Honeywell EGPWS MK V Pilot's Manual page 30

Terrain
Look
Ahead
Alerting
continued
30
This is accomplished (when enabled) based on aircraft posi-
tion, flight path angle, track, and speed relative to the terrain
database image forward the aircraft.
Through sophisticated look ahead algorithms, both caution and
warning alerts are generated if terrain or an obstacle conflict
with "ribbons" projected forward of the aircraft (see following
illustration). These ribbons project down, forward, then up
from the aircraft with a width starting at 1/4 nm and extending
out at ± 3º laterally, more if turning. The look-down and up
angles are a function of the aircraft flight path angle, and the
look-down distance a function of the aircraft's altitude with re-
spect to the nearest or destination runway. This
relationship prevents undesired alerts when taking off or
landing. The look-ahead distance is a function of the aircraft's
speed, and distance to the nearest runway.
A terrain conflict intruding into the caution ribbon activates
EGPWS caution lights and the aural message "CAUTION
TERRAIN, CAUTION TERRAIN" or "TERRAIN AHEAD,
TERRAIN AHEAD". An obstacle conflict provides a "CAUTION
OBSTACLE, CAUTION OBSTACLE" or "OBSTACLE AHEAD, OB-
STACLE AHEAD" message. The caution alert is given
typically 60 seconds ahead of the terrain/obstacle conflict and is
repeated every seven seconds as long as the conflict remains
within the caution area.
When the warning ribbon is intruded (typically 30 seconds
prior to the terrain/obstacle conflict), EGPWS warning lights ac-
tivate and the aural message "TERRAIN, TERRAIN, PULL UP" or
"OBSTACLE, OBSTACLE, PULL UP" is enunciated with "PULL
UP" repeating continuously while the conflict is within the
warning area.
WARN
CAUTION
060-4241-000 • Rev. D - March 2000
MK V & MK VII EGPWS Pilot Guide