190-00728-04 Rev. A
Embraer Prodigy® Flight Deck 100 Pilot’s Guide
357
HAZARD AVOIDANCE
6.2 AIRBORNE COLOR WEATHER RADAR
SYSTEM DESCRIPTION
TheGarmin GWX 68 Airborne Color WeatherRadar is a 4-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EmbraerPhenom100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 reflected 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returnedsignalisthenprocessedanddisplayed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.