.2Search 2Short range precision mapping on ranges of 10 miles or less.Figure 7.4.2-1.Search 27.4.3Search 1Sea clutter rejection effect on ranges of 10 miles or less.Figure 7.4.3-1.Search 1
Tilt Management (Cont.)Tilt Management (Cont.)38RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide398.3EARLY DETECTION OF ENROUTE WEATHERTo set the Antenna Tilt to optimize the radar’s ability to quickly identify significant weather, follow these steps:1.Select the Wx (Weather) or WxA (Weather Alert) mode of operation.Adjust brightness control as desired.2.Select the 40 or 80 nm range.3.Adjust the Antenna Tilt control down until the entire display is filled withground returns.4.Slowly work the Antenna Tilt up so that ground returns are painted on orabout the outer one third of the indicator area.5.Watch the strongest returns seen on the display. if, as they areapproached, they become weaker and fade out after working back insidethe near limit of the general ground return pattern, they are probablyground returns or insignificant weather. If they continue strong afterworking down into the lower half of the indicator, you are approaching ahazardous storm or storms, and should deviate immediately.6.Examine the area behind strong targets. If radar shadows are detected,you are approaching a hazardous storm or storms, and should deviateimmediately. Regardless of the aircraft’s altitude, if weather is beingdetected, move the Antenna Tilt control up and down in small incrementsuntil the return object is optimized. At that angle, the most active verticallevel of the storm is being displayed.Antenna Tilt Angle Altitude (ft) 10” 12” 18” Line-of-Sight Range (SM) 5,000 +7.0° +6.0° +5.0° 87 10,000 6.0° 5.0° 4.0° 123 15,000 5.5° 4.0° 3.0° 150 20,000 4.5° 3.5° 2.5° 174 25,000 4.0° 3.0° 2.0° 194 30,000 3.5° 2.5° 1.5° 213 35,000 3.0° 2.0° 1.0° 230 40,000 2.5° 1.5° 0.5° 246 Figure 8.3-1.Weather TargetIf target is shown at or beyond the line-of-sight range listed above, thechances are good that it is a weather target.Table 8.3-1.Antenna Tilt Control SettingsNote+The TILT position inStep 4 should be thatshown in the chart.The exact setting willdepend upon the air-craft’s pitch altitudeand the flatness ofthe terrain.8.2TILT PERFORMANCE CHECKA good performance check of your radar system in flight is to lower the tiltslowly and observe the maximum range of solid ground returns. As a ruleof thumb, this range in miles should approximate the square root of youroperational altitude.Figure 8.2-1.Altitude vs. RangeFor example, at 5,000 ft. the maximum displayed ground target rangeshould be about 70 nautical miles. You should perform this test on everyflight. Don’t wait until you’re penetrating severe weather to discover thatyour system is not providing optimum performance.If the radar is operating normally when you reach cruising altitude, selectthe longest display range and lower the antenna tilt until ground targets aredisplayed. Now, slowly raise the tilt until the ground returns disappear. Thiswill give you the optimum tilt setting for your cruise altitude. Each time anew range is selected, however, the tilt control must be readjusted, downfor a shorter range, and up for a longer one.
Antenna Stabilization (Cont.)Antenna Stabilization40RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide419.3COMPENSATIONThere are some compensations the pilot can use for antenna stabilizationerrors. When the system has been operating properly in level flight, the pilotmay be able to correct for ground return showing on one side and not theother by tilting the antenna up until all ground returns are cleared. Duringtakeoff, the pilot can raise the antenna tilt to clear the ground returnscaused by gyro acceleration error, then as the airplane stops accelerating,readjust the antenna tilt back toward level. Adjusting antenna tilt is also theremedy for ground returns that appear because of gyro precession in a pro-longed turn. Good operating practices include:•Adjust radar and obtain weather picture before takeoff•Compensate antenna tilt for gyro precession•Evaluate weather in the immediate sphere of operation•Do not “over-scan” weather targets•During excessive aircraft maneuvers, recognize the limitations of stabilization9.0ANTENNA STABILIZATIONAirborne radar antennas are stabilized to preserve a normal cockpit displaywhen the aircraft is climbing, descending or turning. When the aircraftdeparts from straight and level flight, the stabilization system automaticallyadjusts the antenna position to compensate for the change. Both limits anderrors associated with antenna stabilization are important to the pilot.9.1LIMITSThe limits of antenna stabilization are different for climbing or descendingand turning while climbing or descending. For straight ahead climbs anddescents, the limits are simply the mechanical stops at 30 degrees. Whenturning, the tilt and bank angles determine the stabilization limits (the ruleof thumb is a total of 30 degrees) so moderate turns combined with mod-erate climbs and descents will stay within limits.Figure 9.1-1.Aircraft Pitching/Rolling ±30°9.2ERRORSThere are two sources of stabilization errors: acceleration and drift.Accelerations and decelerations cause the gyro to precess in pitch. Thepilot may not notice a small temporary discrepancy between the altitudeindicator and visible horizon, but on the radar screen the antenna pitch pre-cession will appear as an exaggeration of the desired tilt. Drift errors(appearing on the attitude indicators pitch and roll precession accumulatein turns) disappear slowly after the aircraft returns to straight and level.Gyro precession errors directly affect radar stabilization and the quality ofthe return displayed on the screen.
Beacon Mode (Cont.)Beacon Mode42RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s Guide4310.1BEACON FORMAT SELECTIONThe RDR-1600 will always display all beacon signals on the screen as theyrespond to the radar interrogation, regardless of the format selection.To identify a particular beacon and place an identification number beside it,you must first identify whether the beacon is the standard or DO-172 format. This is accomplished by observing the beacon responses.If the beacon is of the standard format, there will always be only 2 “slash-es” on the display spaced 7 nm apart or more. The RDR-1600 can identifyany one of nine standard beacons in this mode.Figure 10.1-1.Standard Beacon10.2DO-172A selected beacon utilizing the DO-172 format will have two framing “slash-es” which are positioned approximately 2 nm apart. Within these two“frames” will be a combination of up to four slashes. Varying the combina-tions of the inner slashes makes it possible to identify any one of fifteen dif-ferent DO-172 beacon codes. This feature is especially beneficial whenoperating in areas of multiple beacon activity.Figure 10.2-1.DO-172After the beacon type has been identified and the proper format selected,the operator may now select the desired beacon number by pressing theCOURSE/CODE (CRS CODE) button the proper number of times.10.0BEACON MODESIn the Beacon (BCN) mode, the RDR-1600 can interrogate, receive and dis-play signals from fixed transponder beacons on all ranges. The beaconitself is displayed as curved “slashes”, with the position of the beacon located approximately in the center of the closest slash.The RDR-1600 will also display the bearing and radar distance to anyselected beacon; this information is displayed in the lower left corner of theindicator display.For greater flexibility, the beacon mode may be operated alone or in com-bination with the weather or search modes.
TM106101(8/01)RDR-1600 Pilot’s Guide45Multiple Indicators44RDR-1600 Pilot’s GuideTM106101(8/01)Course Bearing Cursor (Cont.)12.0MULTIPLE INDICATORSAn additional MFD unit, is required for multiple indicator installations.Since all controls for the radar system are located on the control panel, bothMFD observers will see the same display.•Operating modes•Search and beacon gain•Antenna tilt angle•Antenna scan angle•Beacon codeAll indicators independently control:•Display range•Desired brightness levelThe RDR-1600 will perform dual scan operation when the range of indica-tor No. 1 (or 2) is greater than or equal to 20 nm and indicator No. 2 (or 1)is less than or equal to 10 nm, and the mode of operation is either search1 or search 2. In this situation, the short range will use a short transmittedpulse, and the long range will use a long transmitted pulse. This is anincompatible situation in that the transmitter cannot transmit both a longand short pulse at the same time. In this situation, indicator No. 1 will beupdated on the right to left sweep of the antenna, and indicator No. 2 willbe updated on the left to right sweep of the antenna.11.0AC 90-80The FAA allows lower minimums in radar approaches to clusters of rigs,when both the radar altimeter and “course bearing cursor” are operatingand are used as described in AC 90-80. For details on minimum approachheights and distances, refer to FAA AC 90-80.Note+Advisory Circular AC 90-80, Approval of Offshore StandardApproach Procedures. . .can be downloaded from www.faa.govinAdobe Acrobat format.Click on:•Aviation Support and Regulation, then•Guidance, Reference, Advisory, then•Index of FAA Advisory Circulars (AC)Go to the search engine at the bottom of the AC page and enterthe title in quotations to find the AC.
TM106101(8/01)RDR-1600 Pilot’s Guide47System Specifications (Cont.)46RDR-1600 Pilot’s GuideTM106101(8/01)System Specifications13.3CP-113K CONTROL PANELEnvironmental Qualification:DO-160A Env. Cat. F1A/PKS/XXXXXXABABAAltitude:55,000 feetTemperature:-20 degrees C. to +55 degrees C.(-4 degrees F. to +131 degrees F.)Cooling:May be required as determined by ambienttemperature range in aircraft cockpit.Mounting:Panel mounted, DZUS.Weight:1.7 lbs. maximum (0.77 kg)TSO:C63cOverall DimensionsHeight:2.25 inches maximum (57.2 mm)Width:5.75 inches maximum (146.0 mm)Length:6.5 inches maximum (165.1 mm)Input PowerVoltage+28 Vdc inputs per DO-160ACategory B. Two inputs available.Power Draw Using2.5 watts maximum electrical power drain+28 Vdc Lighting from +28 Vdc power bus plus 7.5 wattsPower Busmaximum lighting power drain from +28 Vdc lighting bus.Power Draw using 5 Vac,10 watts maximum electrical and lighting400 Hz Lightinginput power drain from +28 Vdc power bus.Power BusOne milliamp power drain from 5 Vaclighting bus (reference).13.0SYSTEM SPECIFICATIONS13.1RT-1601 RT UNITFrequency:9375 MHz Xmit/Rec; 9310 MHz BCN RECRF Power Output:10 KW Peak PowerPRF/Pulse Width:Short Range Search 1500 P.P.S./0.2 secLong Range Search and Beacon; 200 P.P.S./2.35 secAltitude:50,000 ft.Temperature:-50°C to +55°CSize:5”w x 6-1/4”h x 13-7/8”d (1/2 ATRI)Weight:16 lbs. (7.26 kg)TSO:C63c13.2DA-1203A ANTENNA DRIVE ASSEMBLYReflector Size:10”, 12”, or 18” Flat PlateScan Angle:120° or 60°Tilt Angle:±15°Scan Rate:28°/secStabilization Accuracy:±1°Altitude:50,000 ft.Temperature:-50°C to +55°CWeight:10”, 0.88 lbs. (4 Kgs), 12”; 1.1 lbs. (0.498 Kgs), 18”; 2.2 lbs. (1.0 Kgs)Drive Assembly:6.5 lbs. (2.95 Kgs)Counterbalanced Drive Assembly:9.5 lbs. (4.32 Kgs)TSO:C63b
TM106101(8/01)RDR-1600 Pilot’s Guide49Advisory Circulars (Cont.)48RDR-1600 Pilot’s GuideTM106101(8/01)Advisory CircularsAC 00-24B1/20/83b.Tornadoes.(1)The most violent thunderstorms draw air into their cloud baseswith great vigor. If the incoming air has any initial rotating motion, it oftenforms an extremely concentrated vortex from the surface well into thecloud. Meteorologists have estimated that wind in such a vortex canexceed 200 knots; pressure inside the vortex is quite low. The strongwinds gather dust and debris and the low pressure generates a funnel-shaped cloud extending downward from the cumulonimbus base. If thecloud does not reach the surface, it is a "funnel cloud"; if it touches a landsurface, it is a "tornado."(2)Tornadoes occur with both isolated and squall line thunder-storms. Reports for forecasts of tornadoes indicate that atmospheric con-ditions are favorable for violent turbulence. An aircraft entering a tornadovortex is almost certain to suffer structural damage. Since the vortexextends well into the cloud, any pilot inadvertently caught on instrumentsin a severe thunderstorm could encounter a hidden vortex.(3)Families of tornadoes have been observed as appendages ofthe main cloud extending several miles outward from the area of lightningand precipitation. Thus, any cloud connected to a severe thunderstormcarries a threat of violence.c.Turbulence.(1)Potentially hazardous turbulence is present in all thunderstorms,and a severe thunderstorm can destroy an aircraft. Strongest turbulencewithin the cloud occurs with shear between updrafts and downdrafts.Outside the cloud, shear turbulence has been encountered several thou-sand feet above and 20 miles laterally from a severe storm. A low levelturbulent area is the shear zone associated with the gust front. Often, a"roll cloud" on the leading edge of a storm marks the top of the eddies inthis shear and it signifies an extremely turbulent zone. Gust fronts oftenmove far ahead (up to 15 miles) of associated precipitation. The gust frontcauses a rapid and sometimes drastic change in surface wind ahead ofan approaching storm. Advisory Circular 00-50A, "Low Level Wind Shear,"explains in greater detail the hazards associated with gust fronts. FigureA-1 shows a schematic cross section of a thunderstorm with areas out-side the cloud where turbulence may be encountered.(2)It is almost impossible to hold a constant altitude in a thunder-storm, and maneuvering in an attempt to do so provides greatly increasedstress on the aircraft. It is understandable that the speed of the aircraftdetermines the rate of turbulence encounters. Stresses are least if the air-craft is held in a constant attitude and allowed to "ride the waves." Todate, we have no sure way to pick "soft spots" in a thunderstorm.DEPARTMENT OF TRANSPORTATIONFederal Aviation AdministrationWashington, D.C.Subject: THUNDERSTORMSDate: 1/20/83AC No.: 00-24BInitiated by: AFO-260Change: 1.PURPOSE. This advisory circular describes the hazards of thunder-storms to aviation and offers guidance to help prevent accidents causedby thunderstorms.2,CANCELLATION. Advisory Circular 00-24A, dated June 23, 1978, iscanceled.3.RELATED READING MATERIAL. Advisory Circulars 00-6A, AviationWeather, 00-45B, Aviation Weather Services, 00-50A, Low Level WindShear.4.GENERAL. We all know what a thunderstorm looks like. Much hasbeen written about the mechanics and life cycles of thunderstorms. Theyhave been studied for many years; and while much has been learned, thestudies continue because much is not known. Knowledge and weatherradar have modified our attitudes toward thunderstorms, but one rule con-tinues to be true - any storm recognizable as a thunder-storm should beconsidered hazardous until measurements have shown it to be safe. Thatmeans safe for you and your aircraft. Almost any thunderstorm can spelldisaster for the wrong combination of aircraft and pilot.5.HAZARDS. A thunderstorm packs just about every weather hazardknow to aviation into one vicious bundle. Although the hazards occur innumerous combinations, let us look at the most hazardous combination ofthunderstorms, the squall line, then we will examine the hazards individu-ally.a.Squall Lines. A squall line is a narrow band of active thunder-storms. Often it develops on or ahead of a cold front in moist, unstable air,but it may develop in unstable air far removed from any front. The linemay be too long to detour easily and too wide and severe to penetrate. Itoften contains steady-state thunderstorms and presents the single mostintense weather hazard to aircraft. It usually forms rapidly, generallyreaching maximum intensity during the late afternoon and the first fewhours of darkness.
TM106101(8/01)RDR-1600 Pilot’s Guide51Advisory Circulars (Cont.)50RDR-1600 Pilot’s GuideTM106101(8/01)Advisory Circulars (Cont.)AC 00-24B1/20/83(2)As hailstones fall through air whose temperature is above 0°C,they begin to melt and precipitation may reach the ground as either hail orrain. Rain at the surface does not mean the absence of hail aloft. Youshould anticipate possible hail with any thunderstorm, especially beneaththe anvil of a large cumulonimbus. Hailstones larger than one-half inch indiameter can significantly damage an aircraft in a few seconds.f.Low Ceiling and Visibility. Generally, visibility is near zero within athunderstorm cloud. Ceiling and visibility also may be restricted in precipi-tation and dust between the cloud base and the ground. The restrictionscreate the same problem as all ceiling and visibility restrictions; but thehazards are increased many fold when associated with the other thunder-storm hazards of turbulence, hail, and lightning which make precisioninstrument flying virtually impossible.g.Effect on Altimeters. Pressure usually falls rapidly with the ap-proach of a thunderstorm, then rises sharply with the onset of the firstgust and arrival of the cold downdraft and heavy rain showers, fallingback to normal as the storm moves on. This cycle of pressure changemay occur in 15 minutes. If the pilot does not receive a corrected altimetersetting, the altimeter may be more than 100 feet in error.h.Lightning. A lightning strike can puncture the skin of an aircraft andcan damage communications and electronic navigational equipment.Lightning has been suspected of igniting fuel vapors causing explosion;however, serious accidents due to lightning strikes are extremely rare.Nearby lightning can blind the pilot rendering him momentarily unable tonavigate either by instrument or by visual reference. Nearby lightning canalso induce permanent errors in the magnetic compass. Lightning dis-charges, even distant ones, can disrupt radio communications on low andmedium frequencies. Though lightning intensity and frequency have nosimple relationship to other storm parameters, severe storms, as a rule,have a high frequency of lightning.i.Engine Water Ingestion.(1)Turbine engines have a limit on the amount of water they caningest. Updrafts are present in many thunderstorms, particularly those inthe developing stages. If the updraft velocity in the thunderstormapproaches or exceeds the terminal velocity of the falling raindrops, veryhigh concentrations of water may occur. It is possible that these concen-trations can be in excess of the quantity of water turbine engines aredesigned to ingest. Therefore, severe thunderstorms may contain areas ofhigh water concentration which could result in flame-out and/or structuralfailure of one or more engines.(2)At the present time, there is no known operational procedurethat can completely eliminate the possibility of engine damage/flameoutAC 00-24B1/20/83d.Icing.(1)Updrafts in a thunderstorm support abundant liquid water withrelatively large droplet sizes; and when carried above the freezing level,the water becomes supercooled. When the temperature in the upwardcurrent cools to about -15°C, much of the remaining water vapor subli-mates as ice crystals; and above this level, at lower temperatures, theamount of supercooled water decreases.(2)Supercooled water freezes on impact with an aircraft. Clearicing can occur at any altitude above the freezing level; but at high levels,icing from smaller droplets may be rime or mixed rime and clear. Theabundance of large, supercooled water droplets makes clear icing veryrapid between 0°C and -15°C and encounters can be frequent in a clusterof cells. Thunderstorm icing can be extremely hazardous.Figure 14-1.Cross-Section of a Thunderstorme.Hail.(1)Hail competes with turbulence as the greatest thunderstormhazard to aircraft. Supercooled drops above the freezing level begin tofreeze. Once a drop has frozen, other drops latch on and freeze to it, sothe hailstone grows - sometimes into a huge iceball. Large hail occurswith severe thunderstorms with strong updrafts that have built to greatheights. Eventually, the hailstones fall, possible some distance from thestorm core. Hail may be encountered in clear air several miles from darkthunderstorm clouds.
TM106101(8/01)RDR-1600 Pilot’s Guide53Advisory Circulars (Cont.)52RDR-1600 Pilot’s GuideTM106101(8/01)Advisory Circulars (Cont.)AC 00-24B1/20/83radar echoes depends on echo intensity, spacing between the echoes,and the capabilities of you and your aircraft. Remember that weatherradar detects only precipitation drops; it does not detect turbulence.Therefore, the radar scope provides no assurance of avoiding turbulence.The radar scope also does not provide assurance of avoiding instrumentweather from clouds and fog. Your scope may be clear between intenseechoes; this clear area does not necessarily mean you can fly betweenthe storms and maintain visual sighting of them.f.Remember that while hail always gives a radar echo, it may fallseveral miles from the nearest visible cloud and hazardous turbulencemay extend to as much as 20 miles from the echo edge. Avoid intense orextreme level echoes by at least 20 miles; that is, such echoes should beseparated by at least 40 miles before you fly between them. With weakerechoes you can reduce the distance by which you avoid them.7.DO'S AND DON'TS OF THUNDERSTORM FLYING.a.Above all, remember this: never regard any thunderstorm lightlyeven when radar observers report the echoes are of light intensity.Avoiding thunderstorms is the best policy. Following are some do's anddon'ts of thunderstorm avoidance:(1)Don't land or takeoff in the face of an approaching thunder-storm. A sudden gust front of low level turbulence could cause loss ofcontrol.(2)Don't attempt to fly under a thunderstorm even if you can seethrough to the other side. Turbulence and wind shear under the stormcould be disastrous.(3)Don't fly without airborne radar into a cloud mass containingscattered embedded thunderstorms. Scattered thunderstorms not embed-ded usually can be visually circumnavigated.(4)Don't trust the visual appearance to be a reliable indicator of theturbulence inside a thunderstorm.(5)Do avoid by at least 20 miles any thunderstorm identified assevere or giving an intense radar echo. This is especially true under theanvil of a large cumulonimbus.(6)Do circumnavigate the entire area if the area has 6/10 thunder-storm coverage.(7)Do remember that vivid and frequent lightning indicates theprobability of a severe thunderstorm.(8)Do regard as extremely hazardous any thunderstorm with tops35,000 feet or higher whether the top is visually sighted or determined byradar.AC 00-24B1/20/83during massive water ingestion. Although the exact mechanism of thesewater-induced engine stalls has not bee determined, it is felt that thrustchanges may have an adverse effect on engine stall margins in the pres-ence of massive water ingestion.(3)Avoidance of severe storm systems is the only measure as-sured to be effective in preventing exposure to this type of multiple enginedamage/flameout. During an unavoidable encounter with severe stormswith extreme precipitation, the best known recommendation is to followthe severe turbulence penetration procedure contained in the approvedairplane flight manual with special emphasis on avoiding thrust changesunless excessive airspeed variations occur.6.WEATHER RADAR.a.Weather radar detects droplets of precipitation size. Strength of theradar return (echo) depends on drop size and number. The greater thenumber of drops, the stronger is the echo; and the larger the drops, thestronger is the echo. Drop size determines echo intensity to a muchgreater extent that does drop number. Hailstones usually are covered witha film of water and, therefore, act as huge water droplets giving thestrongest of all echoes.b.Numerous methods have been used in an attempt to categorize theintensity of a thunderstorm. To standardize thunderstorm languagebetween weather radar operators and pilots, the use of Video IntegratorProcessor (VIP) levels is being promoted.c.The National Weather Service (NWS) radar observer is able toobjectively determine storm intensity levels with VIP equipment. Theseradar echo intensity levels are on a scale of one to six. If the maximumVIP Levels are 1 "weak" and 2 "moderate," then light to moderate tur-bulence is possible with lightning. VIP Level 3 is "strong" and severe tur-bulence is possible with lightning. VIP Level 4 is "very strong" and severeturbulence is likely with lightning. VIP Level 5 is "intense" with severe tur-bulence, lightning, hail likely, and organized surface wind gusts. VIP Level6 is "extreme' with severe turbulence, lightning, large hail, extensive sur-face wind gusts, and turbulence.d.Thunderstorms build and dissipate rapidly. Therefore, do notattempt to plan a course between echoes. The best use of ground radarinformation is to isolate general areas and coverage of echoes. You mustavoid individual storms from in-flight observations either by visual sightingor by airborne radar. It is better to avoid the whole thunderstorm area thanto detour around individual storms unless they are scattered.e.Airborne weather avoidance radar is, as its name implies, for avoid-ing severe weather - not for penetrating it. Whether to fly into an area of
TM106101(8/01)RDR-1600 Pilot’s Guide55Advisory Circulars (Cont.)54RDR-1600 Pilot’s GuideTM106101(8/01)Advisory Circulars (Cont.)ADVISORY CIRCULARAC 20-68BDEPARTMENT OF TRANSPORTATIONFederal Aviation Administration, Washington, D.C.Recommended radiation safety precautions for ground operation of airborne weather radar.Initiated by: AFO-512PURPOSEThis circular sets forth recommended radiation safety precautions to betaken by personnel when operating airborne weather radar on the ground.CANCELLATIONAC 20-68A, dated April 11, 1975, is canceled.RELATED READING MATERIAL•Barnes and Taylor, Radiation Hazards and Protection (London: GeorgeNewnes Limited, 1963), p. 211.•U.S. Department of Health, Education and Welfare, Public HealthService, Consumer Protection and Environmental Health Service,“Environmental health microwaves, ultraviolet radiation and radiationfrom lasers and television receivers – An Annotated Bibliography”, FS2.300: RH-35, Washington, U.S. Government Printing Office, pp. 56-57.•Mumford, W.W., “Some technical aspects of microwave radiation haz-ards”, Proceedings of the IRE, Washington, U.S. Government PrintingOffice, February 1961, pp. 427-447.BACKGROUNDDangers from ground operation of airborne weather radar include the possibility of human body damage and ignition of combustible materials byradiated energy. Low tolerance parts of the body include the eyes andtestes.PRECAUTIONSManagement and supervisory personnel should establish procedure foradvising personnel of dangers from operating airborne weather radars onthe ground. Precautionary signs should be displayed in affected areas toalert personnel of ground testing.AC 00-24B1/20/83b.If you cannot avoid penetrating a thunderstorm, following are somedo's BEFORE entering the storm:(1)Tighten your safety belt, put on your shoulder harness if youhave one, and secure all loose objects.(2)Plan and hold your course to take you through the storm in aminimum time.(3)To avoid the most critical icing, establish a penetration altitudebelow the freezing level or above the level of -15°C.(4)Verify that pitot-heat is on and turn on carburetor heat or jetengine anti-ice. Icing can be rapid at any altitude and cause almost in-stantaneous power failure and/or loss of airspeed indication.(5)Establish power settings for turbulence penetration airspeed rec-ommended in your aircraft manual.(6)Turn up cockpit lights to highest intensity to lessen temporaryblindness from lightning.(7)If using automatic pilot, disengage altitude hold mode and speedhold mode. The automatic altitude and speed controls will increasemaneuvers of the aircraft thus increasing structural stress.(8)If using airborne radar, tilt the antenna up and down occasional-ly. This will permit you to detect other thunderstorm activity at altitudesother then the one being flown.c.Following are some do's and don'ts during the thunderstorm pene-tration:(1)Do keep your eyes on your instruments. Looking outside thecockpit can increase danger of temporary blindness from lightning.(2)Don't change power settings; maintain settings for the recom-mended turbulence penetration airspeed.(3)Do maintain constant attitude; let the aircraft "ride the waves."Maneuvers in trying to maintain constant altitude increase stress on theaircraft.(4)Don't turn back once you are in the thunderstorm. A straightcourse through the storm most likely will get you out of the hazards mostquickly. In addition, turning maneuvers increase stress on the aircraft.WILLIAM T. BRENNANActing Director of Flight Operations
56RDR-1600 Pilot’s GuideTM106101(8/01)Advisory Circulars (Cont.)General•Airborne weather radar should be operated on the ground only by quali-fied personnel.•Installed airborne radar should not be operated while the aircraft is in ahangar or other enclosure unless the radar transmitter is not operating,or the energy is directed toward an absorption shield which dissipatesthe radio frequency energy. Otherwise, radiation within the enclosure canbe reflected throughout the area.Body Damage.To prevent possible human body damage, the fol-lowing precautions should be taken:•Personnel should never stand nearby and in front of radar antenna whichis transmitting. When the antenna is not scanning, the danger increases.•A recommended safe distance from operating airborne weather radarsshould be established. A safe distance can be determined by using theequations in the Appendix. This criterion is now accepted by many indus-trial organizations and is based on limiting exposure of humans to anaverage power density not greater than 1 milliwatt per square centime-ter.•Personnel should be advised to avoid the end of an open wave guideunless the radar is turned off.•Personnel should be advised to avoid looking into a wave guide, or intothe open end of a coaxial connector or line connector to a radar trans-mitter output, as severe eye damage may result.•Personnel should be advised that when power radar transmitters areoperated out of their protective cases, X-rays may be emitted. Stray X-rays may emanate from the glass envelope-type pulsar, oscillator,clipper, or rectifier tubes, as well as magnetrons.Combustible Materials. To prevent possible fuel ignition, aninstalled airborne weather radar should not be operated while an aircraft is being refueled or defueled.M.C. BeardDirector of AirworthinessAC 20-68B8/8/80
AppendixTM106101(8/01)RDR-1600 Pilot’s GuideA-1APPENDIXSAFE DISTANCE DETERMINATIONThe following information can be used in establishing a minimum safe dis-tance from the antenna for personnel near an operating airborne weatherradar. NEAR FIELD/FAR FIELD INTERSECTIONThe distance to the near field/far field intersection can be computed by:Ri = Gλ8π where Ri=intersection distance from the antenna (in meters)= Wave length (in meters)= Antenna gainDISTANCE TO 1 MW/CM2SAFE LIMITFor a far field power density of 1 mw/cm2, the distance (in meters) fromthe antenna may be calculated by:where Rs=the minimum safe distance in meters.P = Transmitted average power in watts.G = Antenna gainPROCEDURESThe above formulas may be used to determine the minimum safe distance.In either case, the following procedures apply:a.Determine the distance (Ri) to the near field/far field intersection (para-graph 1)b.Determine the distance (Rs) to 1 mw/cm2power density c.If the distance (Rs) determined in item b is less than (Ri) found in item a,use distance (Ri) as the minimum safe distanced.If the distance (Rs) determined in item b is greater than (Ri) found in itema, use distance (Rs) as the minimum safe distance π40GPRs =
Appendix (Cont.) Appendix (Cont.)A-2RDR-1600 Pilot’s GuideTM106101(8/01)TM106101(8/01)RDR-1600 Pilot’s GuideA-3CAUTIONMaintain prescribed safe distance when standing in front of radiatingantenna.Never expose eyes or any part of the body to an unterminated waveguide.EXAMPLEThe following is typical data for the airborne weather radar.Antenna Diameter:18 inches = 45.6 cmTransmitter Frequency:9375 +30 MHzWave Length:3.2 cmPulse Length:2.5 microseconds (search)Pulse Repetition:200 HzPeak Power:10 kilowattsAverage Power:5 watts (search)Antenna Gain:1250 (31 dB)Calculations(1)Distance (Ri) to the near field/far field intersectionRi = Gλ8πRi = (1250 x 0.032)8π=1.6 meters = 5.25 feet(2)Distance (Rs) to 1 mw/cm2safe limit= 7.05 meters = 23.1 feetThe distance (Rs) is greater than (Ri), therefore, the minimum safe distanceis 23.1 feet. π40GPRs =π40(1250)(5)=
Copyright 2001TelephonicsTM106101(8/01)Command Systems Division815 Broad Hollow Road, Farmingdale, NY 11735Phone: 1 (631) 755-7004 • Fax: 1 (877) 577-7701www.telephonics.comAppendix (Cont.)A-4RDR-1600 Pilot’s GuideTM106101(8/01)MAXIMUM PERMISSIBLE EXPOSURE LEVEL (MPEL)In order to avoid the envelope in which the radiation level exceeds the U.S.Government standard of 1 mW per square centimeter, all personnel shouldremain beyond the distance indicated in the illustration below. The distanceto the MPEL boundary is calculated upon the basis of the largest antennaavailable with the RDR-1600 system, rated output power of the transmitterand in the non-rotating or boresight position of the antenna. With a scanning beam, the power density at the MPEL boundary is significantlyreduced.

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