REFLECTOR: Oildyne Retract Pump Spool Valve

[Ron Brown]

My hangar mate has a Lancair 320 RG which has exactly (or very nearly) the 
same hydraulic pump that we have in our Velocity RG's.  I have observed 
similar operation as Mike describes below in his note that I copied from the 
Lancair "Reflector".  Any body else notice this hesitation at the final 
stage of retract, like the nose gear doors don't quit shut all the way, the 
pump has already shut off, then it runs again and the doors finally close. 
The hydraulic lock that occurs after flying for a couple of hours where the 
reset button has to be pressed to relieve the down side pressure so the pump 
will run is also similar to the descriptions below.  Scott B., have you all 
heard anything about this???


Mark,

The operation of the system may seem to be almost completely normal
with the spool valve reversed. Without gauges, the only symptom may
be a slightly weak retraction at the top of the cycle, and you can
overcome that problem by raising the high-side pressure switch
setting. That was the way I had my system set up initially with the
spool-valve problem. There is one other symptom, but it doesn't
normally come up under normal operation. The gear won't come down
immediately after a retraction or during a retraction near the top of
the cycle (this is because the low-side pressure has increased during
the retraction and the low-side pressure switch is open as the
pressure bleeds off). If the spool valve is in correctly, you will be
able to lower the gear at any point during the up cycle without the
system hesitating. I say it doesn't come up under normal operation
because once you raise the gear, you normally don't lower if for a
while, and the pressure has time to bleed off. Therefore, it is
possible to have a reversed spool valve and not really have any
significant symptoms, if you don't have pressure gauges.

If you are seeing pressure in the low side during the retraction
cycle (increasing a little from the down setting all the way up),
then I would check the spool valve.

Mike Reinath
LNC2 at 460 hrs TT
San Jose, CA (RHV)

After looking at the picture, it appears that the pump could use either side 
as the high pressure one, as long as one knew which way the "O" ring 
pointed. Is it possible the "reversed spool valve" was the design intention 
of the manufacturer? Could we (builders) or Lancair just be putting the 
pressure valves in the wrong ports? If I had your picture prior to putting 
the hydraulic system together I think I would have opened the pump up, 
ascertained which way the spool valve pointed and put the pressure switches 
in accordingly.

Thanks again for taking the mystery out of an unknown!

Mark

We do in fact use the pump in a non-standard configuration with the work
being done during cylinder retraction instead of extension. Therefore,
when viewing the generic pump schematic from Oildyne, high and low side
are backwards.
My original pump was assembled correctly. Some time after '95 the build
instructions from Lancair got mixed up and every pump was being
assembled with a reversed spool valve. Every pump I have worked on
since then was backwards including the spare I bought for a hydraulics
test bench. I'm sure there are quite a few out there still needing to
be fixed.
Chris Zavatson
N91CZ
360 std


Below is a communication thread between Parker and myself about the 
hydraulic pump on the 360.
I thought it would be helpful for those of you that have not yet experienced 
the joys of trouble shooting the hydraulic pump issues on your 360, to post 
this sad story. Even with the help of Randy, Scott, Lorn and Gerard, I was 
unable to remove the shuttle valves to get to the spool valve. 
So................... I decided to apply some pressure......bad idea! The 
pressure needs to be applied in the proper place and to make a long story 
short...... I damaged the manifold. In my own defense, Parker Hannifin was 
initially unclear on where to apply this pressure. I do have to commend 
their customer service which was very responsive but I still had a broken 
pump. At this point, the remainder of the damaged pump, (after a very 
detailed explanation by an Oildyne service guy) was performed (it took five 
minutes) and guess what, the spool valve was reversed.
   Oildyne found me a replacement manifold, which comes complete with 
internal pieces (spool valve, etc.) in Orlando, so after spending some money 
I was back in business. As I was looking at the new manifold, it occurred to 
me that Oildyne probably learned their lesson years ago about the correct 
orientation of the spool valve. They probably received thousands of 
complaints from the field over the years about the improper assembly issue 
which did not comply with the engineering drawings and brought this to the 
attention of their people. I decide to check and low and behold the spool 
valve was installed reversed!!! I check the drawing again to make sure my 
eyes weren't fooling me. AGGGGGGGGGGGGGG..........HH. (This is why I haven't 
bought and American car in fifteen years.)
   I reversed the spool valve, transferred the motor and the rest of my good 
pump pieces to the new manifold and reinstalled the assembly. The system 
worked perfectly. The gauges read the correct pressures, the high and low 
were not fighting each other and even the hydraulic gear door cylinders 
started operating without starts and stops of before. I now have a big smile 
on my face but my stomach churns thinking about the time I wasted working on 
this system that had a simple problem. Another lesson learned and now I am a 
hydraulic pump "expert". Someday, maybe this plane will fly.

ONE MORE SAD BUILDER STORY!

MARK QUINN

Christian,
   Attached below is a drawing showing the orientation of the spool valve. 
The
down side referred to in the e-mail below is to the right. You need to pull
out both end plug retainers and the poppet assemblies also. Then with a 
small
diameter punch inserted through the poppet seat from the left hand side 
(High
pressure) strike the punch with a small hammer. Not much contact is needed.
This will push the spool valve against the poppet seat on the right hand 
side
(Low Pressure) and cause it to come out. Continue to push the spool valve
until it comes out and note on which end of the spool the o-ring is 
installed.
THE O-RING SHOULD BE TOWARD THE LEFT END OF THE SPOOL VALVE. If it is not,
flip the spool valve over and reinsert it toward the high pressure side and
reassemble the manifold. Once you see it you will understand the above
instructions. Let me know if you have any questions. O-rings in my unit did
not need to be replaced.

 MARK QUINN
 DAYTONA BEACH, FLORIDA

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