Correcting fuel imbalance

[luscombeguy 4]

I started a flight from KABQ to KSLC and about 20 minutes into the flight I got a fuel imbalance warning. Have no idea how it happened but could figure out no way to correct it. It was about 1800 lbs imbalance. All the QRH would tell me is to correct imbalance. How do you do that? No fuel in center tank.

[davierosoft 13]

APU running

[MartinBeauchemin 0]

It's probably because you had the APU running too long. Just switch the fuel cross feed on until the fuel levels are equal

[davierosoft 13]

He must also turn off the pumps of the tank with less fuel.

 

and obviously turn off the APU if wants to save fuel.

[rocketfs 2]

He must also turn off the pumps of the tank with less fuel.

 

and obviously turn off the APU if wants to save fuel.

 

I guess the APU was switched off before takeoff. I would have been destroyed otherwise, no?

 

Bert Van Bulck

[Jack_C 1]

To be 1800 lbs imbalanced even with the apu running on the ground is a lot. You wouldn't get that much imbalance even after 3 hours of the apu running.

JackColwill

[davierosoft 13]

The APU will not be destroied if left on, it is also practice to use it for bleed or electrical supply in case of an aircraft bleed/gen failure or if you need full engine power and packs (for example).

The unbalance is a bit high, probably is due to the old fuel scavenge issue, so the product is not updated to sp1 (a?)

 

It is easy to troubleshoot:

Just see the tank with more fuel, if it is the left, the product is not updated to the last version, if it is the right, fuel was burned by APU.

Other than those factors, a different thrust setting or a leakage, or a different fuel load on the beginning are the only possible cause.

[ajacied551 1]

I started a flight from KABQ to KSLC and about 20 minutes into the flight I got a fuel imbalance warning. Have no idea how it happened but could figure out no way to correct it. It was about 1800 lbs imbalance. All the QRH would tell me is to correct imbalance. How do you do that? No fuel in center tank.

To correct the fuel imbalance, Open the crossfeed valve and switch OFF the Fuel boost pumps of the fuel tank that has less fuel in it Now both engine's uses pressurized fuel from one fuel tank. When the fuel imbalance is corrected switch ON fuel boost pumps that where previously switched OFF and close the crossfeed valve.

There is no need to start the APU to correct the fuel imbalance during flight.

P.S. To balance fuel if there are no indications of an engine fuel leak. See QRH 12.13.

[luscombeguy 4]

Thanks guys, the APU was off. I have no idea how I got the imbalance but the mistake I made trying to correct it was not turning off the pumps on the low fuel tank.

[Oliver Branaschky 2]

Hi all,

 

I had a fuel imbalance occur today for the first time during a flight from Frankfurt EDDF to Santorini LGSR. APU was off, got the latest SP and fuel was equally distributed prior to take-off. At some time into the flight, and after the center fuel pumps had been turned off, the left main tank suddenly showed approximately 500 kgs less than the right side. A fuel leak can be ruled out. Re-balancing worked fine, however.

 

The only thing "out of the ordinary" was me using time acceleration for the first time with the NGX. Could this have been the reason?

 

Regards,

Oli