fuel inbalance on long hauls

[Guest 737767]

On my last few intercontinental flights, I got a fuel inbalance indication on the EICAS. The flights are usually planned to have some 6-7 tons fuel as final reserve. Upon approach left main tank contains about 3,3 while having 2,4 on the right side. This occurs independently wether I open the cross feed valve or not. Does anybody have a hint?Andreas HermesEDDH

[Peter Clark]

It's a feature :) Same thing happens in the real aircraft because of the difference in engine fuel burn, etc.Occasionally during cruise you should open the crossfeed valve and turn off the fuel pumps to the lower tank. This will allow the fuller tank to fuel both engines. Once the fuel level is the same again, turn on the fuel pumps, close the crossfeed valve and then check back later to keep them relatively level.Safe flights.P

[Guest Muppet22]

AndreasWhen you switch on the fuel crossfeed button, ensure that you turn off both the 'AFT' & 'FWD' fuel pump switches for tank with the least fuel in it. This will ensure that fuel is burnt from the tank with the most fuel in it.Apologies if you are already using this procedure - in which case I don't know what the problem is.However you are right - my number 2 engine always seems to burn less than the number 1, which is of course true - no engine is exactly the same with regard to fuel consumption afaik; the imbalance with PIC though is very exaggerated. Seeing how well aircraft (on the whole) are maintained, I would be surprised to see such an imbalance occur on a 767 with two well maintained engines.

[Chris Willis BAW976]

Hi all,To save embaressment, remember to open the cross feed to fully open before closing the lower fuel tank switches, otherwise it can get very interesting!!Regards,Chris,

[Qavion]

"It's a feature Same thing happens in the real aircraft because of the difference in engine fuel burn, etc."If the fuel continued to drop faster in one tank than the other after the crossfeed valve(s) had been opened, wouldn't this suggest two problems (engine fuel burn AND (unequal) fuel pump pressure output)? :-)Cheers.Ian.

[Peter Clark]

"If the fuel continued to drop faster in one tank than the other after the crossfeed valve(s) had been opened, wouldn't this suggest two problems (engine fuel burn AND (unequal) fuel pump pressure output)? :-)"Not only that, but if one tank continued to drop REALLY fast you have a bigger issue to contend with :)

[Guest geoffwilson]

...but a guaranteed low landing weight :( Geoff

[Guest HPSOV]

Of course youd never fly with the crossfeed valves open and all fuel pump switches on... unless directed to do so by the low fuel non-normal checklist ;-)In reality it is common to see an imbalance of up to 500kg at the end of a flight, which is normally corrected in the last hour of cruise to ensure they're even for landing. I have a few times seen aircraft with leaky crossfeed vavlves which results in large imbalances occuring throughout the flight. If both engines are indicating the same fuel flow, and you end up with a large imbalance then you must suspect a fuel leak until you can determine the cause.

[Guest 737767]

Thanks for the hint, Tom! Of course, I should have turned of the fuel pumps of the tanks having least fuel :9The interesting thing is that FF, N1 and N2 readouts are exactly the same for both engines. Maybe a PICv2 will feature slightly different indications as already realized by PSS in their new buses.. Andreas HermesEDDH