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Unequal fuel in wings


Al Downs

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I know this has been discussed many times but this may be different.

 

I am putting my wings on today and put a couple of gallons in each tank to check for leaks. Sure enough I had a leak. So I proceed to to drain the tanks. Left tank drained dry and right side showed 1.5 gallons. Sitting on level floor. Fuel drain did slow up but even raising right wing up did not increase drain. Clamped off fuel line so I could fix leak on left side. I don't know what to think after reading all the previous discussions.

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When you say 'did not increase drain' do you mean rate of drain or amount that will drain?

 

It sounds as though you are saying that your right wing has 1.5 gallons unusable fuel. If your 1.5 gallons remains inboard and ported some may siphon in the air.

 

My CTSW claims 0.5 unusable.

 

The previous conversations were about un-even fuel flow and how to manage which is really a different subject.

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I put 2 to 2.5 gallons in each side. Because of leak I had to drain the tanks again. Left tank drained dry and right tank had 1.5 gallons and drained pretty slow. Lifting the right side did not increase the rate of flow as I thought it would. If I were to put 10 gallons in one side and let it sit overnight I would think the tanks would equal out at 5 gallons or so. The tank level does not change when there is more fuel in one side no matter how long it sits level.

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With the left tank dry you can drain from the gascolator and see the right wings flow rate, which must be slow due to something. Then put some fuel in the left wing and you should see a normal flow at the gascolator. As soon as you establish that the one wing drains slowly, you can work on determining the reason.

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Hi Al,

 

Did you lift the wing with the fuel up higher to see if it would drain any better?

Our tanks are well vented and with that little fuel it would not have sufficient time to pull a vacuum.

If the short rubber hose coming out of the fuel bulkhead isn't kinked from the bulkhead fitting to that first clamp that goes down the "A" post then it may be an obstruction. (which by the way I have never seen) You can use air pressure to blow the line out.

I would pull the line apart at the fuel filter in the instrument panel and blow down to that point. Might as well at this point take a look inside the fuel filter while you're into it this far. Then blow from the fuel filter out through the gascolator. Clamp the other fuel line side off so the air only goes where you want it.

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Yes Roger I did lift the wing thinking I would see a greater flow or maybe a rise in the level in the other wing. When I finished last night I filled one side and added 12 to the other side. Nothing changed overnight, still the same levels. I don't think this has anything to do with the work that was done as I have always had this situation but it is the first time I checked it when tanks were drained.

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I know people claim fuel transfer from sitting. I rarely really see this unless there is a large fuel disparity or the wings aren't as level as they think. I have been measuring a lot of wings to see if they are level and find many aren't. I would be many of these uneven wings are a result from a few hard landings, but the tweak in the gear isn't enough to really notice with the eye and or sometimes the floor isn't perfectly level or a tire is much lower than the other.

I have tried to level my own plane, put 15 gal in one wing and ten in the other and leave it over night. Nothing happened. There just wasn't enough head pressure to make the climb back up to the other wing when things were level. Now if I raise one wing then its a new story.

 

You should however be able to open the gascolator and and start a fuel flow. Then pinch off one wings fuel flow and see how the open wing drains and then swap sides pinching the other side. They should flow and not be clogged up.

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