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I hear you Wolfgang,
Temperature changes result in pressure changes,
Pressure changes can then affect the switches on the pump.
If the pressure switches on the pump are open, then a good course of action is to open the dump valve long enough to allow the switch to close, then the pump works.
So in essence, if temperature changes are the root cause, it is very likely that the dump value cures it (at least for that particular instance).
I think Chris Z has a bunch of information about how I may be able to cure the problem on a permanent basis.
Thanks
Kevin
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From: Lancair Mailing List [lml@lancaironline.net] On Behalf Of Wolfgang [Wolfgang@MiCom.net]
Sent: Monday, April 21, 2014 10:26 AM
To: lml@lancaironline.net
Subject: [LML] Re: Gear Down...INOP
Hitting the dump valve may or may not help the problem.
It depends on how much of a temperature increase you incurred.
Wolfgang
----- Original Message -----
From: "Kevin Stallard" <kevin@arilabs.net>
To: <lml@lancaironline.net>
Sent: Monday, April 21, 2014 11:43 AM
Subject: RE: [LML] Gear Down...INOP
Do you have hydraulic pressure gauges installed so you can see the pressure on the high and low side?
I suspect that quickly opening and closing the dump valve would cure your problems, because yes, there is an interaction that occurs
between the high and low side and the poppet valve in your pump. But unless you know the pressure on the high and low side when
the problem occurs, I can't say for sure.
I've seen this once on my plane. Hitting the dump valve quickly solved the problem.
Kevin
________________________________________
From: Lancair Mailing List [lml@lancaironline.net] On Behalf Of William Ford [willydford@gmail.com]
Sent: Wednesday, April 16, 2014 8:06 AM
To: lml@lancaironline.net
Subject: [LML] Gear Down...INOP
I believe that I recently experienced something in my Legacy that I remember reading about but can't remember all the details. I
looked into the LML archives and was unsuccessful. Could someone out there please briefly summarize the situation, reason and any
possible remedies for gear extension failure following high altitude cruise in cold air followed by a decent and landing in hot air.
I seem to remember a discussion about boosted pressure in the hydraulics plumbing due to the rapid rise in temperature which in turn
had an effect on the operation of the pressure switch In my recent experience...after opening the dump valve, the hydraulic pump
did run, confirming continuity to the pump. After working the nose gear into the locked position, the landing was uneventful but I
would like to avoid this uncomfortable situation in the future. Would a tweak on the pressure switch adjustment be called for here
or just expect to momentarily crack open the dump valve to relieve excess pressure. Thanks for your thoughts.
William Ford
N11LL
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