MD-11 Flight Crew Operations Manual
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FMS -
Controls and Displays
FMS.30.106
The FMS supports DUAL, INDEPENDENT, and STANDBY operation modes.
One MCDU must be available to operate any FMS mode. Dual mode is the normal
mode of the FMS. In DUAL mode the two FMCs communicate with each other
(crosstalk) and is operable in any FMS transfer switch configuration selected on
the source input select panel (SISP). When CAPT ON 2 or F/O ON 1 is selected,
the Captain or F/O MCDU will display the MENU page. If FMC2 or FMC1 is
available, the <FMC-2 or <FMC-1 prompt is shown in line 1L of the MENU page
for pilot selection.
DUAL mode operation involves both FMCs operating together with one acting as
master and the other as spare. Following a long term power transient, the first
FMC up is designated the master and begins crosstalk communication with the
spare by comparing databases, operational programs, and aircraft configuration
data (aero model, engine type) as displayed on the A/C STATUS page. If this data
is identical, the master FMC will begin memory synchronization (including
pilot-entered data) of the spare. Upon completion of memory synchronization,
DUAL mode will be established.
If a single FMC generates an automatic reset in DUAL mode operation, then it
will be resynchronized by the master FMC. However, if both FMCs generate an
automatic reset at the same time, then the pilot must reenter data (GW, ZFWCG,
F-PLN, radio tuning). The MCDU STANDBY flight plan and radio tuning will
also be cleared. The pilot will be prompted to reenter data by SP messages
displayed on the MCDU.
An FMC change could cause the FMS to operate in INDEPENDENT mode (no
crosstalk) if the data in each installed FMC is not the same. Any discrepancy on
the A/C STATUS page generates the MCDU message A/C STATUS
MISMATCH.
After DUAL mode is established, both FCCs will select only one FMC to be 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.
If the onside FCC fails, all FMS modes will disengage on the onside FMS. If the
offside FCC fails, there should be no effect. All FMS modes should be available.
To correct the loss of FMS modes the pilot should push the AUTOFLIGHT button
on the FCP and then reselect FMS modes.
In DUAL mode operation, aircraft present position, gross weight, and active thrust
limit is computed independently by each FMC. Individually computed data is
compared and any significant errors are annunciated with an MCDU message as
follows:
October 02, 2006
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