Mailing List lml@lancaironline.net Message #61485
From: <Sky2high@aol.com>
Sender: <marv@lancaironline.net>
Subject: Re: [LML] LNC2 gear diagnosis
Date: Wed, 28 Mar 2012 09:05:41 -0400
To: <lml@lancaironline.net>
Danny,
 
From what you reported it would seem that the nose gear actuator is the real problem.  How about the door actuators?  One possible analysis is that you don't see the 1200 psi because the leak is greater at the higher pressure and then slows a bit as the pressure goes down or the actuator has its worse leak at full retraction and less when the piston is not at the full retraction position...
 
Scott Krueger
 
In a message dated 3/27/2012 10:32:25 P.M. Central Daylight Time, danny@n107sd.com writes:

If any of you have a suggestion, I’d appreciate your input.

 

On my last flight home, with no early signs of failure, my gear pump was tripping on about every 2 seconds to maintain pressure.  I figured I had a leaky actuator and would have to rebuild it to resolve this; no big deal.  I found one leaking and figured where there is one, there may be more.  So, I’m rebuilding all of them.  But, before doing so, I put a gauge on the high pressure side of the pump to see if I had internal leaks there too.  What I found was that my pump will only pressurize to about 950 psi (should be ~1200 psi) and then it bleeds down slowly.  I tried to adjust the pressure switch but it made very little difference.  To verify the bleeding, I isolated all actuators out of the system except the nose wheel.  I put the gauge on the high pressure side of the NW actuator line, selected gear up to pressurize the system, and then quickly crawled under the plane to look at the gauge.  It was bleeding down so fast that by the time I got down there to look at it (~2 sec.), it had already lost about 200 psi and then bled down the rest of the way in about 7 more seconds.  So, and here’s the question, do I have a faulty gear dump valve, a leaky pump, or both?

 

 

Danny

LNC2-360, ~550 hours

N 38° 43' 25.7"

W 77° 30' 38.6"

 

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