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From: "Mike S. Reinath" <mreinath@mail.arc.nasa.gov>
Subject:  [LML] Re: Almost Back Flying, Again
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<<Why is oil Dyne charging you anything?  They installed the spool 
valve backwards didn't they?  Seems they should just be glad that it 
didn't cause other problems....>>

The spool valve can be installed either way. Its orientation depends 
on whether the shaft-side of the hydraulic cylinder is connected to 
the low or high side of the pump (i.e. other users of the pump may 
use the pump with the cylinders flipped 180 as compared to our 
configuration). The amount of fluid that must return to the tank 
during cycling of the cylinder differs by the volume of hydraulic 
fluid displaced by the shaft inside the cylinder. The spool valve 
takes care of this problem. The company ships pumps with the spool 
valve oriented both ways. I'm not sure how the error was made or who 
is responsible, but some of us received pumps configured incorrectly 
for application. It may not have been Oildyne's fault.

I've posted this before: A simple test to check if your spool valve 
is okay is to put the plane on jacks and raise the gear. With the 
gear 95% up, put the switch back in the down position. The pump 
should stop and reverse immediately, and the gear should start back 
down. If the pump just stops and then delays before reversing, then 
the spool valve is probably in backwards. Depending on the pressure 
switch settings, and the low-side pressure relief-valve setting, the 
delay may be a few seconds to maybe 10  or 20. In my case, it was 
closer to 20.

Mike Reinath
360 at 146 hours
N3602M