TidBits from a tech review

My local EAA tech councilor crawled over my plane yesterday, a bit of a pre-instpection review. The only thing he took exception with was the rigid mounting of the seatbelt anchors. He felt they should be able to swivel a little to insure that under load the belt is aligned with the anchor and evenly loaded. He suggested that I replace the AN-4A / Ny-locs with AN-4 and castle nuts just over finger tight. His reasoning seems sound and he is my DAR so I planning to make the change, thought comments or concerns?

Hi Dorsal,

I would agree with the the idea that the seat belt would be better off if it swiveled at the anchor so the belt would have an even distribution of stress over its width. There might be a couple ways to accomplish this. Not clamping up the bolt tightly is one way - and it won't affect the strength of the assembly anyway. I also have a series 7 and the hole in the seat belt end was quite a bit bigger than the bolt that went through the fuselage anchor hole - in this case - it was pretty easy to cut a piece of tubing a bit longer than the thickness of the seat belt end plate to fit between the bolt and seat belt end plate - then the bolt clamps up against the spacer made from the tubing and the assembly can freely rotate - this depends on what size the hole is in the seat belt end - there might be different seat belts that have been used over the years . Auto belts use a shoulder bolt to accomplish the same thing.

Sincerely,

Dave S

Dave,

That's the exact same way my seat belts attach in my 1959 172A. Allows the belt to swivel freely while the attaching bolt is snubbed up nice and tight.