Garmin GNS 530 Pilot's Manual And Reference page 202

SECTION 12
TERRAIN
TERRAIN NOT AVAILABLE ALERT TERRAIN FAILURE ALERT
along with specific vertical accuracy minimums. Should
the navigation solution become degraded or if the aircraft status. If the terrain/obstacle database is not available,
is out of the database coverage area, the annunciation
and the aircraft is within the database coverage area, the
Figure 12-9: TERRAIN FAILED Display
Figure 12-8: TERRAIN NOT AVAILABLE Display
190-00181-00 Rev. G
12-8 GNS 530(A) Pilot's Guide and Reference