Cockpit Reference Guide

Garmin G1000 Pilot’s Guide for the Piper PA-46 Meridian
190-00763-02 Rev. A330
HAZARD AVOIDANCE
SYSTEM
OVERVIEW
FLIGHT
INSTRUMENTS
EICAS
AUDIO PANEL
& CNS
FLIGHT
MANAGEMENT
HAZARD
AVOIDANCE
AFCS
ADDITIONAL
FEATURES
APPENDICESINDEX
SYSTEM
OVERVIEW
FLIGHT
INSTRUMENTS
EICAS
AUDIO PANEL
& CNS
FLIGHT
MANAGEMENT
HAZARD
AVOIDANCE
AFCS
ADDITIONAL
FEATURES
APPENDICESINDEX
NEXRAD AND AIRBORNE WEATHER RADAR
BothAirborneWeatherRadarandNEXRADmeasureweatherreectivityindecibels(dB).Adecibelisa
logarithmicexpressionoftheratiooftwoquantities.AirborneWeatherRadarmeasurestheratioofpower
againstthegainoftheantenna,whileNEXRADmeasurestheenergyreectedbacktotheradar,ortheradar
reflectivity ratio.
Bothsystemsusecolorstoidentifythedifferentechointensities,butthecolorsarenotinterchangeable.
AirbornecolorradarvaluesusedbyGarminAirborneColorWeatherRadarshouldnotbeconfusedwith
NEXRADradarvalues.
ANTENNA BEAM ILLUMINATION
Theradarbeamismuchlikethebeamofaspotlight.Thefurtherthebeamtravels,thewideritbecomes.
Theradarisonlycapableofseeingwhatisinsidetheboundariesofthebeam.Thegurebelowdepictsaradar
beam’scharacteristics.Thegureillustratesverticaldimensionsoftheradarbeam,althoughthesameholds
trueforthehorizontaldimensions.Inotherwords,thebeamisaswideasitistall.Notethatitispossibleto
missareasofprecipitationontheradardisplaybecauseoftheantennatiltsetting.Withtheantennatiltset
tozerointhisillustration,thebeamovershootstheprecipitationat15nauticalmiles.
Figure 6-44 Radar Beam from a 10 inch Antenna
80
Altitude (x1000 ft.)
Range (nautical miles)
Antenna at Zero Tilt
Half Power at Beam Sidelobes
18,000 ft.
18,000 ft.
Max Power at Beam Center
10°
0
30 0 45 60 75 90 15
Thecurvatureoftheearthcanalsobeafactorinmissingareasofprecipitation,especiallyatrangesettings
of150nauticalmilesormore.Herethebeamovershootstheprecipitationatlessthan320nauticalmiles.
320 nm
Figure 6-45 Radar Beam in Relation to the Curvature of the Earth