Squirrely nose-wheel steering after annual

[THill182]

I wonder if someone here can give me advice on how to diagnose this (2000 M20R Ovation):

 

After my last annual (when an elevator skin was replaced due to hangar damage), it seems that the nose wheel is now “dynamically unstable” with respect to steering.

 

It used to be that as the plane accelerated on take-off or just touched down, the nose-wheel would automatically straighten out (was dynamically stable), and it was easy to correct direction through small rudder inputs. Now a small input is amplified at speed, so that when I give it a small input to the right for example, as I go faster the airplane wants to veer farther to the right. It is very difficult not to get into oscillations (left-right) on take-off and landing, as the airplane feels “squirrely” until it slows down.

 

Does anyone have ideas how to adjust this? Looking at the nose-wheel there is nothing obvious. I would like to give the right direction to my mechanic here on the field who is not very experienced with Mooneys (or else take it somewhere else if required).

 

Thanks for any input!

[MB65E]

It's a bit strange it's noticeable now post maintenance. I'd check with your IA to see if they "rigged" anything, then ask them to "re-rig" it again. Also, wouldn't be the first one to be tweeked by ground Equiptment. Those little rod ends up there are no match for a 3000lb tug.

cheers,

-Matt

[jetdriven]

Check your nose gear faster per Mooney SI m20-202.  Also don maxwells article, "eight second ride"

[Hank]

Memory says that it matters which way the shims are installed. If your nose wheel was removed, maybe it was put together backwards. Don's article explains it all.

[helitim]

After O/H'ing my nose gear last year, I had the same problem.  Putting the new biscuits in changed the camber of the gear just enough to make it very sensitivity.  We followed the SB and checked the angle with a plumb bob after leveling the plane,as described.  Ended up having to reshim the gear.  Problem solved. 

[Guest]

First question would be what if anything was changed?  If nothing was changed why is this happening? Something damaged or broken and about to fail

Correct castor angle check and adjustment is in the maintenance manual.

Clarence

[Marauder]

Here is what was done with mine. This look right Clarence?

 

[jetdriven]

That doesnt change the caster of the nose wheel. But, disassembling and reassembling the nose gear, they likely left out the small and easily forgotten M20-202 spacer under the nose gear shock tube collar.  get a mirror and look at it.

[THill182]

Thanks for all the advice.

This started to happen after my annual at Don Maxwell, and best I can recall no work was done on the nose gear (and if it had, I am pretty sure it would be right). I have no other explanation really, but it is of course possible that someone moved the plane and damaged the nose gear.

Anyway, I will have my local mechanics here first check for damage; then I will try to find a local mechanic with the right tools and experience to rig it correctly.

By the way, I have no chimmy'ing, and I lost my nose gear hub cap after the instability happened (after the annual).

Thanks again!

 

[carusoam]

Hub caps are screwed on aren't they?

Is it possible that some Maint was started and hasn't been completed?

worn nose gear issues start to happen with many thousands of hours on the airframe.

That is starting to sound weird enough to not be using it yet.

have local maintenance Jack the nose up see if it is loose.

PP concerns.  I haven't heard of any LB loose nose gear stories...

Best regards,

-a-

[M20Kid]

I had a similar issue with my M20K after annual except in only pulls to the right.  Right crosswinds are particularly interesting, but Left crosswinds make the airplane roll right on down the centerline.  All this started after annual at Don's shop, too.  I would really like to know what changed and how to get it back to normal.

[jhbehrens]

I'be had this happen with my Eagle and it turned out the rigging was off. The nose wheel was about 1" too far forward. The fix was to reverse the collar which in my case was asymmetrical. Procedures for checking rigging are in the manual but essentially involve using a plumb-line on the bolt on the side of the trunnion. It should be close to centre-axle. SB M20-202 explains the procedure as well.

[M20Kid]

Thank you, jhbehrens!  I pulled down that service bulletin and it seems easy enough.  Hopefully it will be an easy fix!

[M20Kid]

On closer inspection of that SB it appears to only affect up to 1977 models up to and including Js.  Mine is 1981 M20K so I don't believe this procedure would be appropriate for my airplane.  If it fixed your Eagle, then perhaps it's off on my airplane, too.  I'm only referencing SB M20-202 for my current information.

[Guest]

4 hours ago, M20Kid said:

On closer inspection of that SB it appears to only affect up to 1977 models up to and including Js.  Mine is 1981 M20K so I don't believe this procedure would be appropriate for my airplane.  If it fixed your Eagle, then perhaps it's off on my airplane, too.  I'm only referencing SB M20-202 for my current information.

It spelled out in maintenance manuals for newer models.  

Clarence 

[M20Kid]

19 hours ago, M20Doc said:

It spelled out in maintenance manuals for newer models.

And sure enough it's right there in my maintenance manual!  Thank you for pointing that out.  I'm going to be working with a mechanic in the next week or so and I'll make sure this gets check right away.

[THill182]

Just wanted to close the loop on this: Turns out that the nose wheel was too "tight". The way I understand it, there is an adjustment that tightens the nose wheel pivoting mechanism. When we tried to move the nose wheel by hand it was almost impossible to do so. A small adjustment made it loose again, and the steering is back to normal.

I am not sure how that happened, but most likely, "something was adjusted" during the annual, and this one was too tight.

The lesson I take away: During a high-quality thorough annual, many things get checked and tweaked. As is really normal best-practice, be very conscious of how everything feels when picking up the plane after such annuals. There is simply a good chance that a few things need to be re-adjusted. Of course, we all know that, and every annual is always a bit scary....

[carusoam]

Great follow-up TH.

Thanks,

-a-

[Guest]

7 hours ago, THill182 said:

Just wanted to close the loop on this: Turns out that the nose wheel was too "tight". The way I understand it, there is an adjustment that tightens the nose wheel pivoting mechanism. When we tried to move the nose wheel by hand it was almost impossible to do so. A small adjustment made it loose again, and the steering is back to normal.

I am not sure how that happened, but most likely, "something was adjusted" during the annual, and this one was too tight.

The lesson I take away: During a high-quality thorough annual, many things get checked and tweaked. As is really normal best-practice, be very conscious of how everything feels when picking up the plane after such annuals. There is simply a good chance that a few things need to be re-adjusted. Of course, we all know that, and every annual is always a bit scary....

Mooney SI M20-109 lowered the torque on the bolt which holds the nose gear to the trunnion.

http://www.mooney.com/en/si/M20-109.pdf

Clarence

[Hector]

That doesnt change the caster of the nose wheel. But, disassembling and reassembling the nose gear, they likely left out the small and easily forgotten M20-202 spacer under the nose gear shock tube collar.  get a mirror and look at it.

This! I replaced my gear donuts this annual and left the spacer out intentionally thinking would not need it with the new donuts. Bad idea! Spacer back in.