.
red PULL UP lights illuminate

.
aural TERRAIN, TERRAIN PULL UP message is annunciated

.
aural OBSTACLE, OBSTACLE PULL UP message is annunciated

.  
green TERR lights illuminate and the Terrain Display Self Test pattern is displayed on the WXR display

.
red PULL UP lights extinguish

.  
Terrain Display Self Test pattern and green TERR lights extinguish after several sweeps of the terrain/obstacle display

.  
amber Ground Proximity INOP and Terrain Display Select INOP lights extinguish

A system self test must be performed before the first flight of the day.

GROUND PROXIMITY Gear Inhibit Switch
GEAR INHIBIT – inhibits or cancels warnings/alerts caused by landing gear not down.
NORMAL (guarded position) – landing gear position logic is provided for GPWS.

GROUND PROXIMITY Flap Inhibit Switch
FLAP INHIBIT – inhibits or cancels warnings/alerts caused by flaps not in 30 or 40 position.
NORMAL (guarded position) – flap position logic is provided for GPWS.
Copyright . The Boeing Company. See title page for details.
15.10.8   August 1, 2003

Warning Systems -Controls and Indicators 737 Operations Manual

GROUND PROXIMITY Terrain Inhibit Switch
TERR INHIBIT – inhibits terrain/obstacle alerting.
NORMAL (guarded position) – Enhanced GPWS features are enabled.

GPWS Terrain Display Select Switch

Terrain (TERR) Display Select Switch
(located lower right hand edge of each EHSI)
Push – . one panel is dedicated to the Captain and the other panel is dedicated to the First Officer.
.  
when a WXR or TERR switch is selected, either the weather or EGPWS terrain awareness display is shown on the associated pilot’s EHSI display.

.  
pressing the WXR switch when weather is displayed, or pressing the TERR switch when terrain is displayed, will deselect the display function.

Warning Systems -Controls and Indicators 737 Operations Manual

Terrain Display

Copyright . The Boeing Company. See title page for details.
15.10.10  August 1, 2003

Warning Systems -Controls and Indicators 737 Operations Manual

Terrain Display
Color and density vary based on terrain height vs. airplane altitude:
.  
dotted green: terrain from 2,000 feet below to 500 feet (250 feet with gear
down) below the airplane’s current altitude

Note:  When all terrain (within the display range) is greater than 2,000 feet below airplane altitude, only the highest peaks are displayed. A peak is defined as any terrain that is equal to or higher than the top 50% of the highest terrain within the display range. For example, if an airplane is at 6,000 feet (20 nm display range selected), and the highest terrain within the display range is a 3,000 foot mountain, only the top 1,500 feet of this mountain and all other terrain that is at least 1,500 feet high, is displayed.

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dotted amber: terrain 500 feet (250 feet with gear down) below to 2,000
feet above the airplane’s current altitude

.
dotted red: terrain more than 2,000 feet above airplane’s current altitude

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dotted magenta: no terrain data available

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solid amber: look–ahead terrain caution active

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solid red: look–ahead terrain warning active.

Note:  In areas without terrain data, look-ahead terrain alerting and display functions not available. Radio altitude based terrain alerts function normally.
Note: Terrain within 400 feet of nearest airport runway elevation does not show.
Automatically shows when:
.
a look–ahead terrain alert occurs, and

.
neither pilot has the terrain display selected, and

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in expanded MAP, center MAP, expanded VOR, or expanded APP modes.

Updates with a display sweep, similar to weather radar display.

Terrain Mode Annunciation
TERR (cyan) – Terrain display enabled (manual or automatic display).

TERRAIN/OBSTACLE Annunciation
TERRAIN (amber) – look–ahead terrain caution alert active.
TERRAIN (red) – look–ahead terrain warning alert active.
OBSTACLE (amber) – obstacle alert caution active.
OBSTACLE (red) – obstacle alert warning active.
Shows in all navigation display modes.
Warning Systems -Controls and Indicators 737 Operations Manual

TERR (Terrain) Elevation
Displays elevation of highest and lowest terrain.
The color of the elevation display corresponds to the color of the terrain display:
.
green – terrain elevation is more than 500 ft below airplane altitude
　
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