Taws-A Abnormal Operations - Garmin GTN 625 Pilot's Manual

10.5.11 TAWS-A Abnormal operations

Foreword
TAWS-A continually monitors several system-critical items such as database
Getting
validity, flap and landing gear position, radar altimeter input, and GPS status.
Started
If the GTN does not contain Terrain, Airport Terrain, and Obstacle databases
Xpdr Ctrl
(or the databases are invalid), the aural message "TAWS System Failure" is
generated along with the "TAWS FAIL" alert annunciation.
Com/Nav
TAWS-A requires a 3-D GPS navigation solution along with specific vertical
accuracy minimums. Should the navigation solution become degraded or if
FPL
the aircraft is out of the database coverage area, the annunciation "TAWS N/A"
Direct-To
is generated in the annunciation window and on the TAWS-A page, the aural
message "TAWS Not Available" is generated if airborne, some TAWS-A terrain
Proc
alerts will not be issued, and GPWS alerting (which are not dependent on GPS
position) will continue to operate. When the GPS signal is re-established and the
Wpt Info
aircraft is within the database coverage area, the aural message "TAWS Available"
is generated.
Map
TAWS-A also requires radar altimeter input. Should the radar altimeter input
fail or become degraded, the annunciation "GPWS FAIL" is generated in the
Traffic
annunciation window and on the TAWS-A Page. The aural message "GPWS
Terrain
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
Weather
system has failed, GPWS-based alerts will not be available, while other TAWS-A
alerting remains unaffected.
Nearest
Multiple TAWS or GPWS annunciations cannot be displayed at the same
Services/
time. When multiple annunciations exist, an asterisk will be present next to the
Music
annunciation. The display of each annunciation will alternate with each being
Utilities displayed for approximately five seconds.
System
Messages
Symbols
Appendix
Index
10-60
Garmin GTN 625/635/650 Pilot's Guide 190-01004-03 Rev. F