The the four place airplanes there are brackets that the seat bolt into with the clevis bolts. These brackets are held to the spar with AN3-6A bolts with a MS35333-39 star washer and a AN960-10L thin washer. Some plane had the shorter AN3-5A bolt used, and others have had an extra star washer placed between the bracket and the spar. This will eventually work loose and your seat will wiggle, or fail to latch on one side. Heck you might even loose your balls, ball bearings, that is in the seat rails. And yes it is a pain to get them back in. Don’t ask.One bad end

The other bad news

Finally, the really bad news, torn rivnut in spar.

As part of removing the seat to gain access to the under panel area, it was notice the seat was missing 4 ball bearings. One found when the pilot side carpet was taken up. Checking the bracket showed a lot of play and no middle bolt. The lower bolt was an AN4-5A with a stack of (4) AN960-416 washer so it only engaged the tapped AN3 rivnut a few threads. Needless to say it was not holding. The holes in the bracket a wallowed out and the bracket needs to be replaced. The rivnut in the spar will be drilled out and replaced with new countersunk rivnut. It is never fun drilling the spar, so you say the shepherds prayer, “Alan Sheppard”, “Oh lord, please don’t let me mess up”

Roscoe
Yankee-Aviation.com
513-519-7008