P337H 1980 Gear up issue
 

Hello everyone,
I have had a P337H with the call sign N330LC since 1980. For the last two weeks, I have had a issue with the landing gear extension sequence. I would like to describe the problem and hope you can help me, please.

On Thursday, I had a flight from the maintenance shop to my home airport. During maintenance, they checked the jacks 20 times, and the landing gear worked without any issue.
During the test flight, I performed four touch and-go, each time with the landing gear extended and retracted. No issue , the landing gear worked great.

Upon arrival at my home airport, I again extended the landing gear perfectly before landing and landed safely. The system worked great.

Yesterday, I was doing a training flight, but after takeoff, the landing gear did not retract. The system behaved as follows:
lever up, hydraulic pump running, landing gear door opened, but landing gear did not retract, green light still on, pump running with difficulty in the next phase! The circuit switch tripped. Then I reset the circuit switch I returned the lever to its gear down position and the landing gear door back closed normally. It seems to me that the landing gear cannot be released.

The accumulator has 500 PSI
Hydraulic fluid - Full
No visible fluid leaks anywhere
No visible mechanical damage to the chassis anywhere

Thank you for your help and advice.
Lubomir

Check the nose gear squat switch for broken wires, etc.
337 Service manual 18-91 thru 18-94
Item S-1377-1

If the strut is difficult to extend, or dirty, etc., the switch will not "make", and the motor runs, doors open, but gear will not retract.

It worked on jacks, because the strut was extended for all jacking events, without being compressed between events.

I have a new, in box, never used switch. Will check for the pn, and if you need it we can "make a deal."
Switch is listed in parts heading.

Randy
Not exactly sure how the electric hydraulic squat switch works in the system but what you describe is this how it protects the gear retraction on the ground? The doors will open?
As you probably know with the gear driven pump on the earlier models the gear handle is locked out to avoid any possible gear retraction on the ground or weight on wheels.

Just curious

Herb.
Hope you are doing well.
That is exactly the way it worked on my 76 "G" model.
The handle moves to "UP", starting the sequence.
The powerpack operates, the doors open, building up pressure, to start the gear legs to move. The squat switch still shows "ON GROUND". (either by strut not extended, or wiring not made, etc.
The airplane, when on jacks, kind of does a "twang", but the motor keeps running until the breaker pops, or something worse.
Put the gear handle back down: The pressure is already up, so the door sequence starts to close them.. they close, pump pressure builds up, kicks the motor off. LIke normal.
Oddly enough, I had this EXACT thing happen.. the strut was stiff, cold, whatever, and on jacks would not extend, making the retraction not work.
A head scratcher at the time..

In the service manual, page 5-78 (rev. 6), it gives a quick explanation about the door valves, and the gear valves. The pump motor is on a seperate CB from the gear handle. The solenoids, both gear and doors, are set up for pressure, to make the
gear retraction / extention work.
I'm not sure how the early ones worked, exactly, never dealt with one.