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on aircraft speed such that the alert threshold is ramped
060-4241-000 • Rev. E - December 2003
MK V & MK VII EGPWS Pilot Guide 15
between 245 feet at 159 knots to 1000 feet at 250 knots.
Below 245 feet AGL and less than 159 knots airspeed, the Mode
4B aural alert is “TOO LOW FLAPS”. For turboprop and select
turbofan aircraft, the “TOO LOW FLAPS” warning curve is
lowered to 150 feet AGL and less than 148 knots.
If desired, the pilot may disable the “TOO LOW FLAPS” alert
by engaging the Flap Override switch (if installed). This precludes
or silences the Mode 4B flap alert until reset by the pilot.
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.
For either Mode 4B alert, subsequent alert messages occur for
each 20% degradation in altitude. EGPWS caution lights extinguish
and aural messages cease when the Mode 4B alert
envelope is exited.
MODE 4B
Continued
If the Aural Declutter feature is disabled, mode 4B alert
messages are repeated continuously until the Mode 4B
envelope is exited.
The Mode 4C alert is intended to prevent inadvertent controlled
flight into the ground during takeoff climb into terrain that
produces insufficient closure rate for a Mode 2 alert. After
takeoff, Mode 4A and 4B provide this protection.
MODE 4C
060-4241-000 • Rev. E - December 2003
16 MK V & MK VII EGPWS Pilot Guide
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.
MODE 4C
Continued
060-4241-000 • Rev. E - December 2003
MK V & MK VII EGPWS Pilot Guide 17
MODE 5 Mode 5 provides two levels of alerting for when the
aircraft descends below glideslope, resulting in
activation of EGPWS caution lights and aural messages.
The first level alert occurs when below 1000 feet Radio
Altitude and the aircraft is 1.3 dots or greater below the
beam. This turns on the caution lights and is called a
“soft” alert because the audio message “GLIDESLOPE”
is enunciated at half volume. 20% increases in the
below glideslope deviation cause additional
“GLIDESLOPE” messages enunciated at a progressively
faster rate.
The second level alert occurs when below 300 feet Radio
Altitude with 2 dots or greater glideslope deviation.
This is called a “hard” alert because a louder
“GLIDESLOPE, GLIDESLOPE” message is enunciated
every 3 seconds continuing until the “hard” envelope is
exited. The caution lights remain on until a glideslope
deviation less than 1.3 dots is achieved.
Excessive
Deviation
Below
Glideslope
To avoid unwanted Below Glideslope alerts when
capturing the localizer between 500 and 1000 feet AGL,
alerting is varied in the following ways:
• Below Glideslope alerts are enabled only if the localizer
is within 2 dots, landing gear and flaps are selected,
Glideslope Cancel is not active, and a front course approach
is determined.
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18 MK V & MK VII EGPWS Pilot Guide
• The upper altitude limit for the alert is modulated with
vertical speed. For descent rates above 500 FPM, the upper
limit is set to the normal 1000 feet AGL. For descent rates
lower than 500 FPM, the upper limit is desensitized
(reduced) to a minimum of 500 feet AGL.
Additionally, both alert levels are desensitized below 150 feet
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