Nut Plates installed in 170B rear spar carry through

[Richgj3]

What size are they? I think they are #10. I ask because I’m still trying to get shoulder harness belts installed. The Wag Aero STC requires an AN4 bolt there. How has anyone accomplished that? I think the BAS inertial belts use that nut plate but not for load bearing. I think they require drilling through the cabin top for structural support. I say “I think” because I don’t know. Looking for education.

[Bruce Fenstermacher]

The factory shoulder harness nut plate holds an AN-3 bolt. If I recall correctly the Wag Aero STC has you drill a hole in the skin to install a nut plate. Hooker Harness STC has plates or a U-channel (I forget which) the is attached to the carry through spar by drilling front to back and inserting bolts. The harness then is attached to the plates or channel. I used the Hooker STC to install shoulder harnesses in my 170A.

[GAHorn]

Here are the B.A.S. installation instructs:

Illustration:

Complete Instructs:

BAS Instructions Cessna 170-210F R1 Rev A 5-1-2003.pdf

(1.73 MiB) Downloaded 65 times

[Richgj3]

Thanks Bruce and George. Much more clear now.

[Richgj3]

So the nut plates installed by the factory are AN366F1032. It’s item 7 in the IPC page 46 and 47. They are noted “nut plate (attach shoulder harness)”.

Has anyone attached pma’d shoulder belts to this attach point? I don’t want to beat a dead horse, but I also don’t want to drill holes in my airplane if this could be a legal solution. Were shoulder belts an option in 1952?

Rich.

[Bruce Fenstermacher]

Yes shoulder harness were an option in '52 and they were attached to the spar using an AN-3 bolt into that nut plate. Minor alteration to install shoulder harnesses in this case (and many others).

Many people think the AN-3 is to small until they consider the shear load an AN-3 can handle and they learn their body can not come close to handling the same load.

[Richgj3]

Thank you Bruce. Very helpful.

Rich

[GAHorn]

Keep in mind that ANY shoulder harness is better than No shoulder harness…and FAA agrees. You do not have to buy TSO or PMA or FAA approved even. Automotive is OK if you don’t make any structural changes…such as if you use that nut-plate.

Here’s the approval basis: viewtopic.php?f=43&t=8

[Richgj3]

Thanks George. We are good to go. My friend is also my IA. He is also a DAR and very thorough. He verified with our FSDO that we can make the install as you described. The FAA guy did say the belts should be PMA’d but that’s no big deal because that’s what I have. That may be his opinion. I agree with your interpretation of the ACE that you linked. But as they say, no need to “sell past the close”

Thanks again.