060-4241-000 • Rev. D - March 2000
MK V & MK VII EGPWS Pilot Guide
System constraints for the EGPWS are:
• If terrain data is unavailable for a particular area, then
Terrain and Obstacle alerting and display is not available for
that area and the affected display area is colored MAGENTA.
• The display of terrain and obstacle information is intended
to serve as a situational awareness tool. It does not provide
the accuracy and/or fidelity to be the sole source for
deciding terrain or obstacle avoidance. Navigation must not
be predicated upon the use of the EGPWS terrain/Obstacle
• If there is no source of aircraft position data meeting the
accuracy requirements for the TAD and TCF functions, then
these enhanced functions are automatically inhibited with a
resultant Terrain inoperative or unavailable indication.
• TAD/TCF functions should be manually inhibited within 15
nm on approach to an airport that is not in the airport
database to avoid unwanted alerts.
• TAD/TCF functions should be manually inhibited during
QFE operations if GPS data is unavailable or inoperative.
• TAD/TCF functions should be manually inhibited for
ditching or other off-airport landings.
• When the TAD/TCF functions are inhibited and the EGPWS
is otherwise functional, the EGPWS reverts to providing
basic GPWS functions (Modes 1 to 6 and Windshear). In
this state, the EGPWS may give little or no advance warning
time for flight into precipitous terrain where there are few or
no preceding obstructions. This particularly applies if:
• The aircraft is in the landing configuration.
• The aircraft is in a stabilized descent at a
normal approach descent rate.
• There is no ILS GLideslope signal being recieved by the
EGPWS (not tuned, not available, or inoperative).
• Terrain clearance or descent rates that are not compatible
with required minimum regulatory standards for Ground
Proximity Warning equipment may cause unwanted alerts.
• If enabled, the EGPWS uses onboard measurement of air
mass parameters and aircraft acceleration for detection of
windshear. This is a reactive system and cannot predict
windshear, which may be ahead of the aircraft.