Fuel Tank Feed F22A

[RobertP]

My F22A has 20USG Tanks in each wing
with sight guages at each wing root. The sight guages are very accurate but I often note in flight having started out with equal fuel in each tank and the
sight guages showing the same that after a period of time of an hour or so one tank will be showing say nearly full with the
other one showing only a quarter or so.

When I land eventually the sight tubes show that the fuel has levelled out
between each tank.

I try to avoid flying with this in
ballance as I am fearful of the tanks
failing to cross feed and running out of fuel! Is what is happening normal?

I should say that I had a tank replaced / repaired a couple of years ago and as far as I am aware the engineer tested the fuel flow.

[RobertP]

Re: Fuel Tank Feed F22A

Sorry should have said that it takes about 15 minutes for the fuel to level out after landing & no I don't fly round in circles all the time!

[3Dreaming]

Re: Fuel Tank Feed F22A

I'm not sure how the tanks a vented, but sometimes un-even pressure in the tanks can cause this. Otherwise you are flying wing low or in a yaw. Many other airplane have the same problem. The fuel flow from one tank should be good for the engine to keep running. Just watch if your tanks are really low you could unport the tank with fuel in a slip or turn.

[Forrest Barber]

Re: Fuel Tank Feed F22A

venting may be the problem , is it always the same tank?

[RobertP]

Re: Fuel Tank Feed F22A

Thanks both, as you suspect the problem seems to be venting as I removed the venting pipe ( Don't know the correct name ) on the top of Port wing and it seemed to be partially blocked where it joins the wing tank. I use a cover over the pipe when the aircraft is not being used but looked like insect crud! Hopefully when the rain finally stops! I can get out to test it. If that fails I will take a more detailed look and check on the tanks and report back. Thanks again for the suggestions.

[Mark Julicher]

Re: Fuel Tank Feed F22A

Robert,
Thank You for the report. Interesting that despite using covers the insects got in there.
I shall add "Insect Crud" to my technical lexicon.

[RobertP]

Re: Fuel Tank Feed F22A

Mark,

It could go back to the days when the wing was taken off and stripped to repair the tank as the bits were lying around with the engineer for what seemed a lifetime and perhaps since then it gathered a bit extra in flight or whilst I was having a bacon butty at some place or the other!

I think it is a good point that with these visual sight fuel tubes you can actually see the AV Gas in the tanks so you see much more in flight as to what is going on than in your average spam can with very dodgy guages!