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RV7A fuel pickup tubes

bbanitt

Member
Hi all,

Perhaps this has been addressed in an earlier thread I could not locate. If so, please direct me :)

I am flying off the 40 hrs on my RV7A with a Fuel injected 0360. I experience fuel starvation on steep turns if I do not switch the fuel selector to the high wing tank. This makes sense as the fuel will move away from the lower wing tank on turns.

Although this makes sense to me, I wanted to see if I may have missed something on my build that would eliminate this issue. As you probably all know, when the RV engine cuts in and out it resembles bull riding and mild fear.

Thanks in advance!

Brad
 
SB-06-2-23

Easy to miss during build, check Vans SB-06-2-23 and see if it (or part of it) applies to your situation.
 
Brad,

How much fuel in your tank when this happens? Would you say it happens when in a coordinated turn or only when slipping? Does having your boost pump on change the outcome?

Interesting... and the fact that you only call it "mild fear" when the fan stops... solid dude!
 
Are your steep turns coordinated? If so, gravity should not favor the low-wing tank. Maybe there's something else going on.
 
I installed the optional "Trap Door" in the first interior rib, to reduce the rate of fuel leaving the inboard bay. It is on the fuel tank plans, related to the flop tube. I didn't install the flop tube but thought the trap door was a simple, neat idea.
 

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Thanks

Thanks for the replies. I believe I am coordinated, but will double check. The Service bulletin and trap door posts will require a bit of work, but will check them out. I wish I would have done the trap door.....

I was running 24psi pump pressure on the mechanical pump. I will try the boost pump. I know it is not recommended to fly with both tanks on, but it does not act up when I run on both or when I switch to the high wing tank.

This is a plane I finished from 80% with 90% left. It still needs interior and better paint. My plan is to sell it after the 40 hours. Want to make sure I have all the bugs worked out.

Really appreciate the advice.

Thanks,
Brad
 
That's never happened to me in over 1600 hrs (RV-6) and I've never heard of it from anyone else. I can't speak to FI or issues with the pump but I would also check SB-06-2-23 as someone else mentioned, and make sure your baffle holes were drilled correctly (hopefully you have pictures from the build). Have you checked that it will still run when close to empty one one or the other tank? Unusable fuel should be very close to zero on these planes.
 
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thanks

I have not checked the low fuel scenario. Will do. I had to reseal the endplates when I got it and the baffles I believe are correct. Will check the SB as mentioned earlier. Appreciate the feedback!
 
What kind of fuel valve do you have? I don’t think you should have a both position. It doesn’t sound like a fuel pickup problem if it doesn’t happen when in the both position. When feeding from the both position it will suck air from either tank if unported.
 
In a coordinated turn at any bank angle the fuel system reacts as if the aircraft were flying wings level. Something odd is at play and needs to be rectified before further fight.
 
As post #9 says. If you have a fuel valve with a both selection on a low wing aircraft, it is not a good thing. Start there. Post a photo of the valve so we can see what you have.
 
found it

It was the selector valve. I was flow testing each tank and plumbing. I moved to the right tank and the flow decreased. I did it again and the flow was normal. Several times and about half the time the valve was restrictive. I removed the valve and looking into the port could see that sometimes the valve stayed partially closed even when the selector clicked into position. I had a new Adair valve from another project I put in. Problem is gone. Thanks to all for your input.
 
Wow. That's scary! Imagine if the valve core shifted around to the full off position...

Was it the brass fuel valve? If so was the center core nylon or brass (real old style) also?
 
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