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What's between Left and Right on an Andair Valve?

claycookiemonster

Well Known Member
Mostly curious here. If the valve options are Left - Right and Aft = Off, what happens if you get distracted and leave the selector pointing straight ahead? Midway between Left and Right?
 
It is in such way that either Left is open or Right. I have not been able to get it in the position that both would be open or both would be closed.
 
From their FAQ page:
Question: What is the difference between a FS20-3 and a FS20-4?
Answer: There is no difference to the valves except that the FS20x4 has a detent in the middle position for BOTH, whereas the FS20-3 has no detent. It is Not recommended that the FS20x3 is used in the centre position as vibration could cause the valve to move round to the position in between LEFT and BOTH and here there is a restriction in the fuel supply.

This would lead me to believe that you would be feeding from both tanks at the same time, even though it isn't labelled as both. Since there's no detent, it may walk out of position, but it sounds like they design the valves in a "make before break" configuration.
 
Please don’t try to use a valve with a “both” setting, or don’t try to use that valve in between settings.. that’s asking for trouble. It’s already been hashed out here that you shouldn’t do that a low wing, as the first tank to run dry, the fuel system sucks air and the engine quits.
 
I absolutely understand all the reasons why "Both" is not appropriate in a low wing airplane. Not interested in Chuck Yeagering that. I was more curious about EXACTLY what happens as you switch from Left to Right. And, seriously, if you got distracted mid-switch, you wouldn't be doomed. Your answers confirmed my suspicions: that the valve does what my Flight Engineer Instructor told me when discussing cross-feeding on the 727: Always do something GOOD (open a valve) before you do something BAD (closing a valve) So, as the valve handle moves from L to R, the R side opens up before the L side closes. Just as any of us would do if we had to manage the process.
 
Having chatted to Andy of andair he explained one of the features of his valves is that if you stop 1/2 way between selected tanks it won’t shut the fuel off.

Regards

Peter
 
I spoke with the guys an Andair a while back when researching their product. I'm familiar with the concept from applying transfer valves in the power industry.

It is not a ported ball valve (routing fluid from a point to a point). The assembly body is basically open inside. It utilizes pads/seals affixed to the shaft to isolate (block) the undesired ports; e.g. selecting "right" would block the left port. Fluid fills the body left port and exits the supply. A nice application for critical systems that can't be taken off-line for maintenance. The US and probably International patent was owned by Alco, I think.

In short summary; intermediate position in the short term is benign. In the longer term could cause suction loss/vapor lock.

The Andair product appears to be a good design but it's not "sailor proof" (to quote my Ex-NAVY nuke friends).
 
I'm not really sure how you would get distracted switching from left to right. It's a pretty fluid motion rotating that big red handle. The valve has positive stops on L & R, and unless you pull up on the knob that prevents it from going to OFF, it's hard to mess that up. Plenty of other people have weighed in on how the valve works, as it's a good valve design.

My Andair valve was installed during the build after talking to an RV driver that starved his engine of fuel on its first flight right after take off. By his own admission, he was "calorically challenged", and his big ole knee bumped the original Van's valve when he applied right rudder. He put his brand spanky new plane down in a mobile home park just past the end of the airport property. He walked away, but he strongly recommended using a different valve.

Yeah, I know plenty of people will dispute that. I'm just giving one guy's viewpoint and why he felt that way. With that guy's experience in mind, I felt it was worth a few extra bucks to mitigate that specific risk.
 
This answer is easily found out by going to altitude and applying the thought pattern.
I shut the fuel off to my engine anytime my passenger say "what happen if you run out of fuel"????? That is if my passenger is willing to here the engine stop.
But, that said, the only way I would ever get ""distracted"" was if somebody shot up my bird and put a bullet in my body or missile in my backside.
It is such a small motion, how could one get distracted?
Go fly and enjoy the silence of no engine running.
Thanks for the laugh in the morning.
Art
 
No, I've never been flipped upside down while switching fuel tanks. Is that surprising?

No I meant being flipped upside down.


Someone asked what would distract someone in the middle of switching tanks.

It is not unheard up to be flipped upside down by flying through a wake.

So.....flying through a wake while switching tanks would be enough distraction. Doesn't matter what the odds are.

What matters is that's an example of enough distraction.

So it being cut off by some other airplane you hadn't seen.
 
Well, I'm the one who posed the question, so I guess I'll answer it. What I was fundamentally wondering was if there was some sort of "dead zone" in the valve between Left and Right? Was there a minimum time to make the switch? A maximum time in transit? What would happen if I was mid switchover at the exact moment I hit some turbulence encounter some negative G's?

These are the places my mind goes if I've primed too many parts without opening the garage door.
 
Well, I'm the one who posed the question, so I guess I'll answer it. What I was fundamentally wondering was if there was some sort of "dead zone" in the valve between Left and Right? Was there a minimum time to make the switch? A maximum time in transit? What would happen if I was mid switchover at the exact moment I hit some turbulence encounter some negative G's?

These are the places my mind goes if I've primed too many parts without opening the garage door.

Those are good questions.
 
FAR Part 23.995

As Andair states in their "promo", their valves are designed to FAR Part 23.995 standards which mandate (among other things) that: (g) Fuel tank selector valves must -

1. Require a separate and distinct action to place the selector in the "OFF" position; and

2. Have the tank selector positions located in such a manner that it is impossible for the selector to pass through the "OFF" position when changing from one tank to another.

So when changing tanks with their valves, you will not go through a position where the fuel is cutoff entirely - notice the regs don't say how much reduction in flow is acceptable when in the "cross over" zone, just that it will not be zero.

HFS
 
...

So when changing tanks with their valves, you will not go through a position where the fuel is cutoff entirely - notice the regs don't say how much reduction in flow is acceptable when in the "cross over" zone, just that it will not be zero. ...
I feel kind of dumb for not testing this during my fuel flow tests - I just assumed that as soon as you start moving the value, flow stops, so don't dilly-dally. I've never heard any kind of stumble when changing tanks, either with or without the secondary fuel pump on, so it does make sense that there is flow during the transition period.
 
As Andair states in their "promo", their valves are designed to FAR Part 23.995 standards which mandate (among other things) that: (g) Fuel tank selector valves must -

1. Require a separate and distinct action to place the selector in the "OFF" position; and

2. Have the tank selector positions located in such a manner that it is impossible for the selector to pass through the "OFF" position when changing from one tank to another.

So when changing tanks with their valves, you will not go through a position where the fuel is cutoff entirely - notice the regs don't say how much reduction in flow is acceptable when in the "cross over" zone, just that it will not be zero.

HFS

Interesting. I flew a Mooney for over twenty five years. The fuel selector moved through the "off" position when switching tanks. A carbureted motor would run ~ 1/2 minute when switched to off at normal cruise fuel flows. An injected model had a few seconds. Probably a case where the component slipped in under the aircraft TC versus meeting the reg on it's own. Not an unusual approach.
 
It is not unheard up to be flipped upside down by flying through a wake.

So.....flying through a wake while switching tanks would be enough distraction. Doesn't matter what the odds are.

What matters is that's an example of enough distraction.

Actually, yes, the odds *do* matter. Anyone can come up with scenarios that are so unlikely to occur that it's not worth any time or effort to mitigate them. In our risk management process at work, those are given a Likelihood rating of
epsilon, and we spend precisely zero effort on them.

I'd say the odds of being flipped inverted by wake turbulence at precisely the same moment one is switching fuel tanks are so ridiculously low that it has *never* happened yet to anyone.

The point is, as someone pointed out before, the physical act of switching the fuel selector itself is so fast that there's almost no chance of it being interrupted, so mitigating such a failure scenario is only likely to introduce additional complexity and potential failures into the system. And if the selectors meet the regs, then you can't shut off the flow if for some reason you leave the selector mid-way between the two positions, anyway (you could ultimately end up sucking air if you run one tank dry, but if you're regularly switching tanks to keep your aircraft in trim, even that would be fairly long odds, since you'd see your mistake on the next tank change).
 
Actually, yes, the odds *do* matter. Anyone can come up with scenarios that are so unlikely to occur that it's not worth any time or effort to mitigate them. In our risk management process at work, those are given a Likelihood rating of
epsilon, and we spend precisely zero effort on them.

.

Nope.

I wasn't speaking to mitigation. You clearly are in your mind. I'm not.

I was providing an example of a distraction that can interrupt the tank switch (along with being cut off).

Period.

End.


As for odds:

I wish I lead as charmed a life as yours where:

something completely unexpected and low probability never happened and

it never happens at the worst possible time.
 
Well, I sure wouldn't design a system around all of the ultra-low-likelihood events that the universe can throw at you.

Hey, a satellite could get hit by a meteor, and break apart and have chunks come falling down out of the sky and impact your aircraft, too. But there's little sense in either worrying about it, or doing anything in the design or building of your airplane to handle it.

Same here.
 
I spoke with the guys an Andair a while back when researching their product. I'm familiar with the concept from applying transfer valves in the power industry.

It is not a ported ball valve (routing fluid from a point to a point). The assembly body is basically open inside. It utilizes pads/seals affixed to the shaft to isolate (block) the undesired ports; e.g. selecting "right" would block the left port. Fluid fills the body left port and exits the supply.

I have an Andair F20 valve (180 deg between Left & Right positions) and a Vans brass valve lying around, so decided to to try to map the flow based on lever position.

Andair F20 - (I'm not sure all Andair valve models work this way so you should check yours to be sure...)
-OFF at 180 deg detent position, no flow between 135 thru 225 deg
-LEFT at 270 deg detent, flow gradually starts opening up at 225, full flow at 270, pinches off but slight flow at 315 deg,
moving lever clockwise flow starts opening up to full both at 360 degrees, than tapers off again at 045 degrees
-RIGHT at 090 deg detent, flow again gradually starts at 045 with full flow at 090, than tapers off to nothing at 135 deg
If you moved the lever exactly 45 degrees off Left or Right, there would be some power loss, but if you were half way (360) in between, you would be fully feeding off both tanks & not know it.

Vans Brass fuel valve - 4 detents LEFT, RIGHT, OFF, OFF
-OFF (no flow) is a 180 degree sweep (at the bottom of the swing if you will)
- (moving lever clockwise) flow starts gradually 45 deg before the LEFT detent, full flow at the LEFT detent, than half way between the Left & Right detent, the flow reduces, than increases again to full flow at the RIGHT detent, flow starts to reduce to shut off 45 degrees before the lever moves to the OFF detent.
So, if you were unfortunate enough to turn & land the lever exactly 45 degrees between Left & Right, yes there would be a restriction of flow, but maybe enough to bring the engine to idle (?), but nudge it a few degrees either side, would keep the engine going with probably enough power loss to tell you you have to do something!
 
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Well, I sure wouldn't design a system around all of the ultra-low-likelihood events that the universe can throw at you.

Hey, a satellite could get hit by a meteor, and break apart and have chunks come falling down out of the sky and impact your aircraft, too. But there's little sense in either worrying about it, or doing anything in the design or building of your airplane to handle it.

Same here.



No on is asking you to design a system around all of the ultra-low-likelihood events that the universe can throw at you.

Or worry about meteor strikes.

Certainly not I.

This is being overthought on this score...more interpretation is being imparted than was meant by the example.

It's. Just. An. Example.

Nowhere did I say it was likely.

You are wasting brain cycles on something that was never said. If you want to continue to do that - well...it's your brain cycles.

But I'm not wasting any more of my time responding to complaints about something I never said.
 
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Andair valve

Well, I'm the one who posed the question, so I guess I'll answer it. What I was fundamentally wondering was if there was some sort of "dead zone" in the valve between Left and Right? Was there a minimum time to make the switch? A maximum time in transit? What would happen if I was mid switchover at the exact moment I hit some turbulence encounter some negative G's?

These are the places my mind goes if I've primed too many parts without opening the garage door.

I too have been painting too much without Good ventilation. Thanks for posing the question because I think it helped answer a question I had about my Andair valve.
 
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