Shoulder belt retrofit J3

[sdischer]

I am sharing this in case it provides some extra safety for another J3 owner. I make no representation to compliance with any applicable regulations. I encourage you to read FAA Policy Statement Number ACE-00-23.561-01 and make your own decision.

I am relying on ACE-00-23.561-01 as a guide to retrofit shoulder belts in a J3 not previously equipped with shoulder restraints and I am signing it off in the logbooks as a minor change as an A&P.

I did a good bit of research and most of the solutions out there were expensive or seemed very flimsy. My solution is to use some steel-billet, machined clamps that fit the 7/8" OD tubing overhead and the 1" OD tubing diagonal brace perfectly, directly behind the rear passenger's head.

I fabricated a backing ring and escutcheon plate from .060 aluminum (I actually drew the pattern and sent it to https://sendcutsend.com and they laser cut them, excellent work BTW).



I purchased two harness sets from Hooker (Hooker Harness FAA-PMA shoulder restraints 2Y563030-3).



The D anchor rings to attach the belt to the bolts came from Aircraft Spruce.



I made a little hammock out of vinyl to keep the lap belt out of the way when not in use.



I suspect someone will flame me and tell me what laws I broke but I feel safer with my son flying the airplane with proper restraints and I believe this is a minor modification as there was no cutting, welding, drilling or alterations to the structure.

I have these pieces left over and will sell them basically for my cost which is $50 plus shipping. There is a 7/8" clamp and a 1" clamp, enough for one setup. You just need riv-nuts installed in the backer ring, the shoulder belts and the D anchor points. These parts are not approved by any regulatory agency, only common sense and good engineering.



Attaching my DXF file in case you want to have your own aluminum pieces cut.

View attachment Drawing2.dxf

Here is how I wrote the logbook entry:

Installed shoulder restraints in the front and rear seats of the aircraft using FAA Policy Statement Number ACE-00-23.561-01 as a reference. The retrofit shoulder harness installation qualifies as a minor change as it involves no drilling, welding, changes to the structure.

1. Installed a machined, billet steel tube clamp above the left side of the cockpit, clamped to the 7/8” O.D. tubing overhead.
2. Installed a machined, billet steel tube clamp behind the head of the rear passenger on the diagonal tubing.
3. Fabricated a fabric backing ring and slotted cover from .060 aluminum sheet metal to act as an escutcheon for the belt to penetrate the fabric headliner inside the cockpit behind the rear passenger’s head and secured with #8 screws and riv-nuts.
4. Installed two each Hooker Harness FAA-PMA shoulder restraints 2Y563030-3 in front and read seat positions.
5. Tested and adjusted belt operation.

 

[wireweinie]

Hey! I saw that intercom system!

Web

 

[sdischer]

I am giving my son dual in that airplane and believe me, shouting, or pulling on the shirttails is for the birds, lol.

 

[skywagon8a]

View attachment 65643

Where does the lower end of the front belt attach? At the buckle in the middle or lower on the right side? If at the buckle, this belt is only protecting the left shoulder allowing the rest of the body to twist and slip out of the belt.
The rear belt is protecting both shoulders restraining the entire upper body.

 

[sdischer]

Where does the lower end of the front belt attach? At the buckle in the middle or lower on the right side? If at the buckle, this belt is only protecting the left shoulder allowing the rest of the body to twist and slip out of the belt.
The rear belt is protecting both shoulders restraining the entire upper body.

Front and rear belts are "Y" harness, 4 point systems. I suspect it looks like a single shoulder belt stowed.

 

[skywagon8a]

Front and rear belts are "Y" harness, 4 point systems. I suspect it looks like a single shoulder belt stowed.

That's better than it looks. It still is pulling to one side.

 

[sdischer]

That's better than it looks. It still is pulling to one side.

Top center would be perfect. Without adding a tubular bracket between the two top diagonal tubes I don't think I can get perfect but it's so much better than lapbelt only. Sitting in the front seat with the belts all properly tightened it feels very secure.

 

[cubdriver2]

Pa11



J3



Glenn

 

[bob turner]

Pulling in the center of that tube, which is already loaded in compression, is not good. I always thought I was the only person in the whole world who held that view, but by golly, the federales do, too! I just noticed this yesterday:


In general, shoulder harness installations should not use the center of an unsupported wing carrythrough tube or other unsupported member as an attachment point. This type of attachment may pose a risk to the structural integrity of the airplane. Although the attachment may be a clamp-on fitting that does not alter the existing airframe, the installation may result in a major change in the type design. This is because the shoulder harness attachment may introduce new loading conditions into the carrythrough tube.
It is acceptable for the carrythrough structure to be damaged in an emergency landing. However, it is unacceptable for the tube to fail in-flight. Carrythrough tubes, highly loaded in compression, may experience a beam- column 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.

 

[bob turner]

No, you missed the point. That particular tube is under compressive load in normal flight, unlike the tubes your passengers grab. The feds are suggesting that attachment in the middle of that tube is at least a major alteration if not outright dangerous during normal operation.

 

[sdischer]

No, you missed the point. That particular tube is under compressive load in normal flight, unlike the tubes your passengers grab. The feds are suggesting that attachment in the middle of that tube is at least a major alteration if not outright dangerous during normal operation.

Comment Removed: Sorry I did not see you were responding to a Post comment and not the OP. Removed to retain OP clarity.

 

[bob turner]

Well, me neither - except for the rear belt, which will collapse a diagonal tube that is not under load. I thought we were having a theoretical discussion about attaching the front harness to the center of that tube separating the rear spar mounts. I will go back and look at what triggered my initial comment.

While I am doing that, consider this FAA comment - contained within the above quote:

[FONT=&quot]Although the attachment may be a clamp-on fitting that does not alter the existing airframe, the installation may result in a major change in the type design. This is because the shoulder harness attachment may introduce new loading conditions into the carrythrough tube.

So, properly read, this says if you do attach to the center of that tube with a clamp, you “may” be in major alteration territory.[/FONT]

 

[sdischer]

Comment Removed: Sorry I did not see you were responding to a Post comment and not the OP. Removed to retain OP clarity.

 

[bob turner]

Yes. My post was triggered by Glenn’s photo, not yours. And I stand by my comments.

As an aside, my shoulder harnesses were illegal from about 1972 until the FAA policy came out. They were beautiful new Air Force belts.

A buddy bought the Wag STC for his J3, and I was horrified! The FAA approved a 1/8” thick bracket with a huge AN bolt (I think it was an AN-6) mounted in the center of that beam. The beam itself is .032 wall tubing; it would fail long before an 8-32 machine screw would. And worse, the failure would aim that bolt right in to the skull of the rear seat occupant.

 

[bob turner]

We crossed posts. As far as I can tell, we are not in disagreement about anything except you thinking I aimed my comment at your installation. I did not.

 

[sdischer]

Yes the Wag clamp is frightening.

 

[cubdriver2]

Yes. My post was triggered by Glenn’s photo, not yours. And I stand by my comments.

As an aside, my shoulder harnesses were illegal from about 1972 until the FAA policy came out. They were beautiful new Air Force belts.

A buddy bought the Wag STC for his J3, and I was horrified! The FAA approved a 1/8” thick bracket with a huge AN bolt (I think it was an AN-6) mounted in the center of that beam. The beam itself is .032 wall tubing; it would fail long before an 8-32 machine screw would. And worse, the failure would aim that bolt right in to the skull of the rear seat occupant.

Where does a SC front seat shoulder belt mount

Glenn

 

[skywagon8a]

Where does a SC front seat shoulder belt mount

Glenn

PA-18 EAB

Front seat Back seat

Front seat will buckle rear carry through, pulling wings aft. If on a certified -18 I would connect the front and rear attach points with a cable or some other suitable tension support.

 

[RaisedByWolves]

I’m not an engineer but it seems like even on the carry through it’s going to slow your face down as you eat the panel a lot more than no shoulder harness.


Sent from my iPhone using Tapatalk

 

[bob turner]

Of course it will. The problem is that it will probably kill your passenger, for whom you may have some feelings of affection.

For Super Cubs, Atlee Dodge has some pretty good bolt-on brackets.

like Mr. Discher, most of us mount the front harness at the side, near the rear spar cluster. I have thousands of hours with that angled harness around my torso, and simply never noticed the angle.

 

[hotrod180]

PA-18 EAB

Front seat View attachment 65666

.

What if you secured the strap by wrapping it around the tube it goes over, just aft of the x-brace intersection?
Seems like it'd be pretty difficult to bend that short tube.
FWIW I've seen where someone will weld a plate gusset onto a tube to beef it up,
with the shoulder harness usually bolted to that gusset.

 

[behindpropellers]

I’m not an engineer but it seems like even on the carry through it’s going to slow your face down as you eat the panel a lot more than no shoulder harness.


Sent from my iPhone using Tapatalk

Exactly. If you are bending that tube, there are probably going to be other things to worry about.

Tim