MD-11 Flight Crew Operations Manual
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Automatic Flight -
Description and Operation
Auto.10.13
When the aircraft is below 1500 feet and is tracking both the localizer and
glideslope, the electrical busses will be split to provide complete electrical
isolation between AP systems. If the busses do not split, DUAL LAND will not
be available.
When a land mode is engaged, all other modes except go-around are inhibited.
Prior to land engagement the aircraft is controlled by a single channel of the
engaged AP. The second channel of the engaged AP and both channels of the
second AP are on stand-by.
At DUAL LAND engagement the three AP channels on stand-by become
operational and their associated control surface actuators are engaged. Also at this
time, the upper and lower rudder actuators engage in the parallel mode. The FMA
roll and altitude annunciations turn green and LOC, G/S DUAL LAND is
displayed. The AP annunciation below the FMA which annunciates AP1 or AP2
in all other modes, switches to AP.
Reversion to SINGLE LAND may occur if:
• The second AP is invalid.
• The autothrottles are invalid or not engaged.
• The electrical busses are not split.
• The sensor redundancy required for DUAL LAND is not achieved.
At SINGLE LAND engagement the FMA roll and altitude annunciations will
remain white and LOC, G/S SINGLE LAND is displayed. The AP annunciation
below the FMA displays AP1, AP2 or AP. If AP1 or AP2 is displayed, the two
channels of the engaged AP are operational in addition to parallel engagement of
one rudder. If AP is displayed, both APs are engaged and all surface actuators are
controlled as in a DUAL LAND.
A reversion from DUAL LAND to SINGLE LAND is indicated by the FMA
altitude control window annunciating G/S SINGLE LAND in white accompanied
by the roll control window annunciation turning white. Also, the altitude
annunciations flash five times to alert the pilot to the reversion. DUAL LAND
reversions are inhibited below 100 feet.
A reversion from SINGLE LAND to APPROACH ONLY is indicated by the
FMA altitude control window annunciating G/S APPROACH ONLY and flashing
five times.
When descending through 150 feet RA in either SINGLE or DUAL LAND, the
FMA roll control window annunciates ALIGN. If a crosswind is present, a side
slip runway alignment maneuver is initiated to remove any existing crab angle.
The crab angle is removed by the rudder and the up-wind wing is lowered to
maintain the localizer center.
October 02, 2006
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