337 for rib repair

[4945]

I've found an A&P to work with to re-cover a set of wings. The wings need either some new ribs or repairs on ribs where the cap flanges broke at the spar. The A&P pointed out that rib repairs need to be documented on a 337 as a major repair, but replacement doesn't, since it's replacing a part with a new part authorized for the airplane.

Has anyone done a similar repair and documented it on a 337? Repair would be easier and cheaper than replacement, unless the paper work turns fiddly.

Gary

[4945]

I just looked it up. Replacing a rib would require a 337, as well, if I'm reading Part 43 right.

[6643]

Replacing a main rib is a major repair. It is questionable if a nose rib or trailing edge qualifies as a main rib. I say no. If I'm wrong, I'm sure someone will chime in.

Any major repair (or alteration) must be recorded on a form 337. The kicker is, every form 337 requires approved data. If you're just removing and replacing a rib by riveting, then you can cite AC43.13-1b (or whatever it is today.) If you're splicing e.g. a longeron and you can find an example in AC43.13 showing how to make an equivalent repair, you can cite that and you're good to go. If you're making a structural repair on a 120/140 and can't find applicable data in AC43.13 you might want to re-think what you're doing...

[rominoff]

Replacement of a wing main rib is an airframe major repair when replacement is by fabrication such as riveting or welding. As I read it, either repair or replacement will get a 337.

[4945]

Replacing a main rib is a major repair. It is questionable if a nose rib or trailing edge qualifies as a main rib. I say no. If I'm wrong, I'm sure someone will chime in.

Any major repair (or alteration) must be recorded on a form 337. The kicker is, every form 337 requires approved data. If you're just removing and replacing a rib by riveting, then you can cite AC43.13-1b (or whatever it is today.) If you're splicing e.g. a longeron and you can find an example in AC43.13 showing how to make an equivalent repair, you can cite that and you're good to go. If you're making a structural repair on a 120/140 and can't find applicable data in AC43.13 you might want to re-think what you're doing...

Thanks for the reply,

There's a somewhat similar arrangement in the 43.13, but not exact. It shows a repair where a one-piece rib attaches to a spar. The the 140 rib center section attaches at the capstrips and on the webs. The capstrip broke where it attaches to the spar, but the webs are still firmly attached. There are several similar repairs on the wings that were there when I bought them. Someone posted a photo of a doubler/reinforcement made by Cessna to fix this exact problem on this forum, and these ribs have several of those. They're thicker than the rib, 0.032". Apparently this was an issue on non-metal wing 140s and 170s, and Cessna sent a letter to dealers explaining how to use these parts to repair ribs that had broken. That was on the old association website, and was lost when everything shifted.

Everything else on the ribs is fine. The webs are straight, nothing's bent, nothing else is cracked. The only problem is the short piece of capstrip that extends over the spar and has one rivet holding it on a half dozen ribs between both wings.

I'm going to contact Cessna to see if they have anything that might help. If I could dig up that letter and a drawing or photo of the doubler, that would serve as approved data for the repair.

Gary

[4004]

Study AC43-13-!B page 4-29 upper left illustration. not seeing your exact problem, however, I think as a "typical repair', with some latitude permitted, this reference cited, probably will solve your problem. I did something similar on a Piper Clipper PA-16 wing that I was recovering many, many years ago - possibly in the old CAM 18 days. 2C
Everyone triggered my memory, I was one of the many invited to submit mark- ups to the document when it was being revised in the 90s - I had just retired and spent a month doing such.

[6643]

That was on the old association website, and was lost when everything shifted.

If you can remember anything identifiable about that post I may be able to dig it up. Date, specific text, etc.

[4945]

That was on the old association website, and was lost when everything shifted.

If you can remember anything identifiable about that post I may be able to dig it up. Date, specific text, etc.

I can't remember the year, let alone the date. The best search terms I can come up with is rib reinforcement or rib doubler. I posted a reply saying that it looked like .032 metal, which the poster confirmed. I really should have downloaded it when I saw it. You looked for it in the past and couldn't find it.

I posted the question on this thread to see if anyone has done any rib repair on a 337 to see what authorized data they used.

I sent an email to Cessna explaining the situation and asking if they have any related records. If I can just show that the doubler/reinforcement was a Cessna part, I'm most of the way to success. Repairing that tab would be the least costly and safest way to fix the problem. Replacing the rib section requires removing the nose and trailing edge ribs to allow the new part to be riveted in place. Yet it would require the least documentation.

Gary

[4004]

Prof. John C: It may be an appropriate time for you include your lecture, for the benefit of the "new folks", about 337 and "approved data" citing the 3 criterion listed in the AC43.13-1B, whereby the AC43.13-1B can become "approved" data rather than just "acceptable" data. Any A&P can generate the 337 and with an IA sign off ( or the A&P does his own) the 337 goes directly to OK city without any FAA FSDO participation like we had to do years ago! The 337 doesn't have to be too detailed, just have to reference the AC location in the verbiage.

[6643]

You mean this?

Types of Approved Data

Approved data to be used for major repairs and major alterations may be one or more of the following.

1. Type Certificate Data Sheets
2. Aircraft Specifications
3. Supplemental Type Certificates (STC's) (Note: Persons interested in using an STC must have approval in accordance with 49 U.S.C., section 44704, from the holder of the STC, prior to it's use.)
4. Airworthiness Directives (AD's)
5. Manufacturer's FAA Approved Data (DOA)
6. Designated Engineering Representative (DER) Approved Data With FAA Form 8110-3, Statement of Compliance (Note: This type of data usually requires additional approval.)
7. Designated Alteration Station (DAS) Approved Data
8. Appliance Manufacturer's FAA Approved Manuals (Excluding Installation Instructions)

AC 43.13-1, Acceptable Methods, Techniques, and Practices (Aircraft Inspection and Repair), may be used directly as approved data (for repairs only) without further approval only when there is no manufacturer repair or maintenance instructions that address the repair and the user has determined that it is:
• appropriate to the product being repaired;
• directly applicable to the repair being made; and
• not contrary to manufacturer's data.

AC 43.13-2, Acceptable Methods, Techniques, and Practices – Aircraft Alterations 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:
• appropriate to the product being altered;
• directly applicable to the alteration being made; and
• not contrary to manufacturer's data.

FAA FIELD APPROVAL (FAA FORM 337) issued for duplication of identical aircraft may be used as approved data only when the identical alteration is performed on an aircraft of identical make, model, and series by the original modifier. (I recall the form 337 used to have a block you could check if you were applying for multiple approvals, sort of like a personal STC.)

FAA Form 337s approved in 1955 or earlier may be used as approved data.

Previously approved 337s from 1956 and later can be used as acceptable data in support of a field approval.