Gear retraction issue

[Galvine]

I have a 1979 P337H
I am having a gear retraction issue

After take off, I raise the gear handle, the green light goes off, but the gear doesn’t retract
If I lower the gear handle, the green light stays off
If I pump the emergency gear handle once, the green light comes on again and then if I raise the gear handle again, it cycles normally

And if I cycle it over and over , it works normal

I have had it in the shop twice
Fluids all good
Cycles normally when plane on jacks

Appreciate any thoughts

Greg

[Learjetter]

Consider checking these:
- check accumulator pressure is 500psi
- squat switch (check switch function at nose terminal block pins 1 &2 on left side nose gear bay) and check nose strut pressure to ensure strut extending fully)
- check each up lock and downlock switch for system continuity
- check main gear handle switch (incl diode in wire S-GD12 to contactor)
-add a little more fluid to reservoir (in case climb deck angle is causing pump to suck air/foam)
- might also be sticking door and gear solenoids (remove and clean)

- those are the quick and easy checks — good luck!

-LJ

[Galvine]

Ok
Thanks so much for the response
I’ll start there

[RandyArizona]

Landing gear control system, dwg 1571000, page 18-92 in electrical wiring diagrams, service manual.
(Picture/diagram of contactor page 18-96.. item 18)
This contactor is located, copilot side, fwd of Hyd power pack, on nose gear tunnel wall. ( inside cabin, behind a bunch of wiring)
If yours is like the usual, it is original, and in bad shape.
Easy to replace, just overlooked.

[Galvine]

Thanks for that advice
I’ll look into that as well

Greg

[Scudrunner]

Having a similar issue 1974 337G, if I pump the gear doors down on my preflight the gear will cycle normally.

If I don’t, the gear won’t cycle up, a few pumps on the handle and then select it up it will cycle.

The other day I had pumped the doors open on preflight as normal did a thorough inspection. Took off selected gear up and got the horn and gear didn’t cycle. I then selected back down horn stopped, I pumped the handle down as what usually solved the issue selected gear up again horn and didn't cycle.

Came back in did a touch and go, didn’t finesse it on just a firm landing. Gear retracted normally after that…….

I suspect a squat switch but thought I would ask the brain trust here. Plane had sat for past two months with the cold weather.

[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.”