Gear retraction issue

[RandyArizona]

Originally Posted by Scudrunner

Having a similar issue 1974 337G, if I pump the gear doors down on my preflight the gear will cycle normally.
Plane had sat for past two months with the cold weather.

You may have a couple of related issues.
First, it sat for a couple of months, so it "lost it's prime", for lack of a better term. By this, I mean, the fluid leaked down from where it usually sits with pressure. By you pumping the doors open, ( I would suspect quite a few pumps until you felt the pressure come up), you pressurized the system.

This is an internal electro/hyd. pump/reservoir issue.

When was it last rebuilt? Or is it original equipment/?

Second, When were the door and gear solenoids serviced?
(I would also bet, if you really thought about it, a few months back.. the doors were open after landing, and parking. They came up after master off, and then master back on....You didn't think anymore about it.)

The solenoids get sticky, and if they get hot, they really stick. They need be serviced at least at annual, I serviced mine when ever the center console cover came off, or when I was at the hangar and wanted something to do.

The hyd pump / reservoir leak down issue can only be fixed permantly by a rebuild, or you can just pump up the pressure each time before you fly.

Also, check the reservoir fluid prior to first flight of the day, at least.

Good luck.

[Scudrunner]

Appreciate the advice, I can’t recall if it was more or less pumps than usual. I’ll dig through the logbooks to see if I can find when it was rebuilt etc.
I forgot to mention we have the rear main gear door delete stc so not as many moving parts back there.

Fluid was topped up I’m pretty diligent with that, never found any signs of fluid leaking anywhere yet.

I’ll taker for a rip this weekend see what I can discover.

[RandyArizona]

Originally Posted by Scudrunner

Fluid was topped up I’m pretty diligent with that, never found any signs of fluid leaking anywhere yet.

I’ll taker for a rip this weekend see what I can discover.

Ah, no doors... Never dealt with a "no doors" aircraft.

The powerpack would be leaking internally, I doubt there would be Hyd fluid leaking anywhere to be seen.

Good on checking the fluid.

[Learjetter]

Something else to check: the hydraulic accumulator sits under the floor in the tunnel between the pilot seats. It’s normally charged with 500psi nitrogen, and it helps keep pressure on the power pack. If it looses charge, you’ll get drooping doors after the plane sits for a week or so, and when you turn on master power the pump will activate and tighten up the doors closed. The accumulator helps the powerpack keep its “prime.”

[Galvine]

So a follow up on my gear issue (1978 P337H)
I’m still having the exact same issue a year later ( it did work for about 5-6 months but then same issue)

It always works normal in the shop on jacks so it’s been hard to pinpoint

We have replaced ( overhauled ) the gear power pack, all the limit switches etc, just rebuilt the “accumulator” under the floor board

And same issue
Basically, first flight of day, select gear up, green light goes out, and gear doesn’t move
Select gear down ( still no green light ), pump the emergency handle 2x, and gear green light comes back on. Then select up again, and gear cycles normal. And will work normal over and over on that flight if needed ( ie multiple
Approaches etc)

Again, in the shop on jacks, they have never been able to reproduce it. Not once.
And its been in the shop off and on for a year maybe 7-8X looking at this problem

Any more suggestions appreciated

Thx

Greg

[pilotpat]

One thing we came across was a sticking pressure switch plunger: the plunger sits on top of the hydraulic pack and moves up and down by the system pressure to actuate a microswitch, which turns the pump off/on. The plunger was intermittently sticking (so pump may not start and gear may not continue moving after the accumulator pressure bleeds off) until fixed by a new o-ring kit, no problems since.
Good luck!
Pat

[Jhogan0101]

What happens on ground when RPM is 1800 and you pull handle down?
Does it snap back to down after a few seconds?
Fyi you can put this on a T fitting on hose coming from pump for “testing purposes only” if you want to see live hydraulic pressure.
It sends bluetooth signal out and can be paired with ipad with their app.
Normal gear pressure is around 1500psi.

https://www.hydracheck.com/catalog/p...ging-5000-psi/