737 Flight Crew Operations Manual
Flight Management, Navigation -
Flight Management Computer
Boeing Proprietary. Copyright © Boeing. May be subject to export restrictions under EAR. See title page for details.
11.32.6 D6-27370-866-EGP
Prior to U10.8, the FMC would shut down after three consecutive software resets
within 60 seconds. U10.8 and on, is revised such that FMC resets are managed
more effectively. The software exceptions handling logic has been revised to
prevent a complete FMC restart in the event of most software exceptions. If
performance data is entered, an exception in most processing will result in a
downgrade of FMC operation, not a complete loss of function.
In the downgrade mode:
• LNAV and Map are retained
• FMC Predictions are halted
• VNAV is disconnected
If the software exception occurs in processing of the active flight plan, an alerting
level message, VNAV INVALID - PERF, will be displayed for the pilot indicating
re-entry of Cost Index is required in order to restart the internal software
predictions process, which is required before reengagement of VNAV. Predictions
can be restarted allowing VNAV to be reengaged after entry and EXEC of Cost
Index on the PERF INIT page.
When a software reset occurs in the MOD PLAN and not the ACT PLAN, the
FMC will delete the MOD PLAN. An advisory message, INVALD MOD PLAN,
will be displayed for the pilot indicating that this has occurred. LNAV and VNAV
will remain engaged for this case.
When a software reset occurs in an INACTIVE PLAN, the FMC will delete the
INACTIVE PLAN (no change from current operation). An advisory message,
INVALD INACTIVE PLAN, will be displayed for the pilot indicating that this
has occurred.
This improvement will not prevent all restarts; it does not cover those that may
leave the FMC’s memory in an inconsistent state.
September 15, 2016
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