Honeywell EGPWS MK V - Page 23

Mark V and Mark VII EGPWS Pilot’s Guide
060-4241-000 System Description
Rev H, August 2011 17
MODE 4C
Continued
Mode 4C is based on an EGPWS computed Minimum Terrain
Clearance (MTC) floor that increases with Radio Altitude. It
is active after takeoff when the gear or flaps are not in the
landing configuration. It is also active during a low altitude
go-around if the aircraft has descended below 245 feet AGL
(or 150 feet depending on aircraft type).
At takeoff the Minimum Terrain Clearance (MTC) is zero
feet. As the aircraft ascends the MTC is increased to 75% of
the aircraft’s Radio Altitude (averaged over the previous 15
seconds).
This value is not allowed to decrease and is limited to 500 feet
AGL for airspeed less than 190 knots. Beginning at 190 knots,
the MTC increases linearly to the limit of 1000 feet at 250
knots.
If the aircraft’s Radio Altitude decreases to the value of the
MTC, the EGPWS caution illuminates and the aural message
“TOO LOW TERRAIN” is enunciated.
EGPWS caution lights extinguish and aural messages cease
when the Mode 4C alert envelope is exited.
If the Aural Declutter feature is disabled, mode 4C alert
messages
are repeated continuously until the Mode 4C
envelope is exited.