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