Fuel Quantity Processor
The value of FMC calculated fuel quantity is set equal to the total
fuel quantity from the fuel quantity processor when the airplane is on
the ground and there is no fuel flow. When fuel flow begins, the
initial fuel quantity value is saved for all future calculations and the
fuel flow input data from the EICAS computer is integrated, summed
and saved. FMC calculated fuel is computed by subtracting the fuel
flow sum from the initial fuel quantity value. Throughout the flight,
the difference between FMC calculated fuel and total fuel quantity is
computed. If the difference exceeds 1360 kgs, a CDU alert message
is generated (FUEL DISAGREE - Prog Pg 2). To avoid false alarms
due to slosh during maneuvers the fuel discrepancy must exceed 910
kgs for 6 minutes before the 1360 kg threshold is checked.
After recieving a "Fuel disagree Progress 2/2" message in the FMS scratchpad, what actions are taken?
Not sure what actions, I guess you could look for a possible fuel leak.
I.E If you started with 50k, and your fuel Totaliser is now indicating 40k, yet the left eng fuel flow transmitter has counted 4k used and the right eng fuel flow transmitter has counted 4k (8k total burn) what has happened to the other 2k??
One of a few things is the prob here.
1) one of the fuel flow transmitters is inaccurate.
2)The fuel quantity indication system is inaccurate.
3) Fuel is being lost somewhere.
4)EICAS computer is sending bad info to FMC
5)FMC is stuffing up its calculations.
This defect pops up from time to time and we generally replace one of the eng fuel flow transmitters.