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Date: Thu, 23 Nov 2006 14:04:42 -0500
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From: Lorn H Olsen <lorn@dynacomm.ws>
Subject: Re: Electrical /Hydraulic system questionslancair235/320

Randy,

When the gear lever is up, the low pressure builds from the high side  
at cold temperatures. The high pressure builds from a short burst of  
the pump that you have probably not noticed.

When I fly at high altitudes, where it is cold, just about every hour  
on the hour the pump burps. That means that my high side pressure has  
gone down about 300 lbs. The pump burp just brought it back up. Where  
did that pressure go? It went to the low side. After a couple of  
hours of high (cold) flying, the low side pressure has built up to  
600 lbs. At a low side pressure of 600 lbs the pump will not turn on  
to let the gear down when the the gear lever is pulled down. At that  
time I have to open the dump valve for just a split second. The pump  
then comes on, I close the dump valve and everything is honky dory.

I can put my plane on jacks for 2 days and not lose 1 lb of pressure  
in the hanger. At altitude, I believe that it is caused by the cold.  
The hide side leaks to the low side at a rate of about 300 lbs per  
hour. Again, this leak does not occur in the hanger. I believe that  
it is caused by the cold.

Lorn

On Nov 23, 2006, at 9:28 AM, randy snarr wrote:

> Chris,
> .
> .
> .
> I am absoluteley baffled over how both the high and low sides build  
> pressure during flight.
>
> Thoughts?
>
> Randy.

--
Lorn H. 'Feathers' Olsen, MAA, DynaComm, Corp.
248-345-0500, mailto:lorn@dynacomm.ws
LNC2, O-320-D1F, 1,200 hrs, N31161, Y47, SE Michigan