The super 170

[FredMa]

Is that a mechanic or a mechanic with his IA doing the work for you? It would definitely require a 337.

[54170b]

IA.
Got my cleave land tool today, gonna finish this tomorrow hopefully!

[54170b]

And according to the faa, an IA has the authority to decide if it requires a 337 or not. If you think it should, then if you ever do this mod, get a 337.

[FredMa]

Yep, and the IA performing annuals in the future can decide that it should of had a 337. It would be much easier to make sure now than have to fix a paperwork problem in the future.

[c170b53]

I've been trying to avoid commenting and I'm sure I'm not alone. There's lots of stuff you can get away with because the visual clues that something has been altered can be very subtle and or a natural progression of the design has taken place. Take the fuel vent discussion, the relocation of the vent in later models was an improvement. Some who desire to maintain the original production, have no desire to change. Some may have different wings installed with respect to the tanks and have no need for the goose neck. Funny in that case that one member would have a misunderstanding of the age of a member when clearly we all know the time they are talking about is the difference. One guy has time in while the other sounds relatively new to our planes. The reason I mention this in this thread is because essentially the same thing is occurring here.
To say that you have changed the design of a structural member and some of the secondary structure associated with the carry through spars (ie; the attachment of the forward cap) under the advice that this is not a significant modification, is a mistake in my mind and I believe I'm not alone in this thought. If you had some engineering support you might have had the opportunity to make your own STC but now I fear you've only set back your project rather than move it closer to completion. There's lots of stuff that can be undertaken to these planes but the basis for approval often limits what can be done. Good luck and in the future you might want to consider undertaking the area 51 approach as your likely to be operating in stealth mode .

[minton]

And according to the faa, an IA has the authority to decide if it requires a 337 or not. If you think it should, then if you ever do this mod, get a 337.

In the past I have worked with the FAA to determine if there is a need for a determination of Major or Minor. They will be glad to issue a written determination which would follow along with the log books. I would never take that on myself as an AI if there were any question.

Just my humble opinion.

[bagarre]

Since this involves both carry thru spars and is replacing a structural component of the fuselage with a substitution of materials (roof skin thicker with holes in it), it's not difficult to see how most folks might call this a major alteration.


Does an IA have the authority to decide if its a major alteration or does he have the responsibility to determine if its a major alteration based on the guidance provided in 43 appendix a?

[minton]

Since this involves both carry thru spars and is replacing a structural component of the fuselage with a substitution of materials (roof skin thicker with holes in it), it's not difficult to see how most folks might call this a major alteration.


Does an IA have the authority to decide if its a major alteration or does he have the responsibility to determine if its a major alteration based on the guidance provided in 43 appendix a?

I have to chime in here:

First, just an observation, which is a few of our forum readers posts have lead me to believe that they operate under some rules that are not within the scope of CAT 3 certificated aircraft but may fall under A/C 20-27G.

I choose not to address who has what authority.

43.13 A/ does address major vs minor within CAT 3 aircraft. I myself, if presented this project, would determine it to be a major project and has elements that throw it into the "Alteration category". This then presents the need to get with the owners and give him or her your views and recommend that a higher authority (FAA) get involved before the drilling commences. I would go this route to get the "Authorized Official" supportive paper trail established to get me off of the hook if I sign off either the project or annual.

My other take on this is, if I were to come upon this modification during an annual inspection the next thing I would do is look for the documentation. If I was not able to find any that satisfied me I'd be calling the owner first and if required, my PMI.

Trying to get approval after the fact is not a good place to begin.

If the project can be supported by prior "approved" modifications or factory installations and is a duplication of such, the A/C 43-210 process should have been used and approved prior to commencement.

I see no "Sky Light" or the like referenced in the 170B IPC. If it were included there would only be the need for a reference to the parts, log book signature and FAA Form 337.

I have included references to some of the issues involved:
FAA Guidance manual 8900.1 chg 159
A/C 43.13 Inspection, Repairs and Alterations
FAR 21.303 Owner producted parts
A/C 43-210 Application & Guidance for Field Approvals
A/C 23-27 Fabrication and Replacement Parts and Substitution
Cessna 170B series IPC
Cessna 100 series service manual
Other "Approved or Accepted Data" ie 337's, STC's, etc.

Again, just my humble opinion

[54170b]

Thanks, Minton. But I kindly ask that you stay out of my approval process, because you do not know every detail.
I am on this form to share what I am doing, and if I am going to be argued with, I will leave. I have heard opinions from both sides, but MY IA is on the side of no major alteration: Structure was not changed, structure and aerodynamics are as good as or better than the factory installation.
Also if you read, you will find that there is little to no pressure on that section of the skin. What pressure is there is handled by the frame.

[minton]

Thanks, Minton. But I kindly ask that you stay out of my approval process, because you do not know every detail.
I am on this form to share what I am doing, and if I am going to be argued with, I will leave. I have heard opinions from both sides, but MY IA is on the side of no major alteration: Structure was not changed, structure and aerodynamics are as good as or better than the factory installation.
Also if you read, you will find that there is little to no pressure on that section of the skin. What pressure is there is handled by the frame.

10-4 You are right, I don't. Others should'nt either but there are concerns over other (less informed) than you or I. BUT I'll stay out of it at your request

[54170b]

This is a remarkable tool. I found that cheap masking tape dosent do the job, then sticks hard to the surface, but blue painters tape works great; dosent stick, and no marring.

[54170b]

It actually handled the curves quite well

[54170b]

It gave the edges a real nice, factory look.

[54170b]

Minton, the instrument panel WAS field approved.

[jrenwick]

Thanks, Minton. But I kindly ask that you stay out of my approval process, because you do not know every detail.
I am on this form to share what I am doing, and if I am going to be argued with, I will leave. I have heard opinions from both sides, but MY IA is on the side of no major alteration: Structure was not changed, structure and aerodynamics are as good as or better than the factory installation.
Also if you read, you will find that there is little to no pressure on that section of the skin. What pressure is there is handled by the frame.

10-4 You are right, I don't. Others should'nt either but there are concerns over other (less informed) than you or I. BUT I'll stay out of it at your request

Wow. I like this. It's so much better when "basis of approval" discussions can focus on facts about what actually got approved, rather than opinions about what might or might not become approved. Moderators, you can set the tone for this. What everyone needs to understand (and our moderators have said this over and over again) is that approval for non-run-of-the-mill mods and repairs is an understanding between the IAs who approve them and their regional FSDOs. An owner who wants to make unusual modifications to certified aircraft needs to get to know an IA who has a productive, cooperative relationship with the FSDO, and proceed as recommended by the IA who's going to sign it off. Once the work is done and properly documented, the mod is legal. That's that. Factual stories about what can become approved are what we're interested in. A personal opinion that a particular mod could or should not ever become approved is not of much value, as long as everyone understands what the actual approval process is.