Major Repairs

If a repair is called out in the manufactures maintenance manual but is also listed in FAR 43 appendix A (Major Repair) would this drive a FAA Form 337 with an FAA signature approval in block 3 or a FAA Form 8110-3 engineering substantiation for this?


First, you must determine if the repair is a Major Repair.

The FAA’s definition of a Major Repair is a repair:

(1) That, if improperly done, might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness; or

(2) That is not done according to accepted practices or cannot be done by elementary operations.

There is a good decision tree for determing a major or minor repair in Appendix 1 of AC 120-77 titled Maintenance and Alteration Data. You can download a copy of AC 120-77 from the “Advisory Circular” section of this website.

The majority of the time it will come down to the last statement on the decision tree – If improperly done, would it affect the airworthiness of the aircraft? – if the answer is yes, then it is a Major Repair

Secondly, you must determine if the data used to make the repair is FAA approved data.

As you noted, a Major Repair needs to be documented on a FAA Form 337. Block 3 however would only be required if there is no approved data for the repair. These types of approvals are called “field approvals” and are not so widely used anymore. The only other option would be to have the data approved on an FAA Form 8110-3 by a DER. You would still need to record the Major Repair and reference the 8110-3 approved data on an FAA Form 337.

I would think if the manufacture authorizes this repair in their maintenance manuals then there seems little need to have this approved through the FAA or DER. You are correct, but a determination still needs to be made whether it is major or minor for documentation purposes.

On this same subject how is this viewed through the use of manufactures structural repair manual or overhaul manual?

ANSWER: It is viewed in the same way.

How would I determine if these manuals or sections of them are FAA accepted or approved?

ANSWER: The aircraft Type Certificate Data Sheet (TCDS) usually has a note regarding approved service documents. You can download a copy of the TCDS for a specific aircraft by following the link in the “Reference Links” section of this website.

What is the standard process of AEG involvement with manufactures maintenance manuals on approval or acceptance?

ANSWERS: The FAA Aircraft Evaluation Group (AEG) reviews and coordinates maintenance and operational aspects of proposed documents for acceptance. The Aircraft Flight Manual and Instructions for Continued Airworthiness (Maintenance Manuals, Structure Repair Manuals, etc.) are included in those documents.

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