Garmin GNC 420W Pilots Guide - Page 188
Terrain Not Available Alert, Terrain Failure Alert,
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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. 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 has failed' is generated on the TERRAIN Page (Figure 10-9). Figure 10-8: TERRAIN NOT AVAILABLE Display Figure 10-9: TERRAIN FAILED Display 10-8 GNC 420(A) Pilot's Guide and Reference 190-00140-20 Rev. K
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