Major vs. Minor

(b) The holder of a mechanic certificate...

(c) The holder of a repairman certificate...

(d) A person working under the supervision of a holder of a mechanic or repairman certificate...

(e) The holder of a repair station certificate...

(f) The holder of an air carrier operating certificate or an operating certificate issued under Part 121 or 135...

(j) A manufacturer may -

(1) Rebuild or alter any aircraft, aircraft engine, propeller, or appliance manufactured by him under a type or production certificate..."

So, the person performing the maintenance is the one who decides if the repair or alteration is major or minor and that person could be a mechanic, a repairman (who, by the way, must be employed by a repair station), a person under the direct supervision of a mechanic or repairman, or a repair station. The manufacturer may only rebuild or alter the aircraft unless they are certificated as a repair station as well.

So now we know who is responsible to make the determination on whether a repair or alteration is major or minor. Great, but how will they decide?

The definitions regulation says this:

14 CFR Part 1.1

Major alteration means an alteration not listed in the aircraft, aircraft engine, or propeller specifications -

(1) That 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.

Minor alteration means an alteration other than a major alteration.

Major repair means 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.

Minor repair means a repair other than a major repair.

Not much help when we are considering a specific repair or alteration. As mentioned in 43.3 (a) above, Appendix A to Part 43 also provides us with a list of what is considered a major alteration or major repair. This list is a part of the regulations that is outdated and difficult at times to apply to a particular situation. I will not include all of the descriptions here but please take the time to pull out your Regulation Book and take a gander at the list.

When you look at the list you will find it obviously has not been revised significantly since its inception April 23, 1964. However, it remains as the list used to help us make the major/minor decision. Because of the subjectivity introduced here, it is far better to err on the safe side and execute the 337 when in doubt. That sounds simple enough but there is another big difference between a major repair/alteration and a minor repair/alteration. Major repairs or alterations must be performed in accordance with approved data.

Considering the difficulty we all face now in obtaining approved data either from the FAA or from manufacturers, many are tempted, when on the fence, to subjectively decide that the repair or alteration is minor and does not need a 337 or approved data. My advice? Don't take the risk. If the repair you are performing could be construed as major by the FAA or a future purchaser of the aircraft, figure out how to get the approved data.

There is one exception to the requirement for use of an FAA Form 337. It is found deeper into Appendix B (b) to Part 43.

"(b) For major repairs made in accordance with a manual or specifications acceptable to the Administrator, a certificated repair station may, in place of the requirements of paragraph (a) [FAA Form 337] -

(1) Use the customer's work order upon which the repair is recorded;

(2) Give the aircraft owner a signed copy of the work order and retain a duplicate copy for at least two years from the date of approval for return to service of the aircraft, airframe, aircraft engine, propeller, or appliance;