Seat on M20J not securing

[Beard]

I own a 1984 M20J. The pilot's seat had a habit of sliding back in all positions except one. There was no issue with the passenger seat.

 I recently swapped seats and now the pilot's seat is secure in all positions, but the passenger's seat slides back. This leads me to believe that the problem is not the seat rails but the seat itself. I have cleaned out the holes in the seat rails.

 Does anyone have any advice or experience in this matter? Is there a specific part on the seat that needs to be repaired or replaced?

 Thank you,

[LANCECASPER]

21 minutes ago, Beard said:

I own a 1984 M20J. The pilot's seat had a habit of sliding back in all positions except one. There was no issue with the passenger seat.

 I recently swapped seats and now the pilot's seat is secure in all positions, but the passenger's seat slides back. This leads me to believe that the problem is not the seat rails but the seat itself. I have cleaned out the holes in the seat rails.

 Does anyone have any advice or experience in this matter? Is there a specific part on the seat that needs to be repaired or replaced?

 Thank you,

Probably the rollers on the seat

[PT20J]

If the rear rollers are severely worn the seat may rock back enough so that the locking pins, which are in the front, don’t fully engage the holes in the seat track, especially if the entrances to the holes are worn which is common. Also, there are springs on the bar that raises the pins to hold the pins down and they might be weak or one might be broken. 

[Tim-37419]

I had the exact same issue and also swapped the seats. I bought new rollers, they now roll smoother but that one seat still won't hold.

 

I can't find the root cause but - if the seat is cranked down to the lowest position, the seat is secure. As I turn the crank to raise the seat, the hold gets weaker and eventually the seat doesn't need much wiggling before it shoots to the back. 

 

Something must be bent or worn. I put the two seats side by side and couldn't find a difference. 

 

FWIW - my seats were reupholstered at some point in their life but not recently.

[PT20J]

I would take out both seats and turn them upside down side-by-side and compare the mechanics. Something must be different.

[0TreeLemur]

58 minutes ago, Tim-37419 said:

if the seat is cranked down to the lowest position, the seat is secure. As I turn the crank to raise the seat, the hold gets weaker

The pilot's seat in our '83 J has  the same issue.  If I don't raise it, it feels rock solid.  If raised, it becomes scary. This is on my todo list when the seats are out for annual.

[IFLYIFR]

I had the same problem on both front seats in my 1990 M20J in 2021. I thought it was due to one of the usual likely problems - e.g. the rails, the holes in the rails, the pins, the rollers, or the springs. The actual reason was that some of the welded joints at the corners of the metal rectangular frames under the seat cushions failed (in both seats). The metal frame(s) were not holding 90 degrees angles at the corners. The shop doing the annual sent the metal frames to a shop that re-welded them. Both seats have worked perfectly since March 2021.


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[Tim-37419]

13 minutes ago, IFLYIFR said:

I had the same problem on both front seats in my 1990 M20J in 2021. I thought it was due to one of the usual likely problems - e.g. the rails, the holes in the rails, the pins, the rollers, or the springs. The actual reason was that some of the welded joints at the corners of the metal rectangular frames under the seat cushions failed (in both seats). The metal frame(s) were not holding 90 degrees angles at the corners. The shop doing the annual sent the metal frames to a shop that re-welded them. Both seats have worked perfectly since March 2021.


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if you had posted this earlier I would be on my way to the airport right now to check  I have a strong feeling that’s my problem since I already had both seats out and saw no difference between them.

[IFLYIFR]

One more point. The out-of-squareness worsened when the seats were cranked up toward the highest position.


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[0TreeLemur]

On 10/10/2023 at 6:36 PM, IFLYIFR said:

One more point. The out-of-squareness worsened when the seats were cranked up toward the highest position.
 

Great info.  I'll have them check that during annual in Dec.!

[Aerospace]

Likely the old bent bar on seat adjuster mechanism reduces engagement into holes. Clear to see and easy to fix if you have the seat up on a work bench and you are handy at fixing things and working with metal. I've seen it alot, my own J, and tons of other seats that work the same way, boats, cars, etc.

If you aren't handy and confident at fixes like this, then maybe this is best left to your go-to person.

[Fly Boomer]

1 hour ago, Aerospace said:

Likely the old bent bar on seat adjuster mechanism reduces engagement into holes. Clear to see and easy to fix if you have the seat up on a work bench and you are handy at fixing things and working with metal. I've seen it alot, my own J, and tons of other seats that work the same way, boats, cars, etc.

If you aren't handy and confident at fixes like this, then maybe this is best left to your go-to person.

Did you have to remove the upholstery and heat that bar before bending it back, or were you able to bend it cold?

[Tim-37419]

I went to the hangar this morning, excited that all I needed to do was bend something but found a crack instead... two photo's below, one of the crack and another of the pilot side seat that looks like it may have been repaired or re-enforced.  

[Beard]

I too went to my hangar today to see if the problem could be solved with a simple bending of something. And, I too found a crack in the seat frame. Mine is on the opposite side to N5779Y, but very similar. See my pictures below. I will look to see if I can buy new bushings and rollers for when I put it back together. Does anyone know where I can buy these parts? I am very please with finding this problem as it has worried me for quite some time.

[Tim-37419]

@Beard I bought 4 at lasar.com about 6 months ago

 

[IFLYIFR]

Tim-37419 and Beard, the photos in your posts are just like the weld failures I found in my M20J front seats in March 2022. Mine were so bad the annual shop sent them out to a welding company near San Antonio to re-weld them. As I said in my posts a few days ago, I did not need to replace any rails, pins, springs, rollers, etc. I got the name of the aerospace welding company from Hector at Aero Comfort. The welding company only took about a week to do the work. Let me know if you need the name of the welding shop. John.


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[Aerospace]

On 10/13/2023 at 1:14 PM, Fly Boomer said:

Did you have to remove the upholstery and heat that bar before bending it back, or were you able to bend it cold?

bent easily without heat

[skykrawler]

On 10/10/2023 at 2:43 PM, 0TreeLemur said:

The pilot's seat in our '83 J has  the same issue.  If I don't raise it, it feels rock solid.  If raised, it becomes scary. This is on my todo list when the seats are out for annual.

Why would anyone wait to have this problem repaired?    This is deferring maintenance for a true airworthiness issue.

[Tim-37419]

I'm my case, as long as the seat was in the lower third of its height using the right crank, the seat would stay in position. I had also moved it to the copilot aka non pilot wife side.

 

You still have a good point, I just wanted to share what I had done to minimize the risk.

 

[1980Mooney]

On 10/15/2023 at 8:06 AM, Tim-37419 said:

I'm my case, as long as the seat was in the lower third of its height using the right crank, the seat would stay in position. I had also moved it to the copilot aka non pilot wife side.

You still have a good point, I just wanted to share what I had done to minimize the risk.

 

On 10/15/2023 at 7:26 AM, skykrawler said:

Why would anyone wait to have this problem repaired?    This is deferring maintenance for a true airworthiness issue.

 

Good point.  In fact I am surprised that this does not become an AD for immediate inspection that grounds planes with cracked/broken welds.  This is a well known cause of stall on take-off crash fatalities for Cessna's.  There was a $480 million settlement by Cessna in 2001 and 2010 AD.

Perhaps because Mooney pilots can grab the center frame tubular to pull themselves forward (instead of the yoke), there have been fewer fatalities when the seat slides back during take-off.

 

[Tim-37419]

7 minutes ago, 1980Mooney said:

Good point.  In fact I am surprised that this does not become an AD for immediate inspection that grounds planes with cracked/broken welds.  This is a well known cause of stall on take-off crash fatalities for Cessna's.  There was a $480 million settlement by Cessna in 2001 and 2010 AD.

 

I had the exact same thought. 

[LANCECASPER]

I keep my hand on the throttle on take-off so that if my seat moves back, the throttle pulls back. That doesn't solve everything but it sure makes it easier when you're back at idle. 

[kortopates]

I keep my hand on the throttle on take-off so that if my seat moves back, the throttle pulls back. That doesn't solve everything but it sure makes it easier when you're back at idle. 

I am not so sure about that. If it’s going to slip back it’s much more likely to occur after rotation and is pretty unpredictable. A short field takeoff requires right about 12 degrees pitch up and climbing steeply out is not the time i’d want to risk the throttle going back to idle.
Best to let go if it ever happens IMO. It did happen to me once in climb before i changed out all 4 seat rails; luckily i just let it go.


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[LANCECASPER]

1 minute ago, kortopates said:

I am not so sure about that. If it’s going to slip back it’s much more likely to occur after rotation and is pretty unpredictable. A short field takeoff requires right about 12 degrees pitch up and climbing steeply out is not the time i’d want to risk the throttle going back to idle.
Best to let go if it ever happens IMO. It did happen to me once in climb before i changed out all 4 seat rails; luckily i just let go.


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That's been my habit since I flew Cessnas.

A couple of yers ago I had the seat slide back on acceleration and was glad I had my hand on the throttle. Even though the rudder trim was full right, the airplane was still was veering to the right, without me being able to reach the right rudder. I pulled the throttle back and got things back under control. Thankfully I was on an 80 foot wide runway. I pulled off on the taxiway collected my thoughts and taxied back for take-off, starting my checklist all over, and took off again after I had confirmed twice that my seat was secure.

In this case it worked, but like I mentioned it wouldn't solve every situation if this happens.

[Echo]

Jesus people!  If your seats are broken…FIX THEM!