An animal so rare it may not exist . . .

wrote:
Folks:

I have a rather irritating fuel line situation that has several
possible solutions, each more complicated and / or expensive than the
last. Specifically I need a remotely mounted fuel cutoff valve, but it
is so remotely mounted that the standard valve-on-a-long-ujoint
solution is not going to work (too much stuff in the way, too many
corners, etc.).

In discussing this with the local EAA guys, the tech counselors, and
even talking to the local FAA, they all look at the problem and
eventually say, "you know what you need is a solenoid."

Ok. My reply to them is that I understood that solenoid valves for
fuel control were deeply frowned upon unless you are Boeing. I am not
Boeing. Part of my understanding as to why solenoids are not a good
thing is that they will obviously have a fail-open or fail-closed
failure mode, either of which can be deadly depending on the nature of
a given situation.

However the local FAA guy told me that he has seen solenoid valves made
specifically for fuel applications that fail in place, i.e. if they
crap out the valve simply stays in it's last selected position.

I can't find one. Partly this is because I don't know what they might
be called, but I have tried everything I can think of, including
calling some of the larger solenoid valve manufacturers to see what
they might suggest. If anyone has any insight into this, it is most
appreciated.

Thank you for your assistance--

Steve.

PS: I have also seen electrically actuated rotary valves, which appear
to simply be a fairly traditional selector valve actuated by a stepper
motor. They fail in place, which is good. But in doing some research,
they appear to have a much lower MTBF than a solenoid.

Solenoid valves might be OK for an airplane that has backup
electrical systems, but in the average lightplane with a single system
you might find yourself unable to shut the fuel off in the event of an
emergency that requires shutdown of the electrical system.
I'd adapt an ordinary ball valve lever to operate using a
push-pull cable, even if the heavier PTO cable was necessary. It would
still be simpler, lighter and more reliable. You could even use a pair
of 1/16" control cables and a pulley or sector on the valve, but if
corners must be negotiated you'd need more pulleys, adding complexity
and weight.

Dan