Landing gear motor failure advice please

[Joe Larussa]

Well this is what I can tell you so far. We pulled the electric motor out Saturday.

Called George's electric today and here is the deal. He will fix and or overhaul the motor but you have to remove the drive shaft or worm gear as well. They will not just fix the motor without sending the drive shaft that have the gears in it to Lasar to be disassembled, checked and relubed. Not a cheap adventure when all is said and done but beats the hell out of a gear up episode!!

[Joe Larussa]

 

Wow, how did you find that out?

Any issues with the back-up LG system?

Motor brushes are usually pretty easy to replace.  They can be some small dollar parts.  They get replaced as a normal part of maintenance.  They are designed to be removed and replaced easily. Generators have these wonders as well.

Running the brushes completely out may scratch the rotating surface they are gliding on.  An electric motor OH shop is pretty good at handling these kind of things.

Selecting a good electric motor shop may take a recommendation from somebody around here....

Or was the resulting damage significantly worse?

Best regards,

-a-

Brushes were completely gone. Nothing left but the spring that is designed to hold them in. The caps that hold the brushes in are epoxy shut. Nothing in my logs that suggest any maintenance has ever been done in 3800 hours. I'm guessing about 1500.00 bones when this is over including R&R. Doing the manual crank down was a non event really.

[carusoam]

Joe,

They must be tiny in size compared to brushes on electric motors that run continuously.  

If the average flight is an hour long, your gear has only been run 3800 times.  Up and down takes a handful of seconds.

If you get to ask any questions at the electric motor shop ask them how many cycles or hours that motor Is expected to run before swapping out the brushes again?

Something may have roughened the surface they were riding on to wear them out.

just speculating,

-a-

[RobertE]

 

Joe,

They must be tiny in size compared to brushes on electric motors that run continuously.  

If the average flight is an hour long, your gear has only been run 3800 times.  Up and down takes a handful of seconds.

If you get to ask any questions at the electric motor shop ask them how many cycles or hours that motor Is expected to run before swapping out the brushes again?

Something may have roughened the surface they were riding on to wear them out.

just speculating,

-a-

Wow.  Never would have thought about that.  So 3800 X 7 seconds per extension or retraction X 2 = 53,200 seconds or 887 minutes or 14.8 hours.  That's not a lot of time.

[jetdriven]

I think we've cycled the gear 1000 times in 650 hours.  But I should add it up. 

I thought it was ~65 turns to lower the gear. It's a lot more when you realize you didn't quite engage the little lever on the sidewalk.  And quite exciting when you put the circuit breaker in and it the gear up with that handle still extended and engaged.  

That service letter only deals with inspecting the actuator gears, noting in them about the motor brushes. 

Also, my gear comes up softly but the seat rail gives slightly when the gear locks down. It used to bow the seat rail enough to jam the pilot seat when up. Further investigation showed the retraction truss jammed against the mechanical stop when up. The gear had 1/2" to go. Re rigging the gear completely fixed that. 

[markejackson02]

Mine burned out in flight November.  If I recall it was about $800 to overhaul.  Took about 50 turns to get the gear down.

[Guest]

 

Brushes were completely gone. Nothing left but the spring that is designed to hold them in. The caps that hold the brushes in are epoxy shut. Nothing in my logs that suggest any maintenance has ever been done in 3800 hours. I'm guessing about 1500.00 bones when this is over including R&R. Doing the manual crank down was a non event really.

I would strongly suggest having the gears inspected and lubricated.  Even with 40:1 gears if/when they fail you will be having a gear up landing.  One of the poor designs in the Mooney gear system leaves you with no way to lower the gear should the small gears fail.

The gear transmission in a Piper Comanche allows you to disconnect the transmission from the retraction linkage and then lower the gear.

Clarence

 

[Joe Larussa]

 

Mine burned out in flight November.  If I recall it was about $800 to overhaul.  Took about 50 turns to get the gear down.

By chance do you remember how many hours it to R&R ? Did you pull the jack screw and have it done at the same time?

[NotarPilot]

Mine failed about 2 or 3 years ago. I called LASAR and they sent a replacement motor but I had to send my old one in as a core once my A&P removed it. I can't remember the exact cost for the motor but it was probably $450 if I remember right. Plus another $260 for labor to have it R&R. Not that bad for something that was an original part and had never been replaced.

[markejackson02]

 

By chance do you remember how many hours it to R&R ? Did you pull the jack screw and have it done at the same time?

It was $900 to overhaul including parts and I believe 8 hours labors to R&R then swing the gear.

[Joe Larussa]

 

Mine failed about 2 or 3 years ago. I called LASAR and they sent a replacement motor but I had to send my old one in as a core once my A&P removed it. I can't remember the exact cost for the motor but it was probably $450 if I remember right. Plus another $260 for labor to have it R&R. Not that bad for something that was an original part and had never been replaced.

Wow that's a smoking deal!

[steingar]

Johnson bar rules!

 

I know, I'm being an asshole.

[Joe Larussa]

So here is the end of this story. A hair under 1,000 bones to overhaul the motor and the jack screw. Roughly six hours to R&R swing gear and make a few adjustments. Now gear goes up and down like God intended.

[carusoam]

Nice follow-up Joe.

Best regards,

-a-