14 CFR Part 43 Deep Dive: Maintenance, Preventive Maintenance, Rebuilding & Alteration

What Is 14 CFR Part 43?

14 CFR Part 43 — officially titled Maintenance, Preventive Maintenance, Rebuilding, and Alteration — is the FAA regulation that establishes the standards for all maintenance work on US-registered aircraft. It is the rule that turns a mechanic's knowledge into a legally recognized action: without Part 43 compliance, no maintenance is valid and no aircraft may be returned to service.

The FAA knowledge tests draw heavily from Part 43. The General knowledge test (60 questions, 2 hours, 70% pass mark) covers regulations and publications as one of its core subject areas, and Part 43 dominates those questions. The Airframe and Powerplant tests (100 questions each, 2 hours, 70% pass mark) also reference Part 43 requirements, particularly return-to-service rules and inspection records. You can retake a failed knowledge test by re-registering and paying the test fee again.

The rule is organized into seventeen sections plus three appendices. Not every section attracts the same number of questions — the ACS defines a focused scope. Understanding exactly which sections are included and, just as importantly, which ones attract the most questions, is the key to efficient study.

For a broader overview of how regulations fit into the full A&P certification picture, including exam format details and general study advice, read our FAA regulations guide. This deep dive goes further, providing granular detail on every section of Part 43, exact regulatory references, and advanced question-type analysis.

Sections of Part 43 Tested on the Exams

The Aviation Mechanic ACS specifies that regulations questions draw from the full scope of Part 43, with particular emphasis on §§43.3, 43.5, 43.7, 43.9, 43.13, and the appendices. Each section carries a different weight, and within each section, specific requirements are tested more frequently than others. Here is the complete breakdown.

§43.1 — Applicability

§43.1 defines the scope of the rule: it applies to aircraft having a US airworthiness certificate, and to airframes, aircraft engines, propellers, and appliances installed or used on such aircraft. It also establishes key exceptions — work performed by a manufacturer under a type certificate or production certificate, and work on products before they are installed, are generally outside Part 43.

Key points tested:

• What the rule covers — US-certificated aircraft, airframes, engines, propellers, and appliances. Questions may test whether a particular product falls under Part 43.
• Excepted operations — Maintenance performed by the holder of a type certificate or production certificate on products of that design, and work performed by certificated repair stations under their own rules, may fall outside Part 43 requirements.
• Scope of "maintenance" — Part 43 covers maintenance, preventive maintenance, rebuilding, and alteration — four distinct categories with different rules and record-keeping.

Study tip: Memorize the four categories (maintenance, preventive maintenance, rebuilding, alteration) and what distinguishes each. Appendix A provides the preventive maintenance list; anything beyond it that restores or preserves condition is maintenance.

§43.2 — Records of Inspection and Maintenance Work

§43.2 places record-keeping obligations on owners and operators: they must keep records of inspection and maintenance work performed on their aircraft, and these records must be available for FAA inspection. While mechanics create the records under §43.9, owners and operators are responsible for maintaining and retaining them under this section.

Study tip: Questions on this section usually test the distinction between the mechanic's duty (make an accurate record, §43.9) and the owner/operator's duty (keep and retain the records, §43.2, with retention specified in §91.417).

§43.3 — Persons Authorized to Perform Maintenance

§43.3 is one of the most heavily tested sections in Part 43. It lists who may perform maintenance, preventive maintenance, rebuilding, and alterations: certificated mechanics (within their ratings), certificated repair stations (within their ratings), and manufacturers. Recent graduates of a Part 147 school may perform maintenance under the direct supervision of a certificated mechanic before receiving their own certificate.

Key points tested:

• Rating limits — An Airframe-rated mechanic may work on airframes and their components; a Powerplant-rated mechanic on engines, propellers, and their components. Work outside your rating is not authorized.
• Repair station authority — Repair station personnel act under the repair station certificate and its operations specifications, not under individual mechanic certificates.
• Uncertificated personnel under supervision — §43.3(d) allows a person working under the supervision of a certificated mechanic or repairman to perform the maintenance their supervisor is authorized to perform, if the supervisor personally observes the work to the extent necessary to ensure it is done properly and is readily available in the vicinity. The supervisor — not the helper — signs the record and approves return to service.

Study tip: Build a table of "who may do what": mechanic (airframe rating), mechanic (powerplant rating), repair station, manufacturer, IA, Part 147 recent graduate. The exam frequently asks who is authorized for a given task.

§43.5 — Approval for Return to Service After Maintenance

§43.5 states that no person may approve an aircraft for return to service after maintenance, preventive maintenance, rebuilding, or alteration unless the work was performed in accordance with §43.13 (acceptable data and practices) and, for major repairs and major alterations, in accordance with the applicable approved data. This is the legal gate between "work done" and "aircraft airworthy."

Study tip: §43.5 and §43.7 work together: §43.5 sets the conditions for approval, §43.7 lists who may grant it. A common exam scenario presents a completed repair and asks whether it may be approved — the answer turns on whether the work used approved data and whether the person approving holds the right certificate.

§43.7 — Persons Authorized to Approve Return to Service

§43.7 lists the persons who may approve an aircraft, airframe, engine, propeller, or appliance for return to service after maintenance, preventive maintenance, rebuilding, or alteration. This is among the single most heavily tested sections in the entire Part 43 curriculum.

Key points tested:

• The mechanic who did the work — The holder of an airframe and/or powerplant rating who performed, supervised, or inspected the work may approve return to service (subject to rating scope).
• The IA — The holder of an Inspection Authorization may approve return to service after any inspection performed under §43.15, including annual and 100-hour inspections, and after major repairs and major alterations.
• Repair stations and manufacturers — A repair station approves work within its ratings per its operations specifications; a manufacturer approves work on products it produced.
• What an apprentice cannot do — Persons without a mechanic certificate, including students and apprentices, may not approve return to service under any circumstances.

Study tip: Practice the "who signs what" matrix: annual inspection → IA; 100-hour inspection → A&P mechanic or IA; major repair/alteration → mechanic who performed/supervised work (with Form 337); preventive maintenance → anyone permitted to perform it (including pilots for certain items) but approval must still be per §43.7.

§43.9 — Content, Form, and Disposition of Maintenance Records

§43.9 prescribes exactly what a maintenance record entry must contain after maintenance, preventive maintenance, rebuilding, or alteration. Every entry must include: a description of the work performed (or a reference to the acceptable data), the date of completion, the name and certificate number of the person performing the work, and their signature. For major repairs and major alterations, the entry must be on FAA Form 337.

Key points tested:

• Four required elements — Description (or data reference), date, name + certificate number, signature. Missing any element makes the record non-compliant.
• Form 337 for major work — Major repairs and major alterations must be recorded on FAA Form 337, per §43.9(b).
• Rebuilding vs overhaul — A rebuilt engine must be identified as such in the records, with the manufacturer's recommendations followed.

Study tip: This is a memorization section — the four elements of a §43.9 entry appear on nearly every General exam. Write them out from memory until you can do it without thinking.

§43.11 — Content, Form, and Disposition of Inspection Records

§43.11 covers the records for inspections performed under Parts 91 and 125 and §135.411/135.419 — the annual and 100-hour inspections. In addition to the §43.9 elements, inspection records must include the type of inspection, the aircraft total time in service, and the inspection authorization number (for annual inspections). The person approving the aircraft for return to service signs the record.

Study tip: Compare §43.9 vs §43.11 side by side. The inspection record adds: inspection type, total time in service, and IA number. Questions love testing the differences between the two sections.

§43.13 — Performance Rules (General)

§43.13 is the "how to do the work" section — and the source of the famous rule that every mechanic must follow. Each person performing maintenance must use the methods, techniques, and practices prescribed in the current manufacturer's maintenance manual or instructions for continued airworthiness, or a method, technique, or practice acceptable to the FAA (which is where AC 43.13-1B and -2B come in). Work must be done in a manner that avoids "appreciable change" to the product's characteristics, and special requirements apply to welding, non-destructive testing, and weight & balance.

Key points tested:

• Accepted data hierarchy — Manufacturer's current instructions first; AC 43.13-1B as acceptable data; other FAA-accepted methods.
• "Same and equal" parts — A part may be replaced with one that is "same and equal" to the original (same form, fit, function) if not specified otherwise.
• Special processes — Welding of structural components must be performed by a qualified welder; NDT must follow approved procedures.

Study tip: Know what AC 43.13-1B is (Acceptable Methods, Techniques, and Practices — Aircraft Inspection and Repair) and when it applies (when no manufacturer's data exists or as an accepted alternative). This is a frequent multiple-choice favorite.

§43.15 — Additional Performance Rules for Inspections

§43.15 adds specific rules for annual and 100-hour inspections: the inspection must be performed in accordance with Appendix D of Part 43 (the scope and detail of items to be included), and it must include a check of all applicable airworthiness directives, with compliance recorded. The person performing the inspection must also ensure any defects found are reported to the owner/operator.

Study tip: §43.15 + Appendix D = the "what gets inspected" pair. Appendix D lists the general items (fuselage, cabin, engines, landing gear, etc.) — knowing its structure helps you answer inspection-scope questions.

§43.16 — Airworthiness Limitations

§43.16 requires that each person performing maintenance, preventive maintenance, or alteration on an aircraft with an FAA-approved airworthiness limitations section (ALS) must comply with those limitations. Airworthiness limitations include mandatory replacement times, inspection intervals, and structural inspection programs — they are legally binding, not advisory.

Study tip: Distinguish airworthiness limitations (mandatory, part of the type design, §43.16) from other maintenance instructions (advisory). "Life limits" and "mandatory replacement times" are the keywords that signal this section.

§43.17 — Maintenance of Life-Limited Parts

§43.17 prohibits performing maintenance, preventive maintenance, or alteration on any life-limited part that has reached its airworthiness limitation (life limit). A life-limited part that has exceeded its limit cannot be returned to service — it must be removed and retired.

Study tip: Questions on §43.17 usually describe a part with a mandatory replacement time and ask whether it may be reused or returned to service. The answer is always no once the limit is reached.

Appendix A — Major Alterations, Major Repairs, and Preventive Maintenance

Appendix A is one of the most tested parts of Part 43. Paragraph (a) lists major alterations (e.g., changes to the airframe structure affecting strength, changes in the basic design of the powerplant). Paragraph (b) lists major repairs (e.g., splicing a primary structural member, replacement of a wing spar, overhaul of an accessory case). Paragraph (c) lists the operations considered preventive maintenance — the items that do not require a mechanic certificate to perform, such as servicing landing gear struts, replacing tires, changing oil, and lubricating not requiring disassembly.

Key points tested:

• Major vs minor classification — If the operation is listed in Appendix A, it is major; otherwise it is minor. This binary test is the key to classification questions.
• The preventive maintenance list — Know the common items: tire/brake replacement, servicing struts, oil changes, battery replacement, cleaning fuel strainers, repacking wheel bearings, replacing safety wire/cotter pins.
• Consequences of classification — Major work requires approved data, a Form 337, and specific record-keeping; preventive maintenance can be signed off by non-mechanics (e.g., a private pilot on their own aircraft) but still needs a logbook entry.

Study tip: Create flashcards of the Appendix A major-repair and major-alteration lists and the preventive maintenance list. Classification questions are pure recall — you either know the list or you do not.

Appendix B — Recording of Major Repairs and Major Alterations

Appendix B prescribes how major repairs and major alterations are recorded: on FAA Form 337, with the form prepared by the person approving the work for return to service, and a copy forwarded to the FAA Flight Standards District Office (FSDO) within 48 hours. The form must identify the aircraft, describe the work with a reference to the approved data, and be signed by the approving mechanic.

Study tip: The 48-hour forwarding requirement is a classic exam detail. Also remember the form number (FAA Form 337) and who prepares it (the person approving return to service).

Appendix D — Scope and Detail of Annual and 100-Hour Inspections

Appendix D defines the scope of the annual and 100-hour inspections: fuselage and hull, cabin and cockpit, engines, propellers, landing gear, and the various systems (fuel, electrical, hydraulic, etc.), each with specific items to be checked. The appendix also covers the operational checks required (e.g., flight control operation, engine run-up) and notes that the person performing the inspection may use checklists that meet the appendix's requirements.

Study tip: You do not need to memorize every line of Appendix D, but you should know its structure and the major categories of items inspected. Questions typically ask which items are included in an annual/100-hour inspection scope.

Most Tested Sections Summary

Based on the Aviation Mechanic ACS and extensive candidate feedback, here is a ranked list of the most frequently tested Part 43 topics on the General knowledge test:

1. §43.7 (Persons authorized to approve return to service) — consistently the most heavily tested single section
2. Appendix A (Major repairs, major alterations, preventive maintenance classifications)
3. §43.9 (Content, form, and disposition of maintenance records)
4. §43.13 (Performance rules — accepted data and AC 43.13-1B)
5. §43.3 (Persons authorized to perform maintenance)
6. Appendix B (Form 337 recording and the 48-hour rule)
7. §43.5 (Approval for return to service conditions)
8. §43.11 (Inspection records — annual/100-hour content)
9. §43.15 / Appendix D (Inspection performance rules and scope)
10. §43.16 / §43.17 (Airworthiness limitations and life-limited parts)

If you master these ten areas, you will have covered the vast majority of Part 43 questions that appear on the exams.

Common Question Types

Part 43 questions fall into three broad categories. Understanding the format of each type will help you approach them strategically on exam day.

1. Direct Regulation Questions

These questions ask you to recall a specific section number, requirement, or detail. They are the most straightforward type and test your ability to remember exact Part 43 references.

Example: "Under §43.9, which of the following is required on every maintenance record entry?"

These are "easy marks" if you have done the memorization work. The key is not just knowing the section number but understanding what it actually requires. Multiple-choice options for direct questions often include plausible-but-wrong sections from the same part.

2. Scenario-Based Questions

These questions describe a real-world maintenance scenario and ask you to identify the correct regulatory response. They are the most challenging question type because they require you to synthesize knowledge from multiple sections and apply it to a specific situation.

Example: "A mechanic discovers a fatigue crack in a wing spar during a scheduled inspection. The aircraft is operated under Part 91 by a flight school. What is the correct sequence of actions under Part 43?"

Scenario questions test your ability to navigate the regulatory framework — not just book knowledge. They require you to determine which sections apply, in what order, and what documentation or approvals are needed. The best preparation for these questions is working through as many practice scenarios as possible.

3. Classification Questions

These questions ask you to classify a maintenance action into the correct regulatory category — major repair, major alteration, minor repair, or preventive maintenance. They test your understanding of Appendix A and the boundaries between categories.

Example: "Replacing an engine on an aircraft is classified as what type of operation under Part 43?"

Classification questions require precise knowledge of Appendix A. The same action might be classified differently depending on the context — for example, servicing a landing gear strut by adding nitrogen is "servicing" (preventive maintenance), but replacing the strut seal is a "repair." These nuances are exactly what classification questions test.

Exam strategy tip: When you encounter a scenario question, read the question first (before the scenario), then read the scenario with the question in mind. This helps you focus on what is relevant and filter out extraneous details that might be included as distractors.

Study Tips for Part 43

Part 43 rewards a specific type of study approach. Here are the strategies that consistently produce the best results:

1. Read the Actual Rule Text

Do not rely solely on third-party summaries. The FAA drafts exam questions directly from the regulatory text, and the precise wording matters. A summary might say "records must be signed," but §43.9 specifies the exact four elements — and those details are what the exam tests. Read Part 43 on the eCFR website (it is free) and focus on the exact wording of the sections listed above.

2. Use the ACS as Your Checklist

The Aviation Mechanic ACS lists every learning objective and task for the regulations subject area. Print it out and use it as a checklist. For each learning objective, ask yourself: "Can I explain this to a fellow apprentice without looking at the book?" If you cannot, you have not fully mastered that objective. The ACS is freely available on the FAA website and is the single most authoritative study resource.

3. Practice with Realistic Mock Exams

The best predictor of exam performance is practice test performance. Take timed mock exams under realistic conditions — 60 questions in 2 hours, no notes, no interruptions. After each mock exam, review every question you got wrong and every question you guessed on. Understand why the correct answer is correct and why each distractor is wrong.

4. Create a Section Number Mnemonic System

The exam requires you to know specific section numbers (§43.7 for return to service, §43.9 for records, §43.13 for performance rules). Create mnemonics to lock these numbers in memory — for example, "43.9 = record in the logbook (nine lines of paperwork)." The more memorable the association, the better it sticks in exam conditions.

5. Study the Interconnections

Part 43 is not isolated — it connects to Part 65 (who holds which certificate), Part 91 (when inspections are due and how records are retained), and Part 39 (AD compliance recorded during inspections). Understanding how these parts connect is what separates passing scores from high scores. Draw connection diagrams showing how the parts reference each other.

For more advanced study strategies, including time management techniques and the most common mistakes candidates make, see our FAA regulations study guide.

Sample Part 43 Exam Question

Here is one realistic Part 43-style question similar to what you will see on the actual FAA General knowledge test. Try to answer it before revealing the answer below.

Want more practice questions like this? Try our free A&P practice questions — 10 realistic questions covering General, Airframe, and Powerplant subjects, with the same reveal answer format. No signup required.

How Sky License Prepares You for the FAA Knowledge Tests

Sky License was built specifically to address the unique challenges of the FAA knowledge exams. Our platform combines AI-powered adaptive learning with a question bank aligned to the Aviation Mechanic ACS. Here is how it works:

• Adaptive difficulty — The AI identifies your weak areas across all subject areas and generates targeted questions to strengthen them. If you consistently miss questions about §43.7, the system will give you more scenarios from that section until your performance improves.
• Detailed explanations — Every practice question includes a full explanation of why the correct answer is correct and why each distractor is wrong, with direct 14 CFR references. This transforms every practice session into a learning opportunity.
• Realistic exam simulation — Our timed exam mode replicates the actual PSI testing conditions: 60 or 100 questions with the 2-hour clock and the same mix of direct, scenario-based, and classification questions.
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The Sky License General module is aligned specifically with the Aviation Mechanic ACS and covers every regulation section discussed in this deep dive — from §43.1 applicability to the Form 337 requirements of Appendix B.

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Putting It All Together: Your Part 43 Study Plan

Here is a suggested 3-week study plan based on the breakdown above:

• Week 1: Read the full text of Part 43 on eCFR. Master §§43.1, 43.3, and 43.5. Create your section-number flashcards. Take a baseline practice test to identify initial strengths and weaknesses.
• Week 2: Deep dive into §§43.7, 43.9, and 43.11 — return to service, maintenance records, and inspection records. Spend at least 6 hours on these three sections and the differences between them.
• Week 3: Appendix A classifications and Appendix B (Form 337). Study §43.13 and the AC 43.13-1B relationship, plus §§43.15–43.17 and Appendix D. Take 2–3 full-length timed mock exams. Review every mistake and drill your weakest sections.

For a complete overview of all three FAA knowledge tests and how the regulations fit into the broader certification process, read our FAA A&P written tests guide. And to understand the full experience and certification pathway from start to finish, see our A&P apprentice and OJT guide.

Frequently Asked Questions