Landing Roll-Out Stability

[John Mininger]

In talking to other Mooney pilots, it never ceases to amaze me how many have, or have had trouble with tracking stability on landing roll out or take off. And the problem simply turns out to be that the collar on the top of the shaft that holds the donuts together on the nose gear was installed upside down. I was one of them.

I bought my Mooney from a shop in Florida that was not a Mooney Service Center. So, when I brought it home to Pennsylvania, I took it to Air-Mods over at Trenton-Robbinsville NJ and had some Mooney specific things checked out. Low and behold, the collar holding the nose gear donuts together was installed upside down.

The airplane didn’t feel all that stable on the ground at higher speeds, but being new to Mooneys, I just thought that that was how it was. But when that collar was installed correctly it made a noticeable improvement in the stability on roll out when landing.

So, I guess the moral of this story is. As the older, experienced Mooney A&Ps retire. With all the tribal knowledge that they’ve attained through the years. Make sure you remind the shop to install that collar right side up when you have your shock discs replaced.

John

[David Lloyd]

Talking with a mechanic a couple weeks ago, he was replacing the nose gear truss on a early J.  He said this one did not track very good, just like a couple old Mooneys he had owned.  I asked if he was familiar with SB102.  Nope, I explained about the 8 second ride and the need to measure the caster as shown in the service manual and SB.  Printed him a copy.  Did not even think of the collar being installed upside down.

[carusoam]

I bet the collar orientation alters the caster a small amount…. 

Nice pirep for Air-Mods AirMods…

Best regards,

-a-

[John Mininger]

11 hours ago, David Lloyd said:

Talking with a mechanic a couple weeks ago, he was replacing the nose gear truss on a early J.  He said this one did not track very good, just like a couple old Mooneys he had owned.  I asked if he was familiar with SB102.  Nope, I explained about the 8 second ride and the need to measure the caster as shown in the service manual and SB.  Printed him a copy.  Did not even think of the collar being installed upside down.

My understanding is that SB 202 included all the early models, up through and including some very early Js. In mid-1977 Mooney started using a one-piece collar with the hole drilled off center, making the bottom portion of the collar thicker than the top part and eliminating the need for the .120” spacer. The problem was, for an inexperienced A&P the collar could just as easily be installed upside down than right side up. If it’s installed upside down, it doesn’t compress the donuts sufficiently to rake back the nose gear.

I once read an article somewhere by an experienced Mooney A&P (and I wish I could find it again) that when replacing the nose gear discs, half the collars that he removed had been installed upside down.

I’m not an A&P. I’m an owner who’s trying to gain the necessary tribal knowledge as I go. So, if anyone disagrees with me about any of this, please let me know.

John

[MikeOH]

Is this upside down collar something that can be determined visually, without any disassembly?

[laytonl]

Don’t mean to hijack this thread, but I need to order donuts for my ‘92J.  Anybody got a good source?  Lee

[John Mininger]

16 hours ago, MikeOH said:

Is this upside down collar something that can be determined visually, without any disassembly?

I don't know. When I asked that question to some experienced Mooney A&Ps, they said probably not. But when I look at mine, it sure looks like the thick side of the collar is down against the plate.

If you're having stability issues, and it looks like the heavy side of the collar is at the top, you should probably get it checked out by someone who knows what they're looking at.

[Will.iam]

Do you have a picture of said thicker part on the bottom side?

[John Mininger]

37 minutes ago, Will.iam said:

Do you have a picture of said thicker part on the bottom side?

I'll take one and post it next time I'm down at the hangar. Probably tomorrow, Sunday.

[John Mininger]

2 hours ago, Will.iam said:

Do you have a picture of said thicker part on the bottom side?

Here's a couple that I had. I am going to try and get some better ones, with a better camera.

[Dickard]

On 8/30/2022 at 5:43 PM, John Mininger said:

In talking to other Mooney pilots, it never ceases to amaze me how many have, or have had trouble with tracking stability on landing roll out or take off. And the problem simply turns out to be that the collar on the top of the shaft that holds the donuts together on the nose gear was installed upside down. I was one of them.

My M20M has been squirrelly on a few occasions.  The worst being the other day during a tailwind landing where I ended up in the grass.

[N201MKTurbo]

One thing I’ve learned in the last 40 years of Mooney maintenance. If there is an easy way and a hard way to assemble something on the Mooney, the hard way is the correct way.

[T. Peterson]

5 hours ago, John Mininger said:

Here's a couple that I had. I am going to try and get some better ones, with a better camera.

Am I understanding that this picture is of the plate incorrectly installed? The thicker plate is on top, but should be underneath?

[N201MKTurbo]

6 minutes ago, T. Peterson said:

Am I understanding that this picture is of the plate incorrectly installed? The thicker plate is on top, but should be underneath?

No, its the collar with the bolt through it. If you look closely, there is about 1/16 of an inch more distance from the bolt hole to the bottom than to the top. It is easier to install it with the short distance down, but the correct way is with the short distance up. When installed correctly the collar and shaft align on the top. If installed incorrectly the collar will sit proud of the shaft.

BTW,

Its designed that way because you can't get a socket on it if it is any closer to the bottom and they are trying to keep the shaft as short as possible so the shaft doesn't hit anything when you hit a big bump. To put it on upside down, you have to compress the pucks some to get a wrench on it, you would think that would be a clue...

[Will.iam]

26 minutes ago, N201MKTurbo said:

No, its the collar with the bolt through it. If you look closely, there is about 1/16 of an inch more distance from the bolt hole to the bottom than to the top. It is easier to install it with the short distance down, but the correct way is with the short distance up. When installed correctly the collar and shaft align on the top. If installed incorrectly the collar will sit proud of the shaft.

BTW,

Its designed that way because you can't get a socket on it if it is any closer to the bottom and they are trying to keep the shaft as short as possible so the shaft doesn't hit anything when you hit a big bump. To put it on upside down, you have to compress the pucks some to get a wrench on it, you would think that would be a clue...

Ok now I’m thoroughly confused are we talking about the red, green or blue arrowed part? Or the thickness of the yellow brackets on top of the bolt compared to the thickness of the yellow brackets on the bottom with the thicker being on the bottom for correct installation?

 

[N201MKTurbo]

5 minutes ago, Will.iam said:

Ok now I’m thoroughly confused are we talking about the red, green or blue arrowed part? Or the thickness of the yellow brackets on top of the bolt compared to the thickness of the yellow brackets on the bottom with the thicker being on the bottom for correct installation?

 

The yellow brackets. 

[Will.iam]

Thanks. And just to be clear thicker on bottom is correct as pictured?

[T. Peterson]

4 minutes ago, N201MKTurbo said:

The yellow brackets. 

Wow! And that is enough to cause nose gear drift on the runway! I am impressed you fellas even noticed. I could stare at that collar for a millennium and not see it. A lot of savvy guys on this forum!

[EricJ]

Interesting.   I looked in the SMM for the J model to see if it said which way to install it, so if you just followed the manual you'd get it right.   It references the usual SB M20-202 for the "eight second ride" to make sure that there's enough caster to keep the nosewheel stable.   That SB recommends adding a spacer under the collar if there is insufficient caster per the SB.

The interesting part, is that the M20J SMM also has a note that says, in 32-50-02, 

"5. Add SB M20-202-3 spacer under collar to reposition axle if required.

NOTE:  Some collars have holes drilled off center and may be turned over to change axle position."

So some may have been intentionally installed "upside down" if the geometry allowed it, but it does seem that if one follows the SM, at least for the M20J, that one would know to check the geometry per SB M20-202 and install the collar appropriately to keep the caster in spec.   It is reasonable to assume that if the handling is not acceptable, that flipping the collar with the thicker side down is appropriate and if that doesn't provide sufficient caster, then add the spacer.

[Will.iam]

14 minutes ago, T. Peterson said:

Wow! And that is enough to cause nose gear drift on the runway! I am impressed you fellas even noticed. I could stare at that collar for a millennium and not see it. A lot of savvy guys on this forum!

Well i did zoom in on the picture with my ipad to see it better. Thank goodness for higher resolution cameras on phones these days or that would have turned into a burry mess. 

[John Mininger]

I took another pic yesterday that (I believe) clearly shows the thicker part of the collar at the bottom.

And I like N201MKTurbo's comment that you can't get a socket on the bolt without compressing the donuts if the collar is installed upside down.

 

[Jpravi8tor]

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

a quick link to the S/B for ease of reading

[John Mininger]

I wish Mooney would issue a service bulletin emphasizing that A&Ps install the collar right-side-up on aircraft manufactured after 7/6/1977. Or at least a service letter.

[John Mininger]

On 9/3/2022 at 8:58 PM, Will.iam said:

Thanks. And just to be clear thicker on bottom is correct as pictured?

Yes.

[PT20J]

2 hours ago, John Mininger said:

I wish Mooney would issue a service bulletin emphasizing that A&Ps install the collar right-side-up on aircraft manufactured after 7/6/1977. Or at least a service letter.

It’s not at all clear from the M20J SMM as Eric posted above that the collar should always be installed this way. The SB says to measure and add a shim if necessary. The SMM says that later models can turn the collar around in lieu of a shim. The implication is that the need for shimming varies due to manufacturing tolerances. So, the starting point is to make the measurement described in the SB and SMM and then add a shim or flip the collar.

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