Trim Jackscrew Binding

[PeytonM]

To be clear, mine was a different issue: the trim jackscrew in the empennage was bound so tightly in the nut that I could not move trim wheel manually at all, even at TO trim.

The SI does not address this issue. 

 

[Stephen Skinner]

Hi, I just replaced mine this week while replacing the link attached to the actuator. The whole trim system was moving very freely full travel up and down.

The rebuilt one is stiff and will not move all the way to the down position.

How much play is acceptable?

My old one had 0.030" of play (installed & under load).

The rebuilt one (installed & under load has 0.015" of play).

Should I disassemble and clean the old one or the new one?

[Guitarmaster]

On 1/16/2017 at 5:37 PM, PeytonM said:

1989 J. 3300 hours. Hangared. I've become less dependent on the electric trim because of my own experience that I reported on MS, as well as others.'  I use the manual trim wheel when flying the airplane, especially on departure and landing.

Upon returning to my home airport after a short flight last week, I reached down to the wheel to begin trimming for the approach and landing.  I could not budge it!  I could not move it at all. I used the electric trim to set up the approach, but I could tell the trim wheel was moving much more slowly than usual. I landed and taxied back to the hangar. I tried using the manual trim to no avail. I repositioned the trim to "Take-Off" with the trim switch, closed the door and walked away!  

Please note: trim was never at either extreme of full nose up or down.

After a few calls and suggestions, I removed the belly panel, checked the trim screw and chain; they both looked a little dirty, but not bad. I cleaned them off and checked to see if that helped; it did not. In the battery compartment, I decoupled the electric trim motor from the system to no avail. I opened an inspection panel on the right side of the tailcone and removed a bolt that connects to the the trim actuator to the jackscrew. (bolt #26 on Illustrated Parts Catalog page 27-40-01) The trim wheel moved freely. I plan to fully access the jackscrew by removing the fairings and move the boot to see what I can see.

I remember back to the last times that I used the trim wheel, and it seemed stiff. I wrote it off to the single digit weather. Maybe my Mooney was talking to me and I was not listening!!

Any guesses what I'll find? Has this happened to anyone? What steps should I take to look for the problem?  I'd sincerely appreciate your thoughts and suggestions. 

I don't know what the trim indicator look like in the "J", but I had the same problem with my '75F.  After chasing the problem with much frustration, it turns out the trim indicator cable was sticky and nearly frozen.  I lubed up the cable and all is good!!

[carusoam]

New and old should both move smoothly from full up to full down.

The amounts of play in the system is probably not the sticky or stiffness issue.

The trim wheel uses a chain.  Expect some play caused by the looseness of the chain system.

PP thoughts, not a mechanic...

Best regards,

-a-

[Andy95W]

On 1/26/2017 at 6:00 PM, PeytonM said:

It was a real mess! After cleanup, it looks brand new.  Looking forward to smooooth operation! Thanks Jason! 

http://www.jed-aireaviation.com/

I just removed mine today (easier than I thought it was going to be) and got it disassembled. 

Long story short, it doesn't look like this.  Evidently a 64 M20C has a different assembly.

Still, it is a fairly straightforward job.  And thanks again to PeytonM and Cnoe for posting pictures.

[Vlakvark]

I have the same issues with a sticky trim tab. Might go and get mine clean. Thanks for the great info. 

[Yetti]

This reminds me.   Mine trim used to have a sticky spot in it.   After two annuals of cleaning/lubing the chain and all the little u joints up and down the shaft.   I don't recall feeling the hitch in the giddy up recently.  

[cnoe]

This reminds me.   Mine trim used to have a sticky spot in it.   After two annuals of cleaning/lubing the chain and all the little u joints up and down the shaft.   I don't recall feeling the hitch in the giddy up recently.  

For those of you north of the Mason-Dixon line and/or east of the Mississippi, that means it's no longer sticky.


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[carusoam]

Great translation, CNOE...  

thanks and best regards,

-a-

[Jerry Pressley]

I have a complete trim setup from a 1991 MSE with the large trim wheel if needed.  also an extra large wheel assy from a 231.  offers?

jerry  423 231 3491

[Emmet]

On 9.2.2017 at 2:57 AM, Sabremech said:

All done and ready to fly. Rigging was quite easy as we took some measurements before disassembly and then used those to start with on reassembly. 

David

Can you tell how many hours it take for removal, cleaning and reinstallation?

[jetdriven]

20 hours and it’s actually worse than it was before. 3 days of fooling with it. Taking that thing  apart is very hazardous beicae jr will always be binding after that and in fact still way too tight so finally bought a different one to swap out. Yes I  took it all apart and it wasn’t the cable, it wasn’t the floor gearbox, it wasnt the universal joints, it wasn’t the pillow bearing at the electric trim actuator, it wasn’t the trim motor,  it’s the trim jackscrew itself. It has  2 KP16A deep groove radial ball bearings in it but only one bears the load from the tail on the ground. I replaced both bearings and for some reason  Unless it’s shimmed exactly right it’s a nightmare

Edited February 1, 2018 by jetdriven

[N201MKTurbo]

On ‎1‎/‎23‎/‎2017 at 6:51 PM, Sabremech said:

So tonight we removed the trim jackscrew from Peyton's airplane. It will get sent out for repair and then we'll reinstall it. It's a good challenge to remove.

David

What was the challenge when you removed it? The hardest part is taking off the panels.

[N201MKTurbo]

When you put it back together, pack as much grease as you can in the hollow shaft. Just make sure you don't make a hydraulic lock. That grease will stay clean and keep it lubed for a long time.

[Sabremech]

3 hours ago, Emmet said:

Can you tell how many hours it take for removal, cleaning and reinstallation?

Maybe a couple of hours to remove it which included confirming that the trim jacks crew was the problem. Peyton sent it out for cleaning, inspecting and lubing. Another couple of hours to reinstall and check rigging.

Not too bad of a job. I’ll be doing mine in March during my annual. I’ll take mine apart and go through it. 

Thanks,

David

[Sabremech]

1 hour ago, N201MKTurbo said:

What was the challenge when you removed it? The hardest part is taking off the panels.

Hardest part was getting to the hardware under the boots. 

David

[N201MKTurbo]

1 minute ago, Sabremech said:

Hardest part was getting to the hardware under the boots. 

David

Yea, that can be a pain.

[Andy95W]

Did mine last year, twice.  A couple of hours to remove, a couple of hours to disassemble, clean, grease, and reassemble. A couple of hours to reinstall. 

Read the lubrication chart wrong.  Put in the wrong grease.  Couldn't understand why the trim wheel was still "jumpy".

Took less time the second time and now it's very smooth.

[Piloto]

I had a similar problem. Lubricated the jackscrews with WD-40 and problem solved. I lubricate them on every annual. WD-40 works very well on removing rusted screws.

[Brandontwalker]

My jack screw was very tight and the electric trim would regularly bind up. I disassembled everything around a year ago as outlined above, soaked the parts in jet a and cleaned everything well. Then all was reassembled with fresh grease. It is smooth as butter now.


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[jetdriven]

2 hours ago, Piloto said:

I had a similar problem. Lubricated the jackscrews with WD-40 and problem solved. I lubricate them on every annual. WD-40 works very well on removing rusted screws.

The worst advice ever. The WD-40 is not a lubricant and it washes away the grease that is there. So then it can seize at an inopportune time. Maybe even crash and kill someone.

Follow the service manual folks, not advice from an electrical engineer who pisses on his plane. 

[mike_elliott]

10 hours ago, Piloto said:

I had a similar problem. Lubricated the jackscrews with WD-40 and problem solved. I lubricate them on every annual. WD-40 works very well on removing rusted screws.

And it prevents icing on the Jack screw

 

[Piloto]

12 hours ago, jetdriven said:

The worst advice ever. The WD-40 is not a lubricant and it washes away the grease that is there. So then it can seize at an inopportune time. Maybe even crash and kill someone.

Follow the service manual folks, not advice from an electrical engineer who pisses on his plane. 

Boat owners buy WD-40 by the boxes. During my college days I used to work part time on cargo ships and WD-40 was used extensively. I guess boat operators know a little bit more about rusty environments than pilots.

José 

[Sabremech]

23 minutes ago, Piloto said:

Boat owners buy WD-40 by the boxes. During my college days I used to work part time on cargo ships and WD-40 was used extensively. I guess boat operators know a little bit more about rusty environments than pilots.

José 

Rust isn’t the problem in the trim jack screw. Old knarly grease is the problem with binding. 

 

[N201MKTurbo]

19 minutes ago, Sabremech said:

Rust isn’t the problem in the trim jack screw. Old knarly grease is the problem with binding. 

 

It is old grease mixed with dirt, WD-40, Tri-Flo, Fluid Film, Mouse Milk and whatever else someone decides is the proper lube for the jack screw. 

A lot of the sprays have solvent properties that will wash the oil out of the grease leaving the thickener behind. The only proper way to periodically service it is to loosen one end of the boot and smear some new grease on the screw with your finger.