----- Original Message -----
Sent: Thursday, March 03, 2005 9:53
PM
Subject: [FlyRotary] Re: fuel cutoff
valve necessary?
When your
electric system starts to act up, you might not be able to shut down your
pumps! You still can stop your engine by cutting the fuel!
You're reaching a bit here. A fuel pump is an
on/off device. It's not like we have a bank of CPU's running the pumps
:-) Not at all!! I fly quite a few hours every month
in a machine that has an electric clutch engagement. It happens quite often
that something in that installation goes dead (microswitches in the tension
adjustment system) and the system stays "on" or "off" - point is, it can keep
a circuit open/closed - eg. your pumpswitch brakes and the pump stays on via
the relay (if so installed) or what if the master solenoid "freezes" - happens
also quite a lot.
But keeping it to a
part that is not really a shut off valve, like the fuel pump, no way! What if
the pump shortens out/gets hot/leaks/etc. I want to be able to cut the fuel at
the source!
What if your
fuel valve connections leak, or the shaft of the valve? Then you're
sucking air, which is a much more ominous problem. If it is just used as a emergency shut off, there should be no
leaks as you hardly ever move it.
My point is, I want a system that I can shut down no
matter if I have electric power or not or if it is shortening out somewhere.
Have a look at the shut offs Robinson uses, never saw one leaking. Though the
tank drains start to leak frequently, especially when they get rather
dated....
Everyone has their comfort level, so feel free to
install a cutoff valve. There are certainly situations where it could be
needed, but for every one of those, I can come up with one where it's an extra
danger :-)
As a point of trivia, Van's specifically
recommends against using braided hose in place of the normal aluminum tubing
from the wing tanks. The theory is that in an accident, the wings
will be pulled back, and the fuel line will be torn loose. The
aluminum line will tend to pinch itself closed when it bends and breaks, but
the braided hose will stay open when it breaks. The difference is a big
leak vs a small leak. Van's not so dumb
:-)
Sounds like good advice, did they ever test it by
ripping some nive RV wings of a nice RV-body? :))
Cheers,
Rusty (my beer's
empty)
Saludos,
Thomas J. (no beer allowed for another 3 weeks
:(()