787 Flight Crew Operations Manual
DO NOT USE FOR FLIGHT
Flight Management, Navigation -
Flight Management Computer
Copyright © The Boeing Company. See title page for details.
D615Z003-TBC 11.32.7
Loss of FMC Electrical Power
The FMC must have continuous electrical power to operate. When the electrical
power is interrupted and returns, the FMC restarts.
After restart, the performance data displayed on the PERF INIT page must be
re–entered. The route previously in use is available but must be reactivated.
The flight crew must modify the active waypoint to activate LNAV. Selecting the
applicable active waypoint and proceeding direct or intercepting a course to the
waypoint allows LNAV activation.
FMC Failure
Single FMC Failure
At powerup, the three FMCs are designated as master, spare and backup. All
Flight Management computing tasks are accomplished by the master (active)
FMC. The spare (standby) FMC automatically becomes active and assumes all
FMC functionality in the event the master FMC fails. The backup FMC then
assumes the role of the spare FMC. This transition occurs automatically and is not
apparent to the crew. No crew action is necessary. LNAV and VNAV, if active,
remain active and all flight plan and performance data is retained.
Dual FMC Failure
If two FMCs fail in flight, the third FMC automatically takes over in a single FMC
configuration. The EICAS advisory message SINGLE FMC is displayed. All data
is retained, NDs continue to operate, but LNAV and VNAV is disengaged. The
flight crew needs to reactivate and execute the flight plan, and reselect LNAV and
V N AV.
A software reset may occur while in single FMC operation. This is a
self-protection mode which prevents permanent loss of the FMC in the unlikely
event the FMC is presented with an insoluble computation. Resets are
accompanied by the appropriate CDU help window message. Symptoms of a reset
may include the active route becoming inactive, performance data being erased,
and LNAV and VNAV disengaging. To regain FMC operation, select another roll
and/or pitch mode on the MCP, enter necessary performance data on the PERF
INIT page, activate and execute the flight plan, and re-engage LNAV and VNAV.
August 14, 2009
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