2.1 Scope of Part 43 & Authorized Maintenance Personnel

2.1 Scope of Part 43 & Authorized Maintenance Personnel

[!NOTE] Regulatory Foundation: 14 CFR Part 43 establishes the core regulatory framework governing the maintenance, preventive maintenance, rebuilding, and alteration of United States civil aircraft. For candidates preparing for the FAA Inspection Authorization (IAR) examination, Part 43 defines jurisdictional boundaries, identifies who holds legal authority to turn wrenches and approve work, and establishes strict limits on supervised work and required inspections.

Civil aviation safety in the United States relies upon rigorous, codified standards for aircraft maintenance. Title 14 of the Code of Federal Regulations (14 CFR) Part 43 defines the statutory rules that dictate how civil aircraft, their engines, propellers, appliances, and component parts must be maintained and altered. As an Inspection Authorization (IA) holder, you will serve as a primary regulatory gatekeeper, ensuring that all work performed under your supervision or presented for your inspection strictly complies with these foundational rules.

---

1. Statutory Scope and Applicability of 14 CFR Part 43 (§ 43.1)

Under 14 CFR 43.1(a), the rules of Part 43 apply directly to the maintenance, preventive maintenance, rebuilding, and alteration of:

1. Any aircraft having a U.S. airworthiness certificate (including standard and special airworthiness certificates);
2. Any foreign-registered civil aircraft used in common carriage or carriage of mail under the provisions of 14 CFR Part 121 or 14 CFR Part 129; and
3. Airframes, aircraft engines, propellers, appliances, and component parts of such aircraft.

Exclusions Under 14 CFR 43.1(b)

The scope of Part 43 is not universal. A frequent area of testing on the FAA IA examination involves aircraft categories excluded from Part 43 jurisdiction under 14 CFR 43.1(b):

• Amateur-Built Experimental Aircraft: Under § 43.1(b)(1), Part 43 does not apply to any aircraft for which the FAA has issued an experimental airworthiness certificate, unless the FAA has previously issued a different kind of airworthiness certificate for that aircraft. An experimental amateur-built (E-AB) aircraft built from a kit or plans that has held only an experimental certificate is completely exempt from Part 43 maintenance and alteration rules.
• The Prior Standard Certificate Distinction: If a production aircraft originally manufactured under a standard airworthiness certificate (such as a Beechcraft Bonanza or Cessna 172) is later placed into the experimental category for research and development, exhibition, or market surveys, it remains subject to 14 CFR Part 43. This distinction is a classic FAA exam trap: the aircraft's certification history determines applicability, not merely its current operating placard.
• Light-Sport Aircraft (LSA) Distinctions: Under § 43.1(b)(2), Part 43 does not apply to an aircraft issued an experimental airworthiness certificate under § 21.191(i)(3) or (l) that was previously issued a special airworthiness certificate in the light-sport category under § 21.190 — the classic E-LSA transition case. Factory-built Special Light-Sport Aircraft (S-LSA) certificated under § 21.190 remain inside Part 43, subject to the tailored provisions of § 43.1(d) for products not produced under an FAA approval.
• Small Unmanned Aircraft: Under § 43.1(b)(3), Part 43 does not apply to any aircraft operated under Part 107, except as described in § 107.140(d).
• Operating Limitations Nexus: Although pure amateur-built experimental aircraft are exempt from Part 43 performance rules, their FAA operating limitations issued under 14 CFR 91.319 invariably require an annual condition inspection performed by the original builder holding a repairman certificate or an A&P mechanic. Operating limitations frequently instruct the inspector to use the scope and detail of 14 CFR Part 43 Appendix D, but this procedural reference does not bring the aircraft under Part 43 maintenance rules.

---

2. Authorized Persons Under 14 CFR 43.3

Federal law prohibits unauthorized individuals from performing maintenance on civil aircraft. 14 CFR 43.3 establishes an exhaustive list of authorized persons who may perform maintenance, preventive maintenance, rebuilding, and alterations:

The General Prohibition (§ 43.3(a))

Paragraph (a) is not a grant of authority — it is the prohibition that makes the rest of the section meaningful: except as provided in § 43.3 and § 43.17, no person may maintain, rebuild, alter, or perform preventive maintenance on an aircraft, airframe, engine, propeller, appliance, or component part to which Part 43 applies. It also points to Appendix A for the listing of major alterations, major repairs, and preventive maintenance. Candidates who memorize "(a) = mechanics" get every paragraph letter in this section wrong by one.

Certificated Mechanics (§ 43.3(b))

A certificated mechanic holding an Airframe rating, Powerplant rating, or both (A&P) issued under 14 CFR Part 65 may perform maintenance, preventive maintenance, and alterations within the scope of their assigned ratings. An Airframe mechanic cannot work on engines, and a Powerplant mechanic cannot work on airframes, unless working under direct supervision.

Certificated Repairmen (§ 43.3(c))

A certificated repairman holding a certificate issued under 14 CFR Part 65 Subpart E may perform maintenance, preventive maintenance, and alterations, but only within the specific scope of the repair station or commercial operator that recommended them for certification. Unlike an A&P mechanic, a repairman's privileges are tied to their employer's facility and certificate. A repairman cannot freelance, operate an independent maintenance shop, or perform maintenance away from their employer's organizational oversight.

Certificated Repair Stations (§ 43.3(e))

A certificated repair station may perform maintenance, preventive maintenance, and alterations as provided in 14 CFR Part 145 — that is, within the ratings, limitations, and operations specifications approved by the FAA.

Air Carriers and Part 121/135 Certificate Holders (§ 43.3(f))

The holder of an air carrier operating certificate, or an operating certificate issued under Part 121 or 135, may perform maintenance, preventive maintenance, and alterations as provided in Part 121 or 135 — through its own approved program and authorized personnel rather than through individual certificate privileges.

Manufacturers (§ 43.3(j))

Paragraph (j) grants a manufacturer three distinct privileges:

1. 43.3(j)(1) — rebuild or alter any aircraft, engine, propeller, or appliance manufactured by it under a type or production certificate.
2. 43.3(j)(2) — rebuild or alter any appliance or part manufactured by it under a TSO authorization, an FAA Parts Manufacturer Approval (PMA), or a Product and Process Specification.
3. 43.3(j)(3) — perform any inspection required by Part 91 or Part 125 on aircraft it manufactured under a type certificate, or currently manufactures under a production certificate. This is the paragraph that lets a manufacturer sign an annual inspection.

Note the boundary in (j)(1) and (j)(2): the privilege attaches to products the manufacturer itself built. It is not a general repair-station privilege.

Pilot-Owners (§ 43.3(g))

Under § 43.3(g), the holder of a pilot certificate issued under 14 CFR Part 61 (Private, Commercial, or Airline Transport Pilot) may perform preventive maintenance on any aircraft owned or operated by that pilot, provided the aircraft is not operated under 14 CFR Part 121, 129, or 135. The pilot must have registered ownership or legal operational control; a renter pilot is not authorized to perform preventive maintenance under this paragraph.

---

3. Performance Under Direct Supervision (§ 43.3(d))

In practical aviation maintenance, uncertificated apprentices, mechanics-in-training, and technicians working outside their ratings perform substantial hands-on maintenance. 14 CFR 43.3(d) permits uncertificated persons to perform maintenance, preventive maintenance, and alterations, provided two strict legal conditions are met simultaneously:

1. Personal Observation: The supervising certificated mechanic or repairman must personally observe the work being done to the extent necessary to ensure that it is being done properly.
2. Physical Availability: The supervisor must be readily available, in person, for consultation.

Non-Delegable Supervision Restrictions

The FAA enforces strict statutory boundaries on supervised work. Under § 43.3(d), direct supervision does not authorize any person to perform:

• Any inspection required by 14 CFR Part 91 (such as a 100-hour inspection, annual inspection, or progressive inspection);
• Any inspection required by 14 CFR Part 125; or
• Any inspection performed after a major repair or major alteration.

A certificated A&P mechanic or IA can never delegate or supervise an inspection. An uncertificated apprentice may assist in opening cowlings, removing inspection covers, cleaning components, and repacking wheel bearings, but the supervising certificate holder must personally conduct the inspection and make all airworthiness determinations. Furthermore, approval for return to service is an exclusive certificate privilege that cannot be delegated to an apprentice.

---

4. Maintenance Permissions & Privilege Matrix

---

5. Common Exam Traps & Regulatory Distinctions

[!WARNING] High-Yield Exam Traps:

• The Renter Pilot Fallacy: A private pilot renting an aircraft for a weekend trip notices a burned-out position light bulb or low tire pressure. The pilot cannot replace the bulb or service the tire under § 43.3(g) because they do not own or hold registered operational control over the aircraft.
• The Remote Supervision Fallacy: An A&P mechanic cannot supervise maintenance via phone, video call, or photographs. 14 CFR 43.3(d) explicitly mandates physical presence in person to the extent necessary and in-person availability for consultation.
• The Supervised 100-Hour / Annual Inspection Fallacy: An IA or A&P mechanic cannot allow an apprentice to perform a 100-hour or annual inspection under supervision. The supervisor must personally conduct every required inspection item.
• The Experimental Category Loophole: Assuming all experimental aircraft are exempt from Part 43 is a major error. If an aircraft previously held a standard or special airworthiness certificate of a different kind, Part 43 applies in full.