An animal so rare it may not exist . . .

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.

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

wrote in message
ups.com...
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.

.snippage..

Something like this?

http://www.jcwhitney.com/autoparts/P...002072/c-10101

(cap the unused inlet)

???

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

wrote:
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.).
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.

If it is a simple fuel shutoff issue, then just mount the appropriate
valve for which ever you consider (or your FAA guy considers) less
critical. That is, normally open or normally closed. Loss of
electrical system reverts it to the "normal" position.

The only other real failure mode is that it sticks... and hey, it stays
in its last position.

Depends on what you consider most critical... if this is a "fuel tank
selector" thing you are trying to create, then two of them - mounted
NO, and held closed by the electrical system. Mount a mechanical 90
degree cutoff valve somewhere for those times when you want to work on
things on the ground. In flight you have a left-selected, or
right-selected, or (lose your electrical system) both.

Yes, these things do fail... but not NEAR as often as the standard
Piper in-cockpit mechanical fuel tank selector.

jmk wrote:


If it is a simple fuel shutoff issue, then just mount the appropriate
valve for which ever you consider (or your FAA guy considers) less
critical. That is, normally open or normally closed. Loss of
electrical system reverts it to the "normal" position.

I doubt that they'll approve it. Too dependednt on the system
one way or another. If you had a fuel leak in flight that resulted in
an engine compartment fire, you'd need to shut everything down, fuel
and electrical, in order to have any decent chance of making a
survivable forced landing, and you wouldn't be able to shut the fuel
off. If you left the elecrical on, the fire would shut it off for you.

The only other real failure mode is that it sticks... and hey, it stays
in its last position.

Depends on what you consider most critical... if this is a "fuel tank
selector" thing you are trying to create, then two of them - mounted
NO, and held closed by the electrical system. Mount a mechanical 90
degree cutoff valve somewhere for those times when you want to work on
things on the ground. In flight you have a left-selected, or
right-selected, or (lose your electrical system) both.

If it's a low-wing airplane, you don't want a BOTH position. If
one tank runs dry before the other, the pump will happily suck air from
the dry tank instead of fuel from the one with fuel. FAR 23.951
addresses this issue in certified airplanes.

http://www.airweb.faa.gov/Regulatory...2?OpenDocument

There are a bunch of FARS that are worth paying attention to when
designing a fuel system. I've been around homebuilding since '73 and
have read too many accident reports involving homebuilt airplanes that
fell down because their builders didn't have the information to alert
them to possible problems.
Fuel tank venting is one of the really big killers. In a
gravity-feed system using two or more tanks fed through a valve that
has a BOTH position or though two valves that may be ON at the same
time, the tanks must be vented together to keep pressures equal lest
uneven fuel flow results. I was involved in a Glastar project, and that
airplane had two wing tanks with separate vents. Uneven fuel flow was a
problem, and if the pressures had been far enough apart the fuel from
the tnak with the lower pressure would have had trouble reaching the
engine once the other tank ran dry. The pressure in the dry line will
keep fuel from dropping through the other line.
The Glastar's vents were also at the wingtips, and if the tanks
were full or nearly full, the fuel would run out of the low vent if the
airplane was the least bit off level. Fuel would crossflow through the
system from the higher tank into the low tank and a lot of fuel ended
up on the floor.
The lesson: copy a certified system.

Dan

On 28 Nov 2006 08:18:32 -0800, wrote:

Even with a certified gravity fed system I understand you can get
cross flow. Didn't the 210s have this problem when parked on an
uneven surface?




Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

wrote

The Glastar's vents were also at the wingtips, and if the tanks
were full or nearly full, the fuel would run out of the low vent if the
airplane was the least bit off level. Fuel would crossflow through the
system from the higher tank into the low tank and a lot of fuel ended
up on the floor.
The lesson: copy a certified system.

It always seemed like the best place for a vent on a low wing would be up high
on the fin, with a T to supply both tanks equal pressure. Does anybody know of
a certified vent setup like that?
--
Jim in NC

Morgans wrote:
wrote

The Glastar's vents were also at the wingtips, and if the tanks
were full or nearly full, the fuel would run out of the low vent if the
airplane was the least bit off level. Fuel would crossflow through the
system from the higher tank into the low tank and a lot of fuel ended
up on the floor.
The lesson: copy a certified system.

It always seemed like the best place for a vent on a low wing would be up high
on the fin, with a T to supply both tanks equal pressure. Does anybody know of
a certified vent setup like that?
--
Jim in NC

In a high nose-up attitude the vent line might fill with fuel,
and the weight of it might act as a drag on the fuel trying to flow
through the outlet lines to the engine. Not good. There are some
systems with a vent at the wing root above the wing, but these tend to
ice up. Cessna sticks them behind the strut to prevent icing. Not that
we should be flying these tiny airplanes in ice, anyway. Cessna just
has to protect themselves from those who try it.
Designing a trouble-free venting system can be a real pain.

Dan

Roger wrote:
On 28 Nov 2006 08:18:32 -0800, wrote:

Even with a certified gravity fed system I understand you can get
cross flow. Didn't the 210s have this problem when parked on an
uneven surface?

All the Cessna singles do it, both the simple 150 system that
has a tee between the two lines before the fuel enters the shutoff
valve, and the other systems that use the left-right-both-off selector
valve. They'll crossfeed in the "both" position, which is where most of
them stay most of the time. Placing the selector in the left or right
or off position will stop the crossfeeding. Shutting off a 150's valve
won't stop crossfeed.
The tanks on the Cessnas are vented together to keep pressures
as equal as possible. A cracked fuel cap gasket or broken valve vent
check valve will upset the pressure balance, especially on the right
wing tank, causing the left tank to drain sooner.
Having vents at the tips aggravates the spillage by increasing
the head pressure at the vent opening. Cessna keeps them close to the
tank's outboard wall.

Dan

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.).


Have you considered just putting an electric fuel pump back there. The
pumps I have will block flow when they are turned off.