too much "free movements" of rudder Pedals by taxing

[brndiar]

Hi folks,

Just got my bird from annual. Among other things, the Donuts were replaced.

By first 2 landing after annual  I noticed  "S" curves during landing roll (crosswind situation). I assumed error in my Landing technique. Thereafter by taxing I noticed  cca 1-2cm of free movement of rudder Pedals for the first time. In my past 200+ hours I did not noticed that problem.  On ground there is cca 0,5 cm free movement of rudder too. How huch is tolerance? Any ideas? 

Thanks in advance.

Milos

 

[Hank]

Milo's, my feet aren't calibrated within 5mm! There will be some slack in the system between the pedals and the tail, and some likely lesser amount between the pedals and nose wheel.

The Service Manual gives a limit for free movement of the rudder (~1/2"), but I don't recall anything specific for the rudder pedals.

All I remember from my new donuts in Dec '13 was how much smoother both taxiing and landing were. Sorry . . . . .

[Shadrach]

There is some slack in the system as Hank says.  It is possible that the new donuts have changed the geometry of nose gear in a way that causes more immediate "turn in" making it feel more squirrely to you.  

Edited July 27, 2021 by Shadrach

[mike20papa]

The bearings in the rudder pedals can wear.  If you take hold of the top of the pedal and can rotate it a slight amount with out the control rod moving - the bearings are worn.  Mine were worn on the pilot side.  I think it was a matter of replacing the inner bearing races.  

[carusoam]

+1 for reading about the effects of worn nose gear parts…

DMax has a write up about it called the eight second ride… a reference to riding a bull…

Lasar sells the OH parts…

Best regards,

-a-

[brndiar]

2 hours ago, carusoam said:

+1 for reading about the effects of worn nose gear parts…

DMax has a write up about it called the eight second ride… a reference to riding a bull…

Lasar sells the OH parts…

Best regards,

-a-

link?

thanks in advance

lg,

m

[PT20J]

Agree with Ross, sounds like the geometry (caster) got changed which will cause the airplane not to track straight. There is a procedure in my M20J service manual for setting this. I presume the same applies to the M20C since it’s essentially the same gear. 

Skip

[mike20papa]

If you have noticed that new amount of slop in the rudder pedals after the extensive disassembly of the nose gear required to install new shock disks, I would get your mechanic to put the airplane up on jacks and you require him to find out what happened during the gear over haul

The "8 second ride" is in reference to a SB mooney put out requiring a shim be inserted in the nose wheel shock tower assembly.  Read the service bulletin as it pertains to only a select number of aircraft and gives a method for measuring the system.  Also, there is a linkage in the nose wheel that wears.  LASAR sells this link (it is painted white).  All of this nose wheel assembly linkage needs to be free of any slop.  (Don't know what German is for "slop" but I'm sure you have a term that is "a little kaput".   When you get the AC up on jacks and chase down the slop, you'll have a clue, otherwise your just chasing your tail.  

Edited July 28, 2021 by mike20papa

[Mooneymite]

7 hours ago, PT20J said:

Agree with Ross, sounds like the geometry (caster) got changed which will cause the airplane not to track straight. There is a procedure in my M20J service manual for setting this. I presume the same applies to the M20C since it’s essentially the same gear. 

Skip

Yep.  Same, same.

[mike20papa]

If I read your post correctly you are describing a new, post maintenance issue with excessive nose wheel steering linkage play.  All of those linkage pieces have a very short moment arm and are subject to high stress and any loose fitting components wear are amplified thru the longer travel of the rudder pedals.   The castor angle is not going to effect the play in the steering linkage and neither will simply installing new donuts (if done correctly).  Put the airplane up on jacks and grab the nose wheel and shake it right to left.  You'll see it, hear it.  

[brndiar]

Thanks for tips.

Below video. There is cca 0,8 inch free movement of the rudder, free movement of rudder Pedals cca 0,5 inch, but NO free movement in the nose wheel linkages.

 

 

lg,

M

[Guest]

Place a piece of wood across the co pilots pedals and secure with two C clamps.  Then go to the wheel well, gently wiggle the nose wheel until you identify where the excess movement is coming from.  Typically loose bolts, worn rod end bearings and wear in the steering tee.

The 8 second ride is caused by improper castor angle of the nose gear, sometimes introduced with nose shock disc replacement.  Here is the SB.

https://mooney.com/wp-content/uploads/2020/12/SBM20-202.pdf

Clarence

[mike20papa]

Remove the two exhaust well covers either side of the nose wheel well.  That will expose the rudder pedal bearings and interconnecting mechanism.  IF the pedal bearings are worn an excessive amount of "push/pull" is required to take up the wear before a rotational movement is initiated.  Looks to me that is what you have .. an excessive amount of "push/pull" before any pure rotational displacement is made at the base of the rudder pedals.   At the 45 sec. you will notice a tube (mostly hidden) that runs horizontal that connects the pedals.  I believe I see that tube moving forward and backward as well as rotating.  I believe it should only be rotating.   Also, can you move the top of the pedals right/left or slightly rotate them right/left?  

 

[Guest]

There appears to be two loose bolts/ or rod ends in the video.

 

[SSimpson77]

I believe I can see the slop in the steering horn from just that video. Looks like time for a horn rebuild. I’m getting close to doing mine too so if you find a 2 for 1 deal I’ll go in with you! haha

[PT20J]

Most Mooneys have some slop in these parts. And it might be worth fixing because it will make taxiing straight at slow speeds easier. But, the airplane should track straight at landing speed if the geometry is right just as you can ride a bicycle downhill without holding onto the handlebars. Wear builds up slowly over time. But this apparently came on after the donuts were replaced. All this points to a need to check the caster which is easy and inexpensive. 

Skip

[mike20papa]

Most Mooneys have slop in these parts .. REALLY?!  Slop belongs in the hog trough .. Not my Mooney.

[PT20J]

12 hours ago, mike20papa said:

Most Mooneys have slop in these parts .. REALLY?!  Slop belongs in the hog trough .. Not my Mooney.

The technical term is “lost motion”. All the bearings and rod ends have tolerances and they are additive in a mechanical system, so even a brand new airplane will have some lost  motion. 

Skip

[brndiar]

I let the shop to check again bearings and rod ends.

Thanks for SB20-20. I do not unterstand Instruction Nr. 4:  "IF AXLE POSITION, FORWARD OF PLUM LINE, EXCEEDS   .06.   ????       (0,6 INCH?)

First picture below - taken from left (Left Edge of the picture is front).

Mmike20papa20, M20Doc, Simpson77, all you where right, there are  two loose bolts in the steering horn, simply worn nose gear parts. Time for a horn rebuild.....

My Bottom line: with Donuts replacement (my were 40+ years old) it is very practical to have nose gear parts exactly checked, because:

1, save second visit of the shop.

2, you avoid "rodeo ride" instead of expected smooth landing   (I exaggerated here a little :-))))) ).

LG aus Austria,

Milos

Edited August 3, 2021 by brndiar

[PT20J]

Per the M20J service manual it is 0.06 so, that agrees with the information in the SB. 

[carusoam]

.06

Expect that is 0.060”  (?)

Based on all things are in American units…

Interesting precision based on a piece of string hanging a bob…

Loss of clarity often happens when the engineers pass details to the typists…. 

PP thoughts only, not a mechanic…

Best regards,

-a-

[Guest]

From the C model manual.