M20C Trim Jack Screw Issues

[Mx_edge]

Hi all... New to the group with a 62 M20C.  The tail trim jack screw has excessive movement and my AP has requested I find a replacement before the up coming annual. I have looked around the MS forums for a possible discussion without success.  Not sure where to get the proper part number without removing the existing unit. Any ideas where I should look?  Can this unit be overhauled?    

 

[carusoam]

Welcome aboard edge!

There are plenty of maintenance issues with the Jack screw…

But, I have never heard of anyone replacing the screw itself.

Most issues are related to how old the grease is, on or around it…

 

For part numbers…

Start with a pic… a nice clear pic of the worn/damaged part can be really helpful…

Look it up in a parts manual… there are parts manuals in the download section…and available through your MSC… electronically…

Or call Lasar…

 

Most likely… very few of those parts are around in new condition (NOS)

We have a few resources if you really need to replace that device…

 

PP thoughts only, not a mechanic…

Best regards,

-a-

[Vance Harral]

Obligatory pedantry: you really need to get your own copy of the official parts manual, and your A&P isn't technically allowed to work on the airplane without owning or having access to that manual.

Turning to something more helpful... the tail trim mechanism does indeed include a jack screw assembly, but it is a complex assembly of multiple parts, and it is not necessarily the screw itself that causes play.  Attached to this post are pages from my copy of Mooney MAN 205, the "M20 series parts catalog issues 1976 revised June 1977", detailing the trim mechanism.  Make sure you map your specific serial number to the applicability list on the last of these pages.

There is also an extensive thread here on Mooneyspace about the jack screw assembly, in which both binding and play in the trim mechanism are discussed:

Working on your jack screw assembly will require removing it from the airplane, which is discussed in the above thread.  Once it's out, some mechanics are brave enough to open up the assembly and perform their own overhaul using parts sourced from a Mooney MSC.  Others who are more chicken (like me) pack up the assembly and send it to an MSC for mechanics experienced with the mechanism to perform an overhaul.  We had our jackscrew assembly overhauled by LASAR in 2018, it's holding up well 3 years later.

 

[carusoam]

Nice work Vance!

Go MS!

Best regards,

-a-

[Hank]

Wow! That's'a lotta parts and pieces!!  

[PT20J]

I would suggest you remove the inspection panels and you and your mechanic verify exactly where the "excess movement" is coming from. It would be unusual for the jackscrew itself to have a lot of movement. There are thrust bearings inside the assembly that might need shimming, but that would also be unusual unless someone had it apart and didn't shim it correctly. Usually the problem with the trim system is lack of lubrication that causes the trim wheel to be stiff. The entire empennage is one unit attached to the tailcone with three hinge bolts which are a more common source of play. Is your mechanic familiar with Mooneys?

Skip

[DCarlton]

1 hour ago, PT20J said:

I would suggest you remove the inspection panels and you and your mechanic verify exactly where the "excess movement" is coming from. It would be unusual for the jackscrew itself to have a lot of movement. There are thrust bearings inside the assembly that might need shimming, but that would also be unusual unless someone had it apart and didn't shim it correctly. Usually the problem with the trim system is lack of lubrication that causes the trim wheel to be stiff. The entire empennage is one unit attached to the tailcone with three hinge bolts which are a more common source of play. Is your mechanic familiar with Mooneys?

Skip

Any idea what the spec is on allowed movement?  There used to be a recommended spec.  I wiggle mine (pull up on the tail cone) every time I pre-flight.  No change that I can feel over the last 15 years. 

Edited August 7, 2021 by DCarlton

[Vance Harral]

2 hours ago, DCarlton said:

Any idea what the spec is on allowed movement?

Allowable empennage slop is spec'd in Mooney Service Bulletin M20-62: https://mooney.com/wp-content/uploads/2020/12/SBM20-62.pdf  With respect to the fore/aft play involving the trim system, the spec is 5/16" movement as measured at the bottom of the rudder trailing edge.

When we purchased our airplane in 2004, the play in this area was a little under 1/4".  Over the course of 14 years, it came to exceed the 5/16" spec.  I admit we let is slide a few years when it was really a tad over spec.  After LASAR overhauled our jackscrew assembly in 2018, and we re-installed the overhauled unit with new AN hardware, it's back well under 1/4".  LASAR installed new bearings and a new shim set, but the jack screw itself and the threaded structure that receives it did not need to be replaced.

[cliffy]

Before you condemn the jack screw check the play in the link (76) and bushing (77) at the rear of the jack screw

Movement is visible visually if its loose or worn

Mine was worn quite a bit at one time before being replaced

If you pull the jack screw you can block the tail hinge open with a short length of 2X4  

[DCarlton]

8 hours ago, Vance Harral said:

Allowable empennage slop is spec'd in Mooney Service Bulletin M20-62: https://mooney.com/wp-content/uploads/2020/12/SBM20-62.pdf  With respect to the fore/aft play involving the trim system, the spec is 5/16" movement as measured at the bottom of the rudder trailing edge.

When we purchased our airplane in 2004, the play in this area was a little under 1/4".  Over the course of 14 years, it came to exceed the 5/16" spec.  I admit we let is slide a few years when it was really a tad over spec.  After LASAR overhauled our jackscrew assembly in 2018, and we re-installed the overhauled unit with new AN hardware, it's back well under 1/4".  LASAR installed new bearings and a new shim set, but the jack screw itself and the threaded structure that receives it did not need to be replaced.

Appreciate the link to M20-62.  The only *slight* movement I've ever felt was para. C when force Fc is applied.  My plane is opened up for annual now.  I'll take another look.  Thanks.  

[Mx_edge]

With the cover removed, the screw itself is observed rotating from up and down pivoting within the housing and the housing being secure.  This may be the shimming described above.  The link from the screw-end connecting the tail rotates up and down following the screw movement.  

With the gained knowledge from here we'll do a closer inspection and take a photo.  A video may be a better choice to show the issue if it can be down loaded.

Thanks for the documents guys!  The journey begins... 

Thanks again, John

[N201MKTurbo]

hay, there is a guy parting out a Mooney on another thread who is selling a trim jackscrew assy. for $100

[Mx_edge]

Video attached.

Have not measured  "C"  play but appears to be out of spec.

[Mx_edge]

Video link not working.  Sorry...  

Rich,  I Looked around for the Mooney jackscrew.  Can you give me some direction where?  This might be an potion for sure.

Thanks!

[carusoam]

Video is fine on my iPad…

Inviting @M20Doc to have a look… (wobbly jack screw, video)

Best regards,

-a-

[Guest]

From manual #104 for the 1962-1967 model years, free play at the rudder trailing edge is 0.080”.  A definite disagreement with the SB quoted above.

In any event the one in the video deserves disassembly and further investigation and repair.

Clarence

[David Lloyd]

12 hours ago, cliffy said:

Before you condemn the jack screw check the play in the link (76) and bushing (77) at the rear of the jack screw

Movement is visible visually if its loose or worn

Mine was worn quite a bit at one time before being replaced

If you pull the jack screw you can block the tail hinge open with a short length of 2X4  

I had excessive movement, replaced the link and bushing.  All now good.

[47U]

3 hours ago, M20Doc said:

From manual #104 for the 1962-1967 model years, free play at the rudder trailing edge is 0.080”.  A definite disagreement with the SB quoted above.

Doc… could that reference be applicable to the amount of rudder free play in its hinges?  80 thousandths is a pretty tight tolerance for the entire empennage.  

As always, we appreciate the knowledge and expertise you bring to MooneySpace.

[Guest]

Several different manuals refer to this play,  the J manual goes on to tell you to look at the trim link, bolts and bushing.

Clarence

[47U]

No wiggle room there, Doc!  Regardless of Mooney mx manual’s evolution over time, your references, as always, are rock solid.

[carusoam]

aaaahhhhhh….
 

Realizing this just now…

That is the play we All check on the pre-flight…(?)

Lift the rudder… the more worn it is the bigger the motion…

A tight system barely moves, with a clunk at the stop…

A loose system like my old M20C, moved measurably more with a clunk at the stop…

 

I was surprised by how tight the newer one was supposed to be…

PP thoughts and fuzzy memories…

Best regards,

-a-

[Guest]

With the limits being very small, it’s best to place a stand under the tail tie down ring so the airframe doesn’t wiggle up and down.  The side of the tail navigation light has a small rivet in the side which make a convenient index point to measure from.  3/32” is close enough to .080” that is the limit for most models.  I also set the trim to neutral, in most cases replacing the bolts or trim link brings things back in limits.

Clarence

[N201MKTurbo]

14 hours ago, Mx_edge said:

Video link not working.  Sorry...  

Rich,  I Looked around for the Mooney jackscrew.  Can you give me some direction where?  This might be an potion for sure.

Thanks!

 

[Mx_edge]

Thank you all...!    I can see we have a wealth of knowledge here on MS.

Going to dive into the Jackscrew project soon and will report back.

John

 

[carusoam]

15 hours ago, Mx_edge said:

I can see we have a wealth of knowledge here on MS.

 

Looking at the responses in this thread….

You are a very perceptive individual John!  

I like the way you think!

 

Go MS!

Best regards,

-a-