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-   -   Not drawing from the right hand tank (https://vansairforce.net/community/showthread.php?t=136164)

Dbro172 03-28-2016 07:43 PM

Quote:

Originally Posted by N941WR (Post 1066181)
I was taught that if the plane is slightly uncoordinated, wing low, etc, the fuel will drain from one tank before the other in a high wing.

Exactly! What I'm pointing out is that these ground tests may likely reveal a perfectly operating fuel valve in all three positions, on the ground... But it may not work the same in flight, where it matters. So regardless, get rid of the BOTH.

This is an easy mistake for a builder to make, one may think they are actually installing a better valve with a BOTH position, or maybe that's what they're used to flying and don't even know there is a difference in low vs. high.

Dbro172 03-28-2016 07:54 PM

Another thought
 
Here's another thought; everybody checks their minimum useable fuel, tail low, high... But how about with the ball one half out of center?

BillL 03-28-2016 08:35 PM

Yep - -
 
Quote:

Originally Posted by Dbro172 (Post 1066192)
Here's another thought; everybody checks their minimum useable fuel, tail low, high... But how about with the ball one half out of center?

Already on my list. Full rudder slip. It has to be an inflight test. The details for obtaining the fuel measurement will be fun. Any clue as to what that amount might be?

The EAA has a good (recorded) webinar on this, just watched it last week.

RV7A Flyer 03-28-2016 08:44 PM

Quote:

Originally Posted by Saville (Post 1066108)
The issue is that while the selector was on BOTH it was drawing only from the Left Tank whereas before it was drawing form both.

I need to know why even if I never use BOTH again.

Now I have no confidence that when I switch it to RIGHT, I'll be drawing fuel from the Right.

I'm not trying to beat a dead horse here, but...that's an Andair valve, and it has precisely 2 inputs (assuming it's not a dual valve with the return lines and all that)...Left and Right. If you simply took it out, and replaced it with the *drop-in replacement* proper valve, you'd never have to a) worry about being on Both again, and b) know for a fact that when you're on Left, it's drawing from the left, and when you're on Right, it's drawing from the right. You don't even have to change the lines from the valve to the tank or from the valve forward to the engine. Just the valve body.

Plus, you'd now be using the *correct* style valve for a *low-wing airplane*.

Do this, then run the usual flow tests on each tank, plus whatever crazy attitude tests you want to try.

There's right, and then there's not right...and fuel systems are NOT the place to not do it right.

rvbuilder2002 03-28-2016 09:38 PM

Quote:

Originally Posted by RV3bpilot (Post 1066186)
One of the fuel caps are not sealed and so there is no air pressure from the fuel vent on that tank... The same thing happened to me just last week...

The design of the fuel system on all the RV's with wing tanks does not require pressure in the tank for feeding fuel.
All that is needed is an open vent so that air can be replacing the empty space vacated by the fuel.

The vents are specified to be cut at an angle or faced fwd to assure that a vacuum is not getting pulled on the tank.

David-aviator 03-29-2016 06:06 AM

There is only one Andair Valve that feeds from both tanks, it is the FS20 TYPE 4 VALVE and the plumbing is internal, no need to T the tanks together.

The problem sited in the original message is easily resolved, do not use the BOTH position. Use only LEFT or RIGHT. Also appropriate, label the valve, DO NOT USE BOTH.

Confirm on the ground which tank is feeding to be sure left is left and right is right.

Problem over, no need to change the valve it's a darn good one. Go fly and enjoy the 8, it is a wonderful airplane.

Saville 03-29-2016 06:59 AM

Quote:

Originally Posted by David-aviator (Post 1066270)

The problem sited in the original message is easily resolved, do not use the BOTH position. Use only LEFT or RIGHT.

Seeing the left tank draining towards the red line - when on BOTH and when that never happened before ever - shook me up so much that now I want to confirm that both tanks are operative: left tank on LEFT and right tank on RIGHT. In the past - when flying on BOTH, both tanks drained.


Confirm on the ground which tank is feeding to be sure left is left and right is right.

Yes I now feel compelled to do this.

Problem over, no need to change the valve it's a darn good one. Go fly and enjoy the 8, it is a wonderful airplane.



I have no trouble with the concept of not using BOTH, and wil not be using it in the future. But now I MUST confirm that the left and right tanks are feeding and that the fuel system is operating properly , for my own peace of mind.

rmartingt 03-29-2016 08:02 AM

Quote:

Originally Posted by Saville (Post 1066281)
I have no trouble with the concept of not using BOTH, and wil not be using it in the future. But now I MUST confirm that the left and right tanks are feeding and that the fuel system is operating properly , for my own peace of mind.

It's good to check that fuel will feed from each side. But I think many here would agree that you should still replace that fuel selector valve with one that doesn't have a "both" position. Yeah, you can leave the current one in, and say "using 'both' causes problems, so I won't use it" but it's better to just not have the potential failure mode there in the first place. Further, you might know not to use that setting any more, but anyone else who might fly the plane, or anyone you sell it to, might not.

If I were an A&P, and I was doing your condition inspection, I would refuse to sign the airplane off until that valve was replaced.

Saville 03-29-2016 08:31 AM

Quote:

Originally Posted by rmartingt (Post 1066308)
It's good to check that fuel will feed from each side. But I think many here would agree that you should still replace that fuel selector valve with one that doesn't have a "both" position. Yeah, you can leave the current one in, and say "using 'both' causes problems, so I won't use it" but it's better to just not have the potential failure mode there in the first place. Further, you might know not to use that setting any more, but anyone else who might fly the plane, or anyone you sell it to, might not.

If I were an A&P, and I was doing your condition inspection, I would refuse to sign the airplane off until that valve was replaced.


Thank you for your input.

Toobuilder 03-29-2016 11:26 AM

I have not read every post, but have you considered doing a quick ground run on the right tank to verify it is feeding or not, and if so, take off on the left tank (which you KNOW is feeding), climb to a safe altitude over the airport and then switch to the right? You should have a definitive answer in about 5 seconds.

After that you can evaluate changing out the fuel selector, but if the right side feeds at least you can use the airplane again.


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