Airworthy Prep14 CFR Part 43 Appendix A lists examples of major alterations and major repairs (split into airframe, powerplant, propeller and appliance) and the full list of work that counts as preventive maintenance (14 CFR part 43, appendix A). The tests behind those lists are the definitions in 14 CFR 1.1: a major alteration or major repair might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics or other airworthiness qualities, or is not done according to accepted practices or cannot be done by elementary operations. Anything that is not major is minor, and the classification decides whether a logbook entry is enough or you also need FAA Form 337.
The definitions in 14 CFR Part 1
These terms are listed by name in the Aviation Mechanic ACS, FAA-S-ACS-1 as element AM.I.I.K6 (p. 14).
| Term | 14 CFR 1.1 definition (shortened) |
|---|---|
| Major alteration | An alteration not listed in the aircraft, engine or propeller specifications that (1) might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics or other qualities affecting airworthiness, or (2) is not done according to accepted practices or cannot be done by elementary operations |
| Major repair | A repair that (1) if improperly done, might appreciably affect the same list of qualities, or (2) is not done according to accepted practices or cannot be done by elementary operations |
| Minor alteration | An alteration other than a major alteration |
| Minor repair | A repair other than a major repair |
| Preventive maintenance | Simple or minor preservation operations and the replacement of small standard parts not involving complex assembly operations |
| Maintenance | Inspection, overhaul, repair, preservation and the replacement of parts, but excludes preventive maintenance |
Note the major repair test says “if improperly done”: it asks what a bad repair could do. And each definition’s two halves are joined by “or,” so either half makes the work major (14 CFR 1.1).
Repair or alteration? Decide that first
Per the Aviation Maintenance Technician Handbook - General, FAA-H-8083-30B, a repair basically returns the aircraft to its previous, unaltered condition, such as replacing magnetos, an exhaust system, tires or brakes. Even replacing a whole engine is still a repair if it is the engine properly specified for that aircraft. An alteration always changes the aircraft from its previous state, such as installing winglets, new avionics, or an engine not listed in the type certificate data sheet (AMT General handbook, ch. 2, p. 2-15).
Then decide major or minor. The handbook points you to Part 1 and Appendix A “for additional clarification and examples” (ch. 2, p. 2-15).
What 14 CFR Part 43 Appendix A contains
Appendix A has three paragraphs (14 CFR part 43, appendix A):
- (a) Major alterations, in four groups: airframe, powerplant, propeller, appliance.
- (b) Major repairs, in the same four groups.
- (c) Preventive maintenance, a list of 31 items.
The handbook calls the appendix “a comprehensive, but not exclusive, list” (ch. 2, p. 2-20). So if a job is not on the major list, you still apply the Part 1 test.
The airframe, powerplant and propeller alteration lists apply only when the change is not listed (or, for propellers, not authorized) in the FAA aircraft, engine or propeller specifications (appendix A, paras (a)(1) to (a)(3)).
Major alteration and major repair examples by class
Selected items only, with paragraph numbers so you can find each one.
| Class | Major alteration examples (para (a)) | Major repair examples (para (b)) |
|---|---|---|
| Airframe | Wings, tail surfaces, fuselage, engine mounts, control system, landing gear (a)(1)(i)-(vi); empty weight or balance changes that increase maximum certificated weight or CG limits (a)(1)(xi); basic design changes to fuel, oil, electrical, hydraulic or exhaust systems, among others (a)(1)(xii) | Spars (b)(1)(iv); fuselage longerons (b)(1)(xiii); damaged metal or plywood stressed covering over six inches in any direction (b)(1)(xxii); splicing skin sheets (b)(1)(xxiv); replacing fabric on wings, fuselages, stabilizers or control surfaces (b)(1)(xxvii); repairing fuel and oil tanks (b)(1)(xxviii) |
| Powerplant | Converting an engine to another approved model with changes such as compression ratio (a)(2)(i); installing an accessory not approved for the engine (a)(2)(iii); converting to a fuel grade not in the engine specifications (a)(2)(vi) | Separating the crankcase or crankshaft of a reciprocating engine with an integral supercharger (b)(2)(i); special repairs to structural engine parts by welding, plating or metalizing (b)(2)(iii) |
| Propeller | Changes in blade, hub, or governor or control design (a)(3)(i)-(iii); installing a governor, feathering or de-icing system (a)(3)(iv)-(v) | Any repair to, or straightening of, steel blades (b)(3)(i); shortening blades (b)(3)(iii); overhaul of controllable pitch propellers (b)(3)(xii) |
| Appliance | Basic design changes not made per the manufacturer’s recommendations or an AD (a)(4); radio design changes that affect performance such as frequency stability or sensitivity (a)(4) | Calibration and repair of instruments (b)(4)(i); calibration of radio equipment (b)(4)(ii); overhaul of pressure type carburetors (b)(4)(v) |
The airframe major repair list has a lead-in that matters. It covers repairs “involving the strengthening, reinforcing, splicing, and manufacturing of primary structural members or their replacement, when replacement is by fabrication such as riveting or welding” (appendix A, para (b)(1)).
The preventive maintenance list in Appendix A(c)
Preventive maintenance “is limited to” the listed work, “provided it does not involve complex assembly operations” (appendix A, para (c)). Selected items:
| Item | Preventive maintenance (para (c)) | The limit written into the item |
|---|---|---|
| (1) | Removal, installation and repair of landing gear tires | |
| (5) | Replacing defective safety wiring or cotter keys | |
| (7) | Simple fabric patches | Not requiring rib stitching or removal of structural parts or control surfaces |
| (17) | Replacing bulbs, reflectors and lenses of position and landing lights | |
| (18) | Replacing wheels and skis | Only where no weight and balance computation is involved |
| (19) | Replacing any cowling | Not requiring removal of the propeller or disconnection of flight controls |
| (20) | Replacing or cleaning spark plugs and setting the gap | |
| (21) | Replacing any hose connection | Except hydraulic connections |
| (22) | Replacing prefabricated fuel lines | |
| (31) | Removing and replacing panel-mounted nav and comm units with tray-mounted connectors | Excludes automatic flight control systems, transponders and DME; an operational check is required before use |
Watch the right-hand column: a hose is preventive maintenance, a hydraulic hose is not.
Who may do it: except for sport pilots, a part 61 pilot may perform preventive maintenance on an aircraft they own or operate that is not used under part 121, 129 or 135 (14 CFR 43.3(g)). Sport pilots are limited to light-sport category aircraft they own or operate (43.3(g)). A person holding at least a private pilot certificate may approve the aircraft for return to service after that preventive maintenance (14 CFR 43.7(f)).
How each class is recorded
| Work | Data needed | Record | Who may approve for return to service |
|---|---|---|---|
| Preventive maintenance | Maintenance record entry under 43.9(a) | Mechanic (43.7(b)), or a pilot under 43.7(f) and (h) | |
| Minor repair or minor alteration | Acceptable data, such as the maintenance manual or AC 43.13-1 (AMT General handbook, p. 2-15) | Maintenance record entry under 43.9(a) | Appropriately rated mechanic (14 CFR 65.85(a), 65.87(a)) |
| Major repair or major alteration | Approved data, such as ADs, STCs, TCDS or FAA-approved service bulletins (AMT General handbook, p. 2-15) | Entry under 43.9(a) plus FAA Form 337 (43.9(d)) | Inspection authorization holder, if the work followed approved data (14 CFR 65.95(a)(1)) |
Every class gets the 43.9(a) entry (14 CFR 43.9). Major work adds the form. Under part 43, appendix B, para (a), you execute Form 337 at least in duplicate, give a signed copy to the owner, and send a copy to the FAA Aircraft Registration Branch in Oklahoma City within 48 hours after return to service. A repair station may use a work order and maintenance release instead, for major repairs only (appendix B, para (b)).
Repair stations, manufacturers and air carriers have their own approval routes (14 CFR 43.7(c) to (e)). A rated mechanic may approve work they performed, supervised or inspected “excluding major repairs and major alterations” (14 CFR 65.85(a), 65.87(a)). The one exception is certain major work on light-sport category aircraft done to the manufacturer’s instructions (65.85(b), 65.87(b)). An inspection authorization holder may approve after a major repair or major alteration done with approved technical data (14 CFR 65.95(a)(1)). A mechanic also may not perform major repairs to, or major alterations of, propellers, or any repair to or alteration of instruments (14 CFR 65.81(a)).
AC 43.9-1G says the person who performs or supervises the major work prepares the form (para 8, p. 2). For a walk-through, see our guide to FAA Form 337 for major repairs and alterations. For logbook wording, see 14 CFR 43.9 vs 43.11 maintenance record entries.
What the A&P General test expects
Subject I of the General test, Regulations, Maintenance Forms, Records, and Publications, makes up 5 to 10 percent of the 60-question test (Companion Guide to the mechanic ACS, FAA-G-ACS-1, Change 2, p. 13). The ACS lists these related elements (FAA-S-ACS-1, pp. 14-15):
- AM.I.I.K5: the purpose and use of FAA forms, including Form 337.
- AM.I.I.K6: Part 1 terms, naming major alteration, major repair, minor alteration, minor repair and preventive maintenance.
- AM.I.I.K7: criteria and responsibility for determining whether a repair or alteration is major or minor.
- AM.I.I.K16: the difference between approved data and acceptable data, and when each is required.
- AM.I.I.S1 and S2 (skill elements): complete an FAA Form 337, and examine one for accuracy.
Common mistakes
- Treating the Appendix A list as complete. It is “not exclusive” (AMT General handbook, p. 2-20). Unlisted work can still be major under 14 CFR 1.1.
- Calling an engine swap an alteration. The same approved engine is a repair; an engine not in the TCDS is an alteration (AMT General handbook, p. 2-15).
- Missing the exceptions inside preventive maintenance items. Hydraulic hose connections (c)(21), wheels needing a weight and balance computation (c)(18) and cowlings needing propeller removal (c)(19) are outside the list.
- Assuming an A&P signs off major work. 65.85(a) and 65.87(a) exclude major repairs and major alterations from the mechanic’s return-to-service approval.
Try one (an original question)
Which of these jobs is preventive maintenance under 14 CFR part 43, appendix A?
A. Replacing a prefabricated fuel line.
B. Replacing a hydraulic hose connection on the brake system.
C. Replacing the fabric covering on a wing.
Answer: A. Replacing prefabricated fuel lines is item (c)(22). B is the trap: item (c)(21) allows replacing any hose connection “except hydraulic connections.” C is an airframe major repair, item (b)(1)(xxvii).
A short study plan
- Read the 14 CFR 1.1 terms in the table above.
- Read part 43, appendix A, then reread paragraph (c), underlining each limit.
- Read 43.3, 43.7, 43.9 and 65.81 to 65.95.
- Read AMT General handbook chapter 2, pages 2-15 to 2-20.
- Quiz yourself with the Regulations, Maintenance Forms, Records, and Publications topic page, and see the A&P General written test guide for the other subjects.
All regulation text here is as of October 2026 (eCFR current as of October 1, 2026).
Common questions
Major alteration vs minor alteration: what is the difference?
A major alteration is not listed in the aircraft, engine or propeller specifications and either might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics or other airworthiness qualities, or is not done according to accepted practices or cannot be done by elementary operations. A minor alteration is any alteration that is not major (14 CFR 1.1).
What is a major repair? Some examples
A repair that, if improperly done, might appreciably affect airworthiness qualities, or is not done according to accepted practices or cannot be done by elementary operations (14 CFR 1.1). Examples: repairs to spars or engine mounts, splicing skin sheets, replacing wing fabric, straightening steel propeller blades and calibrating instruments (14 CFR part 43, appendix A, para (b)).
What is the definition of a minor repair?
A repair other than a major repair (14 CFR 1.1). It is recorded with a 43.9 maintenance record entry and needs only acceptable data (AMT General handbook, ch. 2, p. 2-15).
Where is the preventive maintenance list in Part 43?
In appendix A, paragraph (c), which has 31 items. The work only qualifies if it does not involve complex assembly operations (14 CFR part 43, appendix A, para (c)).