OPERATIONS MANUAL

Warning Systems
EGPWS – Terrain Alerting & Display:
This function generates terrain raster images on the NDs when TERR is
selected on the EFIS control, or when a terrain look ahead alert sounds.
The image is sent through the same raster data bus the weather radar uses,
and is continuously updated by left and right sweeps, similar to radar
sweeps. To prevent confusion with the radar raster, the EGPWS uses special
dot patterns. Also, unlike the radar raster, the terrain raster is composed of
tiles; the lower the ND range, the larger the tiles.—A dot pattern has either
a high or a low dot density; high density patterns appear brighter than low
density patterns. (In the simulator, the dots are slightly enlarged and blurred
in order to avoid flickering moiré effects during map motion.)
When a terrain look ahead caution exists, the predicted collision area is
shown in solid amber; respectively, in solid red if it is a warning. The solid
colored areas provide the highest brightness. During the alert, the NDs
also show the word TERRAIN in amber or red, according to the current
alert level.
High density red
+2000 ft
High density amber
Low density amber
+1000 ft
Aircraft altitude
High density green
-500 ft
-1000 ft
Low density green
Black
-2000 ft
(or 400 ft
above
nearest
runway)
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