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Hollis & Christopher,
I sent my whole pump (1998 vintage) back to the factory to have them rebuild it and calibrate my new pressure switches. I wanted both pressure switches and both relieve valves calibrated. They told me that the spool valve had been in backwards and they fixed it.
I then installed pressure gauges from Lancair under the passenger seat so that I could tell what was going on with the gear. I tested my gear on the ground and it stayed in the up position with no loss of pressure for over 15 hours. The high side had 1,200 lbs of pressure, the low side had 0.
When my gear is up and I fly at high altitudes, every hour I can hear the pump run for 1 second while it re-pressurizes the high side. That means that I have lost 300 lbs in the high side. I know that the 300 lbs is going to the low side because I can see it with my pressure gauges. There is no atmospheric venting.
After 2 hours of flying, the high side will have 1,200 lbs and the low side will now have 600 lbs of pressure. When I put the gear in the down position, nothing will happen because the low side only comes on when the pressure is below 400 lbs. The low side runs from 400 to 700 lbs of pressure and the high side runs from 900 to 1,200 lbs (it may be 700 to 1,000 lbs, I forget). I have to open my dump valve to relieve some of the pressure.
Now for the real cause of the problem. I believe that the rubber O rings that we use in our activators contract enough at cold temperatures that there is a leak from the high side of the activators to the low side. I fly a lot at 15,000 feet and it is a lot colder up there. My high flights are where I have noticed the problem. I don't think that I have the problem at low altitudes.
Any further suggestions and/or observations are welcome.
Sincerely,
Lorn
From: "Christopher Zavatson" <Christopher.Zavatson@udlp.com>
Dave,
<<It seems to occur when there is an internal leak that allows the high pressure side to slowly leak across to the low pressure side,>>
When the spool valve is installed correctly the down circuit is essentially open to atmospheric pressure via the reservoir.
.
.
--
Lorn H. 'Feathers' Olsen, MAA, DynaComm, Corp.
248-478-4300, mailto:lorn@dynacomm.ws
LNC2, O-320-D1F, N31161, Y47, SE Michigan
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