Current ACA process specs

[Big Ed]

See posts below for ACA factory covering process specifications.

I'm not an expert on FAA rules and regs, but here is how I understand it: covering an aircraft is a major repair under the FAA definition, and must be done using FAA approved data. Specifications used by the Type Certificate holder are approved data, and can be cited in the 337 documenting the major repair.

Key point: this is not an STC. We are following the TC.

Any IA's care to correct or add more to this discussion?

I don't know whether permission from ACA is required to use these specs, like it would be for an STC. I purchased my covering kit from them, partially as a rationale for using the specs.

 

[Big Ed]

Fabric attach specification

 

[Big Ed]

Paint spec

 

[Big Ed]

Frame powdercoat spec

 

[Bob Turner]

If the factory uses it, it is approved data. Major repair, no further permission required.

If it is changed to, say, Stitts or Stewarts, then it is a major alteration, and you need specific permission in writing for your N- number - the first time you do it! Written permission is free for fabric systems, usually.

Both require you to file a 337. When filing a 337, remember, anything listed on the back must be "approved data."

 

[Big Ed]

If the factory uses it, it is approved data. Major repair, no further permission required.

Thanks Bob! Seems pretty cut and dried.

 

[Bob Turner]

Actually, it takes some study to understand the 337. I am one of those lucky guys who can pass a multiple choice test without knowledge of the subject matter - but unhappily that can place us lucky folks in positions beyond our competence.

Hence, when I got my IA, I had an incomplete knowledge of such things as "approved data." Subsequent study has helped.

The 337 has too many uses - major repair, major alteration using approved data (factory, maybe AC 43-13) or STC, or field approval. Then it requires either two or three signatures. (Also used for ADSB, and I still don't understand that).

Mechanics everywhere do not understand this process. I routinely see 337s signed by an IA without approved data of any sort. I bet I have fixed one a year with field approvals after the fact, and am struggling with one as we speak. Even the FAA is fuzzy about the rules.

 

[Bartman]

Thanks for posting those Ed, I'll stick this thread to the top so it's easy to find.

 

[Bob Turner]

I just heard that the factory has for some time been using what is essentially the Stewart process, but with a PPG finish coat. My iPad won't open Ed's documents above, so they may say the same thing.

The PPG paint is something like "Delfleet Evolution" but that is from memory. I will correct it soon. (corrected - it is Delfleet Evolution primer, and Delfleet Essential, or Delta, for top coat. There is some discussion of clear coat, but even modern automobiles do not survive long with clear coats.)

Any truth to that rumor?

Well, I opened Ed's Service Letters on the big computer - they go into downloads, then become readable. Without getting too carried away, it seems like the factory approves all normal adhesives, such as Stitts and Ceconite, and additionally 3M 30NF, which is quite similar to the Stewarts glue. A Stewarts rep is quite peeved at me for even suggesting that the two are similar, but here we have a major airframe manufacturer using the 3M stuff instead of the significantly more expensive Stewarts.

Now here are some thoughts: My airplanes all have STCs for Stitts and Ceconite from when you could use any top coat you wanted, so I can and do use Butyrate dope, Acrylic enamel, or whatever. House paint is legal on those aircraft. But Stewarts is good stuff - the glue and initial UV blocker (called Eko-Fill) are water based, and easy to apply with good results. They are expensive, and have a limited shelf life, but I like to use them.

I am not good enough at measuring or spraying to even attempt the Stewarts top coat. I do have the equipment to spray the PPG stuff, but it scares me a bit (cyano-acrylates are really toxic, as are urethanes). I have often lamented that Stewarts did not get approval for top coats other than their own proprietary formula, but here, at least for ACA aircraft, you can apparently use water base glues as with Stewarts, then finish up with PPG and flex agents. I have heard of folks getting exceptional results with the Stewarts top coats, but so far have not seen an example in the flesh - the ones I have seen are flawed, in the sense that they were sprayed by hobbyists with less than spectacular results.

I find myself skeptical that the factory can get good results by spraying Delfleet Primer directly on bare fabric, but hey - they do look good! And apparently, except in the slipstream, they do last at least two decades.