744 Fuel leak and Fuel Flow

[Cheju]

Hi, I would really appreciate if anyone can explain why the fuel flow gets high when there is a fuel leak? (As per QRH) I know the fuel flow will be sensed right after the engine fuel valve and if there is fuel leak somewhere, wouldn't the fuel flow become less? as the amount of fuel going through the engine fuel valve become less? Or...will the fuel metering unit demand more fuel if that's the case? (Hence increase the fuel flow??:confused:) :(

[bcgallacher]

It would depend on whether the leak is upstream or downstream of the flowmeter transmitter - if it was downstream of the transmitter a leak would show as higher fuel flow,if upstream, fuel flow would probably be normal but the tank quantity would be reducing at a greater rate than normal for that fuel flow.

[bbthefe]

I think it's good to keep a running tab on EXPECTED fuel remaining (totalizer) and ACTUAL fuel remaining (via fuel flow minus start figure) at regular intervals (hourly) and also critical points of flight before proceeding ! Also a visual check from around D4 if you suspect you have a leak or can't reconcile your fuel figures in flight. Gee, Flight Engineers are good for something !

[bbthefe]

Ps I haven't a copy of the - 400 QRH but I hope the info helps. Sorry I can't give u a specific answer.

[Cheju]

Thanks everyone~