Embraer Prodigy® Flight Deck 100 Pilot’s Guide
190-00728-04 Rev. A
392
HAZARD AVOIDANCE
6.4 TAWS-A
WARNING: Do not use TAWS information for primary terrain avoidance. TAWS-A 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-A(Terrain Awarenessand Warning System - Class A) is an optional feature designed to increase
situationalawarenessandaidinreducingcontrolledightintoterrain(CFIT).TAWS-A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.WhenTAWS-Aisinstalled,itsupersedestheTAWS-Bfeature.
TAWS-AsatisesTSO-C151bClassAandTSO-92crequirementsforcertication.
ClassATAWSrequiresthefollowingcomponents:
•Avalidterrain/obstacle/airportterraindatabase
•Avalid3-DGPSpositionsolution
•Validapandlandinggearstatusinputs
•Avalidradaraltimeter
TAWS-A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-Ausesinformation from the GPS receiver to provide a horizontal position and altitude, along with
additionalaltitudeinput fromthe radaraltimeter.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inparttodetermineTAWS-A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-Aarereferencedto meansealevel(MSL). UsingtheGPS
positionandGPS-GSLaltitude,TAWS-A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 GPS-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-Acanprovideadvancedalertsofpredicteddangerousterrainconditions.