GNC 420(A) Pilot’s Guide and Reference
SECTION 3
NAV PAGES
3-15
190-00140-20 Rev. K
3.5 TERRAIN PAGE
NOTE: The TERRAIN Page does not appear on
GNC 420 units that are not properly equipped
with or configured for TERRAIN. See Section 9
for a full description of TERRAIN functions.
TERRAIN Page
To display the TERRAIN Page, select the NAV Page
Group and turn the small right knob until the TERRAIN
Page is displayed (Figure 3-26 and 3-27). The TERRAIN
Page displays:
• GPS-derived MSL altitude shown in increments of
20 feet or 10 meters, depending on unit configu-
ration. The ‘G’ to right of the MSL altitude display
reminds the pilot that altitude is GPS-derived.
• Aircraft ground track
• Terrain Range - Indicates the terrain elevation in
colors relative to the aircraft altitude
• Range marking rings - (1 nm, 2 nm, 5 nm, 10 nm,
25 nm, 50nm, and 100 nm)
• Heading Indicator - The heading indication on the
TERRAIN Page always displays ‘TRK’ for Track-
up, unless there is no valid heading
• Obstacles
• Potential Impact Points
Figure 3-26 TERRAIN Page 120˚ View
GPS-derived
MSL Altitude
Red Terrain (Warning - Terrain Above or
Within 100’ Below Aircraft Altitude)
Number of Pages in
Current Page Group
Position of
Current Page
within Current
Page Group
Current Page Group
Heading
Indicator
Figure 3-27 TERRAIN Page 360˚ View
Yellow Terrain (Caution
- Terrain Between 100’
and 1000’ Below Aircraft
Altitude)
Black Terrain (No Danger
- Terrain More than
1000’ Below Aircraft
Altitude)
Range
Marking
Ring
Selectable Display Settings
The TERRAIN Page has two selectable view settings:
• 360˚ View - View from above aircraft depicting
surrounding terrain on all sides
• 120˚ View - View of terrain ahead of and 60˚ to
either side of the aircraft ight path (Figure 3-27)
NOTE: The TERRAIN Page gives a ‘Track Up’
display orientation, as indicated by the ‘TRK’
label shown on the display. This is the only
orientation available on this page.
