060-4314-000 • Rev. C - May 2004
18 MK VI & MK VIII EGPWS Pilot Guide
MODE 4B
Unsafe terrain clearance gear up turbofan (Jets)
MODE 4A
Continued
During Marginal performance go around (gear down then
brought up without a landing) or extended gear up approach
(gear up and either Flap Override on or flaps down) the MK VI/
VIII EGPWS is designed to delay Mode 4A "TOO LOW GEAR" alerts
until the Mode 4B curve is penetrated.
Mode 4B is active during cruise and approach with gear down
and flaps not in the landing configuration.
The standard boundary for Mode 4B is at 170 feet AGL. Penetra
-
tion of this altitude below an airspeed of 150 knots will produce
an aural alert of “TOO LOW FLAPS“. If the alternate airspeed
configuration has been selected, the boundary is 200 feet AGL
and the airspeed limit is 148 knots. For turbofan (bizjet) aircraft,
the boundary is 245 feet AGL and its airspeed limit is 159 knots.
Above 150 knots, the boundary increases linearly with airspeed
to a maximum of 750 feet AGL at 200 knots to produce a “TOO
LOW TERRAIN” aural alert. If the alternate airspeed configura-
tion has been selected, the slope begins at 148 knots and ends at
200 knots and 1000 feet AGL. For turbofan (bizjet) aircraft, the
slope begins at 159 knots and ends at 250 knots and 1000 feet
AGL. (See following graphs)
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