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Landing Gear Circuit Breaker Popped After Gear Gown

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Hello,

 

I have a 68F model. I went flying this weekend after a couple of touch and goes I raised the gear handle and the gear did not come up. It turns out that the landing gear circuit breaker was popped. I put the gear handle back down and reset the circuit breaker. Rather than cycling the gear I full stopped figuring that it's better to think through the problem on the ground.

 

Has anyone had this issue before? It seems odd that the gear would get down and safe and then pop the breaker, but maybe that's because the breaker is old and weak. Or maybe a limit switch has gone out. Or maybe the motor is tired. Or maybe...

 

Any thoughts or suggestions are appreciated.

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I think you did exactly the right thing! ;)    Trouble-shooting a gear problem is best done with the plane up on jacks.

 

I suspect that if the circuit breaker is good, a limit switch just "out of limits".  However, the symptom you mention could be a plethora of different things.

 

Has the gear had any recent maintenance?  Is your gear drive covered by the AD requiring inspection/fresh grease every 100 hours?

 

Any previous history?

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The gear had a major overhaul, all sorts of worn bushings etc were replaced, when we purchased the plane about 4 years ago. About a year after that we replaced a jack screw that had gone bad.  The jack screw was a real eye opener. It was worn at one end and the recirculating balls were jamming the screw. It could have prevented the gear from being lowered either electrically or manually.

 

During the gear overhaul we replaced the gear drive with a 40 : 1 gear drive. I believe it requires annual lube with some sort of special grease.

 

The airframe has about 3100 hours on it now.

 

No recent maintenance that I would think would affect the gear, but it has had a terrible year otherwise: New exhaust, rebuilt prop governor, rebuilt injector servo, new vacuum pump, rebuilt boost pump, and cracked spark plugs. 

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I had a problem with my landing gear breaker popping on gear extension. Never popped coming up. The only problem I had with the gear going up was in cold weather. I would get the gear unsafe message and would need to push the emergency by-pass. My problem with the breaker popping going down was related to a slipping alternator belt. Yeah, weird, I know...

 

Some things to look at:

 

1) As you mentioned, the breaker itself. I replaced several breakers over the past couple of years for popping for no apparent reason. I believe these do wear out over time.

 

2) If you haven't had the gear maintained in a while, now is the time. If the incorrect grease is used (personal experience), it colder weather it makes it harder to retract and extend.

 

3) I would also look for chafed wires or wires that are worn.

 

4) Make sure your electrical system is up to snuff. There is a noticeable amp pull on initial gear movement.

 

Let us know what you find...

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Sorry for overlapping with your response... I was typing while you were responding. Don't discount the breaker. The 20 amp breaker should be fairly hard to pull. Like I said in my last message, I have replaced several of them over the last couple of years. My plane is a '75.

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OMG!  You have had a lot of things done to your gear.  My Mooney has about 4000  hours on it and I haven't had any of the issues you've had repaired.   I'm not sure how similar our electric gear systems are.

 

With all that background, I'd suggest you get a real Mooney guy to do a thorough check before you retract that gear again, unless it turns out to be electrical (circuit breaker, slipping alternator belt, etc.) in nature and not specifically gear-rigging related.

 

Excuse the pun, but there's just too much riding on the gear to take a chance!

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Vince,

 

That’s what I’m hoping. I’m going to take it to my Mooney mech in Flora, gear down, and have the gear swung. I just want to make sure it isn't a mechanical problem before I try to operate it airborne. My jamming jack screw issue got my attention and I don’t want a repeat of anything like that.

 

This plane originally had the 20:1 gearbox. The 20:1 gearboxes were really violent. Now it has the 40:1. I think those old 20:1 gearboxes just beat the hell out of everything and 40 years of that beating caused many of my issues.

 

Patrick

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It might be the electric motor wearing out as well.  They are overhaulable by a guy/shop in CA for reasonable money too.  When mine gave up the ghost, the gear wouldn't extend but it didn't pop the breaker either.

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The down limit switch should be adjusted so the over-center preload springs are 1/2 compressed. All four springs should be compressed equally. If any of the springs are fully compressed the motor will be trying to bend your plane.

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I just had the same issue. The gear did not retract. I opened the belly and moved the gear motor teeth..just a fraction and everything worked again. I cycled the gear a half dozen times. So, with it still on jacks and opened, where do I find replacement parts? It still has the very fast cycle time.

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Likely time for the motor to go to someone like George's Electrical Services in Sacramento.  I believe that is where mine went (via Willmar Mooney Service Center in 2008) when my gear failed to extend.  Very modest cost.

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Outermarker, PLEASE READ!

 

It sounds like you have the same problem I had and I don't think I ever posted the full resolution. Matt, at Midwest Mooney, cycled the gear and noticed that it was not running smoothly. When you operate the gear, at least with the 40:1 gearbox, the gear should run up and down smoothly. You should not hear the motor change speeds as loads vary. The load should not vary. Just a steady whir as the gear moves.

 

As it turned out my jackscrew had a dimple in the end and the recirculating balls inside were jamming up. If these balls jam up thoroughly enough, you will not be able to operate the gear electrically or by hand. So make absolutely certain that the jack screw is operating smoothly. My problems had nothing to do with the motor.

 

Matt found a replacement jackscrew and the gear has never had an issue since.

 

The dimple was probably caused by being run for 40 years with the 20:1 gearbox slamming the gear against the limits. For reasons I do not understand, civilian pilots are taught to cycle the gear for every touch and go. Every civilian CFI I've ever flown with makes you cycle the gear. This adds to the wear and tear on the gear and is usually pointless.

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Outermarker, PLEASE READ!

 

It sounds like you have the same problem I had and I don't think I ever posted the full resolution. Matt, at Midwest Mooney, cycled the gear and noticed that it was not running smoothly. When you operate the gear, at least with the 40:1 gearbox, the gear should run up and down smoothly. You should not hear the motor change speeds as loads vary. The load should not vary. Just a steady whir as the gear moves.

 

As it turned out my jackscrew had a dimple in the end and the recirculating balls inside were jamming up. If these balls jam up thoroughly enough, you will not be able to operate the gear electrically or by hand. So make absolutely certain that the jack screw is operating smoothly. My problems had nothing to do with the motor.

 

Matt found a replacement jackscrew and the gear has never had an issue since.

 

The dimple was probably caused by being run for 40 years with the 20:1 gearbox slamming the gear against the limits. For reasons I do not understand, civilian pilots are taught to cycle the gear for every touch and go. Every civilian CFI I've ever flown with makes you cycle the gear. This adds to the wear and tear on the gear and is usually pointless.

 

+1 for Matt at Midwest Mooney!

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Thanks for the quick reply. The gear motor run smoothly and at a constant speed. The system is well lubed. It seemed that when the gear was last extended it went too far over center causing the teeth to mash and jam. It didn't take much to release the binding by hand, but was too much for the motor and thereby triping the breaker. So, I see two part numbers, the motor and the gearbox. Since the motor seems fine, can the gearbox be replaced with the 40:1 gears and all is well? Who sells the gearbox or overhauls them? I just found out that Transdigm is the new owner of the Dukes products. I will follow the George's Electrical lead as well as a Dick P???? lead. Can my local shop rebuild what I have since it is on their jacks? The plane is where my father lives and I am visiting. I was hoping to fly with him (he is 79) to evaluate his flying before I leave, now I just want it fixed before I leave.

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So I'm having similar problem with gear (1966 C model).  Gear partially lets down, but would not extend fully, and would not retract. Breaker did not pop. Up on jacks, the gear cycled properly several times, then would quit mid-cycle.  It started again when you tap on the down relay, or up relay, or on the motor itself.  So it could be "dead" spots, or sticky relays etc.  My pucks are pretty new, and it was not too cold, so I don't think it's the squat switch.  I'd like to send the motor-actuator to LASAR and have George's Electric rebuild, and install the 40:1 gear upgrade, AND replace the up/down relays.  All in, that's about $3,500, but I think it would be reliable for another 10 years (periodic inspections/lubrication).  Don Maxwell's site says there's a question whether you must comply with the AD and do the 200 hour pull and inspect the worm gear routine if you do the 40:1 upgrade.  Has there been a definitive ruling on that?  What's the convention?

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