1982 M20J seat back broke on T/O

[FlyDave]

So, one day ~ 5 weeks ago I was test flying my airplane for troubleshooting what turned out to be a mag problem (see previous post). I pull out on the runway, line up, advance the throttle and start to accelerate down the runway when suddenly

 

W H A M !!!!!!

 

and I'm lying down with my head in the back seat.

I reach forward and pull the throttle back to idle but have to hold onto the roll cage bar at the center of the windshield to stay upright and keep my feet on the rudders and brakes. I get the airplane slowed down, off the runway and taxi back to my hangar. I'M DARN LUCKY this didn't happen 7 seconds later as I would have been in the air and at best would have had quite a time controlling the airplane close to the ground.

The problem is that my seat back broke where it bolts to the base. See the attached pictures for the piece that broke as well as the right seat that has not yet broken but needs to be fixed. This failure was either caused or exacerbated by someone using bolts that had threads all the way across instead of threaded only at the end where the nut screws on.

I called a couple of FBO's - including LASAR since they are 25 miles from my field - and no one would fix the seat except Don Maxwell (but I'd have to ship the seat back and base from CA to TX). Apparently, the FAA has fairly stringent regulations around working on seats. The FBO that diagnosed and fixed my mag problem, had the welding done and painted/re-glueing cushions on and provided me with a log book entry.

If you have this same type of seat, I urge you to check your seats for wear and also for the correct type of bolts for this attach point. You don't want to experience what I went through!

 

Dave

[Nathan Peterson]

Thanks Dave for the "Heads up".

[Marauder]

I have had mine rotate to the recline position unexpectedly during flight. Couldn't imagine what it would be like during take-off.

[Bob]

A little off topic, but have to share.  I flew with a large pilot in a Cessna a couple months ago.  Part of his pre flight included instruction, knowing that I was a pilot, instructed me to grab control of the plane if his seat would happen to slide back.  Ends up it happened to him, one time in the pas,t and is now on his mind at every flight.  Cessna now offers a goodwill upgrade, of about $1200 that adds a tether strap as a backup to reduce the seat travel.

 

Thanks for sharing!  Many of our planes are 20-50 years old.  The log books never tell us about the fatigue from a past heavy pilot.

[testwest]

Dave, well done handling a really bad situation.

 

If you have your parts manual you will note that bolt (a machine screw, actually) is supposed to be an NAS222-13....but this hardware nomenclature has been superseded, the new part is MS27039-1-13, available here: http://www.aircraftspruce.com/catalog/hapages/MS27039.php?clickkey=3770 , they are $0.15 each.

 

 

Bob is right, those seats take a beating. But the substitution of an all-thread screw because someone way before FlyDave got stymied on the old part designation did not help, either. The information I show here was found in under 5 minutes of Google use.

[jetdriven]

Thats good info, Dave. That reminds me to check ours before flying again. Those threaded bolts will saw right into that frame it appears.

[wishboneash]

There is a thread I started earlier about this. In my case, the break occurred over a long period of time and the bolt was the right one so, there was not cutting through but a gradual weakening of the structure. Only one side broke, so the seat didn't really go back all the way. Pressing down on the top of the seat when trying to get in and out of the aircraft is probably the biggest cause of stress on the seat backs. This is something one has to drill into passengers who are not familiar with small aircraft. 

 

Being able to reach the electric trim could save the day!  I plan to inspect my seats at annuals and take corrective action if needed. 

[OR75]

Two points:

 

- Checking the seats is part of the annual inspection.

 

- Screws, Nuts and bolts: I have done a few owners' assist annual in the past 10 years. For those who have done it, you know it comes down to doing the opening and closing of the small and large belly panels.  By far, the first one was the most painful because over time, mechanics have put the wrong "off the shelf" screws, nuts and bolts. For less than $50 you can make sure the right ones are used.  Subsequent annual have been a breeze as far as opening and closing pannels

[John Pleisse]

Tell you what, take off is a deal breaker. Glad you fared well. I had this happen some years back and the reclining selector gave way (teeth broke clean off). This part was not hard to find. The factory had bunches of them. I don't lean back on take off or pattern work....haven't since.

[wishboneash]

Two points:

 

- Checking the seats is part of the annual inspection.

 

- Screws, Nuts and bolts: I have done a few owners' assist annual in the past 10 years. For those who have done it, you know it comes down to doing the opening and closing of the small and large belly panels.  By far, the first one was the most painful because over time, mechanics have put the wrong "off the shelf" screws, nuts and bolts. For less than $50 you can make sure the right ones are used.  Subsequent annual have been a breeze as far as opening and closing pannels

 

It seems then the seat inspection was missed in the last annual. I am sure the signs were there it was giving way. Thanks, I need to read up more on the annual inspection list.

[fantom]

 If it "pops" or otherwise makes noise, something in there is broken.

 

...and you may have a pissed off owner on your hands, claiming YOU broke it.

[fantom]

...and you may have a pissed off owner on your hands, claiming YOU broke it.

 

That was fast....2 minutes!

 

Did you hear something go "pop", Jim?

[fantom]

Actually I did.  My co-pilot's seat back failed Paul's test the first time that I tried it.  My solution so far has been to avoid testing it again. 

 

Jim

 

You may want to visit a chiropractor, or maybe 'smiles, who offers the service as yet one more sideline

   

[Hank]

Gary,

 

The easy solution to Jim's problem is for him to sit in the left seat, and leave the right seat for his un-favorite passengers . . .