Johnson Bar failure

[KeithN92KD]

Summary: 65 M20E, johnson bar fatigue cracked to failure at base of bar to trunnion. Inspect the weld toe.

Storyline: my polished M20E is a high time airframe 10,000+ hrs. I've flown it for the last decade from 2FD6 in Florida all across the country (just really having a Hoot) St. Thomas, Anchorage, Massachusetts, started in California. Not a hangar queen.

So started an assisted annual and found burnt valve in #4. Had time to do some more extensive maintenance then and chose to remove the main gear for paint. Used the stuff the main assistant spring with washers method of unloading the mains and removed them. As I got out of the jacked up airplane I noticed the nose gear slowly retracting back up. Hmm... thought I had the J-bar locked up. Yep, locked up. While I was thinking why would the nose gear be divorced from the gear handle with the mains removed, I unlocked and the handle came out in my hand.

My buddy said it's not supposed to do that, need to put that back. Then we decided this is the best time for this to happen, no belly landing involved.

Examination revealed it was a multiple step fatigue Crack failure in the aft weld toe, bar to T. I have a practice of WD40 everywhere on annual and it was evident in the extending crack. Therefore we missed it growing!

Defense posture; It is down in there with boots, dark, lots of things going on and these never fail attitude.

Well, change that. I do believe a contributing factor was the gear over-center link preload. I had always thought that, yep the J-bar was difficult but doable and I'm on a grass field where positive lock is important. Besides, it's working. A Mooney specialist had said you might need this someday, and I made a template of his 8444/8442 tool. But that was a decade ago and never got there.

Couldn't find the  8444, 8442 tools so finally made them. Nose gear was over 3x the original manual 100-130 inlbs spec and with the mains also a little tight made for a difficult uplock on the J-bar possibly over stressing over time (cycles).

"Learn from the mistakes of others, you just don't have time to make them all yourself ".

If there's interest, I can make the tools available to others, thinking it's important. 

[Schllc]

Wait.  This cannot be possible. 
the venerable Johnson bar aka “gold standard of perfection” is not subject to failures. 
it has been deemed infallible. 
this must be a ruse. 

[KeithN92KD]

[00-Negative]

1 hour ago, KeithN92KD said:

Summary: 65 M20E, johnson bar fatigue cracked to failure at base of bar to trunnion. Inspect the weld toe.

Thanks for the write up. 

[EricJ]

Ouch.   This is not the first time I've heard of this happening.    I'm glad you caught it on the ground.

[N201MKTurbo]

I have worked on a couple of Johnson bar Mooneys where the gear was rigged where the preloads were so high that you had to bend the Johnson bar every time you put the gear down. Having the gear rigged this way puts way more stress on the weld than it was designed for.

[Jim Peace]

On 9/10/2025 at 10:32 AM, N201MKTurbo said:

I have worked on a couple of Johnson bar Mooneys where the gear was rigged where the preloads were so high that you had to bend the Johnson bar every time you put the gear down. Having the gear rigged this way puts way more stress on the weld than it was designed for.

I came out of annual once from a Florida MSC and they told me they adjusted the preloads...I could not get the gear down unless I used both hands and very slow airspeed. Also I was not convinced it was not going to pop out of the holder if I did not roll it on or if I hit a bump.   I got back on the ground and asked if they swung the gear after adjusting it and I literally got a shoulder shrug indicating they did not know and could not find out....Also they did not know how to fix it.  So I took it to a non-mooney mechanic who was not to proud to call LASAR and it was fixed in 15 minutes.....this is also when I found my oil cooler with just hand tightened loose connections.  The MSC told me my oil leak was just residual from the oil change....

[Sabremech]

On 9/10/2025 at 7:43 AM, KeithN92KD said:

Summary: 65 M20E, johnson bar fatigue cracked to failure at base of bar to trunnion. Inspect the weld toe.

Storyline: my polished M20E is a high time airframe 10,000+ hrs. I've flown it for the last decade from 2FD6 in Florida all across the country (just really having a Hoot) St. Thomas, Anchorage, Massachusetts, started in California. Not a hangar queen.

So started an assisted annual and found burnt valve in #4. Had time to do some more extensive maintenance then and chose to remove the main gear for paint. Used the stuff the main assistant spring with washers method of unloading the mains and removed them. As I got out of the jacked up airplane I noticed the nose gear slowly retracting back up. Hmm... thought I had the J-bar locked up. Yep, locked up. While I was thinking why would the nose gear be divorced from the gear handle with the mains removed, I unlocked and the handle came out in my hand.

My buddy said it's not supposed to do that, need to put that back. Then we decided this is the best time for this to happen, no belly landing involved.

Examination revealed it was a multiple step fatigue Crack failure in the aft weld toe, bar to T. I have a practice of WD40 everywhere on annual and it was evident in the extending crack. Therefore we missed it growing!

Defense posture; It is down in there with boots, dark, lots of things going on and these never fail attitude.

Well, change that. I do believe a contributing factor was the gear over-center link preload. I had always thought that, yep the J-bar was difficult but doable and I'm on a grass field where positive lock is important. Besides, it's working. A Mooney specialist had said you might need this someday, and I made a template of his 8444/8442 tool. But that was a decade ago and never got there.

Couldn't find the  8444, 8442 tools so finally made them. Nose gear was over 3x the original manual 100-130 inlbs spec and with the mains also a little tight made for a difficult uplock on the J-bar possibly over stressing over time (cycles).

"Learn from the mistakes of others, you just don't have time to make them all yourself ".

If there's interest, I can make the tools available to others, thinking it's important. 

I’ve been making and selling these tools for quite some time! A Googke search would have probably found them. The Johnson bar can also get bent by being kicked out of the uplock while at cruise by back seat passengers. When it slams into the instrument panel, it can bend it. Do this a few times on a high time airframe and I’m not surprised you found what you did. 

David

[skykrawler]

I have seen several Moonies with excessive gear pre-load - electric and manual.

What A&P would reduce the preload on a landing gear that came to them and risk being blamed for a gear collapse for any possible reason?

IMHO this sort of mindset is pervasive in the trade.

Typical escape clause:  'aircraft is airworthy with respect to the work performed'

[cliffy]

No liability if-   "adjusted landing  gear preloads to factory specifications per maint manual section xxxx"  

I'll bet I could check 10 Mooneys and find the gear or elevator settings wrong on 50% of them. 

 

[takair]

It’s important to check that the springs on the gear pushrods are actually moving. Early in my ownership I was adjusting preload constantly only to realize the pushrods were effectively solid and not moving. They had corroded due to water getting in there and not enough lube. This can cause preload to go way up. So, suggest not just checking preload but that the springs are doing their job. Older Mooneys have solid link on nose, so a little different, but the main springs still effect all 3. 

[47U]

4 hours ago, takair said:

They had corroded due to water getting in there and not enough lube.

Corroded like this.  After I made the purchase in 2008, at the first annual I addressed this.  My springs were still loose, but… wow.  LASAR had new springs and I stripped and painted all the gear rods.  And all the flight control rods, too.

 

[takair]

2 hours ago, 47U said:

Corroded like this.  After I made the purchase in 2008, at the first annual I addressed this.  My springs were still loose, but… wow.  LASAR had new springs and I stripped and painted all the gear rods.  And all the flight control rods, too.

 

Oof, not like that. Mine looked fine but would not compress. Think it was because I would wash the plane and the tube would fill with water.