Brisk movement of aileron control from R to L causes control wheel to bind

[Bill_Pyles]

I live in the Phoenix area of Arizona and I just got the keys and logbooks back for my 1980 M20J following the annual inspection.  The plane has not been flown since the annual was completed. by a shop here in AZ.

I went to the field today just to make sure the engine would start (not to fly it) since the battery is 2+ years old and the plane has not been started for at least a couple of months.  Engine started normally.

I performed a controls check as if I planned to fly the plane and found that at any elevator position, if I turned the control wheel fully to the right against the stop and then briskly turned the control wheel to the left, the control wheel would almost immediately stop after just a few degrees of rotation as if a control rod was binding up.  If I neutralized the control wheel and then turned the wheel to full right and then slowly turned the wheel to the left, the control would not bind.  I have been the sole owner of this plane for over 12 years and has never exhibited the aberration described.  Performing the test by starting with full left aileron did not produce the binding, but the problem is 100% repeatable going from full right, rapidly to full left.

I got three mechanics from the maintenance shop to look at the plane and they were also able to reproduce the problem, but none of them knew what the issue is, so the plane will have to be re-inspected by removing under wing access panels and the belly panel.

The plane was in the shop for many months and there was nothing big that was wrong with the plane, and no long lead time items that were replaced (just a seat belt and an LED strobe).  

Has anyone experienced such an issue with the controls?

[Bill_Pyles]

The plane was in the shop for the annual inspection for five months and I do not know specifically what was "touched/removed/adjusted" during the inspection or while the plane was sitting in the shop.  I don't know what inspections or adjustments or lubrication the Mooney maintenance manual stipulates during a routine annual inspection.  

[Shadrach]

Something was done. Unlikely that this is a lubrication issue.  

[takair]

There have been two recent threads (within the past two weeks) that are very similar, including color photos and service bulletin and AD references.  

[201er]

Check controls with master on and off. Check the autopilot.

[Bill_Pyles]

I can demonstrate the binding with the engine on or off, but I have not introduced the A/P into the test.  

[Pinecone]

I think the thought was the autopilot may not actually be turning off.

By binding, so you mean a resistance to turning, or a full stop bind?

[Bill_Pyles]

5 minutes ago, Pinecone said:

I think the thought was the autopilot may not actually be turning off.

By binding, so you mean a resistance to turning, or a full stop bind?

Yes, by binding I refer to a full stop bind.  I did not try to force the the wheel to turn past the position where the wheel refused to turn.  It's interesting that the full stop bind is dependent on the speed at which the wheel is turned AND the turn must be initiated from the full turn of the wheel to the right.  If you just casually turn the wheel right and left without going all the way to the right against the stop, it doesn't bind.

I did find the service bulletins that were mentioned by takair---thanks.  

[Pinecone]

Hmm, sounds like a no back spring in operation.  I would take a look at the yoke eyeball bearings.

[N201MKTurbo]

The gussets on the aileron links could be catching on the landing gear bellcrank.

[Ragsf15e]

12 minutes ago, N201MKTurbo said:

The gussets on the aileron links could be catching on the landing gear bellcrank.

Yeah, there’s a couple places in the system where the clearance is minimal.  TheSB covers 1, I think the one @N201MKTurbo mentioned is different but equally tight.

[PT20J]

There is also a bolt down there that can be put in backwards.

[Fritz1]

find out what the shop did remotely close to the aileron linkage, have them take belly pan and aileron linkage access panels on bottom of wing off, have one guy operate the yoke in the cockpit and the other watch from below, check if the aileron linkage catches any of the wiring in the footwells, let everybody know how this plays out!

[Pinecone]

The thing that is strange is that it speed variable.  He reports that it happens only when moving the controls quickly

[Shadrach]

3 hours ago, Pinecone said:

The thing that is strange is that it speed variable.  He reports that it happens only when moving the controls quickly

The pushrods, links, bell cranks and rod ends all contribute to play/flex in the system under load (it's why we have rub blocks).  It's conceivable that if a minimum clearance situation has been created somewhere in the linkage, an abrupt movement might flex the linkage enough to cause interference.

[Shadrach]

41 minutes ago, Fritz1 said:

find out what the shop did remotely close to the aileron linkage, have them take belly pan and aileron linkage access panels on bottom of wing off, have one guy operate the yoke in the cockpit and the other watch from below, check if the aileron linkage catches any of the wiring in the footwells, let everybody know how this plays out!

This^^^.  Time to pull the belly panel to view and feel the center bell crank actuating the aileron links. If nothing stands out visually, the bell crank can be disconnected from both aileron linkages by removing a single bolt.  That should enable you to isolate whether the biding is in the cockpit linkage or in one of the wings.

[wombat]

Maybe have a look behind the panel and see if there is a wire that is catching on it?   If moved slowly, the wire might move out of the way as one part of it is lifted, but when moving quickly, the wire might tend to flex more and get caught.

[0TreeLemur]

4 hours ago, Bill_Pyles said:

Yes, by binding I refer to a full stop bind.  I did not try to force the the wheel to turn past the position where the wheel refused to turn. 

Sorry if I missed this, but once it binds, how do you get it un-stuck?   If it was a wire or bolt catching, it seems that it would be impossible to "un bind" it. 

[Bill_Pyles]

1 hour ago, wombat said:

Maybe have a look behind the panel and see if there is a wire that is catching on it?   If moved slowly, the wire might move out of the way as one part of it is lifted, but when moving quickly, the wire might tend to flex more and get caught.

One of the mechanics did observe under the panel and did not detect any resistance or interference that would have caused the problem.  Thanks, though.

 

1 hour ago, 0TreeLemur said:

Sorry if I missed this, but once it binds, how do you get it un-stuck?   If it was a wire or bolt catching, it seems that it would be impossible to "un bind" it. 

To "un-bind" the control wheel, I turn it slowly back to the right, change elevator position and turn it slowly to the left and it operates smoothly.  There is something about moving the wheel quickly to the left that causes the singularity.

[Bill_Pyles]

3 hours ago, Shadrach said:

The pushrods, links, bell cranks and rod ends all contribute to system play/flex in the system under load (it's why we have rub blocks).  It's conceivable that if a minimum clearance situation has been created somewhere in the linkage, an abrupt movement might flex the linkage enough to cause interference.

Exactly.  My guess  is that the "binding" of the control acts like a direct kinematic singularity occurs after a particular order and velocity of control inputs.  

[Fly Boomer]

15 minutes ago, Bill_Pyles said:

To "un-bind" the control wheel, I turn it slowly back to the right, change elevator position and turn it slowly to the left and it operates smoothly. 

Unless I missed it above, this seems to be a new variable -- can you elaborate?

[0TreeLemur]

14 minutes ago, Bill_Pyles said:

Exactly.  My guess  is that the "binding" of the control acts like a direct kinematic singularity occurs after a particular order and velocity of control inputs.  

Super weird.  The stops should prevent motion excursions, making it velocity independent.  

Thixotropic lubricant behavior?   Maybe you've got a thick wad of old grease somewhere that is dynamically sensitive.  Of course, that's a wild-a$$ stoopid guess.  The fact that you can "un-stick" it by the right combination of slow movements indicates that it's a mechanical hang-up of some sort.   A scary one at that.  

Can you post a video to youtube?   I'm really curious to see the input motion that revealed this to you, mostly so I can subject my test airframe to the same motion to make sure that it doesn't suffer from such weird behavior too.    Good find, and good luck getting it diagnosed and fixed. 

Edited February 8, 2024 by 0TreeLemur
fix.

[Shadrach]

37 minutes ago, 0TreeLemur said:

Super weird.  The stops should prevent motion excursions, making it velocity independent.  

Thixotropic lubricant behavior?   Maybe you've got a thick wad of old grease somewhere that is dynamically sensitive.  Of course, that's a wild-a$$ stoopid guess.  The fact that you can "un-stick" it by the right combination of slow movements indicates that it's a mechanical hang-up of some sort.   A scary one at that.  

Can you post a video to youtube?   I'm really curious to see the input motion that revealed this to you, mostly so I can subject my test airframe to the same motion to make sure that it doesn't suffer from such weird behavior too.    Good find, and good luck getting it diagnosed and fixed. 

The stops set travel limits, they have nothing to do with play/flex within the system’s travel. I’m am glad he discovered this on the ground. It’s conceivable that air loads on the ailerons could cause the same issue without the need for the abrupt movement.

[Bill_Pyles]

The problem appears to be the bar that controls the left aileron servo.  The rod ends have some play and the rod might need to be lengthened a bit by adjusting the rod ends.  At least it was not some FOD left in the wing.

Thanks, everyone for offering ideas.  This is a great group!