Gear retraction issue

[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/

[Galvine]

Thanks for the advice
I’ll ask my mechanic about these ideas

Thx

Greg

[Ryann]

Originally Posted by Jhogan0101

What happens on ground when RPM is 1800 and you pull handle down?
Does it snap back to down after a few seconds?

Greg (user Galvine) has a 1978 P337H, which has the electro-hydraulic pump rather than the engine-driven pump like on the early 337's like your 337B. The gear handle doesn't work the same way, it's just a switch on the electro-hydraulic gear system rather than a valve, and doesn't snap back to down.