MD-11 Flight Crew Operations Manual
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FMS -
Controls and Displays
FMS.30.108
Single Flight Management Computer
The FMS BITE consists of a combination of internal software and hardware
monitors within the FMC and MCDU. The BITE can detect and isolate at least
95% of all failures in the FMS. When an error or failure is detected, the FMS will
attempt to correct the situation with hardware/software resets. During single FMC
operation, if the FMC detects the same software error four times within five
minutes, and the FMS flight phase is not descent or approach, then all pilot entered
data will be automatically cleared during a long term reset. The pilot must reenter
data (GW, ZFWCG, F-PLN, radio tuning). The pilot will be prompted to reenter
data by SP messages on the MCDU. This automatic reset is generated to prevent
the FMC from latching fail. During descent or approach, if the software error
cannot be corrected the FMC will latch fail (completely stop processing) and the
MENU page will display without an FMC prompt.
If the master FMC latch fails, it is detected by itself and the slave FMC. The slave
FMC will then function as the master FMC as selected by the FCCs.
When an FMC latch fails, the affected pilot may select the other FMC with the
SISP FMS transfer switches. During single FMC operation, both NDs will display
proper information as long as the same modes (NAV, VOR, APPR, or PLN) and
ranges are selected on both ECPs. Both MCDUs will function normally to make
inputs to the functional FMC.
If an MCDU failure is detected, the MCDU display is blanked and the FAIL light
on the MCDU (lower left) illuminates.
NO FMS SPD/PROF Message
When the NO FMS SPD/PROF message is displayed on the A/C STATUS page,
the FMS is operating in a limited mode of operation. All functions involving
active performance and vertical guidance will be inoperative (FMS speed, vertical
profile, fuel computation, F-PLAN predictions). If one FMC initiates a NO FMS
SPD/PROF message, the other FMC will revert to the same limited condition.
This condition can be identified by the following indications: NO FMS
SPD/PROF message on the A/C STATUS page, ATS OFF remains amber after
engine start, takeoff green band removed from the stabilizer position display and,
thrust limit values will become dashed.
This condition is caused by lack of valid performance data loaded in the FMC.
October 02, 2006
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