Garmin GNS 430 Pilot's Manual And Reference page 196

SECTION 11
TERRAIN
FLTA Alerts
• 'TERRAIN ADVISORY' advisory - Estimated
potential impact in approximately 60 seconds
after pop-up alert and annunciation (Figure 11-6).
Similarly, an 'OBSTACLE ADVISORY' alert is also
provided.
Figure 11-6 'TERRAIN ADVISORY' Advisory
• 'TERRAIN AHEAD' alert (flashing) - Estimated
potential impact in approximately 30 seconds
after pop-up alert and annunciation (Figure 11-7).
Similarly, an 'OBSTACLE AHEAD'' alert is also
provided.
Figure 11-7 'TERRAIN AHEAD' Alert (flashing)
11-8
Premature Descent Alerting (PDA)
The TERRAIN system issues a Premature Descent alert
when the system detects that the aircraft is significantly
below the normal approach path to a runway. There are
three different scenarios to consider with PDA:
• No Approach Loaded - PDA alerting begins when
the aircraft is within 15 nm of the destination
airport and ends when the aircraft is either 0.5 nm
from the runway threshold OR is at an altitude of
125 feet AGL while within 1 nm of the threshold.
During the final descent, algorithms set a
threshold for alerting based on altitude, distance,
and other parameters.
GNS 430 Pilot's Guide and Reference