Yesterday on departure out of North Las Vegas I could
not get the gear to come up. At first I thought it may
by my airspeed squat swith. After speeding the
airplane up to 140 that was obviously not the problem.
I have pressure gauges in the airplane but with
everything going on I did not notice what they were
reading. After a few minutes with the gear switch in
the up position the gear pump came on and up they
came. About the same time the low pressure gear
hydraulic gauge filled up with fluid and squirt on my
unsuspecting passenger. The 1hr 33 minute flight home
was uneventful except for an occasional burp from the
gear pump keeping the pressure  up. One thing that was
different was that I rarely ever   have the pump burp
in flight. It did it maybe 6 times on the way home.

Upon arrival home, I dropped the gear with the dump
valve and pressured up the system with the gear pump
and landed with no trouble whilst my passenger held a
rag on the face of the bleeding gauge.

The day before, we flew to Nevada at 14,000. We were
at that altitude for around an hour. What I think may
have happened is we cooled the system significantly at
altitude, decended and landed in much warmer temps and
left the airplane on the ramp in the sun. With the
airplane parked, I believe the down side of the system
pressured up with the airplane warming in the sun on
the ramp. I believe it pressured up the down side so
much that it exceeded the limits of the 1200 psi gauge
which failed shortly after take off.( I have ordered
the 2000 psi gauge to match the gear up side)

I theorize that the down side pressured up and either
bled over the the up side or the up side pressured up
with the down side opening up the high pressure
curcuit and not allowing the pump to run. Looking
back,  I should have immediately cycled the dump valve
after looking at the pressure gauge to see if
relieving the pressure would get the gear moving.

Maybe there should be some sort of pressure relief
system added. I have seen the gear hyd pressures go up
1000 psi when pulling the airplane out of a cool
hangar and out into the hot sun and left for 20
minutes or so.
Maybe that is what happened. The gear was dropped with
the system cold. The down side pressures up to 600 or
so while cold. Land the airplane and both sides
pressure up 1300 or so in the heat.That would put the
down side at near 2000 and the up side beyond the shut
off point for the pump.

That could explain what happened.

Chris Z and others,
Ideas, thoughts???

Randy L. Snarr
235/320

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