Garmin GPS 500 Pilot's Manual & Reference page 174

SECTION 10
TERRAIN
TERRAIN NOT AVAILABLE ALERT
TERRAIN 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
'TER N/A' is generated in the annunciation window and
'TERRAIN NOT AVAILABLE' is generated on the TERRAIN
Page (Figure 10-8). When the GPS signal is re-established
and the aircraft is within the database coverage area, the
'TER N/A' visual annunciation is removed.
Figure 10-8: TERRAIN NOT AVAILABLE Display
10-8
TERRAIN FAILURE ALERT
TERRAIN continually monitors several system-critical
items such as database validity, hardware status, and GPS
status. If the terrain/obstacle database is not available,
'TER FAIL' is generated in the annunciation window, and
'TERRAIN FAILED' is generated on the TERRAIN Page
(Figure 10-9).
GPS 500 Pilot's Guide and Reference
Figure 10-9: TERRAIN FAILED Display
190-00181-60 Rev. G