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Not drawing from the right hand tank

Saville

Well Known Member
Well so I check the fuel gauges and I'm astonished to see the left tank much lower than the right....

My fuel selector (Andair I believe) :



Is normally on BOTH. IT was OFF for the annual in January. Then back to BOTH

I fill up often so I didn't notice anything unusual until yesterday's flight. The left tank gauge was going down and was very low while the right tank hadn't budged.

Selector on BOTH. This is not what usually happens. They don't drain precisely at the same rate but it's never been like this.

I landed immediately as I didn't have a whole lot left in the tank.

So now I have a problem to diagnose...why is it not drawing from the right hand tank?

Broken fuel selector?

Plugged line?

Plugged air vent?

My only thought in terms of diagnosis is to fill the left tank, fly around burn down a few gallons with the selector set on RIGHT and see if the right tank level drops.

Or fly around on BOTH.

But this is no diagnosis and I'm hesitant to fill the tank if I now have to dissemble the fuel system.

Any suggestions as what tests to run to determine where the problem is would be appreciated.
 
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I gather you are not the builder.
THIS IS A POTENTIALLY DANGEROUS SITUATION. RV's are not designed to use a "Both" position. If you draw one tank down while on both, the pump will suck air rather than pull gas from the other, full tank. (Unless the airplane has been modified to have a gravity fed sump tank below the valve, rather unusual).
Are you sure "both" does not actually correspond to "right" (e.g. wrong faceplate lettering)?
Check for blockage (mud dauber nest?) in the right vent line (just open the tank cap, and see if you hear bubbles when you blow in the vent).
 
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As Bob already said, low wing airplanes do not typically have a both position on the fuel selector (there is a lot of info regarding why, in previous discussions that you can find with the search function).

If your RV-8 does have a both position (cant tell anything from the photo because it is so out of focus) you have a not per plans fuel system which could cause you trouble at some point in the future.
 
Any suggestions as what tests to run to determine where the problem is would be appreciated.

It wont be necessary to disassemble the system. First, the fuel selector indicator may have NO relevance to what is actually happening. So you need to find out what IS happening with the valve. This would be pretty easy to do.
1. Firewall forward, remove a fuel supply line route it into a container.
2. Take a wooden dowel, stick the tanks, mark the level. Maintain log of levels
3. Turn on your pump, pump out some fuel into a dispenser with the valve in various positions. Make a determination on what the positions are ACTUALLY doing.

Correct indicator as necessary. Get help from a qualified mechanic or RV builder for help. Both is bad.
Thank goodness you have the option to deal with this on the ground. What you will probably find is that both is actually both. And you should not only not use it, but it should NOT be an option on the indicator. Also determining that both is both, can be tricky. What you might have to do is remove the wing root fairings, and remove the fuel supply line from the tank, and cap it. One at a time, to ensure you know what the valve is actually doing.
 
Gauges

All of the above is good advice. However, in the original post you mentioned "the gauges". Did you confirm visually an uneven fuel flow by looking in the tanks? Gauges can lie.
 
All of the above is good advice. However, in the original post you mentioned "the gauges". Did you confirm visually an uneven fuel flow by looking in the tanks? Gauges can lie.

Yes.

Thanks everyone for the advice.

I have no intention of flying to figure this out...that's why I'm looking for diagnostic tests to perform.

The vents are faired and screened so that's the first place to look.



Thanks Kahuna - lots of good ideas there.
 
I think you need to actually understand that BOTH is a bad idea with a low wing aircraft. If you have a BOTH position, don't use it. Feed from either LEFT, or RIGHT only.
 
I think you need to actually understand that BOTH is a bad idea with a low wing aircraft. If you have a BOTH position, don't use it. Feed from either LEFT, or RIGHT only.

If you don't understand this, conduct a practical test - get some clear, flexible tubing and a T connector. Cut three lengths of tubing and put one piece on each leg of the T. Take two glasses with water - one mostly full, and one mostly empty. Put one piece of tubing in each glass, then suck on the third piece. Watch what happens when the first glass runs dry - suddenly you are sucking air, not water. Now, imagine that each glass is a fuel tank, and replace the water with fuel - your engine will stop once the first tank runs dry, no matter how much fuel is in the second tank.

A Both position works on a high wing aircraft because gravity will cause the tank with fuel to feed even if the other tank is empty. Both positions are bad, bad news on low wing aircraft, unless there is a header tank that is fed by gravity from both wing tanks.
 
If you don't understand this, conduct a practical test - get some clear, flexible tubing and a T connector. Cut three lengths of tubing and put one piece on each leg of the T. Take two glasses with water - one mostly full, and one mostly empty. Put one piece of tubing in each glass, then suck on the third piece. Watch what happens when the first glass runs dry - suddenly you are sucking air, not water. Now, imagine that each glass is a fuel tank, and replace the water with fuel - your engine will stop once the first tank runs dry, no matter how much fuel is in the second tank.

Here's an alternate test rig. I recommend Stella Artois for test fluid, but this guy looks like a Bud man:

 
If you don't understand this, conduct a practical test - get some clear, flexible tubing and a T connector. Cut three lengths of tubing and put one piece on each leg of the T. Take two glasses with water - one mostly full, and one mostly empty. Put one piece of tubing in each glass, then suck on the third piece. Watch what happens when the first glass runs dry - suddenly you are sucking air, not water. Now, imagine that each glass is a fuel tank, and replace the water with fuel - your engine will stop once the first tank runs dry, no matter how much fuel is in the second tank.

A Both position works on a high wing aircraft because gravity will cause the tank with fuel to feed even if the other tank is empty. Both positions are bad, bad news on low wing aircraft, unless there is a header tank that is fed by gravity from both wing tanks.



No need - I understand it completely.
 
High wing, doesnt count. ;)

beer%20hat.jpg
 
Yeah, sorta high wing, but I think the tubes come in from the top of the cups! (Not gravity feed)
 
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High wing, doesnt count. ;)

:)


Ok so the test procedure I understand best is the following:

1) First, check the tank vent inlets to be sure they are clear.

2) If I'm not alone, blow air into each vents and listen for bubbles coming out of the appropriate tank. This helps to assure the vent lines are connected and operative.

3) Disconnect the fuel line to the engine, on the engine side of the firewall

4) Attach a hose from that line to a bucket

5) Measure the fuel levels in the two tanks as accurately as possible.

6) Set the tank selector to OFF.

7) Turn aux fuel pump on....no fuel (or very little) should come out of the hose into the bucket.

Question: this is ok for the pump?

8) Set fuel selector to LEFT

9) Turn on pump, for a few seconds

10) Stop pump and measure both tanks.

11) Set fuel selector to RIGHT

12) Turn on pump for a few seconds; stop pump; measure tanks.

13) Set fuel selector on BOTH

14) Turn on pump for a few seconds; stop pump; measure tanks.


This series of steps will tell me if the system is working, and also will indicate how it is plumbed.

Do I have that right?

Anything wrong or unsafe?

Thanks
 
That sounds like a good procedure. On question No. 7, you can run the pump dry, but not for an extended period.

The big takeaway is to either replace the valve with one that has Left, Right and Off positions, or use the existing valve and just never use the Both position. If it were me, I'd replace the valve so there is no possibility of error.
 
:)

2) If I'm not alone, blow air into each vents and listen for bubbles coming out of the appropriate tank. This helps to assure the vent lines are connected and operative.

You can do it alone also....

With the cap removed, blow low pressure air into the vent inlet.
Because the fuel vapors are heavier than air it is easy to see teh vapor plume come out of the filler hole.

Running the pump for a few seconds with the fuel selector off shouldn't hurt it. It will only take a couple seconds to confirm it is not pumping fuel. Don't leave it on for an extended time.

The rest of your test plan looks good.
 
:)


Ok so the test procedure I understand best is the following:

1) First, check the tank vent inlets to be sure they are clear.

2) If I'm not alone, blow air into each vents and listen for bubbles coming out of the appropriate tank. This helps to assure the vent lines are connected and operative.

3) Disconnect the fuel line to the engine, on the engine side of the firewall

4) Attach a hose from that line to a bucket

5) Measure the fuel levels in the two tanks as accurately as possible.

6) Set the tank selector to OFF.

7) Turn aux fuel pump on....no fuel (or very little) should come out of the hose into the bucket.

Question: this is ok for the pump?

8) Set fuel selector to LEFT

9) Turn on pump, for a few seconds

10) Stop pump and measure both tanks.

11) Set fuel selector to RIGHT

12) Turn on pump for a few seconds; stop pump; measure tanks.

13) Set fuel selector on BOTH

14) Turn on pump for a few seconds; stop pump; measure tanks.


This series of steps will tell me if the system is working, and also will indicate how it is plumbed.

Do I have that right?

Anything wrong or unsafe?

Thanks

Safety,
For a recent fuel test we grounded the airframe to the discharged fuel with a bare wire dropped into the fuel container. Ground and un ground it at the clip end, not by dropping in the container.

Testing You are on a good path here. Place the tail up so the plane is level. At that attitude the fuel will siphon out when you remove the hose at the fuel pump, so turn the valve to "off"

Testing with the boost pump to determine the valve function is good. A gravity flow test to verify flow with and w/o fuel cap on can check the vents once you are sure what the valve does.

To measure fuel drop in a tank might be tricky, even at 35 gph, a minute is 1/2 gal, how much is that on a dip stick? Think about that one.

Vent test - do that first, as a boost pump could draw significant negative pressure and be bad for the skin. Or just leave the caps loose for the test.

Have fun learning!
 
"To measure fuel drop in a tank might be tricky, even at 35 gph, a minute is 1/2 gal, how much is that on a dip stick? Think about that one."

I have been...and so far I don't have many ideas. One thought was to plug the vent for the tanks I'm testing to stop the flow while the pump is on.

Have to think on this one some more.
 
"To measure fuel drop in a tank might be tricky, even at 35 gph, a minute is 1/2 gal, how much is that on a dip stick?

Not much.

You will have to run the pump for a while.

If the airplane is protected from wind and you don't bump it, the fuel in the tank should be steady enough that if a plastic ruler is sitting in the filler opening, you should begin to see the level go down after a few minutes.

This will be easier to see if the tank is nearly full because there is a smaller cross section area at the top surface of the fuel.
 
"For a recent fuel test we grounded the airframe to the discharged fuel with a bare wire dropped into the fuel container. Ground and un ground it at the clip end, not by dropping in the container."

Can you describe this a little more?

Metal container?

Mostly closed? Open bucket?

was it the wire touching the container that did the grounding?

Thanks
 
I don't understand the need to measure the fuel level decrease in the fuel tanks. Just mark a container at 1 gallon and, for each tank, pump fuel in to the mark. Use your watch to determine how long it takes for each tank. You'll now know if each tank pumps at the same flow rate, and by doing a little math you can figure out the gpm the pump is capable of when free flowing.

As a data point, IIRC my Andair pump puts out ~50 gpm free flowing.
 
I don't understand the need to measure the fuel level decrease in the fuel tanks. Just mark a container at 1 gallon and, for each tank, pump fuel in to the mark. Use your watch to determine how long it takes for each tank. You'll now know if each tank pumps at the same flow rate, and by doing a little math you can figure out the gpm the pump is capable of when free flowing.

As a data point, IIRC my Andair pump puts out ~50 gpm free flowing.

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.
 
"For a recent fuel test we grounded the airframe to the discharged fuel with a bare wire dropped into the fuel container. Ground and un ground it at the clip end, not by dropping in the container."

Can you describe this a little more?

Metal container?

Mostly closed? Open bucket?

was it the wire touching the container that did the grounding?

Thanks

A little explanation - fuel flowing through an plastic insulated hose can collect a static charge, so if the gasoline flowed into a plastic (HDPE) container it could collect quite a static charge voltage. So - the wire is dropped into the gasoline container- in the liquid. It is grounded back to the airplane. We did this because we used the clear vinyl hose. The aircraft teflon hose is (should be) self grounding.

The container, we used, was a rinsed windshield fluid jug so we could see the fuel level. Large open containers are scary. I would ground any gasoline "can". If you actually have a metal container like an old gas can, that would be grounded to the container, but you can't see the level as easy.
 
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it seems the common denominator with no matter what you do is to replace that valve with the correct valve. Perhaps do that first and then conduct the fuel flow tests, this way you will understand how your new system operates.

Isnt it possible the valve with L/R/B works fine but if you're flying with the slightest slip or skid the tank draw may favor one side or the other?

I know my 182 draws heavily from the right tank, even when on BOTH, I often switch to the left tank in cruise just to draw it down.

I know I could manipulate the reading on my -9A fuel guages by just the slightest rudder input, effectively moving fuel to either the inboard or outboard end of the tank;)
 
...
Isnt it possible the valve with L/R/B works fine but if you're flying with the slightest slip or skid the tank draw may favor one side or the other?

I know my 182 draws heavily from the right tank, even when on BOTH, I often switch to the left tank in cruise just to draw it down.
...
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.
 
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...
 
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.
 
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?
 
Yep - -

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.
 
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.
 
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.
 
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.
 
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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.
 
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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.
 
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.
 
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.
 
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.

I thought of that but:

what if the selector itself is busted and doesn't really switch from the left tank to the right tank but stays on the left no matter how I have the knob set?
 
Please excuse me, if my post sounds harsh, but this topic makes me really nervous. Firstly, because the builder thought that it might be a smart idea to install a fuel selector with a ‘both’ setting (what other brilliant ideas did he have?). Secondly, because this didn’t strike the OP as odd. :eek:
Frankly, I also wonder about the leap from believing that a ‘both’ setting is fine to some fancy testing of the fuel system.

This is what I would suggest:

  • Visually inspect / confirm the type of the fuel selector and the fuel system layout.
  • Remove one end of the fuel hose somewhere after the fuel pump and hang it into a gas can.
  • Turn on the auxiliary pump, test all positions of the fuel selector, confirm that they are in accordance with your observations and measure the flow rate (how long does it take e. g. to fill 3 gal. into the gas can and calculate the hourly flow rate based on that). This will also allow you to confirm your expectation regarding the fuel levels with a dip stick (one side should remain unchanged, the other should have dropped).

I strongly doubt that there is anything wrong with your fuel selector valve. Most likely, it is simply the wrong type which had been installed.
 
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PLEASE!!!!!!!!!!

PLEASE change that valve to the proper one!

Do not fly this aircraft until done!
 
Please excuse me, if my post sounds harsh, but this topic makes me really nervous.

If the post makes you nervous imagine my feeling when a system that worked just fine for months suddenly....behaved differently.

Firstly, because the builder thought that it might be a smart idea to install a fuel selector with a ?both? setting (what other brilliant ideas did he have). Secondly, because this didn?t strike the OP as odd.
:eek:

Sorry I'm not omniscient but I am here to learn. And I learned something.

Frankly, I also wonder about the leap from believing that a ?both? setting is fine to some fancy testing of the fuel system.

Not sure what "leap" you are talking about. The system worked fine until one day it didn't (tanks were never lower than half full at any time BTW). In other words - something changed. THAT is a red flag to me.

After making the original post, I've learned the dangers of a BOTH setting if one tank is low. I've digested that and have moved on to wanting to assess the fuel system.

The fact that it no longer worked as it did was pretty unnerving and now, to me, the OP, this calls into question the fuel system rigging.

The "leap" is because of what you yourself just suggested: what other brilliant ideas did the builder (not me) have? Just how DID he rig that fuel system? Well I'd like to test the fuel system, and, at the same time, determine how it is built. And do it before I fly again - as I've said..

If you are talking about some other leap I'm not sure what that is.





This is what I would suggest:

Your list has already been suggested and corroborated by other posters and is what I'm going to do.


I strongly doubt that there is anything wrong with your fuel selector valve.

Perhaps you'll find a way to pardon me for not just making that assumption - especially given your concern about "other brilliant ideas".

Most likely, it is simply the wrong type which had been installed.

Your post doesn't strike me as harsh.

It does strike me as yet another example of beating a very dead horse with regard to the BOTH setting and the fact that the selector has that setting.

Well I suppose everyone has to get their two cents in about that, and tell me what they would do with regard to signing off my airplane if they were inspecting it and so forth.

In fact I long ago, in this thread, made my decision about the selector.

What does not seem simple to me - what I need to figure out and hope to obtain aid from people in this forum - is figuring out the best way to test the fuel system and determine it's rigging. THAT is where my focus is in this thread.
 
What does not seem simple to me - what I need to figure out and hope to obtain aid from people in this forum - is figuring out the best way to test the fuel system and determine it's rigging. THAT is where my focus is in this thread.

I think it was mentioned before but lost in the shuffle. Disconnect the fuel line to the carb/servo and redirect it to a suitable container. Then turn on the boost pump and cycle thru the valve positions. You can measure the fuel drop in the selected tank against the fuel output to the container to confirm where it's coming from. Worst case is you have to cap off the lines between the valve and tank to assure no flow from that tank. You could do that at the valve or at the wing root.

While you're at it you can also do the max attitude flow test. Put the tail in a hole/ditch and/or jack up the nose to an attitude well above stall and measure the flow rate from each tank with the boost pump. It needs to be greater than the max fuel consumption at SL WOT. There's more specifics in the construction manual (or at least there used to be).
 
What does not seem simple to me - what I need to figure out and hope to obtain aid from people in this forum - is figuring out the best way to test the fuel system and determine it's rigging. THAT is where my focus is in this thread.

1. Open up/remove the covers over the valve
2. Remove any covers over the fuel lines in the cockpit
3. Look with Mark I Eyeballs at which tank is connected to which input on the valve.
 
Please excuse me, if my post sounds harsh, but this topic makes me really nervous. Firstly, because the builder thought that it might be a smart idea to install a fuel selector with a ?both? setting (what other brilliant ideas did he have?). Secondly, because this didn?t strike the OP as odd. :eek:
Frankly, I also wonder about the leap from believing that a ?both? setting is fine to some fancy testing of the fuel system.

This is what I would suggest:

  • Visually inspect / confirm the type of the fuel selector and the fuel system layout.
  • Remove one end of the fuel hose somewhere after the fuel pump and hang it into a gas can.
  • Turn on the auxiliary pump, test all positions of the fuel selector, confirm that they are in accordance with your observations and measure the flow rate (how long does it take e. g. to fill 3 gal. into the gas can and calculate the hourly flow rate based on that). This will also allow you to confirm your expectation regarding the fuel levels with a dip stick (one side should remain unchanged, the other should have dropped).

I strongly doubt that there is anything wrong with your fuel selector valve. Most likely, it is simply the wrong type which had been installed.


I once was a DAR that would NOT issue the Special Airworthiness Certificate to an RV till after the Fuel Selector Valve was changed to one that did not have a BOTH position. It is my belief that it is UNSAFE to have a fuel valve with both position in the present low wing fuel tank RVs. I would not sign off the once a year Condition Inspection as being in a condition for Safe Operation with a BOTH position fuel valve on a low wing fuel tank Experimental aircraft.
 
I once was a DAR that would NOT issue the Special Airworthiness Certificate to an RV till after the Fuel Selector Valve was changed to one that did not have a BOTH position. It is my belief that it is UNSAFE to have a fuel valve with both position in the present low wing fuel tank RVs. I would not sign off the once a year Condition Inspection as being in a condition for Safe Operation with a BOTH position fuel valve on a low wing fuel tank Experimental aircraft.

I'm STILL a DAR. I have certificated over 800 aircraft. and like Gary, I would never sign off an RV with a "Both" position on the fuel selector.
 
An element of paranoia has crept into this thread.

There is nothing unsafe about the BOTH position of this valve. It MAY become unsafe if it is used but even then the airplane won't fall out of the sky.

There are a number of switches in every aircraft that create an unsafe situation if used in flight. Guess what happens if the ignition switch is moved to OFF or the mixture is pulled to OFF? Placards are even not required for these obvious unsafe situations.

It would appear this aircraft was built with some care. I would be most reluctant to condemn the builder, perhaps several EAA tech advisors who frequently inspect before certification, or the DAR (or perhaps FAA inspector) who certified it.

If the valve gives one night mares, change it. My 2 cents worth is I would have no qualms whatever about flying this aircraft with or without a placard to not use the BOTH position.
 
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