Electric gear procedure down lock fail

[M20C_AV8R]

My name is Mat, I have been lurking here for a while and really appreciate all of the great posts and information. 

 

I bought a 1964 Mooney m20c Back in May of this year, it was converted from manual to electric gear in the 70's. My question or asking for your thoughts surrounds the following.

 

Recently some damage was caused by a mechanic cycling the gear in their shop during a tire change and inadvertently left a box under the copilot side gear, they dropped the gear on it while on the stands and bent a rod, it was the long one under the copilot side , they replaced, tested, did the preloads etc and everything checked out good on jacks and they signed it off as repaired and back in service.

 

I flew it post this happening for the first time yesterday and the gear went up fine, but, when I went to drop it, the electric gear would not lock down, I tried cycling it several times before going to emergency gear manual process (I was well below VLo). That process worked and I was so very happy to see that gear down lock finalize on the light indicator as well on the floor using that procedure and then executed a normal landing.

 

More details: During the electric gear down procedure I could see the light flashing trying to lock, I could see the floor indicator close to lock, but the floor indicator kept cycling forward like it was bumping, I could also feel the motor in my seat running and attempting over and over to advance the gear to the locked state, but, the electric could not lock the gear down.

 

It's going back into the mechanic on Tuesday, but, I wanted to ask if anyone else had seen this, I used the search here as well google but could not necessarily find this scenario as well working to educate myself more about the gear.

 

Thank you in advance for any input or thoughts on this.

Edited September 3, 2017 by M20C_AV8R
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[Guitarmaster]

Your down limit switch is most likely out of adjustment.

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[Mooneymite]

1 hour ago, Guitarmaster said:

Your down limit switch is most likely out of adjustment.

I agree.

[carusoam]

Welcome out in the open, Mat.

Time for a different mechanic...?

1) he broke the plane.

2) he sent you to fly the improperly fixed plane.

3) you are still looking to get this fixed.

4) It isn't hard to follow the manual for setting up the landing gear properly. Does he not have the manual?

5) the manual E-gear is closely related to the normal operating gear.  If one system gets broken, the shared brass gear. Both E and normal ops may not work...

PP thoughts on Mooney landing gear. Not a mechanic...

Best regards,

-a-

 

[Guitarmaster]

My name is Mat, I have been lurking here for a while and really appreciate all of the great posts and information.    I bought a 1964 Mooney m20c Back in May of this year, it was converted from manual to electric gear in the 70's. My question or asking for your thoughts surrounds the following.   Recently some damage was caused by a mechanic cycling the gear in their shop during a tire change and inadvertently left a box under the copilot side gear, they dropped the gear on it while on the stands and bent a rod, it was the long one under the copilot side , they replaced, tested, did the preloads etc and everything checked out good on jacks and they signed it off as repaired and back in service.   I flew it post this happening for the first time yesterday and the gear went up fine, but, when I went to drop it, the electric gear would not lock down, I tried cycling it several times before going to emergency gear manual process (I was well below VLo). That process worked and I was so very happy to see that gear down lock finalize on the light indicator as well on the floor using that procedure and then executed a normal landing.   More details: During the electric gear down procedure I could see the light flashing trying to lock, I could see the floor indicator close to lock, but the floor indicator kept cycling forward like it was bumping, I could also feel the motor in my seat running and attempting over and over to advance the gear to the locked state, but, the electric could not lock the gear down.   It's going back into the mechanic on Tuesday, but, I wanted to ask if anyone else had seen this, I used the search here as well google but could not necessarily find this scenario as well working to educate myself more about the gear.   Thank you in advance for any input or thoughts on this.

You said he tested the preloads, but did he follow the WHOLE procedure? Changing or messing with one side will affect the rest. If the procedure is not followed, you can show proper preloads and still not be rigged correctly.


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[M20C_AV8R]

4 minutes ago, Guitarmaster said:

You said he tested the preloads, but did he follow the WHOLE procedure? Changing or messing with one side will affect the rest. If the procedure is not followed, you can show proper preloads and still not be rigged correctly.


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Not sure, I am expecting that he did, he has worked on many Mooneys before and repaired many gear up landings that have happened on the field, so I feel pretty good that he knows these systems. Also, fwiw, everything worked as expected after the work was done while the plane was on jacks i.e. the gear locked down as expected, it just seems to me that going 100 mph in the air puts some kind of extra load in the equation that causes it to struggle, but, I am still learning all about this system so I cannot say. Thank you all for your input so far.

[Guitarmaster]

After re-reading your post, probably your best and most effective as well as quickest method to fix the problem would be to disconnect the whole thing and start from Ground Zero following the manual.
I had a similar problem and after I disconnected everything I found that there was a lot that was out of adjustment even though the preloads were showing okay.
Once the belly is off the airplane, it only takes out 2 hours to do the entire rigging. Probably less if a professional's doing it.

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[MB65E]

I'd be worried about the  Motor and jack screw gearing as well. 

2hrs to check it. All day to rig it fully. 

-Matt

[Alan Fox]

My guess is the left gear rod was bent , it has the downlock switch plunger on it , If the preloads are correct on all 3 , It is probably the switch plunger adjustment ,

[bob865]

My two cents is that you were able to manually extend it and get the down lock indications I would bet that the indication system, i.e. switches/wiring, are all fine.  You said you mechanical indicator and your indicator lights shared the same indications, almost but not fully locked.  This seems to me like it has to be mechanical adjustments. 

Good luck.  Let us know what he finds. 

[Mooney1]

Take it gear down to a MSC. Then send the bill to the guy who screwed up your plane! 

[JoshMan]

Hi, Mat

I actually had a somewhat similar but different issue.  On taxi for whatever reason the gear motor would randomly start to cycle.  Luckily gear would always remained locked.  The initial thought process was that it was the down limit switch.  The metal pad that makes contact with the switch was actually adjusted and the problem stopped; however, you cannot adjust the rod too much because it may completely disrupt the rigging. 

The guys at Willmar weren't convinced this was actually the issue and sent the gear motor out to George's electric in California and said the brake in the actuator looked terrible, so it was ultimately overhauled.

So, I think as the guys above said its either one of three things: the actuator, down limit switch or rigging.  I would not let someone who does not know this gear well mess with the rigging at all.  If your actuator has not been looked at for 30+ years its time to send it out regardless.  I think George's overhauled mine for about $500ish

[M20C_AV8R]

9 hours ago, JoshMan said:

Hi, Mat

I actually had a somewhat similar but different issue.  On taxi for whatever reason the gear motor would randomly start to cycle.  Luckily gear would always remained locked.  The initial thought process was that it was the down limit switch.  The metal pad that makes contact with the switch was actually adjusted and the problem stopped; however, you cannot adjust the rod too much because it may completely disrupt the rigging. 

The guys at Willmar weren't convinced this was actually the issue and sent the gear motor out to George's electric in California and said the brake in the actuator looked terrible, so it was ultimately overhauled.

So, I think as the guys above said its either one of three things: the actuator, down limit switch or rigging.  I would not let someone who does not know this gear well mess with the rigging at all.  If your actuator has not been looked at for 30+ years its time to send it out regardless.  I think George's overhauled mine for about $500ish

Hi Josh,

Sorry to hear you had to deal with that, sounds like it worked out in a good way and similar to what I'm dealing with. I have been working with the mechanics, this week, they completely re-rigged the gear this to the exact specs/tolerances  of the service manual, there appeared to be many areas that they had to adjust, that were quite off and have probably been that way for some time now. We got everything buttoned up today and as soon as it got off the jacks (everything was working as expected and all preloads really good up on the jacks), but, unfortunately it started doing the same thing again when I turned on the master. FYI, the down gear switch was really gummed up, but, now that it's been rigged, all the preloads set, up and down limits set per spec, the next step I am told is to replace the down limit switch. I am going to share this info with my mechanics. It looks like another week or two before this might get resolved. It's ok, I just want it right. I'll update this thread as I learn more.

[Andy95W]

Like Josh said, there is a brake in the actuator.  When the actuator receives power, either up or down, the first thing it does is retract the brake (like it was a big relay).  When there is no current applied, springs hold it in place to provide the resistance from movement.

When the springs get weak, the bungees at each of the gear rods can work together to unwind the actuator because the brake isn't holding like it should.  If the brake is in decent shape, it can be shimmed with a #10 washer at each spring to increase the tension some.

My first Mooney had this problem in the 90's. I took the landing gear motor to Dugosh and Ronnie showed me what I mentioned above.  He didn't want to take any money so I had to "forget" a $20 bill on his bench.  Too bad he retired.  He was a top-notch guy with a ton of knowledge.

Or it's your down limit switch.

[M20C_AV8R]

So, long story short, we are going to just go ahead and put the plane back up on Jacks, replace the up/down limit switches, there are some bushings that are a bit old on the gear getting replaced as well (they are worn, its apparent) as well, the gear assembly, Jack screw, motor etc are all being pulled out and sent to Georges Electrical Services and they will make sure everything is good there. So its going to be another month, figure we mine as well just get it right and set a solid baseline going forward. Thank you all for your input, really appreciate it, I will update this thread with a summary when it all comes back together.

[jetdriven]

Are you sure that there's a brake in the older style Dukes actuators? There's no back spring in those either. 

[Mooneymite]

4 hours ago, jetdriven said:

Are you sure that there's a brake in the older style Dukes actuators? There's no back spring in those either. 

Yes.  Im wondering the same thing.  Why would there be a brake when it is a worm drive?  

[Yetti]

If there are more than two wires going to the motor it probably has a brake in it.  It is actuated by the 4th terminal on the solenoid.

[Andy95W]

16 hours ago, Mooneymite said:

Yes.  Im wondering the same thing.  Why would there be a brake when it is a worm drive?  

I honestly can't answer that.  And my wife will tell you that my memory is going.  She'd probably tell you to your face, with me standing next to her, because she figures I wouldn't remember it anyway.

But I'm pretty sure I'm accurately remembering the hour I spent with Ronnie at Dugosh as he worked on my Dukes landing gear motor 20 or so years ago.  And he was a guy with Mooney knowledge that approached DMax or Paul Loewen. 

[M20C_AV8R]

It’s been several months, as promised I would write out what the ultimate resolution was, and I am happy to report that everything is now working as it should. Basically post the initial accident of the A/P dropping the gear on an object and bent the rod and having a hard hit to the gear as a whole, this opened up a whole can of worms, meaning that I was in the crapper and I knew it from restoring antique cars, a system is only as strong as the weakest link, so here we go. The bent rod was replaced, I had to advise the mechanic that I wanted the motor and jack screw sent off to George’s Electric (btw, I highly recommend them) to be looked at (The motor was damaged by the accident), it took a fair amount of money and time for them to get it right, the Jack Screw was off quite a bit and Lasar fixed it. Also, the left side gear assembly was fairly loose and had probably been that way for some time, the bushings and one of the bars needed to be replaced (that was super expensive). I also made the call to have the rubber donuts shocks replaced on both sides, after doing some reading they play an important role in the overall health of the gear way beyond just a cushion. Post all of this everything came back together, pre-load was easily obtained and all buttoned up. I just now need to figure out if I need to file an insurance claim for the labor/items impacted by the accident because the FBO is not and their invoice is not representative of any accountability for the labor related to the initial accident, including for the part/s they broke and repair of the motor and Jack screw.

Edited December 30, 2017 by M20C_AV8R
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