Cessna Series 100 seats and seat back collapse

[Gary]

My 170b had Cessna series 100 seats installed when I purchased it. The copilot’s seat back has had several sudden collapses while in flight (the first being on my bi-annual review with a CFI! In my investigations of fixes, I found on the Cessna owner’s site an AD for some of the 172 fleet. It called for Cessna Modification Kit MN172-25-10B or a steel lock rod/bar on both crew seat back cylinder lock assemblies. If a steel lock rod/bar has already been installed on the crew seat back cylinder lock assembly, no further action is required. The pilots seat has a different system and is on a screw jack for both the seat back angle and the seat height and does not have the same problem. However, I do sit in the right seat sometimes and would not like to have the seat back move back a notch suddenly. Have any of the 170 drivers with the 172 seats had this problem and how did you fix it. A look like the Cessna Modification part is $200 or so! Any plans on the "steel lock rod/bar mentioned as an alternate method of compliance? Gary

[sphillips]

Our C172N trainer has a copilot seat with the same problem. Took the seat out and found the spring that keeps the notched ratchet engaged was broken. Replaced the spring and all was OK.

Steve

[Gary]

Thanks Steve, I did look at the springs and they seem to be just fine. Maybe they are weak? I dressed the ratchet with a file to make it square and that seemed to work for several months. But it is slipping out again. Can't keep filing it. I had even tried to safety wire it in the notch but didn't have the right places to wire to and it too slipped off. That is why I asked about the AD on Cessna seats, and the fix. My wrench guy was not happy to see the seats in the plane without any paper work in the log book other than "replaced the seats". We did find supporting documentation for the seat change and have it now noted in the log books.
Gary