Garmin Flight Deck 100 User Manual

190-00728-04  Rev. A

®

409

TAWS-A continually monitors several system-critical items such as database validity, flap and landing gear

position, radar altimeter input, and GPS status.

If no GDU contains Terrain, Airport Terrain, and Obstacle databases (or the databases are invalid), the aural

message “TAWS System Failure” is generated along with the ‘TAWS FAIL’ alert annunciation.

TAWS-A requires a 3-D GPS navigation solution along with specific vertical accuracy minimums. Should the

navigation solution become degraded or if the aircraft is out of the database coverage area, the annunciation 
‘TAWS N/A’ is generated in the annunciation window and on the TAWS-A Page. The aural message “TAWS 
Not Available” is also generated if airborne, and some TAWS-A terrain alerts will not be issued (Table 6-12),
while GPWS alerting (which are not dependent on GPS position) will continue to operate. When the GPS
signal is restored and the aircraft is within the database coverage area, the aural message “TAWS Available” is
generated.

TAWS-A also requires radar altimeter input. Should the radar altimeter input fail or become degraded, the

annunciation  ‘GPWS  FAIL’  is  generated  in  the  annunciation  window  and  on  the  TAWS-A  Page.    The  aural
message “GPWS System Failure” is also generated. The ‘GPWS FAIL’ annunciation will also occur if both GPS
altitude and barometric altitude are unavailable. If only the GPWS system has failed, GPWS-based alerts will
not be available (Table 6-12), while other TAWS-A alerting remains unaffected.