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Approval for welded-in shoulder harness tabs

dave

dave

Registered User
Lodi, CA
AC-23-4 states "The FAA does not encourage the approval of retrofit shoulder harness installations as minor changes. The preferred methods of approval are Supplemental Type Certificate or Field Approval. However, the FAA should notforbid the approval of a retrofit shoulder harness installation as a minor change in the front seats of those small airplanes manufactured before July 19, 1978, and in other seats of those small airplanes manufactured before December 13, 1986. A retrofit shoulder harness installation may receive approval as a minor change in these small airplanes if: The installation requires no change of the structure (such as welding or drilling holes).

My question, does anybody know of a way to weld in Atlee Dodge shoulder harness tabs as a minor alteration?
 
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Thanks SB, As I read it welding the tabs becomes a major alteration. I'm sending it on for others to evaluate. DK
 
I think the interpretation is subjective. For instance...
a. Minor alterations are limited to those where no change in the aircraft structure is required for
mounting the harness. If the installation does not
require operations such as drilling holes into or
welding brackets onto the primary structure, it could
be classified as a minor alteration. (See Figure 9-1.)
Two examples of minor alterations for shoulder
harnesses are:
Click to expand...

Is the tab attaching to "primary" structure? If it isn't primary structure, the limitation isn't applicable, right?

In any event, a major alteration with approved data can be signed off by an IA without involving the FAA. The AC gives you the data he needs to do it.
 
We have one engineer's opinion that it does attach to a primary structure.

tabs.jpg
 

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dave said:
We have one engineer's opinion that it does attach to a primary structure.

View attachment 8106
Click to expand...

Looks to me like you added a base for the standoff at the skylight. Nice touch using the standoff base for the harness attach point. :)

Seriously, I understand the general concern about adding a welded tab on a tube. In this case, if there's enough force on the attach tab to do damage to the tube? You probably have bigger problems to worry about. It's a little silly that you can attach the harness anchor to the tube with a cable choker or a tube clamp but not a welded tab. The engineer needs a dose of common sense.
 
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sierra bravo said:
In any event, a major alteration with approved data can be signed off by an IA without involving the FAA. The AC gives you the data he needs to do it.
Click to expand...

When did AC43.13-2B become "approved" data? I always thought it was "acceptable" data? Big difference!!
 
Yes I was just trying to beat you to delete.!!!!
This data generally pertains to minor alterations; however, the alteration data herein may be used as approved data for major alterations when the AC chapter, page, and paragraph are listed in block 8 of FAA Form 337 when the user has determined that it is:
a.
Appropriate to the product being altered,
b.
Directly applicable to the alteration being made, and
c.
Not contrary to manufacturer’s data.

Refer to this

(4) Manufacturer Data. Some manufacturers have developed service kits or service instructions that are FAA-approved for harness retrofit installations. Some manufacturers have developed service kits or service instructions that are FAA-approved for harness retrofit installations. Depending on the complexity, these installations may be performed as major or minor alterations. For example, if the installation consists of affixing harness assemblies to existing hard points such as nutplates, the installation could be classified as minor, with no requirement to complete FAA Form 337. If the kit is FAA-approved but results in modification to the airframe structure, FAA Form 337 must be completed, referencing the approved kit/instructions, with no additional approval required.
(5) Other FAA-Approved Data
 
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If they comply with the AC instructions they do not need further approval. Dave's problem is that the tab in the photo isn't attached adjacent to a tube intersection. The AC doesn't prohibit the tab's attachment elsewhere in the tube, it simply says attachment "should" be near a tube intersection. Should? Near? Pretty subjective. That interpretation thing again. The AC clearly defines a welded tab as a major alteration but with the approved data provided in the AC the 337 can be filed without approval. Frankly I can't believe a DER wouldn't sign it off. The intent is to protect the pilot.
 
Stewart,
Para 903 b. lists the methods to accomplish the major alteration.
Where are you finding other info for accomplishing a major alteration for installing a shoulder harness?
Brian
 
Part 5 of the paragraph that you referenced. The AC document itself is approved data when properly referenced on the 337.
 
Yea.
Not as simple as just entering in logbook, "installed I/A/W 43.13-2B Chapter X para Y."
Brian

( I might have one of these in my shed needing certified when I get done with all the paperwork. Just as well see how they get theirs done first]
 
During the rebuild of our SC, I called Atlee to enquire about his bolt-on shoulder harness fitting. He said, "Isn't this plane all apart with no cover?" I said "Yes". Then a little agitated, he said " Well then just weld the #$%!@ bracket on, don't bother with the bolted on one" So we did and my IA had no qualms about signing it off as a minor mod.
 
Does the FADodge kit have any paperwork for it?

If the kit is FAA-approved but results in modification to the airframe structure, FAA Form 337 must be completed, referencing the approved kit/instructions, with no additional approval required.

Does anyone have a letter from the FAA saying a welded on tab is ok as a minor repair
 
Darrel Starr said:
During the rebuild of our SC, I called Atlee to enquire about his bolt-on shoulder harness fitting. He said, "Isn't this plane all apart with no cover?" I said "Yes". Then a little agitated, he said " Well then just weld the #$%!@ bracket on, don't bother with the bolted on one" So we did and my IA had no qualms about signing it off as a minor mod.
Click to expand...

Steve Kracke made an almost identical statement to me about a rear shoulder harness bracket. My IA had no problem with it being welded either.


Sent from my iPhone from the middle of nowhere using Tapatalk
 
All the SCs around here have welded in shoulder harness brackets. Some of us have been ramp checked without anyone commenting about the brackets.
 
sierra bravo said:
If they comply with the AC instructions they do not need further approval. Dave's problem is that the tab in the photo isn't attached adjacent to a tube intersection. The AC doesn't prohibit the tab's attachment elsewhere in the tube, it simply says attachment "should" be near a tube intersection. Should? Near? Pretty subjective. That interpretation thing again. The AC clearly defines a welded tab as a major alteration but with the approved data provided in the AC the 337 can be filed without approval. Frankly I can't believe a DER wouldn't sign it off. The intent is to protect the pilot.
Click to expand...


correct.. fill out 337, send it to Oak.....
 
I would guess that most people reading this, if they have ever bent a SC, will think that shoulder harness are a good thing. I also think that most will agree that it is perfectly legal to wrap the shoulder harness tiedown around the cross member or use bolt-on attachment
(see http://rgl.faa.gov/Regulatory_and_Gu...LE/AC21-34.pdf, so if the foregoing is correct, just welding a tab is a major alteration??? This is called not being able to seperate the forest from the trees. Maybe the IA has his head up his ---.
 
djfraudman said:
I would guess that most people reading this, if they have ever bent a SC, will think that shoulder harness are a good thing. I also think that most will agree that it is perfectly legal to wrap the shoulder harness tiedown around the cross member or use bolt-on attachment
(see http://rgl.faa.gov/Regulatory_and_Gu...LE/AC21-34.pdf, so if the foregoing is correct, just welding a tab is a major alteration??? This is called not being able to seperate the forest from the trees. Maybe the IA has his head up his ---.
Click to expand...


welding makes it major... thats all.... not what you weld... no biggie..
 
The issue is not what everybody has done and got away with it, but what the regs and A/C's actually say. The aircraft in question is being built for sale, possibly to the head of the FSDO somewhere. Want to sign your name to something that isn't exactly correct.
 
S2D said:
The issue is not what everybody has done and got away with it, but what the regs and A/C's actually say. The aircraft in question is being built for sale, possibly to the head of the FSDO somewhere. Want to sign your name to something that isn't exactly correct.
Click to expand...

most things are not EXACTLY correct , I base my statement on my FSDO guy's answer to that question..... (and ONCE you get a RIGHT answer NEVER ask the question AGAIN!!)

He also thought that 43 2b being good data was a mistake on FAA's part.....
 
There's a simple answer, cut the tab off and bolt on a holder or wrap the shoulder harness around the cross-tube.
 
S2D said:
The issue is not what everybody has done and got away with it, but what the regs and A/C's actually say. The aircraft in question is being built for sale, possibly to the head of the FSDO somewhere. Want to sign your name to something that isn't exactly correct.
Click to expand...

Hey Brian, You are correct. We wouldn't ask Jeff to do anything he is uncomfortable with. I spoke with the Helena FSDO this afternoon and it looks like we can support a 337 based on the criteria described by Brian and SB. My hope is that we can make this process easier for the next guy.
 
dave said:
Hey Brian, You are correct. We wouldn't ask Jeff to do anything he is uncomfortable with. I spoke with the Helena FSDO this afternoon and it looks like we can support a 337 based on the criteria described by Brian and SB. My hope is that we can make this process easier for the next guy.
Click to expand...

That is great Dave. Thanks for spending the time and sharing this with the rest of us. It will definitely help.
 
If one wanted to do a stress test per Para 5 on a mock up what would be the pounds to test to?
 
For the shoulder restraint? Part 924 of the AC defines load and distribution. The prescribed value for the section for the normal category is a 170# occupant and a distribution of 60% of the load to the lap belt, 40% to the shoulder harness. Table 9-1 shows a pre-1969 type certificated airplane static test requirement at 704# in the forward direction.

Again, it's interesting that the determining factors are a 9g load applied statically for 3 seconds without causing permanent damage to the structure. If I endure a 9g load in an airplane for 3 seconds I'm having a bad day. Repairing the harness attach structure would be the least of my problems.

One of the structural engineer types on the site should be able to calculate the defection and failure of a 4130 tube of a defined length with a 704# load. That engineering should be adequate for the purposes of the AC requirements, shouldn't it? Or lacking that, a similar tube should be able to be tested with a welded tab in simulated conditions (same tube specs, same tube span) outside the airplane.
 
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