190-00498-07 Rev. A
Garmin G1000 Pilot’s Guide for Cessna Nav III
SYSTEM
OVERVIEW
FLIGHT
INSTRUMENTS EIS AUDIO PANEL
& CNS
FLIGHT
MANAGEMENT
HAZARD
AVOIDANCE AFCS ADDITIONAL
FEATURES APPENDICES INDEX
381
HAZARD AVOIDANCE
6.8 TAWS-B
WARNING: Do not use TAWS information for primary terrain avoidance. TAWS is intended only to enhance
situational awareness.
NOTE: Terrain data is not displayed when the aircraft is outside of the installed terrain database coverage
area.
NOTE: The data contained in the TAWS databases comes from government agencies. Garmin accurately
processes and cross-validates the data but cannot guarantee the accuracy and completeness of the data.
TAWS-B(TerrainAwarenessandWarningSystem-ClassB)isusedtoincreasesituationalawarenessandaidin
reducingcontrolledightintoterrain(CFIT).TAWSprovidesvisualandauralannunciations whenterrainand
obstaclesarewithinthegivenaltitudethresholdfromtheaircraft.Thedisplayedalertsandwarningsareadvisory
in nature only.
TAWS-BsatisesTSO-C151bClassBrequirementsforcertication.
TAWS-Brequiresthefollowingtooperateproperly:
•Avalidterrain/obstacle/airportterraindatabase
•Avalid3-DGPSpositionsolution
TAWS-Busesterrainandobstacleinformationsuppliedbygovernmentsources.Terraininformationisbased
onterrainelevation informationin adatabasethat maycontain inaccuracies.Individual obstructionsmay be
shownifavailableinthedatabase.ThedataundergoesvericationbyGarmintoconrmaccuracyofthecontent,
perTSO-C151b.However,thedisplayedinformationshouldneverbeunderstoodasbeingall-inclusiveanddata
may be inaccurate.
TAWS-BusesinformationprovidedfromtheGPSreceivertoprovideahorizontal positionandaltitude.GPS
altitudeisderivedfromsatellitemeasurements.GPSaltitudeis thenconvertedtotheheightabovegeodetic sea
level(GSL),which istheheight abovemeansea level(MSL) calculatedgeometrically.GSLaltitude isusedto
determineTAWS-Balerts.GSLaltitudeaccuracyisaffectedbysatellitegeometry,butisnotsubjecttovariations
inpressureandtemperaturethat normallyaffectpressurealtitude sensors.GSLaltitude doesnotrequirelocal
altimetersettingstodetermine MSLaltitude.It isawidely-used MSLaltitudesource. Therefore,GSLaltitude
providesahighlyaccurateandreliableMSLaltitudesourcetocalculateterrainandobstaclealerts.
Theterrainandobstacledatabasesused byTAWS-BarereferencedtoMSL.UsingtheGPS positionandGSL
altitude,TAWS-Bdisplaysa 2-Dpicture ofthe surroundingterrain andobstacles relativeto theposition and
altitudeoftheaircraft.Furthermore, theGPSpositionandGSL altitudeareusedtocalculate and“predict”the
aircraft’sightpathinrelation tothesurroundingterrain andobstacles. Inthismanner,TAWS-Bcanprovide
advanced alerts of predicted dangerous terrain conditions.
Baro-correctedaltitude(orindicatedaltitude)isderivedbyadjustingthealtimetersettingforlocalatmospheric
conditions. The most accurate baro-corrected altitude can be achieved by frequently updating the altimeter
setting to the nearest reporting station along the flight path. However, because actual atmospheric conditions
seldommatchthe standardconditionsdened bythe InternationalStandardAtmosphere (ISA)model(where