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Date: Thu, 29 Mar 2012 15:55:32 -0400
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From: Danny <danny@n107sd.com>
Subject: Re: [LML] LNC2 gear diagnosis
Organization: N107SD, Inc.
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I've asked myself the same questions.  First the leak, then I'll see 
what the pressure switch is doing.

Danny
LNC2-360, 550 hours
N 38° 43' 25.7"
W 77° 30' 38.6"


On 29.03.2012 11:46, Jim Nordin wrote:
> Wouldn’t you want to look at the pressure switches? If the pump
> pressure never exceeds 950 pounds, the pump should never quit 
> running.
> No? Or can the switch shut off the power to the pump at 950 pounds? 
> If
> the pump quits prior to ±1200 pounds, something is afoul in the
> switches or the pump thermally shutdown.
>  Jim
>
> -------------------------
>
> FROM: Lancair Mailing List [mailto:lml@lancaironline.net] ON BEHALF 
> OF
> Danny
>  SENT: Thursday, March 29, 2012 8:03 AM
>  TO: lml@lancaironline.net
>  SUBJECT: [LML] Re: LNC2 gear diagnosis
>
> Nope, I took the NW actuator out of the system and installed a gauge
> on that pressure line to check.  I also played with the dump valve
> today to see if a slight movement of the handle made a difference …
> it did.  This weekend I’ll cap it and see what kind of pressure I
> get but my guess is that’s the problem.
>
> Danny
>
> LNC2-360, 550 hours
>
> N 38° 43' 25.7"
>
> W 77° 30' 38.6"
>
> FROM: Sky2high@aol.com [mailto:Sky2high@aol.com]
>  SENT: Wednesday, March 28, 2012 9:06 AM
>  TO: lml@lancaironline.net
>  SUBJECT: [LML] Re: LNC2 gear diagnosis
>
> 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 [1] 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"
>
>
> Links:
> ------
> [1] mailto:danny@n107sd.com

-- 
Danny
LNC2-360, 550 hours