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 11.32.5
The FMC usually uses the calculated value for performance computations. Before
engine start, the calculated value is set to agree with the fuel quantity indicating
system value. When the FMC receives a positive fuel flow signal at engine start,
the calculated value is independent of the fuel quantity system and decreases at the
fuel flow rate.
When the APU is running, the APU fuel burn schedule is used to decrease the
calculated fuel value.
During fuel jettison, the calculated value is set equal to the fuel quantity system
value. When fuel jettison is completed, the calculated value is independent of the
fuel quantity indicating system and decreases at the fuel flow rate. This fuel
quantity value displays as CALC (calculated) on the PERF INIT page and
CALCULATED on PROGRESS page 2/4.
If the flight crew inputs a fuel quantity, the line title changes to MANUAL and
replaces the calculated value. Like the calculated value, the manual value is
updated by fuel flow rate.
The calculated value is invalid if fuel flow data is invalid. The FMC uses the fuel
quantity indicating system quantity for performance computations. The line title
on the PERF INIT page changes to SENSED and displays as TOTALIZER on
PROGRESS page 2/4.
The fuel used by each engine is calculated with its related fuel flow signal. FUEL
USED displays on PROGRESS page 2/4. FUEL USED values are retained
through flight completion and are subsequently cleared at engine start or
following a long-term power interrupt on the ground. If the fuel flow signal is
invalid while on the ground or invalid for greater than two minutes after airborne,
the display blanks.
The EICAS advisory message FUEL DISAGREE is displayed if the FMC
calculates a large difference between the fuel quantity indicating system quantity
and calculated value. The flight crew should select PROGRESS page 2/4, and
select the fuel value for the FMC to use through landing.
The FMC continually estimates the amount of fuel remaining at the destination
airport if the active route is flown. The EICAS advisory message INSUFFICIENT
FUEL is displayed whenever the FMC estimates that fuel remaining will be less
than the fuel reserve value entered on the PERF INIT page and no MOD is
pending.The CDU help window message INSUFFICIENT FUEL displays if the
estimate is less than the fuel reserve value entered on the PERF INIT page and a
MOD is pending.
Note: FMC calculated fuel predictions assume a clean configuration. Flight with
gear or flaps extended cause fuel prediction errors. Fuel predictions are
accurate after the gear and flaps are retracted.
February 15, 2010
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