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Re: REFLECTOR: Fuel system safety
Simon, your comment about leaking tanks after an incident hit the nail on the
head, as far as I am concerned.
Al, while your checking out the number of fires at the site of an off field
landing, forced or otherwise, check out the number of 'fuel burn' related skin
rashes associated with these landing due to damaged wing tanks. As much as I
hate to point it out, I am aware of several of these instances. Ask Hugh Hyde
One valve on one line is hardly going to prevent this from happening. Leaking
tanks at the site of an accident can easily produce the fumes required to be
ignited by an engine. We must not forget that the liquid is not what burns, it
is the fumes.
But I will concur with the notion that in the event of an inflight fire, there
is nothing to stop the flow of fuel to the engine compartment. A mechanical
valve would appear to be the ticket. I don't know why a valve could not be
placed on the top of the sump tank right near the end of the line coming out
of the sump tank. For those who are not flying or servicing your aircraft yet
will find that this tube is very susceptible to being bent after some time, so
it is advised that a 1/4 pie shape gusset be cut out of 1/4" plywood and
fiberglassed into the arc of the tube coming out of the sump tank to prevent
an accidental bending of this tube. This gusset could be extended to mount a
valve and control cable retainer.
For the life of me I cannot envision an electrically operated valve that could
be safely installed to fit the objectives of its use. In a fail-safe mode,
that being no electrical current needed to keep the valve open, power would
have to be applied to close it. In our off field landing we want to cut our
battery power off as soon as possible, opening up our valve. I thought the
criteria was to be able to close the valve off in such cases.
Next, If power is required to keep the valve open, in the event of an
electrical failure, whether it be the primary source, a switch, the solenoid
on the valve, a broken wire, whatever, the valve closes in flight. I happen to
know first hand that an aircraft can fly just fine with the battery master
switch off, at least in a conventional aircraft. But not if the fuel cutoff
valve is closed.
In either scenario, with the electrically controlled valve there is a risk
factor and safety design criteria that is not meet. My opinion is that if you
opt for a valve at all, make it mechanical so you can control it at your
desecration. But as pointed out in earlier postings, if you don't "exercise"
this valve regularly, the time you need to move it you might find it to be
stuck in position!