4 point restraints

Thanks for the feedback. Both you and Larry mentioned 337. I'm assuming that's an FAA designation for modifications on our planes.

Thanks Larry. I did check with Alpha Aviation and their price is $1450 for a pair of 3-point restraints with the STC. OUCH!

I've just run into this issue with my local feds. I asked for a pre-approval for a 337 using several previous 337s as acceptable data and an engineering document explaining how to connect with fuselage frames F and G using small baking plates on the frames and a 1/4" threaded rod to connect them and hold the clevis for the shoulder harness. Unfortunately that engineering document stated it was only for a specific airframe and even though other 337s were approved using it my fsdo won't, saying I have to re-invent the wheel with my own DER or get specific approval from the original engineer. Unfortunately he passed away in 2005 . There is a policy statement ACE-00-23.561.01 that confirms what your mechanic says. IF there is no change in the structure such as welding or drilling to the airframe, which would be a "major alteration" requiring either a field approval or STC the it would be considered a minor alteration and just require a log entry. I'm currently working on a clamping scheme that will essentially duplicate the method described in the above engineering report. using frames F and G with connecting 1/4" rod. The Alpha STC is another option of course but it's for a three point, not the four point which I prefer.

I don't know if this topic has come up before, but I would like to switch from the lap belt on my 415D to a 4 point restraint.  My mechanic did some research and said that it could be done if we could find a structural member to attach to, but we couldn't drill into the airframe.  It would have to be clamped.  I was also told that it would be best to obtain an STC before installing. Also, how do I know what type of retraint meets FAA standards.  Thanks for any input.