<<< Thanks for that explanation Mike--might explain the nose gear doors reluctance to close...? >>>

Gerard,

Maybe, but I would expect to see all three wheels exhibit a weak retraction.

On my system, it took about 20 to 30 seconds for the down-side pressure to bleed off after a retraction, with the spool valve oriented incorrectly. After that, the gear was all the way up; i, e, once the down-side pressure bleeds off, everything is back to normal -- so all the doors should be closed. During the bleed-off period is when you might see some abnormal behavior. (Remember, more fluid volume has to return to the pump, and the tank, than is being pumped out to the cylinder, during a retraction. This difference occurs because the cylinder shafts displace fluid on the high side only, and that is why the pressure increases on the down side during a retraction, with a reversed spool valve. The spool valve is designed to allow the excess fluid -- equal to the combined shaft volumes -- to return to the tank, if it's oriented correctly.)

If your door starts out not wanting to close, but then ends up closing after 20 to 30 seconds (or maybe up to a minute, depending on how tight your seals are), it could possibly be the spool valve. But I would expect the mains to show somewhat of a weak retraction too.

I have posted this before, but you may have missed it -- A simple test to check the orientation of the spool valve is to do the following. With the plane on jacks, raise the gear (you might also be able to do it in the air, but on jacks it's easier to observe the behavior). Just as the gear is reaching the top of the cycle, but before the pump shuts off, put the gear switch back in the down position (at this point, if there is pressure in the down-side lines, it should be the highest). The pump should reverse, and the gear should start down immediately. If it doesn't, then the spool valve is oriented incorrectly, assuming there is no other major problem. The gear may sit for 20 to 30 seconds, more or less, depending on how tight your seals are, what the low-side pressure switch is set to, and what the low-side pressure relief valve is set to.

Mike Reinath

LNC2 at 460 hrs TT

San Jose, CA (RHV)