Studying FAA regulations for the A&P certificate can feel overwhelming at first. There are a lot of regulation numbers, legal definitions, recordkeeping rules, inspection requirements, and certification terms that all seem to run together.

The trick is not to memorize every regulation word-for-word. The goal is to understand what each regulation does and how it fits into aircraft maintenance.

For A&P students, the most important regulations usually come from:

  • 14 CFR Part 39 — Airworthiness Directives
  • 14 CFR Part 43 — Maintenance, preventive maintenance, rebuilding, and alterations
  • 14 CFR Part 65 — Mechanic certification, privileges, and limitations
  • 14 CFR Part 91 — Aircraft maintenance responsibility, inspections, and records
  • 14 CFR Part 21 — Certification of aircraft, engines, propellers, and parts

This post is written as both a blog article and a study guide. Each section explains the regulation in plain language, why it matters to a mechanic, and what you should remember for the written, oral, and practical exams.

Big Picture: How These Regulations Work Together

Before looking at individual rules, it helps to understand the big picture.

Aircraft maintenance is not just about fixing something. It is a legal and technical process that includes:

  • Approved aircraft design
  • Proper maintenance procedures
  • Qualified people performing the work
  • Proper inspections
  • Correct maintenance records
  • Airworthiness Directive compliance
  • Return-to-service approval
  • Owner/operator responsibility

A good way to think about it is this:

Airworthiness is a chain. If one link is broken, the aircraft may not be legally airworthy.

Part 21 explains aircraft and parts certification. Part 39 makes Airworthiness Directives mandatory. Part 43 explains how maintenance is performed and recorded. Part 65 explains mechanic certification and privileges. Part 91 explains owner/operator maintenance responsibility, inspections, and records.

For an A&P student, Parts 43, 65, and 91 are the core. Part 39 is also extremely important because ADs are mandatory. Part 21 helps explain how aircraft, engines, propellers, and parts are approved in the first place.

Part 43 Appendix A — Major Repairs, Major Alterations, and Preventive Maintenance

Part 43 Appendix A is one of the most important sections for A&P students because it helps classify maintenance work.

That classification matters because it affects:

  • Who may perform the work
  • Who may approve it for return to service
  • What technical data is required
  • What record entry is required
  • Whether FAA Form 337 may be required
  • Whether an IA, repair station, or other approval may be needed

Appendix A covers three big categories:

  1. Major alterations
  2. Major repairs
  3. Preventive maintenance

This is a major study area because the FAA wants mechanics to understand that not all maintenance is treated the same.

Major Alterations

A major alteration is an alteration that is not listed in the aircraft, engine, or propeller specifications and that may appreciably affect important airworthiness factors.

These factors can include:

  • Weight
  • Balance
  • Structural strength
  • Performance
  • Powerplant operation
  • Flight characteristics
  • Other qualities affecting airworthiness

A major alteration is not simply a “large” alteration. Something physically small can still be major if it affects airworthiness.

For example, changing the basic structure, installing a different type of fuel tank, modifying flight controls, or installing equipment that affects aircraft systems may be considered major.

Study Point

Major does not mean big. Major means it can significantly affect airworthiness.

Major Repairs

A major repair is a repair that, if improperly done, might appreciably affect airworthiness.

Appendix A lists examples involving important aircraft structures and systems. These include repairs to major structural members such as spars, ribs, bulkheads, stressed skin, landing gear structure, and other critical components.

Major repairs may involve:

  • Strengthening
  • Reinforcing
  • Splicing
  • Manufacturing
  • Replacing primary structural members by fabrication

A repair can be major because of what it affects, not because of how long it takes.

For example, a small crack repair in a primary structural member may be more serious than replacing a large interior trim panel.

Study Point

Ask what the repair affects, not just how big it looks.

Preventive Maintenance

Preventive maintenance is limited maintenance that may be performed by certain authorized persons under specific conditions.

This is another area where students sometimes get confused. Preventive maintenance does not mean “easy maintenance” or “simple maintenance.” It means maintenance that fits the FAA definition in Appendix A.

Examples commonly associated with preventive maintenance include simple servicing or replacement tasks that do not involve complex assembly operations.

Preventive maintenance is important because certain aircraft owners or pilots may perform specific preventive maintenance tasks on aircraft they own or operate, as allowed by the regulations.

But the work still has to be done correctly, and it still has to be recorded properly.

Study Point

Preventive maintenance is a legal category, not just a difficulty level.

Why Appendix A Matters in Real Life

A mechanic must be able to decide what kind of work is being performed. That decision affects the entire maintenance process.

For example:

  • A minor repair may require a normal maintenance record entry.
  • A major repair may require approved data and additional documentation.
  • A major alteration may require FAA-approved data and FAA Form 337.
  • Preventive maintenance may be allowed for certain non-mechanics under specific conditions.

A&P students should learn to look at maintenance tasks and ask:

  1. Is this maintenance, preventive maintenance, a repair, or an alteration?
  2. Is it major or minor?
  3. What data is required?
  4. Who can perform it?
  5. Who can approve it for return to service?
  6. What record entry is required?

Quick Review: Part 43 Appendix A

Remember these points:

  • Appendix A helps define major repairs, major alterations, and preventive maintenance.
  • “Major” means the work may appreciably affect airworthiness.
  • Preventive maintenance is specifically defined and limited.
  • The classification of the work affects records, approvals, and return-to-service authority.

Oral Exam Style Questions

Question: Does “major repair” always mean the repair is physically large? Answer: No. A repair is major because of its effect on airworthiness, not necessarily its physical size.

Question: Where would you look to determine whether something is listed as preventive maintenance? Answer: 14 CFR Part 43 Appendix A.

Question: Why does it matter whether an alteration is major or minor? Answer: Because major alterations may require approved data, specific documentation, and approval by an authorized person.

§43.9 — Maintenance Record Entries

Section 43.9 covers the content, form, and disposition of maintenance records for maintenance, preventive maintenance, rebuilding, and alterations.

This is one of the most important regulations for a mechanic because aircraft maintenance is not complete just because the physical work is finished. The work must also be properly recorded.

A mechanic should think of §43.9 as the rule for documenting normal maintenance work.

What Must Be in a §43.9 Maintenance Entry?

A maintenance record entry generally needs:

  1. A description of the work performed
  2. The date the work was completed
  3. The name of the person who performed the work
  4. The signature, certificate number, and kind of certificate held by the person approving the work

A simple memory aid is:

What was done, when it was done, who did it, and who approved it.

The description does not need to be a novel, but it must be clear enough to show what work was performed.

Example Maintenance Entry

A basic maintenance record entry might look like this:

Replaced left main tire with new tire. Serviced tire to proper pressure and checked for leaks. Aircraft approved for return to service.

Then the mechanic would sign the entry and include certificate information.

The exact wording can vary, but the entry needs to clearly document the work and approval.

Why §43.9 Matters

Maintenance records are part of the aircraft’s airworthiness history. They show what was done, when it was done, and who took responsibility for approving the aircraft or article for return to service.

Poor records can create real problems.

For example:

  • The aircraft may have missing maintenance history.
  • A future mechanic may not know what was done.
  • An owner may not be able to prove compliance.
  • The aircraft’s value may be affected.
  • Airworthiness may be questioned.

For A&P students, the key idea is that paperwork is part of the job. The FAA expects maintenance to be performed correctly and documented correctly.

Common Student Mistake

A common mistake is thinking the logbook entry only matters for inspections.

That is not correct.

Section 43.9 applies to maintenance, preventive maintenance, rebuilding, and alterations, except for certain inspection entries that are handled under §43.11.

Quick Review: §43.9

Remember these points:

  • §43.9 covers maintenance record entries.
  • The entry must describe the work performed.
  • It must include the completion date.
  • It must identify the person who performed the work.
  • It must include the signature and certificate information of the person approving the work.
  • A proper record entry is part of return-to-service documentation.

Oral Exam Style Questions

Question: What regulation covers normal maintenance record entries? Answer: 14 CFR §43.9.

Question: What should a maintenance entry include? Answer: Description of work, date completed, name of person performing the work, and signature/certificate information of the person approving the work.

Question: Is the aircraft maintenance process complete without proper records? Answer: No. The maintenance must be properly documented.

§43.11 — Inspection Record Entries

Section 43.11 covers inspection record entries.

This section is different from §43.9 because it applies to inspections performed under certain operating rules, including inspections required by Part 91.

A maintenance entry and an inspection entry are not the same thing.

Maintenance Entry vs. Inspection Entry

A maintenance entry under §43.9 documents work that was performed.

An inspection entry under §43.11 documents that an inspection was performed and states the result of that inspection.

That difference matters.

If a mechanic replaces a tire, that is a maintenance entry.

If a mechanic performs a 100-hour inspection, that is an inspection entry.

If an IA performs an annual inspection, that is an inspection entry.

What Must Be in an Inspection Entry?

An inspection entry generally includes:

  • The type of inspection
  • A brief description of the extent of the inspection
  • The date of the inspection
  • Aircraft total time in service
  • The signature, certificate number, and kind of certificate held by the person approving or disapproving for return to service
  • If the aircraft is found airworthy, a statement that it was inspected and found to be in airworthy condition
  • If the aircraft is not found airworthy, a statement that discrepancies were provided to the owner or operator

This is more specific than a normal maintenance entry because inspections determine airworthiness status.

Airworthy vs. Unairworthy Inspection Results

If an aircraft passes an annual or 100-hour inspection, the record entry states that it was inspected in accordance with the applicable inspection and found to be in airworthy condition.

If the aircraft does not pass, the mechanic or IA does not simply sign it off as airworthy.

Instead, the record must show that the inspection was performed and that a list of discrepancies and unairworthy items was provided to the owner or operator.

This distinction is important for the oral exam.

Study Point

An inspection can be completed even if the aircraft is not approved as airworthy.

The inspection result determines what the entry says.

Why §43.11 Matters

Section 43.11 matters because inspections are a formal part of the aircraft’s airworthiness status.

A vague inspection entry can create problems. A proper inspection entry shows:

  • What inspection was performed
  • When it was performed
  • Aircraft time at inspection
  • Who performed or approved the inspection
  • Whether the aircraft was found airworthy or discrepancies were given to the owner/operator

This is especially important for annual and 100-hour inspections.

Quick Review: §43.11

Remember these points:

  • §43.11 covers inspection record entries.
  • Inspection entries are different from maintenance entries.
  • The entry must identify the type and extent of the inspection.
  • Aircraft total time in service is included.
  • The entry must state whether the aircraft was found airworthy or whether discrepancies were provided.

Oral Exam Style Questions

Question: What regulation covers inspection record entries? Answer: 14 CFR §43.11.

Question: What happens if an aircraft fails an annual inspection? Answer: The IA completes the inspection record entry and provides the owner/operator with a list of discrepancies and unairworthy items.

Question: Is a §43.11 inspection entry the same as a §43.9 maintenance entry? Answer: No. §43.11 applies to inspection records, while §43.9 applies to maintenance, preventive maintenance, rebuilding, and alteration records.

Part 39 — Airworthiness Directives

Part 39 covers Airworthiness Directives, commonly called ADs.

An Airworthiness Directive is a legally enforceable FAA rule issued when an unsafe condition exists in an aircraft, aircraft engine, propeller, or appliance, and that condition is likely to exist or develop in other products of the same type design.

For an A&P student, the most important point is simple:

Airworthiness Directives are mandatory.

Why ADs Exist

The FAA issues ADs to correct unsafe conditions.

An unsafe condition may be discovered through:

  • Accidents
  • Service difficulty reports
  • Manufacturer reports
  • Inspections
  • Operational experience
  • Design or manufacturing problems

When the FAA determines that the unsafe condition is likely to exist or develop in other products of the same type design, it can issue an AD.

What an AD May Require

An AD may require different types of action, such as:

  • Inspection
  • Repetitive inspection
  • Repair
  • Replacement
  • Modification
  • Operating limitation
  • Revision of procedures
  • Removal of parts from service

Some ADs are one-time actions. Others are recurring and must be complied with repeatedly at stated intervals.

For example, an AD might require inspection every 100 hours, every annual inspection, or before further flight.

AD Compliance

AD compliance is not optional.

If an AD applies to the aircraft, engine, propeller, or appliance, the owner/operator must ensure compliance. A mechanic may be involved in researching, performing, and documenting that compliance.

A&P students should understand that AD compliance is part of airworthiness.

An aircraft with an overdue applicable AD may not be airworthy.

ADs vs. Service Bulletins

Students often confuse Airworthiness Directives and Service Bulletins.

A Service Bulletin is issued by a manufacturer. It may recommend inspection, repair, replacement, or modification.

A Service Bulletin by itself is usually not mandatory for a typical Part 91 aircraft unless it is made mandatory by an AD, regulation, operating rule, or other approved maintenance requirement.

A simple memory aid:

AD = mandatory. Service Bulletin = not automatically mandatory.

That does not mean Service Bulletins are unimportant. They may contain important manufacturer guidance, and an AD may reference a Service Bulletin as part of the required action.

Special Flight Permits and ADs

Sometimes an aircraft may not currently meet an AD requirement but may still be capable of safe flight to a location where the required work can be performed.

In some cases, a special flight permit may be available. However, the AD itself may limit or prohibit special flight permits.

A&P students should remember:

Always read the AD. The AD controls the required action, timing, and limitations.

AD Recordkeeping

AD compliance should be documented carefully.

A good AD record should show:

  • AD number
  • Method of compliance
  • Date of compliance
  • Aircraft or component time
  • Whether the AD is recurring
  • Next due time or date, if applicable
  • Signature and certificate information, when required

AD status is one of the long-term maintenance record items that matters when determining aircraft airworthiness.

Quick Review: Part 39

Remember these points:

  • ADs are legally enforceable.
  • ADs correct unsafe conditions.
  • ADs may apply to aircraft, engines, propellers, and appliances.
  • ADs may require one-time or recurring action.
  • AD compliance is part of airworthiness.
  • Service Bulletins are not automatically mandatory unless made mandatory.

Oral Exam Style Questions

Question: Are Airworthiness Directives mandatory? Answer: Yes.

Question: Who issues ADs? Answer: The FAA.

Question: Is a Service Bulletin automatically mandatory? Answer: Usually no, unless made mandatory by an AD or other applicable requirement.

Question: What should you check when reviewing AD compliance? Answer: Applicability, method of compliance, date or time complied with, recurring requirements, and next due date or time.

§65.71 — Eligibility Requirements for a Mechanic Certificate

Section 65.71 covers the basic eligibility requirements for a mechanic certificate.

This is the starting point for becoming an A&P mechanic.

A mechanic applicant must meet basic requirements before receiving a mechanic certificate or rating. These include age, language ability, and other requirements established by the FAA.

Basic Eligibility

In general, a mechanic applicant must:

  • Be at least 18 years old
  • Be able to read, write, speak, and understand English
  • Meet the applicable knowledge, experience, and skill requirements

There are limited exceptions related to applicants employed outside the United States, but for most A&P students, the English language requirement applies.

Why §65.71 Matters

This regulation matters because it explains that a mechanic certificate is an FAA airman certificate. It is not just a school completion certificate.

A student may complete training, but the FAA certificate still requires the applicant to meet FAA eligibility, knowledge, experience, and skill requirements.

Quick Review: §65.71

Remember these points:

  • §65.71 gives basic eligibility requirements for a mechanic certificate.
  • The applicant must generally be at least 18.
  • The applicant must generally be able to read, write, speak, and understand English.
  • This section connects to the written, oral, practical, and experience requirements.

Oral Exam Style Questions

Question: What regulation covers eligibility for a mechanic certificate? Answer: 14 CFR §65.71.

Question: How old must a mechanic applicant generally be? Answer: At least 18 years old.

Question: Is graduating from school the same as holding an A&P certificate? Answer: No. The FAA certificate is issued after meeting FAA certification requirements.

§65.73 — Mechanic Ratings

Section 65.73 identifies the mechanic ratings.

There are two mechanic ratings:

  1. Airframe
  2. Powerplant

A person may hold one rating or both ratings. A mechanic who holds both ratings is commonly called an A&P mechanic.

Certificate vs. Rating

It is important to understand the difference between a certificate and a rating.

The mechanic certificate identifies the person as an FAA-certificated mechanic.

The rating determines the scope of work the mechanic may perform or approve.

For example:

  • A mechanic with an Airframe rating has airframe privileges.
  • A mechanic with a Powerplant rating has powerplant privileges.
  • A mechanic with both ratings has both sets of privileges.

The rating matters because a mechanic cannot simply perform any maintenance task on any aircraft system unless it falls within the mechanic’s privileges and limitations.

Why §65.73 Matters

Students often use the phrase “A&P” as if it is one thing. In practice, Airframe and Powerplant are separate ratings.

This matters when deciding who is authorized to perform or approve specific work.

For example, work on aircraft structure is generally airframe-related. Work on an aircraft engine is generally powerplant-related. Some systems may require careful judgment depending on what is being maintained.

Quick Review: §65.73

Remember these points:

  • The two mechanic ratings are Airframe and Powerplant.
  • A mechanic may hold one or both ratings.
  • The ratings define the mechanic’s privileges.
  • “A&P” means the mechanic holds both Airframe and Powerplant ratings.

Oral Exam Style Questions

Question: What are the two mechanic ratings? Answer: Airframe and Powerplant.

Question: Is the mechanic certificate the same as the rating? Answer: No. The certificate identifies the person as a mechanic; the rating determines the scope of privileges.

Question: What does A&P mean? Answer: Airframe and Powerplant.

§65.81 — General Privileges and Limitations

Section 65.81 is one of the most important mechanic regulations because it explains what a certificated mechanic may do and what limits apply.

A certificated mechanic may perform or supervise maintenance, preventive maintenance, or alteration of an aircraft or appliance, or part thereof, for which the mechanic is rated.

That last phrase is important:

For which the mechanic is rated.

A mechanic’s privileges are connected to the ratings held.

Mechanics Must Understand the Instructions

One of the most important parts of §65.81 is that a mechanic may not exercise privileges unless the mechanic understands the current instructions of the manufacturer and the maintenance manuals for the specific operation concerned.

That means an A&P certificate does not give a mechanic permission to guess.

The mechanic is expected to use and understand applicable data, such as:

  • Manufacturer maintenance manuals
  • Service instructions
  • Service bulletins, when applicable
  • Illustrated parts catalogs
  • Wiring diagrams
  • Structural repair manuals
  • FAA-approved or FAA-acceptable data

This connects directly to Part 43 performance rules.

Performing vs. Supervising

Section 65.81 allows a mechanic to perform or supervise certain maintenance within the mechanic’s rating.

Supervising does not mean ignoring the work. A mechanic who supervises work is still responsible for ensuring the work is performed properly within the privileges and limitations of the certificate.

What §65.81 Does Not Do

Section 65.81 does not give unlimited authority.

A mechanic still must consider:

  • Rating limitations
  • Recent experience requirements
  • Required technical data
  • Whether the work is major or minor
  • Whether an IA is required
  • Whether a repair station or manufacturer authorization applies
  • Whether an AD or operating rule imposes additional requirements

Quick Review: §65.81

Remember these points:

  • §65.81 covers general mechanic privileges and limitations.
  • A mechanic may perform or supervise work for which the mechanic is rated.
  • A mechanic must understand current manufacturer instructions and maintenance manuals for the specific operation.
  • A mechanic certificate is not unlimited authority.

Oral Exam Style Questions

Question: Can an A&P mechanic perform any maintenance without looking at manuals? Answer: No. The mechanic must understand the applicable current instructions and maintenance manuals for the specific operation.

Question: Are mechanic privileges connected to ratings? Answer: Yes.

Question: Does §65.81 give unlimited maintenance authority? Answer: No. The mechanic must work within ratings, limitations, data, and applicable regulations.

§91.403 — General Maintenance Responsibility

Section 91.403 is one of the most important Part 91 maintenance regulations.

It states that the owner or operator of an aircraft is primarily responsible for maintaining that aircraft in an airworthy condition, including compliance with Part 39 Airworthiness Directives.

This is a major test point.

Owner/Operator Responsibility

The owner or operator is primarily responsible for maintaining the aircraft in an airworthy condition.

That does not mean the mechanic has no responsibility. The mechanic is responsible for the work performed and for any approval for return to service that the mechanic signs.

But the regulation places primary responsibility for maintaining the aircraft in airworthy condition on the owner or operator.

How Responsibility Is Shared

Aircraft maintenance responsibility is shared in different ways:

  • The owner/operator is primarily responsible for maintaining the aircraft in airworthy condition.
  • The mechanic is responsible for performing maintenance properly and documenting it properly.
  • The person approving return to service is responsible for that approval.
  • The pilot in command is responsible for determining whether the aircraft is in condition for safe flight before operation.

This is why aircraft airworthiness is not the responsibility of only one person.

Connection to ADs

Section 91.403 specifically connects owner/operator responsibility to Part 39 AD compliance.

That is important because ADs are mandatory. If an applicable AD is overdue, the aircraft may not be legally airworthy.

Quick Review: §91.403

Remember these points:

  • The owner/operator is primarily responsible for maintaining the aircraft in airworthy condition.
  • This includes compliance with ADs.
  • Mechanics are responsible for the work they perform and sign off.
  • Airworthiness responsibility is shared, but primary maintenance responsibility belongs to the owner/operator.

Oral Exam Style Questions

Question: Who is primarily responsible for maintaining an aircraft in airworthy condition? Answer: The owner or operator.

Question: Does owner/operator responsibility include AD compliance? Answer: Yes.

Question: Does §91.403 remove responsibility from the mechanic? Answer: No. The mechanic is still responsible for work performed and approvals signed.

§91.405 — Maintenance Required

Section 91.405 explains what the owner or operator must do regarding required maintenance.

This section builds on §91.403.

If §91.403 says the owner/operator is primarily responsible for airworthiness, §91.405 explains some of the specific actions required to meet that responsibility.

What the Owner/Operator Must Ensure

The owner or operator must ensure that:

  • The aircraft is inspected as required
  • Discrepancies are repaired as required
  • Inoperative instruments and equipment are handled properly
  • Maintenance personnel make appropriate maintenance record entries
  • The aircraft is approved for return to service when required

This regulation connects the owner/operator to the mechanic’s work and paperwork.

Why §91.405 Matters to Mechanics

Even though §91.405 is aimed at the owner/operator, mechanics need to understand it.

Why?

Because the owner/operator often depends on mechanics to:

  • Perform required inspections
  • Correct discrepancies
  • Make proper maintenance entries
  • Approve the aircraft for return to service
  • Help identify upcoming inspection or AD requirements

The mechanic’s work supports the owner/operator’s regulatory responsibility.

Quick Review: §91.405

Remember these points:

  • §91.405 lists maintenance actions the owner/operator must ensure.
  • Required inspections must be accomplished.
  • Discrepancies must be handled properly.
  • Maintenance records must be made.
  • Proper return-to-service approval matters.

Oral Exam Style Questions

Question: Who must ensure required inspections are performed? Answer: The owner or operator.

Question: Who must ensure maintenance personnel make appropriate record entries? Answer: The owner or operator.

Question: Why should a mechanic care about §91.405? Answer: Because the mechanic’s work and records help the owner/operator meet regulatory responsibilities.

§91.407 — Operation After Maintenance

Section 91.407 explains when an aircraft may be operated after maintenance, preventive maintenance, rebuilding, or alteration.

This section directly connects Part 91 to Part 43.

The aircraft may not be operated after maintenance unless:

  1. It has been approved for return to service by an authorized person, and
  2. The required maintenance record entry has been made.

This is one of the clearest examples of why paperwork matters.

Return to Service

Return to service is not just a casual statement that the job is finished.

It is a legal approval that the aircraft, airframe, engine, propeller, appliance, or component is approved after maintenance or inspection.

For most A&P students, this is a key idea:

The work is not fully complete until the required approval and record entry are complete.

Operational Checks

Section 91.407 also includes requirements related to operational checks when maintenance may have appreciably changed flight characteristics or substantially affected operation in flight.

In those cases, the aircraft must be test flown and approved before carrying passengers, unless the ground tests, inspections, or both show conclusively that the maintenance has not appreciably changed flight characteristics or substantially affected operation in flight.

This is especially important after major work.

Quick Review: §91.407

Remember these points:

  • §91.407 covers operation after maintenance.
  • The aircraft must be approved for return to service by an authorized person.
  • The required record entry must be made.
  • Some maintenance may require an operational check or test flight before passengers are carried.

Oral Exam Style Questions

Question: Can an aircraft be operated after maintenance without a return-to-service approval? Answer: No.

Question: What two basic things are required before operation after maintenance? Answer: Approval for return to service and the required maintenance record entry.

Question: Why might a test flight be required after maintenance? Answer: If the maintenance may have appreciably changed flight characteristics or substantially affected operation in flight.

§91.409 — Inspections

Section 91.409 covers inspection requirements.

This is one of the most tested Part 91 maintenance sections because it includes annual inspections, 100-hour inspections, progressive inspections, and other inspection program requirements.

Annual Inspection

Many aircraft operated under Part 91 must have an annual inspection every 12 calendar months.

A calendar month means the inspection remains valid through the last day of the month in which it expires.

For example, if an annual inspection was completed on June 10, it is generally valid through the end of June the following year.

An annual inspection must be performed by a person authorized to perform annual inspections, such as an A&P mechanic who holds Inspection Authorization.

Study Point

Annual inspection = every 12 calendar months.

100-Hour Inspection

A 100-hour inspection is required for certain aircraft operations, especially aircraft carrying passengers for hire or used for flight instruction for hire.

A 100-hour inspection is similar in scope to an annual inspection, but the authorization to perform it is different.

An appropriately rated A&P mechanic may perform a 100-hour inspection. An annual inspection requires an IA or another person authorized by regulation.

A 100-hour inspection may be exceeded by not more than 10 hours while en route to a place where the inspection can be performed. However, the excess time is included when computing the next 100-hour inspection.

Study Point

The 10-hour allowance does not reset the clock. It counts against the next 100 hours.

Progressive Inspections

A progressive inspection program allows the aircraft to be inspected in phases instead of all at once.

The full aircraft must still be completely inspected within the required period. Progressive inspections are usually associated with aircraft that fly frequently and benefit from a structured inspection schedule.

Annual vs. 100-Hour Inspection

This is a common exam comparison.

Annual inspection:

  • Required every 12 calendar months
  • Generally required for many civil aircraft
  • Must be performed by an IA or other authorized person

100-hour inspection:

  • Required for certain commercial-type operations such as carrying passengers for hire or flight instruction for hire
  • Based on aircraft time in service
  • May be performed by an appropriately rated A&P mechanic
  • May be exceeded by up to 10 hours only to reach a place where the inspection can be done

Quick Review: §91.409

Remember these points:

  • §91.409 covers required inspections.
  • Annual inspections are based on calendar months.
  • 100-hour inspections are based on time in service.
  • The 10-hour 100-hour inspection allowance is only to get to a place where the inspection can be done.
  • Progressive inspections divide inspection work into phases.

Oral Exam Style Questions

Question: How often is an annual inspection required? Answer: Every 12 calendar months.

Question: Who can perform an annual inspection? Answer: An A&P mechanic with Inspection Authorization or another person authorized by regulation.

Question: Can a 100-hour inspection be overflown? Answer: Yes, by not more than 10 hours while en route to a place where the inspection can be performed, but the excess time counts toward the next 100 hours.

§91.411 — Altimeter System and Altitude Reporting Equipment Tests and Inspections

Section 91.411 covers altimeter system and altitude reporting equipment tests and inspections.

This regulation is especially important for aircraft operated under IFR.

The common study point is that the altimeter system and altitude reporting equipment must be tested and inspected within the preceding 24 calendar months for certain operations.

What Equipment Is Involved?

This section relates to equipment such as:

  • Altimeter system
  • Static pressure system
  • Automatic pressure altitude reporting equipment
  • Altitude reporting system

This connects directly to pitot-static system knowledge.

Why §91.411 Matters

Accurate altitude reporting is critical for IFR operations and ATC separation.

If an aircraft reports incorrect altitude, it can create a serious safety issue. That is why these tests and inspections are required at regular intervals for applicable operations.

Quick Review: §91.411

Remember these points:

  • §91.411 covers altimeter system and altitude reporting equipment tests and inspections.
  • The common interval is 24 calendar months.
  • This is especially important for IFR operations.
  • It is connected to the pitot-static system and altitude reporting.

Oral Exam Style Questions

Question: What regulation covers altimeter system and altitude reporting equipment tests? Answer: 14 CFR §91.411.

Question: What is the common inspection interval? Answer: Within the preceding 24 calendar months.

Question: Why does this matter? Answer: Accurate altitude reporting is necessary for safe IFR operation and ATC separation.

§91.413 — ATC Transponder Tests and Inspections

Section 91.413 covers ATC transponder tests and inspections.

This is another common 24-calendar-month inspection requirement.

Students often study §91.411 and §91.413 together because both involve aircraft systems used by ATC, and both have common 24-calendar-month timing.

Transponder Requirement

The ATC transponder must be tested and inspected as required before use under the applicable conditions.

The transponder allows ATC radar systems to identify the aircraft and receive altitude information when connected to altitude reporting equipment.

§91.411 vs. §91.413

A common student mistake is mixing these up.

Use this memory aid:

§91.411 = Altimeter/static/altitude reporting. §91.413 = Transponder.

Both are commonly remembered with a 24-calendar-month interval, but they cover different equipment.

Quick Review: §91.413

Remember these points:

  • §91.413 covers ATC transponder tests and inspections.
  • The common interval is 24 calendar months.
  • Do not confuse it with §91.411.
  • §91.411 is altimeter/static/altitude reporting.
  • §91.413 is transponder.

Oral Exam Style Questions

Question: What regulation covers ATC transponder tests and inspections? Answer: 14 CFR §91.413.

Question: What is the common transponder inspection interval? Answer: Within the preceding 24 calendar months.

Question: What is the difference between §91.411 and §91.413? Answer: §91.411 covers altimeter/static/altitude reporting equipment; §91.413 covers the ATC transponder.

§91.417 — Maintenance Records

Section 91.417 covers maintenance records.

This is one of the most important recordkeeping regulations for A&P students because it explains what records must be kept and how long they must be retained.

A&P students should understand that aircraft records are not just paperwork. They are part of the aircraft’s airworthiness history.

Two Big Categories of Records

A useful way to study §91.417 is to divide records into two general categories:

  1. Records of maintenance, preventive maintenance, alterations, and inspections
  2. Long-term status records

The first category documents work that has been performed.

The second category shows the continuing status of the aircraft and its components.

Maintenance and Inspection Records

These records include information such as:

  • Description of work performed
  • Date of completion
  • Signature and certificate information
  • Inspection entries
  • Return-to-service approvals

These connect directly to §43.9 and §43.11.

Long-Term Status Records

Long-term records include items such as:

  • Total time in service
  • Current status of life-limited parts
  • Time since last overhaul, if required
  • Current inspection status
  • Current status of applicable Airworthiness Directives
  • Major alterations

These records are critical because they help determine whether the aircraft is currently airworthy.

AD Status Records

The current status of applicable ADs is especially important.

A good AD status record should show:

  • AD number
  • Applicability
  • Method of compliance
  • Date or aircraft time at compliance
  • Whether the AD is recurring
  • Next due date or time, if recurring

Without good AD records, it can be difficult to prove that the aircraft complies with mandatory AD requirements.

Records Transferred With the Aircraft

Certain maintenance records must be transferred with the aircraft when it is sold.

This matters because the aircraft’s maintenance history affects its airworthiness and value.

Missing logs can create major problems for owners, buyers, mechanics, and inspectors.

Quick Review: §91.417

Remember these points:

  • §91.417 covers maintenance recordkeeping.
  • Some records are retained until repeated or superseded.
  • Some records are long-term status records.
  • AD compliance status is a critical record item.
  • Maintenance records are part of the aircraft’s airworthiness picture.

Oral Exam Style Questions

Question: What regulation covers maintenance records under Part 91? Answer: 14 CFR §91.417.

Question: Why are AD status records important? Answer: They show compliance with mandatory Airworthiness Directives.

Question: Are aircraft records part of airworthiness? Answer: Yes. Records help prove the aircraft conforms to required maintenance, inspections, and AD compliance.

Type Certificates, STCs, PMAs, and TSOs

A&P students also need to understand basic certification terms from Part 21.

These terms explain how aircraft, engines, propellers, parts, and certain articles are approved.

The big terms are:

  • Type Certificate
  • Type Certificate Data Sheet
  • Supplemental Type Certificate
  • Parts Manufacturer Approval
  • Technical Standard Order

These are not just paperwork terms. They affect what can be installed on an aircraft and whether the aircraft still conforms to its approved design.

Type Certificate

A Type Certificate, or TC, is FAA approval of the design of an aircraft, aircraft engine, or propeller.

The Type Certificate shows that the product design meets the applicable airworthiness standards.

For mechanics, the Type Certificate matters because an aircraft must conform to its approved type design to be airworthy.

A mechanic should understand that the aircraft is not just “airworthy” because it looks safe. It must also conform to its approved design.

Type Certificate Data Sheet

A Type Certificate Data Sheet, or TCDS, contains important information about the approved design.

A TCDS may include:

  • Model information
  • Engine eligibility
  • Propeller eligibility
  • Fuel requirements
  • Oil requirements
  • Operating limitations
  • Required placards
  • Weight and balance information
  • Certification basis

A TCDS is a very useful document for mechanics because it helps identify what configuration is approved for that aircraft.

Study Point

The TCDS helps show what the aircraft is approved to be.

Supplemental Type Certificate

A Supplemental Type Certificate, or STC, is approval for a major change to a type-certificated product.

An STC supplements the original Type Certificate.

Examples may include:

  • Engine conversions
  • Major avionics installations
  • Fuel system modifications
  • Structural modifications
  • Performance modifications

A good memory aid is:

TC = original approved design. STC = approved major change to that design.

An STC does not mean the mechanic can install anything on any aircraft. The STC must be applicable to the specific aircraft, engine, propeller, or product.

Parts Manufacturer Approval

Parts Manufacturer Approval, or PMA, is an FAA approval that allows a manufacturer to produce replacement or modification parts.

A PMA part is an FAA-approved part, but the mechanic still has to determine whether that part is eligible for installation on the specific aircraft or product.

This is an important real-world point:

An approved part is not automatically approved for every installation.

The part must be eligible for the aircraft, engine, propeller, or appliance where it will be installed.

Technical Standard Order

A Technical Standard Order, or TSO, is an FAA minimum performance standard for specified articles.

A TSO authorization means the article meets the applicable TSO standard.

However, TSO authorization does not automatically approve installation on a specific aircraft.

For example, a piece of avionics equipment may be TSO-authorized, but the installation still must be approved for the aircraft.

Study Point

TSO approval means the article meets a standard. It does not automatically approve the installation.

Why These Terms Matter to Mechanics

A mechanic must think about two separate questions:

  1. Is the part or article approved?
  2. Is it eligible and approved for installation on this aircraft?

Those are not always the same question.

A part can be well made, properly marked, and approved under some approval basis, but still not be correct for a particular aircraft.

This is why mechanics use:

  • Type Certificate Data Sheets
  • Supplemental Type Certificates
  • Parts catalogs
  • Installation instructions
  • Airworthiness Directives
  • Service information
  • FAA-approved or FAA-acceptable data

Quick Review: TC, STC, PMA, and TSO

Remember these points:

  • A Type Certificate approves the original product design.
  • A TCDS contains important approved configuration information.
  • An STC approves a major change to a type-certificated product.
  • A PMA approves production of replacement or modification parts.
  • A TSO is a minimum performance standard for certain articles.
  • An approved article is not automatically approved for every installation.

Oral Exam Style Questions

Question: What is a Type Certificate? Answer: FAA approval of the design of an aircraft, aircraft engine, or propeller.

Question: What is an STC? Answer: A Supplemental Type Certificate approving a major change to a type-certificated product.

Question: What is a PMA? Answer: Parts Manufacturer Approval, which allows production of approved replacement or modification parts.

Question: Does a TSO authorization automatically approve installation on an aircraft? Answer: No. It shows the article meets a standard, but the installation must still be approved.

Final Study Summary

If you are studying for the A&P written, oral, and practical exams, focus on how the regulations connect.

The Core Chain

  • Part 21 explains approved design and approved parts.
  • Part 39 makes Airworthiness Directives mandatory.
  • Part 43 explains how maintenance is performed and recorded.
  • Part 65 explains mechanic certification, ratings, privileges, and limitations.
  • Part 91 explains owner/operator maintenance responsibility, inspections, and records.

Highest-Priority Study Items

Know these cold:

  • Part 43 Appendix A — major repairs, major alterations, preventive maintenance
  • §43.9 — maintenance record entries
  • §43.11 — inspection record entries
  • Part 39 — Airworthiness Directives
  • §65.71 — mechanic eligibility
  • §65.73 — Airframe and Powerplant ratings
  • §65.81 — mechanic privileges and limitations
  • §91.403 — owner/operator airworthiness responsibility
  • §91.405 — maintenance required
  • §91.407 — operation after maintenance
  • §91.409 — inspections
  • §91.411 — altimeter/static/altitude reporting tests
  • §91.413 — transponder tests
  • §91.417 — maintenance records
  • Type Certificates, STCs, PMAs, and TSOs

Best Memory Aids

ADs are mandatory.

Service Bulletins are not automatically mandatory.

Major does not mean physically big; major means it may affect airworthiness.

§43.9 is for maintenance entries.

§43.11 is for inspection entries.

§91.411 is altimeter/static/altitude reporting.

§91.413 is transponder.

The owner/operator is primarily responsible for maintaining the aircraft in airworthy condition.

A mechanic certificate is not unlimited authority; privileges depend on ratings, current data, and regulations.

Closing Thoughts

FAA regulations are easier to understand when you stop treating them as isolated numbers.

The regulations work together.

Part 21 tells us what the aircraft or part is approved to be. Part 39 tells us what mandatory unsafe-condition corrections must be performed. Part 43 tells us how maintenance must be performed and recorded. Part 65 tells us who the mechanic is and what that mechanic may do. Part 91 tells us who is responsible for keeping the aircraft airworthy and what inspections and records are required.

For an A&P student, this is the big idea:

Airworthiness is not just the condition of the aircraft. It is the combination of condition, conformity, maintenance, inspections, records, and regulatory compliance.

Learn that chain, and the FAA regulations will start to make a lot more sense.