MD-11 Flight Crew Operations Manual
Warning and Alerting -
Description and Operation
Copyright © The Boeing Company. See title page for details.
KL Warn.10.17
• Mode 4B - Insufficient Terrain Clearance, Flaps Up. When the landing
gear is lowered, mode 4B is active. Upper boundary has decreased to 245
feet RA. If the aircraft penetrates this boundary at an airspeed below 159
kts and flaps not in landing configuration, the voice warning will be TOO
LOW FLAPS and the amber GROUND PROX message will appear on
the PFD. Above 159 kts the boundary increases linearly (same as mode
4A) and the voice warning is TOO LOW TERRAIN.
• Mode 4C (with EGPWS installed) - Insufficient Terrain Clearance at
Takeoff. Provides a warning based on minimum RA clearance during
takeoff. A value equal to 75 percent of the current RA is stored in a filter.
If the RA begins to decrease, the maximum attained value is stored. If the
altitude decreases below the stored value, a TOO LOW TERRAIN voice
warning will be generated and the amber GROUND PROX message will
be displayed on the PFD.
Mode 5 - Descent Below Glideslope
Mode 5 provides two levels of warning when aircraft descent is below the
glideslope on an ILS approach.
• Mode 5 soft alert - Alert occurs when the aircraft is more than 1.3 dots
below the glideslope. This alert is called soft because the volume level of
the alert is less than the volume of other warnings. This soft alert envelope
has a typical upper limit of 1,000 feet. Voice warning GLIDESLOPE is
generated and the BELOW G/S switch is illuminated.
• Mode 5 hard alert - Alert occurs when the aircraft is below 300 feet RA
with more than 2 dots below the glideslope. It is called a hard alert
because the volume level is raised to that of the other warnings. Provides
the same warnings as the soft alert.
Mode 5 warning can be cancelled by the flight crew by pushing the BELOW G/S
switch on the glareshield at any time below 2,000 feet RA. The warning is reset
by climbing above 1,000 feet or descending below 30 feet.
Mode 6 - Altitude Callouts/Excessive Bank Angle Warning
Mode 6 provides optional callouts for descent through predefined radio altitudes
between 2,500 and 10 feet AGL and excessive roll or bank angle warning.
Bank angle warning provides over-banking protection during approach, climbout,
and cruise. Additionally, the warning protects against wing or engine strikes
during landing.
The bank angle warning limits are determined by two factors as follows:
• The basic bank angle limits that vary linearly from 6 degrees at 0 feet (and
below) RA to 40 degrees at 150 feet RA and above and
• The roll rate adjustment of 1.5 degrees added for every 1 degree roll rate
(limited to +/- 6 degrees).
If RA data is invalid, the bank angle warning limit will be 40 degrees.
November 16, 2009
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