2.2 Major vs. Minor Repairs, Alterations & Preventive Maintenance

2.2 Major vs. Minor Repairs, Alterations & Preventive Maintenance

[!IMPORTANT] Core IA Responsibility: Correctly classifying maintenance activities is one of the most critical legal determinations tested on the FAA Inspection Authorization examination. Classifying a major repair or alteration as minor violates federal regulations, results in unapproved technical data being used, invalidates the aircraft's return to service, and subjects the IA to certificate suspension or revocation.

Every maintenance task performed on a civil aircraft falls into one of three primary regulatory categories: a repair, an alteration, or preventive maintenance. Within repairs and alterations, the Federal Aviation Administration draws a sharp, legally binding dividing line between major and minor actions. This classification determines three critical operational mandates: the level of technical data required (approved versus acceptable), the required documentation (FAA Form 337 versus standard logbook entry), and the authorized return-to-service personnel (an Inspection Authorization holder or repair station versus an A&P mechanic).

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1. Statutory Definitions and the Seven Appreciable Criteria (14 CFR 1.1)

The foundational definitions governing maintenance classification are codified in 14 CFR 1.1. To determine whether an action is major or minor, an Inspection Authorization holder must apply the statutory legal tests:

Major Alteration

Under 14 CFR 1.1, a 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

A minor alteration is defined simply as an alteration other than a major alteration. If an alteration is listed on the FAA Type Certificate Data Sheet (TCDS) or aircraft specification document, it is by definition not a major alteration under the first prong of the test, even if it involves component replacement.

Major Repair

A 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

A minor repair means a repair other than a major repair. Minor repairs require only technical data acceptable to the Administrator (such as AC 43.13-1B or manufacturer maintenance manuals) and may be approved for return to service by a certificated A&P mechanic with a standard logbook entry under 14 CFR 43.9.

The Seven Appreciable Airworthiness Factors

The phrase "might appreciably affect" is the core statutory benchmark. Notice that actual degradation is not required; the mere potential to appreciably affect any of the following seven factors triggers major classification:

1. Weight (e.g., substantial payload or empty weight shifts)
2. Balance (e.g., center of gravity shifts beyond envelope limits)
3. Structural Strength (e.g., cutting or splicing primary structural members)
4. Performance (e.g., changes to stall speed, rate of climb, or service ceiling)
5. Powerplant Operation (e.g., changes to manifold pressure, cooling airflow, or fuel delivery)
6. Flight Characteristics (e.g., changes in control feel, trim authority, or stability)
7. Other Qualities Affecting Airworthiness (e.g., electrical bus loading or environmental systems)

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2. 14 CFR Part 43 Appendix A: Codified Major Classifications

To eliminate ambiguity, the FAA codified non-exhaustive lists of major alterations and major repairs in 14 CFR Part 43 Appendix A. On the IA knowledge exam, candidates must know whether specific operations are codified under Appendix A:

Airframe Major Alterations (Appendix A(a)(1))

Alterations of the basic design of the following parts, or alterations of the following parts that might appreciably affect structural strength or flight characteristics:

• Wings, Tail Surfaces, and Fuselages: Splicing wing spars, changing wing dihedral, modifying control surfaces, adding external pods, or cutting fuselage pressurized skins.
• Engine Mounts and Landing Gear: Altering engine mount geometry, installing skis or floats, or modifying landing gear retraction mechanisms.
• Control Systems: Modifying push-pull tubes, control cables, bellcranks, pulleys, or adding dual flight control systems.
• Cabin Pressurization and Fuel Systems: Modifying fuel routing, installing auxiliary or extended-range fuel tanks, or changing pressurization control valves.

Powerplant Major Alterations (Appendix A(a)(2))

• Converting an engine from one model to another involving changes in compression ratio, propeller reduction gear ratio, or carburetion/fuel injection.
• Installing a turbocharger or supercharger system not listed on the engine TCDS.
• Modifying engine baffles or cowl flaps that appreciably affect engine cooling.
• Converting an engine to use unapproved fuels or electronic ignition systems.

Propeller Major Alterations (Appendix A(a)(3))

• Changes in propeller diameter, pitch, or blade contour beyond approved TCDS limits.
• Installing a propeller governor or pitch-control mechanism on an engine not previously certificated for it.
• Converting a fixed-pitch propeller to a controllable-pitch or constant-speed model.

Appliance Major Alterations (Appendix A(a)(4))

• Installing communication, navigation, or flight control equipment (such as autopilots, primary flight displays, or weather radar) that requires structural modifications or creates substantial electrical bus loads.

Airframe Major Repairs (Appendix A(b)(1))

• Splicing of Spars, Ribs, or Stringers: Any splice of an extruded or built-up wing spar flange, spar web, or fuselage keel member.
• Skin Repairs: Repairing stressed skin over pressurized areas, or repairs to wing or fuselage skins exceeding manufacturer structural repair manual (SRM) allowable damage limits.
• Welding Primary Structure: Straightening or welding damaged tubular steel engine mounts or fuselage trusses.

Powerplant Major Repairs (Appendix A(b)(2))

• Welding cracked crankcases or cylinder heads.
• Machining crankshafts or line-boring engine cases.
• Overhauling internal engine reduction gearboxes or supercharger drives.

Propeller Major Repairs (Appendix A(b)(3))

• Cold-straightening bent metal propeller blades.
• Repairing deep nicks, gouges, or blade erosion beyond minor dressed limits.
• Complete overhaul of controllable-pitch propeller governors.

Appliance Major Repairs (Appendix A(b)(4))

• Overhauling engine fuel pumps, carburetors, fuel injection metering units, magnetos, flight instruments, and hydraulic power pumps.

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3. Appendix A(c): Preventive Maintenance (The 32 Items)

14 CFR Part 43 Appendix A(c) opens with a limiting clause that candidates routinely skip: "Preventive maintenance is limited to the following work, provided it does not involve complex assembly operations." The list is closed — if an operation is not on it, it is not preventive maintenance, no matter how simple it looks. High-yield entries, with their actual Appendix A(c) item numbers:

Watch the qualifiers, because that is where the exam lives: item (21) excludes hydraulic hose connections; item (22) covers only prefabricated fuel lines, not fabricated ones and not oil lines; item (18) evaporates the moment a weight and balance computation is involved; and item (7) fabric patching stops at rib stitching.

[!WARNING] Preventive Maintenance Boundaries: A pilot-owner cannot fabricate replacement rigid hydraulic lines, cannot replace a hydraulic hose connection (excluded by item (21)), cannot overhaul carburetors, cannot balance control surfaces, cannot replace a wheel when a weight and balance computation is involved, and cannot perform structural sheet metal work. And nothing on the list is authorized if it involves complex assembly operations.

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4. Classification & Compliance Matrix

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5. Borderline Job Decision Framework & Exam Scenarios

When an IA evaluates an ambiguous maintenance task, they must apply a structured four-step decision model:

1. Step 1: Consult Type Design: Is the modification or replacement part explicitly listed on the aircraft Type Certificate Data Sheet (TCDS), aircraft specifications, or approved equipment list? If yes, it is generally a minor alteration.
2. Step 2: Check Appendix A: Is the specific operation listed in Part 43 Appendix A(a) or A(b)? If listed, it is codified as a major alteration or major repair.
3. Step 3: Evaluate the Seven Criteria: If not listed in Appendix A, might the work appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or airworthiness? If yes, it is a major repair or alteration.
4. Step 4: Assess Complexity: Can the repair be completed using accepted standard practices and elementary operations? If complex engineering or specialized tooling is required, it is classified as major.