MD-11 Flight Crew Operations Manual
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FMS -
Description and Operation
FMS.10.3
Operation
General
FMC operations include lateral navigation (NAV), vertical profile control
(PROF), and optimum speed control (SPD) functions coupled to the AP/FD
through targets or steering commands. The FMCs also provide AP/FD takeoff
(TO) and go-around (GA) references, variable bank angle limit control in AUTO
position, Vmin bank angle limiting, ILS LOC ONLY mode, VOR mode (option),
and Vmin speed and thrust limiting data.
FMC generated data, command entries and performance data are displayed on the
MCDU pages. Each flight mode has its own page or pages. Other functions of the
FMC are identification, initialization, position reference, radio tuning, navigation
reference, performance thrust limiting, takeoff, approach, go-around,
maintenance, sensor data, route data, route legs, route progress, and standby
operation.
Dual Mode
The FMS modes are DUAL, INDEPENDENT, and STANDBY.
INDEPENDENT and STANDBY modes are covered in the FMS DEGRADED
OPERATION in this chapter.
DUAL mode is the normal operating mode of the FMS. When operating in DUAL
mode, there is cross talk between the FMCs to ensure the following:
• MCDU entries made on one side are entered simultaneously into the other
FMC. The respective MCDUs can display different pages, however, if the
same page is displayed on each MCDU, the display is similar, but the
predicted values may not be the same.
• Initiation of leg sequencing occurs simultaneously in both FMCs.
• Independent calculations of aircraft position.
• Independent calculations of A/C gross weight
• Independent calculations of active thrust limit.
After DUAL mode is established, both FCCs select the FMC on the same side as
the FCC in control. This FMC will then become the master. This selection process
ensures that both Flight Directors (FD) will be controlled with the same steering
commands.
NOTE: Recalculation of data by the FMS may cause momentary
irregularities in displayed data.
October 02, 2006
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