Pilot's Guide

190-00663-02 Rev. B
Garmin G1000 Pilot’s Guide for the Hawker Beechcraft C90A/GT/GTi
329
HAZARD AVOIDANCE
6.2 AIRBORNE COLOR WEATHER RADAR
SYSTEM DESCRIPTION
TheGarminGWX68AirborneColorWeatherRadarisafour-colordigitalpulsedradarwith6.5kilowatts
ofoutputpower.Itcombinesexcellentrangeandadjustablescanningproleswithahigh-denitiontarget
display.Thepulsewidthisfourmicroseconds(µs)onallrangesexceptthe2.5nmrange.TheGWX68usesa
oneµspulsewidthatthisrangetoreducethetargetssmearingtogetheronthedisplayforbettertargetdenition
at close range.
TheKingAir300/B300Seriesusesa12-inchphasedarrayantennathatisfullystabilizedtoaccommodate30º
of pitch and roll.
Tofocusradarscanningonspecicareas,SectorScanningofferspilot-adjustablehorizontalscananglesof
20º,40º,60º,or90º.Averticalscanningfunctionhelpstoanalyzestormtops,gradients,andcellbuildup
activity at various altitudes.
Radarfeaturesinclude:
•ExtendedSensitivityTimeConstant(STC)logicthatautomaticallycorrelatesdistanceofthereturnechowith
intensity, so cells do not suddenly appear to get larger as they get closer.
•WATCH™(WeatherATtenuatedColorHighlight)helpsidentifypossibleshadowingeffectsofshort-range
cellactivity,identifyingareaswhereradarreturnsignalsareweakenedorattenuatedbyintenseprecipitation
(orlargeareasoflesserprecipitation)andmaynotfullyreecttheweatherbehindastorm.
•WeatherAlertthatlooksaheadforintensecellactivityinthe80-320nmrange,eveniftheserangesarenot
being monitored.
PRINCIPLES OF PULSED AIRBORNE WEATHER RADAR
ThetermRADARisanacronymforRAdioDetectingAndRanging.Pulsedradarlocatestargetsbytransmitting
amicrowavepulsebeamthat,uponencounteringatarget,isreectedbacktotheradarreceiverasareturn
echo.Themicrowavepulsesarefocusedandradiatedbytheantenna,withthemostintenseenergyinthe
centerofthebeamanddecreasingintensityneartheedge.Thesameantennaisusedforbothtransmittingand
receiving.TheG1000processesthereturnedsignalanddisplaysitontheMFD.
Radardetectionisatwo-wayprocessthatrequires12.36µsforthetransmittedmicrowavepulsestotravelout
andbackforeachnauticalmileoftargetrange.Ittakes123.6µsforatransmittedpulsetomaketheroundtrip
if a target is ten nautical miles away.
Airborneweatherradarshouldbeusedtoavoidsevereweather, notfor penetratingsevereweather.The
decision to fly into an area of radar targets depends on target intensity, spacing between the targets, aircraft
capabilities, and pilot experience. Pulse type weather radar detects only precipitation, not clouds or turbulence.
Thedisplaymayindicateclearareasbetweenintensereturns,butthisdoesnotnecessarilymeanitissafetoy
betweenthem.OnlyDopplerradarcandetectturbulence.
Airborneweatherradarhasothercapabilitiesbeyondweatherdetection.Italsohastheabilitytodetectand
providedistancetocities,mountains,coastlines,rivers,lakes,andoceans.