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I don't know if the problem is from a spool valve, this is the second pump I've had in my plane and both have done the same thing in warmer weather. And, of course, being in southern California it's usually always on the warm side.

I can see on the gear pressure gauge that as the heat goes up so does the pressure. It's gets to a point where the pressure opens both pressure switches, so when I switch to gear down there's no connection. One small tap on the dump valve and it releases the excess pressure on the low side and the pump lites up.

I've seen this same problem with other Lancairs I fly with but never a solution. There should be a small expansion tank or relief valve going back to the reservoir on the low side of the pump. Last resort would be a relay to over ride the low pressure switch, fed through the high pressure circuit for a momentary pump start. This would have the same effect as tapping the dump valve for a second. I'm not sure what the answer is.

Randy Stuart

LNC2

----- Original Message -----

From: marv@lancair.net

To: lml@lancaironline.net

Sent: Tuesday, April 17, 2007 01:42 PM

Subject: [LML] Re: Gear Trouble

Posted for "Randy" <randystuart@hotmail.com>:

I've always had a problem when the weather warms up at all. The gear won't
come down unless I crack open the dump valve for a second. I don't like doing
that but if I don't I can't get the pressure out of the low switch to start
the pump. I've tried adjusting the pressure switches a little each way to see
if it would help but it doesn't. Maybe a bypass relay to start the pump in the
down position would be the answer.
Randy Stuart
LNC2

[Randy, it almost sounds like you're fighting an internal pump issue. If you've got the pressure switches set to their lowest possible settings to achieve consistently reliable operation at _some_ particular temperature, unless there is something restricting the internal flow there is almost no reason that temperature should be able to be removed from the equation (ie, temp increase = pressure increase, which should be dealt with already). Isn't this one of the
symptoms we hear about so often with the reversed spool valve? Greyhawk...??? <Marv> ]
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