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Approval for welded-in shoulder harness tabs

Not being an A&P I'm reading the above esoteric discussion and thinking--- is it better to have a freaking shoulder harness or is it not??? Just saying. I thought that was the FAA's opinion too and they were supposed to be making it easier to install one. Sorry for the thread creep.
 
This topic has been debated before. I think highly of Atlee Dodge's work, but I suspect they didn't complete the load analysis in this case. I'm no structures man, but as rule, ANY load applied perpendicular to a beamcolumn is excessive.

"Carrythrough tubes, highly loaded in compression, may experience a beamcolumn buckling failure if the occupant applies a load to the shoulder harness attachment. In some cases, very small loads on the shoulder harness attachment may cause beam-column buckling failures." Policy Statement Number ACE-00-23.561-01, Issuance of Policy Statement, Methods of Approval of Retrofit Shoulder Harness http://www.faa.gov/aircraft/gen_av/harness_kits/media/shoulderpolicy.pdf
 
After that beam load is applied to the rear carry-thru I suspect any damage to it is the least of your worries. This is how Univair does it.
100_0206.JPG

From this http://www.pierceaero.net/techdata/rsh.pdf it looks like the FAA thinks something is better than nothing. Also, there are STC's to clamp to this, just none to weld.
 

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If I read the Policy Statement correctly, their concern is in-flight failure of the carry-through caused by the load. Great pic, though, thanks.

I admit the front harness setup design on my -18A is by no means an award winner - actually, it's kind of crappy - but it seems to do the job and it's legal. I don't really like the cross-strap that ties the two shoulder straps together (it's something to get tangled up in), but it does give some lateral protection (the stitching was done in an approved shop). It's adjustable from just behind the head all the way up to about 8" from the carry-through (the higher up the greater the load on the stitches). I set it to about 16" fwd so it limits any head rebound, too. An alternative would be a single diagonal, but those things don't impress me.

2012-07-28_15-58-08.jpg
Back seat shoulder straps anchor

2012-07-28_15-57-18.jpg
harness3.jpg
Front seat shoulder straps anchors

2012-07-28_15-57-00.jpg

Comments would be appreciated. Thanks.
 

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Nice install. I want to pursue an STC for the weld in shoulder harness attach fittings. I have gotten access to the structural test data and have a call into my FSDO for a contact at the ACO to send my packet to. I think this is a much need modification.
 
I've never had the local FSDO turn down a 337 for a welded on shoulder harness bracket. I must be lucky to have a FSDO with some common sense.

John
 
I’ve read through this, and as a mostly non-mechanical type am thoroughly flummoxed. I do not have to my knowledge any logbook entry, and definitely no 337 for my shoulder harnesses in my new -12. Any thoughts on this setup?
 

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Kodiakmack said:
I’ve read through this, and as a mostly non-mechanical type am thoroughly flummoxed. I do not have to my knowledge any logbook entry, and definitely no 337 for my shoulder harnesses in my new -12. Any thoughts on this setup?
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Upon impact that piece of string will break and you will smash your face into the instrument panel. The harness should be threaded through that small triangle behind the X joint. That's what the short cross piece of tubing is there for, to hold the harness at the correct angle.
 
Kodiakmack said:
I’ve read through this, and as a mostly non-mechanical type am thoroughly flummoxed. I do not have to my knowledge any logbook entry, and definitely no 337 for my shoulder harnesses in my new -12. Any thoughts on this setup?
Click to expand...
Make a log book entry referencing the FAA Policy Statement.
 
Kodiakmack said:
I’ve read through this, and as a mostly non-mechanical type am thoroughly flummoxed. I do not have to my knowledge any logbook entry, and definitely no 337 for my shoulder harnesses in my new -12. Any thoughts on this setup?
Click to expand...

Your attachment is bolted on. No biggie but not necessary. I'd loop the strap over the short lateral tube at the X and use a belt adjuster to affix it. There's no need for the bolt-on attach except possibly to attach a retracting reel, and given zero experience with those I'll defer on that.
 

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Your installation method of attachment is not a problem. Route the harness as suggested between the x and the short tube and get rid of the string.

MY BIGGEST WORRY, however is the material type and thickness of the clamp used to hold the anchor to the rear carry-tru tube. (It LOOKS very Thin!) If it is aluminum it will do you no good in an accident as it will likely tear out especially with two bolts per side. If it is steel, it also has this potential because of it's thickness but will tear out at a higher load.

My point is, I would make the clamps with thicker material and make them from steel.
 
I figured as much. The plane isn’t flying and I’ll re-route the belts. More curious about the attach setup.
 
Kodiakmack said:
I’ve read through this, and as a mostly non-mechanical type am thoroughly flummoxed. I do not have to my knowledge any logbook entry, and definitely no 337 for my shoulder harnesses in my new -12. Any thoughts on this setup?
Click to expand...

just attach/wrap it to that short tube at center of X brace, that's what that tube is for... no need for mounting bracket
 
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