Cockpit Reference Guide

190-00763-02 Rev. A
Garmin G1000 Pilot’s Guide for the Piper PA-46 Meridian
333
HAZARD AVOIDANCE
SYSTEM
OVERVIEW
FLIGHT
INSTRUMENTS
EICAS
AUDIO PANEL
& CNS
FLIGHT
MANAGEMENT
HAZARD
AVOIDANCE
AFCS
ADDITIONAL
FEATURES
APPENDICES INDEX
SYSTEM
OVERVIEW
FLIGHT
INSTRUMENTS
EICAS
AUDIO PANEL
& CNS
FLIGHT
MANAGEMENT
HAZARD
AVOIDANCE
AFCS
ADDITIONAL
FEATURES
APPENDICES INDEX
Ground Returns
The intensity of ground target returns depends upon the angle at which the radar beam strikes the
groundtarget(AngleofIncidence)andthereectivepropertiesofthattarget.Thegaincanbeadjustedso
shorelines,rivers,lakes,andcitiesarewell-dened.Increasingthegaintoomuchcausesthedisplaytoll
inbetweentargets,thusobscuringsomelandmarks.
Citiesnormallyprovideastrongreturnsignal.Whilelargebuildingsandstructuresprovidegoodreturns,
smallbuildingscanbeshadowedfromtheradarbeambythetallerbuildings.Astheaircraftapproaches
andshorterrangesareselected,detailsbecomemorenoticeableasthehighlyreectiveregularlinesand
edgesofthecitybecomemoredened.
Bodiesofwatersuchaslakes,rivers,andoceansarenotgoodreectorsandnormallydonotprovidegood
returns.Theenergyisreectedinaforwardscatteranglewithinadequateenergybeingreturned.They
canappearasdarkareasonthedisplay.However,roughorchoppywaterisabetterreectorandprovides
stronger returns from the downwind sides of the waves.
Mountainsalsoprovidestrongreturnsignalstotheantenna,butalsoblocktheareasbehind.However,
overmountainousterrain,theradarbeamcanbereectedbackandforthinthemountainpassesoroff
canyonwalls,usingupallormostoftheradarenergy.Inthiscase,noreturnsignalisreceivedfromthis
area,causingthedisplaytoshowadarkspotwhichcouldindicateapasswherenopassexists.
Angle of Incidence
TheangleatwhichtheradarbeamstrikesthetargetiscalledtheAngleofIncidence.Thegureillustrates
theincidentangle(‘A’).Thisdirectlyaffectsthedetectablerange,theareaofillumination,andtheintensity
ofthedisplayedtargetreturns.Alargeincidentanglegivestheradarsystemasmallerdetectablerangeand
lower display intensity due to minimized reflection of the radar energy.
Figure 6-47 Angle of Incidence
Asmallerincidentanglegivestheradaralargerdetectablerangeofoperationandthetargetdisplayshows
ahigherintensity.Sincemoreradarenergyisreectedbacktotheantennawithalowincidentangle,the
resultingdetectablerangeisincreasedformountainousterrain.