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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
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...
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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