GNS 430(A) Pilot’s Guide and Reference
190-00140-00 Rev. P
11-7
SECTION 11
TERRAIN
Premature Descent Alerting
A Premature Descent Alert (PDA) is issued when the
system detects that the aircraft is significantly below the
normal approach path to a runway (Figure 11-5).
PDA alerting begins when the aircraft is within 15 nm
of the destination airport. PDA alerting ends when the
aircraft is either:
• 0.5 nm from the runway threshold
OR
• at an altitude of 125 feet AGL while within 1.0
nm of the threshold.
700
600
500
400
300
200
100
Height Above Terrain (Feet
)
Distance From Destination Airport (nm)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
“Too Low Terrain”
“Too Low Terrain”
Runway
Threshold
Figure 11-5 PDA Alerting Threshold
TERRAIN Inhibit
TERRAIN also has an inhibit mode that deactivates the
FLTA/PDA visual alerts. Pilots should use discretion when
inhibiting TERRAIN and always remember to enable the
system when appropriate.
Inhibiting TERRAIN:
1) Select the TERRAIN Page and press the
MENU
Key. ‘Inhibit Terrain?’ is selected by default
(Figure 11-6).
Figure 11-6 TERRAIN Page Menu
2) Press the
ENT
Key. The ‘TER INHB’ annunciation
is displayed in the TERRAIN annunciator field
when TERRAIN is inhibited (Figure 11-7).
Annunciator Field
Figure 11-7 Annunciator Field
Enabling TERRAIN:
1) Select the TERRAIN Page and press the
MENU
Key. ‘Enable Terrain?’ is selected by default.
2) Press the
ENT
Key. The TERRAIN system is
functional again.
Summary of Contents for GNS 430
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