|
Craig Blitzer wrote:...after a few
minutes at altitude, the door seal pump light comes on and stays on. I
pull the breaker, light of course goes out indicating pump off now. I
do not loose the door seal because there is no increase in noise at whatsoever
and I can hear the door seal deflate after I land. I am assuming that
the seal is staying inflated during flight because of the one way valve that is
installed.
Any ideas why the "little bit" of pressurization I am
maintaining would cause the door deal pump to want to come on and stay on?
Craig, a couple of thoughts: You should be able to hear
the seal pressurization pump running--this should correspond to the light
if the system is wired IAW the builder's manual (You didn't specify, so I assume
you're talking about an IV-P. I don't know how the other pressurized airplanes
are configured.)
It's possible that the pump will continue to run even with the
seal inflated if the pressure switch is defective, you have a small leak, or the
switch is set to too high a pressure. This is easy to test with the plane on the
ground and the engine off. If the pump won't shut down, check first for
leaks, then for a defective pressure switch. The switch is actually a
"differential pressure" switch, so it's at least theoretically possible for it
to work "normally" on the ground, and to not shut down at altitude because it
can't achieve the required differential pressure. Unlikely malfunction, but
possible. It's also possible that your pump is marginal on achieving the
required pressure output--again unlikely, but possible if it's been run for
a long time. This can be checked by hooking it up to a direct-reading gauge.
My bet is that you have a small leak in the system. If
the seal stays inflated until you flip the switch to deflate it, I'd look first
in the line/connections between the pump and the check valve, but the whole
system needs a good leak check; that's the most likely--and easiest to
find--malfunction.
Hope this helps!
Bob Pastusek
|