Electric gear not fully retracting

[Fred Rhodes]

I am having trouble with my 1977 J model. When it is cold the gear does not want to fully retract. The motor is trying to finish it as the electric meter shows a strain on the battery. I can put it back down and it goes up all the way on the second try. It is electric gear. It gets greased regularly. We swing it on annual inspection and it always goes through the cycle flawlessly. But the hangar is warm. 

[Ragsf15e]

17 minutes ago, Fred Rhodes said:

I am having trouble with my 1977 J model. When it is cold the gear does not want to fully retract. The motor is trying to finish it as the electric meter shows a strain on the battery. I can put it back down and it goes up all the way on the second try. It is electric gear. It gets greased regularly. We swing it on annual inspection and it always goes through the cycle flawlessly. But the hangar is warm. 

Is the circuit breaker popping or the motor stops running without the circuit breaker popping?

[201Mooniac]

Do you know it is not all the way up?  It is just that the motor doesn't stop running, if so it might be an issue where the up limit switch is sticking when cold and not turning off the motor.  I would expect the circuit breaker to pop in that situation though.

[Fred Rhodes]

I have viewed it with a camera attached to the tail tie down. It goes almost all the way up, but not all the way.

[Fred Rhodes]

The circuit breatee does not pop. It shows a short duration discharge.

[Fred Rhodes]

The motor stops trying after the first attempt to take it all the way. It just shows the light saying that the gear is unsafe. 

[EricJ]

12 minutes ago, Fred Rhodes said:

The motor stops trying after the first attempt to take it all the way. It just shows the light saying that the gear is unsafe. 

Something isn't right (obviously).   The motor is on if the unsafe lamp is on, and doesn't turn off until the gear is fully up.    If the gear has jammed and prevented the motor from running the gear all the way up, one would expect the breaker to pop.    If the breaker doesn't pop, I suspect the brushes in the motor may be getting tired and need to be replaced, or there is a potential wiring issue that is limiting the current.

[Fred Rhodes]

That is something that I have not checked 

[KSMooniac]

If the motor has never been rebuilt, I'd start with that.  My '77 quit on me in 2008 and required a motor overhaul.  

[Ragsf15e]

And we’ll all have to be careful comparing ours to this as the lights changed over the years… the “unsafe” light on my ‘68 means the gear is completely up, ie it’s unsafe for landing.  This is a normal condition.  Mine could do exactly as described, even not fully pull the gear in if I had some sloppy ball joints in the main gear area… but again, mine is older.  You need to look at the wiring diagram for your specific year.

Edited October 30, 2024 by Ragsf15e

[Fred Rhodes]

Do you know who does the motor rebuilding? 

[EricJ]

10 minutes ago, Fred Rhodes said:

Do you know who does the motor rebuilding? 

There's nothing special about the motor itself.    Most electric motor shops should be able to work on it.

[1980Mooney]

7 minutes ago, Fred Rhodes said:

Do you know who does the motor rebuilding? 

That is a Dukes actuator on the '77 M20J - right?

If it is more than just the motor then Don Maxwell or Lasar

AD 75-23-04: SB M20-190 | Mysite (donmaxwell.com)

 

[Fred Rhodes]

It is a Dukes actuator. We keep up with the maintenance on the gear part and just changed out the coupling at the last annual.

[N201MKTurbo]

If the motor stops intermittently with the unsafe light on, it may be the contactor. Next time it doesn’t retract, move your seat back and stomp on the floor right in front of the seat and see if it starts back up.

[N201MKTurbo]

FWIW, the brushes they use on those motors are huge. I doubt they will ever ware out. I have had them unscrew, but if that happens the motor won’t move at all. There isn’t anything I can think of that would make the motor only fail in one direction. 

[Fred Rhodes]

The motor doesn't seem to keep trying after it stops. 

[KSMooniac]

I expect it is stopping on a worn spot and needs some service inside.  

Mine was sent to George's Electric or something close to that in CA all those years ago, but I believe they're long-gone now.  If it happened to me today, I'd start with a local electric motor shop and cash to get my homemade fan motor repaired.

[Hank]

When my C started doing that, it began in cold weather and got worse as the winter deepened. The floor indicator showed barberpole, indicating that the gear wasn't all the way up, and speed was down by ~10 knots. Drove me crazy! Replacing the donuts in the landing gear resolved it--there are eleven, four in each main and three on the nose. The new set was 1/2" taller than the old ones.

[Fred Rhodes]

My donuts were replaced about 8 years ago. I will check specs to see if they are needing replaced.

[ArtVandelay]

My donuts were replaced about 8 years ago. I will check specs to see if they are needing replaced.

8 years?! I think they should last 20 years or more.

[Fred Rhodes]

That is my thinking. Also, but i'm not sure it's worth a check

[PT20J]

The symptoms as described do not make sense.

1. Only happens when cold

2. Motor stops before the gear is fully retracted but continues to draw current.

3. Gear CB does not trip

4. Fully retracts if gear is cycled.

If it were a mechanical problem stalling the motor it should pop the breaker.

When the motor stops running, it’s generally because power has been removed by a limit switch, relay or safety switch (squat or airspeed).

Early M20Js have a squat switch on the left main gear. If the shock disks are good, I’d check the switch adjustment.

If your airplane has a red override button next to the gear switch, you can press and hold that and if that causes the gear to retract fully it will confirm that the squat switch is the problem.

[Fred Rhodes]

Mine does not have the override switch. But checking the squat switch will be on my list of things to check. Thanks.

[EricJ]

20 minutes ago, Fred Rhodes said:

Mine does not have the override switch. But checking the squat switch will be on my list of things to check. Thanks.

If you don't have the override switch you likely still have the squat switch, which could be contributing to the problem.    A common modification is to replace the squat swith with an airspeed switch that has the override button.   Mooney used to supply a kit to do that, they may still be able to.