Balancing fuel tanks without crossfeed B757/67

[stilton]

Medically retired for some years now so this memory is a bit foggy

I spent eleven very happy years flying the 757 and 767 around a good part of the world

I was just remembering a technique some pilots used to balance fuel without crossfeeding, it was not in the book or an official procedure


Scenario : you are feeding both engines from the center tank and notice one wing (main) tank has a significantly greater amount of fuel than the other, perhaps approaching lateral limitations


Assuming you don’t have a leak in the lighter tank our normal procedure would be to terminate the center tank feed and feed both engines from the heavier wing tank until balanced then resume feed from the center tank to both engines until that tank is dry then going wing tank to respective engine for the rest of the flight


However some pilots used a different technique, in the same scenario with fuel in the center tank and approaching lateral limits with one wing tank heavier than the other they would just turn off the center tank fuel pump on the ‘heavy side’


So if the right main tank had far more fuel than the left turning off the center tank fuel pump on that side meant the main tank fuel pumps overrode the one running center tank pump, burning down the fuel on the right side to within limits while the center tank continued to feed the left engine


Once the main tanks were balanced you just turned the other center fuel pump back on resuming center tank feed to both engines

It’s quite possible I’m not remembering this correctly now, thoughts and opinions welcome !

[deltahotel]

Yes, that works and I occasionally used it for small corrections. No, it's not written down and not in the Part B2a. Switching off Centre pumps with fuel remaining in the centre runs the risk of centre tank fuel with less than full mains which has a limit of its own. Balancing by asymmetric use of centre pumps runs the risk of imbalancing the other way - if you're balancing using the mains/crossfeed you've got the option of leaving the pump EICAS messages visible as an ongoing reminder. Not sure how you could have a big main tank imbalance with normal Boeing fuel use - empty the centre then use the mains - long use of APU perhaps or poor refuelling operator. You could argue that good SA, knowledge of ac systems etc would allow you to do what you want on this!

So what do (did) I do? Ignore imbalance until centre empty then sort it or occasionally do some recreational fuel balancing.

hth

[rudestuff]

I had this very thing happen recently. Running on centre tanks but somehow developed a fuel imbalance in the wing tanks big enough to generate a fuel configuration Eicas. The QRH does not consider this scenario; it says crossfeeds on, low side off (which of course does nothing when you're running on centre tanks) The options are:
1) follow the QRH and wait until the centre tanks are empty for the wing Pumps to start working and the crossfeed to occur - which could be several hours.
2) turn the centre pump off corresponding to the high side, allowing the high side to burn some fuel and balance out, then turning the centre pump back on - which takes a few minutes.

[stilton]

Originally Posted by rudestuff

I had this very thing happen recently. Running on centre tanks but somehow developed a fuel imbalance in the wing tanks big enough to generate a fuel configuration Eicas. The QRH does not consider this scenario; it says crossfeeds on, low side off (which of course does nothing when you're running on centre tanks) The options are:
1) follow the QRH and wait until the centre tanks are empty for the wing Pumps to start working and the crossfeed to occur - which could be several hours.
2) turn the centre pump off corresponding to the high side, allowing the high side to burn some fuel and balance out, then turning the centre pump back on - which takes a few minutes.

Yes, option 2 is exactly the technique I mentioned with a lot more words !

[stilton]

Originally Posted by deltahotel

Yes, that works and I occasionally used it for small corrections. No, it's not written down and not in the Part B2a. Switching off Centre pumps with fuel remaining in the centre runs the risk of centre tank fuel with less than full mains which has a limit of its own. Balancing by asymmetric use of centre pumps runs the risk of imbalancing the other way - if you're balancing using the mains/crossfeed you've got the option of leaving the pump EICAS messages visible as an ongoing reminder. Not sure how you could have a big main tank imbalance with normal Boeing fuel use - empty the centre then use the mains - long use of APU perhaps or poor refuelling operator. You could argue that good SA, knowledge of ac systems etc would allow you to do what you want on this!

So what do (did) I do? Ignore imbalance until centre empty then sort it or occasionally do some recreational fuel balancing.

hth

Thanks for that reply, understood and a good refresher