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?
This is what does not happen.it won’t shut the fuel off.
i.e. what happens?what happens if you get distracted and leave the selector pointing straight ahead? Midway between Left and Right?
This is what does not happen.
The OP's question is:
i.e. what happens?
T
It is such a small motion, how could one get distracted?
Art
You are flying and in the middle of turning it and:
You hit a wake or something that flips you upside down.
Never happened to you>
Interesting
No, I've never been flipped upside down while switching fuel tanks. Is that surprising?
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 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....
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. ...
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
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 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.
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.
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.