KNR Logo v1                                         MOONEY NOSEWHEEL TRACKING

By Kerry McIntyre
June 2024

It’s been a long winter and spring. You have been getting antsy to use your two-decade old Mooney to do some vacation-type traveling this summer. In preparation for resolve this wanderlust, last fall, you took stock of the overall condition of the plane. Aside from some minor maintenance items, it all looked pretty good, EXCEPT for the condition of the landing gear.

The airplane hadn’t been flown much in the previous year. It mostly sat dormant, outside, under a sunshade, located in the dry southwest. Hardly flown, much less even moved. As a result, the tires had flat spots and the sidewalls were cracked. Overall, the wheels, brakes and landing gear hadn’t been inspected carefully (annuals notwithstanding) or refurbished in over ten years. Of particular focus, on Mooneys, the shock discs should be evaluated. When you reviewed the maintenance logs, the main gear discs were replaced over eight years ago and the nose gear discs had never been replaced! Clearly, this had to be addressed.

Your home field’s FBO A&P mechanic is out of his depth for this job, but a shop at a nearby airport can have the plane on jacks for the shock disc replacement, the wheel and brake maintenance as well as a new annual. They have had some Mooney experience. Taking the plane to a more experienced Mooney IA or dealer is geographically difficult. You make the arrangements and bring them the plane well before winter.

By mid-spring your Mooney has new tires, shock discs, brakes, wheel bearings and annual. You go to evaluate the work and pick up your plane. The shop goes over the work and annual with you. A couple of engine runs, some taxiing and detailed, cowl-off inspections take most of the day. The taxi tests reveal a bit of a softer ride and greatly improved steering and braking response. Afternoon weather necessitates making the home flight the next morning.

The early flight home is wonderful! Clear skies and a smoothly running airplane. Calm winds and an empty pattern make the landing at home very satisfying. You want do get some touch-and-gos, but you have a busy day ahead. Nevertheless, you are feeling pretty smug about spending the time and money on your bird. You did good! The next afternoon, you get back out to the airport to do some pattern work to get your proficiency up to speed. The local traffic is light, there is a moderate cross-wind with slight gusts. Perfect for landing practice.

The first circuit demonstrates how rusty you are. A late-executed go-around works out well, reminding you of the Mooney’s characteristic for needing aggressive trimming during the go-around. The next approach is perfect, but upon lowering the nose, the plane veers rapidly away from the wind. You end up in the dirt, but the shoulder is level and firm, no damage. The crosswind gusts weren’t that strong? As you taxi back on the pavement, you realize the steering is not stable. Shaking from adrenaline, you go to the tie-down. Cursory inspection of the wheels, brakes and nose gear does not reveal the problem.

Why did this happen?

This month’s ShopTalk will explain to the reader how to wreck a perfectly good airplane by doing a good deed. Maybe the title of this article should be, “No good deed goes unpunished.”

Lately we have seen a number of Mooneys with the nose wheel tracking out of limits. This can cause the airplane to be uncontrollable at touch down and dart off the runway at high speed. A lot of times when this happens it is easy to blame the pilot, but if the nose gear shock discs or nose gear leg assembly has been replaced and the tracking was not verified to be within limits while the plane was on jacks it may not be the pilot’s fault.

First a little history. In 1977, Mooney issued Service Bulletin M20-202. This SB covered all Mooney aircraft from M20C to early M20J, but the process applies to all Mooney aircraft that have had the nose gear shock discs or nose gear assembly replaced.

Here is why: The Mooney nose gear assembly consists of a shock link, the 3 shock discs and a collar with a bolt that secure the discs in place. These discs are under great compression when installed. This is basically the same assembly for all Mooneys. Some very early Mooneys used four disks in the nose gear, but the tracking measurement is still the same.

Yes, the part numbers are different as the planes got heavier but the measurement for the tracking is the same on all Mooney aircraft. What started all this and led to SBM20-202 being issued was, some mechanics were installing the collar upside down when replacing the shock discs and or nose gear leg assembly thus changing the tracking of the nose gear.

The early (pre-M20J and early M20J) collar bolt hole was drilled slightly off-center height wise. This was difficult for a non-Mooney mechanic to see and it looked like the collar could be installed either way. Because the collar bolt must be installed with the hole at its highest position in order to maintain the proper tracking limits, SB M20-202 was issued with a 1/8 inch shim in the kit.

This shim when placed under the collar made it possible to maintain correct tracking limits if the collar were installed upside down. In layman's terms it was now mechanic proof.

So what are we talking about when we say proper tracking limits? When the airplane is on jacks, in flight-level position, a plumb line is dropped from the center of the nose wheel axle and a mark is placed on the floor. Another plumb line is dropped from the center of the nose gear retraction pivot point and another mark is placed on the floor. The distance between these two marks can not be more than 0.6”. If this distance is more than that the airplane can be uncontrollable at touchdown at high speeds. This may result in a off-runway excursion and possible damage to the airplane.

Now Mooney makes three different collars, all with the bolt hole drilled off-center height wise. The taller collars are used on the M20M and newer airplanes. This makes proper identification of the different collars an important part of getting the tracking within limits. SB M20-202 only shows the early (shorter) collar and the 1/8 inch shim that is part of the SB kit, but the tracking limits are the same for all Mooney airplanes. So how can one tell the difference between the three collars?

First off, all the early aircraft (pre-M20J) use the part number 510027-007 collar. This collar is . 0.687” tall with the bolt hole drilled slightly off-center height wise. This collar and its 1/8 inch shim is the only collar referenced by SB M20-202.

The next collar is part number 510050-005 and is 0.750” tall with the bolt hole noticeably drilled off-center height wise. If one were to place the short collar on top of the 1/8 inch shim and measure from the bottom to the center of the bolt hole they would discover it is the same distance as the 510050-005 collar.Tracking   service man info

The third collar is part number 510050-007 and it is 0.838” tall with the bolt hole noticeably drilled off-center height wise. So how important is it to check the tracking limits when the plane is on jacks? It is important to Mooney – if one looks in the M20R or TN service manual, the procedure is highlighted in yellow in chapter 32 paragraph 32-50-02, just after the section on how to replace the nose gear shock discs. See insert, Figure 32-24 ----------------------------------→

So how does the height of the collar cause the track limits to change? As the shock disks are compressed during installation using a nose gear shock disc compression tool, such as KNR tool #KTME120, the nose wheel axle moves back towards the nose gear retraction pivot point. The more compressed the discs are, the closer the nose-axle center line is to this pivot point.

To give the reader a recent example of proper collar installation, recently a new owner brought his 1989 M20J into the shop for an annual. We had never seen this plane before and we noticed the nose gear shock discs hadn’t been changed since 2001. With the plane on jacks for the annual, we measured the track and found it was 0.750”, which is beyond the max limit. The new owner was a experienced Mooney pilot but stated some of his landings still need work. If this were a new Mooney pilot I would believe him, but in this case it wasn’t due to lack of experience.

I showed the owner and explained the tracking measurements. We replaced the old shock discs with new ones (just due to age) and installed the collar the correct way. When we remeasured, the distance was now 0.250”, a difference of a ½ inch. That makes a huge difference in how stable the plane is upon landing. The crazy part is that the previous owner lived with this instability for over 20 years.

Unfortunately for the current pilot, he cannot now blame the plane for any crummy landings!

KNR is a small shop. We see about 30 of the same planes year after year. These regulars do not worry about the track as we were the ones to replace the nose gear leg or nose gear shock discs. Every year we will take on 3-5 new customers, and checking the tracking has become a standard item we do while the plane is on jacks. So far, about half have not met the tracking limits. That is what would be expected if the collars are randomly installed; if no attention was paid to the collar orientation. That’s not very good odds considering all the Mooneys out there that have had new shock discs or a new nose-gear leg replaced. This has really opened our eyes to checking all new Mooney customer’s planes when the plane is on jacks.

As the Mooney fleet ages and the experienced mechanics all retire, it is up to those of us in the maintenance field to make sure our clients planes meet their type design and are safe for operations. It only takes 10 minutes to check the track limits when the plane is on jacks. Now the owner may not like what it costs to fix their aircraft if it is found to not be within limits, but this inspection is KNR policy on Mooney airplanes we have previously never seen. Just like checking the gear over-center down-lock tensions, this is just as important.

 Hopefully the owner will want the tracking to be set within limits, but the pilot determines airworthiness before each flight (14 CFR 91.7 “The pilot in command of a civil aircraft is responsible for determining whether that aircraft is in condition for safe flight.”). We mechanics are just advisors, except when the plane is in for an annual. An IA mechanic determines airworthiness and signs a statement to that effect (14 CFR 43.11). A Mooney that is outside the limits on the tracking has not met its type design and therefore not airworthy. Its just that simple.

Until the next ShopTalk, enjoy flying and landing your Mooney. If you have a question about this article or any other of the over 50 articles on our website,, feel free to e-mail me, or call our aircraft repair shop (307) 789-6866.