Sender: <marv@lancaironline.net> (Marvin Kaye)
To: lml
Date: Sun, 03 Nov 2002 21:44:48 -0500
Message-ID: <redirect-1851869@logan.com>
From: "Ian B. Crowe" <ian.crowe@sympatico.ca>
Subject: Fw: LNC 2 hydraulics
Organization: Corvi Trade Consultants Inc
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This is the reply I received from Mark at Lancair.  It may help others with
hydraulic problems.

For the moment my system is partially leaking off the down pressure over the
weekend with the pump off.  The residual pressure is 250 psi when I get in
on Monday morning.  The pump shuts off at 700psi.  If that is the worst I
get I am not too worried.

I hope to have the final inspection finished next week and who knows I may
be airborne shortly thereafter.

Ian Crowe.
----- Original Message -----
From: "Mark Mahnke" <Markm@lancair-kits.com>
To: <ian.crowe@sympatico.ca>
Sent: Thursday, October 31, 2002 1:17 PM
Subject: Re: LNC 2 hydraulics


> Ian -- You have a good understanding of the system and that really
> helps.  Unfortunately,  The next step is to isolate the potential leak
> points.  I usually start by capping off the lines that go to the dump
> and the nose gear then test.....etc...  It may not be worth chasing the
> by-pass if it takes a long while to recycle.  If it only happens in the
> down position and not the up it is not important to eliminate a by-pass.
>  Even every few minutes is not a problem.  I would try to correct it if
> the recycle occurs more than every half hour on the up side.  Have a
> good week.
>
>
>
> Mark Mahnke
> Lancair Technical Support
> 541.923.2244
> markm@lancair-kits.com
>
> >>> "Ian B. Crowe" <ian.crowe@sympatico.ca> 10/27/02 02:04PM >>>
> I have recently tested my hydraulic system for the gear.  I have
> installed
> two pressure guages on the high and low pressure circuits.I have the
> new
> emergency extension cock, there are no visible external leaks and the
> problem is very intermittent.
>
> The gear extends and retracts in 8 to 10 seconds.  On retraction the
> mains
> lead the nose to the extent that the mains are in the well before the
> nose
> starts to retract.
>
> The pressure gauges show only a small increase in pressure on
> retraction
> until the gear is fully up when the pressure rises and the pump shuts
> down.
> The same applies on the extension cycle when the gear is fully down
> and
> locked the low pressure rises to 700 psi and the pump shuts down.  In
> other
> words the system takes very little force to operate until the
> cylinders
> reach their stops.
>
> It is on the extension cycle that a very intermittent problem has
> surfaced.
> The gear goes down and locks.  The pressure builds up to 700 psig and
> the
> pump shuts down.  The low pressure starts to bleed off and it is
> possible to
> see the high pressure gauge move off its zero position as the low
> pressure
> drops..  The pump cuts in restores the pressure, shuts off and the
> cycle
> begins again.
>
> If the gear is retracted and again extended the problem disappears.
> It
> appears as if the low pressure is leaking across to the high pressure
> side
> but not every time.  If you leave the system off overnight in the
> morning
> there will often be 400 to 500psig left in the circuit.
>
> So what is happening?  The gauges suggest that the low pressure is
> migrating
> to the high pressure side either across the emergency extension cock
> or
> across the piston of one or more of the double acting cylinders.  But
> why
> not all the time?  Could it be air in the system?  How do you trouble
> shoot
> an intermittent fault ?  In theory I should be able to blank off the
> LP
> pressure to the cylinders until the fault disappears but I may not get
> the
> fault to reappear on command!  Perhaps I should start  with the cock.
> Another probability is that I have a bubble of air somewhere.
>
> Any ideas anyone?
>
> Ian Crowe
>
>
>