Premature Descent Alerting (Pda); Terrain Failure Alert - Garmin GNS 400W Pilot's Manual & Reference

2 - NAV PAGES
Terrain Alerts

Premature Descent Alerting (PDA)

The TERRAIN system issues a Premature Descent
Alert (PDA) when the system detects that the aircraft
is significantly below the normal approach path to a
runway.
PDA ends when the aircraft is either:
• 0.5 NM from the runway threshold
OR
• is below an altitude of 125 feet AGL while
within
1.0 NM of the threshold.
PDA Severity Levels
CAUTION — The above annunciation and pop-up
terrain alert are displayed during a PDA alert.
48
Premature Descent Alerting (PDA) Threshold
190-00356-00 Rev G

TERRAIN Failure Alert

The TERRAIN system continually monitors
several system-critical items, such as database validity,
hardware status, and GPS status. Should the system
detect a failure, a message is annunciated "TERRAIN
has failed".
"TERRAIN has failed" message