Fuel Disagree

[WAD3 0]

I keep getting a fuel disagree between the calculated amount and what is reading on the fuel page in the EICAS. Is there a way I can adjust it in the FMC. I am not able to adjust it on the PERF page.

[golli 0]

Good day.Are you flying with accelerated sim rate like 16x? Golli.

[WAD3 0]

I was doing just 2x. I have only done that twice and twice I had the issue. Is it related?

[golli 0]

Hi. I only get this issue when going to 16x (yes I dont have time for EDDF-KSFO etc. in real time).So I know what amount of fuel I was suposed to end up with, and I load that amount into her @ TOD.I normally never go beyond 8x, but sometimes my wife calls :-bang :-fume :-hang :-samurai :-bluegrab WOW finally a reason to use those smileys.Golli.

[Qavion 19]

Are you running the APU during flight?The FMC doesn't take APU fuel into accountCheers.Q> イアン

[WAD3 0]

No I havent run the APU in flight. Maybe it is speeding up the flight to 2x. I am going to refly my flight and not use 2x speed. I will see what happens and report back.Thanks

[netshadoe 144]

The FMC uses two different sources for fuel calculation:On the PROGRESS PAGE 2, The fuel quantity at the bottom is only displayed if there is a discrepancy.On the left side is the TOTALIZER FUEL QUANTITY LINE. This indicates the remaining TOTAL fuel quantity directly detected in the tanks by the fuel quantity indicating system (FQIS). This is the total physical fuel left on board.On the right side is the CALCULATED FUEL QUANTITY LINE. This indicates the remaining CALCULATED fuel quantity based on EICAS fuel flow signals. This total does not take into effect any fuel used by the APU at the gate after fueling or during flight.To make a long story short, if you use the APU anytime AFTER you fuel up, the TOTALIZER will always be lower that the CALCULATED fuel totals. In this case, the TOTALIZER will always be more accurate. ***Only if the difference between these numbers is more that 9000lbs/4080KGS, would the FMC give the pilot the option to use the TOTALIZER or the CALCULATED amount.Some real 747 pilots (the ones I know anyway) will calculate his true remaining fuel by adding all the tank totals on the FUEL page on the EICAS. He would have this total BEFORE flight (starting fuel). At his waypoints, he would add the fuel used by each engine on the FMC PROGRESS PAGE 2 and subtract that number from the starting fuel number. The result of this calculation should be in the ball park of the flight plan figure...if it was lower, obviously the pilot would closely monitor the situation for diversion.IE:START FUEL = 150.0 KGSENGINE 1 = 31.1 ENGINE 2 = 31.1ENGINE 3 = 31.2ENGINE 4 = 31.2REMAINING FUEL = 150.0 - 31.1 - 31.1 - 31.2 - 31.2 = 25.4 KGSSo if the flight plan said we needed 23.7 and we had 25.4, then we are in great shape to make out destination!!

[WAD3 0]

Thanks Devin very interesting. Yes I usually sit at the gate on Airport power fuel up, and then just before engine start I fire up the APU so I do see where I was off. Thanks again

[RedLion 0]

I had this once while flying with FS minimized to TaskBar!I always fly with X4 with no probs!Hope it helps.

[Qavion 19]

"On the right side is the CALCULATED FUEL QUANTITY LINE. This indicates the remaining CALCULATED fuel quantity based on EICAS fuel flow signals. This total does not take into effect any fuel used by the APU at the gate after fueling or during flight."Not quite true. On the 744, Calculated value will show Totaliser (FQIS) value until you start an engine. After engine start (fuel lever to RUN), it will begin to use fuel flow transmitter data.During Fuel Jettison, Calculated will show Totaliser (FQIS) value also.Hope this makes sense.Cheers.Q> イアン