Direct Answer — How Part 43 Says Maintenance Must Be Performed
Three rules govern how maintenance must be done, and a fourth governs what you can fly afterward:
- A§43.13(a) — method & tools. Use the methods, techniques, and practices in the current manufacturer's maintenance manual or Instructions for Continued Airworthiness (or other methods acceptable to the Administrator), except as noted in §43.16; and use the necessary (and any manufacturer-recommended special) tools and test apparatus.
- B§43.13(b) — result. Do the work so the condition is at least equal to its original or properly altered condition (aerodynamic function, structural strength, resistance to vibration and deterioration, and other qualities affecting airworthiness).
- C§43.16 — airworthiness limitations. Inspections or other maintenance specified in an Airworthiness Limitations Section of the manufacturer's manual/ICA must be performed per that section, or per opspecs approved under part 121 or 135, or an inspection program approved under §91.409(e). This is the carve-out §43.13(a) points to.
- D§91.403(c) — operate. No person may operate an aircraft whose manual/ICA contains an ALS unless the mandatory replacement times, inspection intervals, and related procedures in that section (or approved alternatives) have been complied with.
Sources, verbatim from Cornell LII / eCFR: 14 CFR §43.13, §43.16, §91.403, and §21.50.
Most aviation maintenance recordkeeping content stops at what goes in a logbook entry. But an FSDO inspector reviewing your records is testing a deeper claim: that the maintenance was performed the way the regulations require it to be performed. That claim has a precise legal structure — the source of the procedure, the standard of the result, and the inviolability of the airworthiness limitations — and the record is what proves it. This is the companion to the §43.9 entry-content rules: §43.9 says what the entry must contain; §43.13 and §43.16 say what the entry must demonstrate was done.
FAA civil penalties for maintenance and recordkeeping violations under 49 U.S.C. §46301 reach $75,000 per violation under 14 CFR §13.301 for amounts assessed on or after December 30, 2024 (a lower individual / small-business cap applies). The deeper exposure, though, is operational: under §91.403(c) an aircraft with an unmet airworthiness limitation is not legal to operate, and under 14 CFR §39.7 operating a product that does not meet an applicable airworthiness directive is itself a violation. The records are how you keep the aircraft on the right side of both lines.
The Performance Rules, and What Each One Demands You Keep
Each clause of §43.13, §43.16, and §91.403(c) — what it requires of the person doing the work, and the record that later demonstrates it.
Use the Right Procedure
§43.13(a)Each person performing maintenance, alteration, or preventive maintenance must use the methods, techniques, and practices prescribed in the current manufacturer's maintenance manual or ICA, or other methods/techniques/practices acceptable to the Administrator — except as noted in §43.16. The operative word is current: a superseded AMM revision or an out-of-date service bulletin is not the prescribed source. This is where most procedure-side findings originate — the work itself may be sound, but the data it referenced was stale.
The record that proves it
The §43.9 entry's description or its reference to acceptable data (AMM chapter/task and revision, SB number, work order). Version-controlled manuals and ICA so the referenced revision is provably the one in effect at the time of the work.
Use the Right Tools
§43.13(a)The same paragraph requires using the tools, equipment, and test apparatus necessary to assure completion of the work in accordance with accepted industry practices — and, where the manufacturer recommends special equipment or test apparatus, using that equipment (or its equivalent acceptable to the Administrator). For calibrated tooling (torque wrenches, test sets), the calibration record is itself a compliance document.
The record that proves it
Calibration certificates for required test equipment, tied to the date of the maintenance event; manufacturer special-tooling references in the work package.
Achieve the Right Result
§43.13(b)Each person maintaining or altering, or performing preventive maintenance, must do that work so that the condition of the aircraft, engine, propeller, or appliance worked on will be at least equal to its original or properly altered condition — with regard to aerodynamic function, structural strength, resistance to vibration and deterioration, and other qualities affecting airworthiness. Following a procedure is necessary but not sufficient; the finished condition is the standard.
The record that proves it
Functional/operational check results captured in or referenced by the §43.9 entry (e.g., leak check, run-up, rigging values), demonstrating the at-least-equal-to-original result.
Honor the Airworthiness Limitations
§43.16Each person performing an inspection or other maintenance specified in an Airworthiness Limitations Section of a manufacturer's maintenance manual or ICA must perform it in accordance with that section, or in accordance with operations specifications approved under part 121 or 135, or an inspection program approved under §91.409(e). The general latitude of §43.13(a) does not reach ALS items — this is the 'except as noted in §43.16' carve-out made explicit.
The record that proves it
Current life-limited-parts status and ALS task status records (the §91.417(a)(2) life-of-aircraft items): part serial numbers, accumulated time/cycles, retirement lives, and the ALS inspection intervals with their next-due values.
Do Not Operate Until Complied With
§91.403(c)No person may operate an aircraft whose manual/ICA contains an airworthiness limitations section unless the mandatory replacement times, inspection intervals, and related procedures in that section — or approved alternatives under part 121/135 opspecs or an §91.409(e) inspection program — have been complied with. This is an operating prohibition on the owner/operator, complementing the §43.16 duty on the person doing the work.
The record that proves it
An auditable airworthiness status snapshot showing every ALS item current as of the operating date — the document set that lets an operator demonstrate §91.403(c) compliance on demand.
The §43.13(c) acceptable-means clause — read it precisely
§43.13(c) provides that, unless otherwise notified by the Administrator, the methods, techniques, and practices in the maintenance manual (or the maintenance part of the manual) of a part 121 or 135 air carrier / operating-certificate holder — and part 129 operators holding operations specifications that require a continuous airworthiness maintenance and inspection program — constitute acceptable means of compliance with §43.13. It is a means-of-compliance provision for the §43.13 method standard. It is not a waiver of §43.16: airworthiness limitations items must still be performed per the ALS, or per opspecs approved under part 121/135, or an inspection program approved under §91.409(e). Conflating the two is a common and consequential error.
The ICA and the Airworthiness Limitations Section — Where Mandatory Limits Live
Almost every clause above points back to one document set: the manufacturer's Instructions for Continued Airworthiness (ICA). Under 14 CFR §21.50(b), the holder of a design approval must furnish at least one complete set of ICA to the owner of each type aircraft, aircraft engine, or propeller — upon delivery, or upon issuance of the first standard airworthiness certificate, whichever occurs later — and must make changes to those instructions available to the persons required to comply with them. The ICA are not optional reference material; §43.13(a) ties the performance of maintenance directly to them and to the current manufacturer's maintenance manual.
Inside the ICA sits the Airworthiness Limitations Section (ALS) — the FAA-approved set of mandatory replacement times, inspection intervals, and related procedures. This is where the life limits on life-limited parts and certain mandatory structural inspections are defined. The ALS is the reason §43.13(a) carries the phrase "except as noted in §43.16": the general freedom to use other acceptable methods stops at the ALS boundary.
§43.16 — verbatim
"Each person performing an inspection or other maintenance specified in an Airworthiness Limitations section of a manufacturer's maintenance manual or Instructions for Continued Airworthiness shall perform the inspection or other maintenance in accordance with that section, or in accordance with operations specifications approved by the Administrator under part 121 or 135, or an inspection program approved under §91.409(e)."
Source: 14 CFR §43.16 (71 FR 44188, Aug. 4, 2006).
And the matching operating prohibition on the owner or operator:
§91.403(c) — verbatim
"No person may operate an aircraft for which a manufacturer's maintenance manual or instructions for continued airworthiness has been issued that contains an airworthiness limitations section unless the mandatory replacement times, inspection intervals, and related procedures specified in that section or alternative inspection intervals and related procedures set forth in an operations specification approved by the Administrator under part 121 or 135 of this chapter or in accordance with an inspection program approved under §91.409(e) have been complied with."
Source: 14 CFR §91.403(c). §91.403(a) makes the owner or operator primarily responsible for maintaining the aircraft in an airworthy condition, including compliance with part 39; §91.403(b) prohibits performing maintenance other than as prescribed in subpart E and part 43.
Two rules, two duty-holders — do not collapse them
§43.16 binds the person performing the ALS inspection or maintenance. §91.403(c) binds the person operating the aircraft. They can be different people, and the record has to satisfy both: the §43.9 entry (or the equivalent part 121/135 program record) shows the ALS task was performed correctly, and the airworthiness status record shows every ALS item is current so the operator can legally fly. An aircraft can have a perfectly executed ALS task and still be un-operatable under §91.403(c) if a different ALS item has gone overdue.
How the ALS items are actually inspected depends on the inspection program the operator is on. For larger and turbine aircraft, §91.403(c) and §43.16 both reference an inspection program approved under §91.409(e), and on-demand charter operators typically run an Approved Aircraft Inspection Program (AAIP) or a Continuous Airworthiness Maintenance Program (CAMP). Whichever program applies, the ALS limits flow through it, and the engine and propeller time-tracking records plus the airworthiness directive compliance records are what demonstrate currency. Where ALS work involves a major repair or alteration, the FAA Form 337 becomes a life-of-aircraft record too.
Provable vs Unprovable — the Same Job, Two Record Sets
A landing-gear actuator overhaul that is governed by an ALS interval. The work may be identical; only the record set differs — and only one survives an inspection.
Provable — §43.13 + §43.16 satisfied
- §43.13(a) source: entry references the current AMM task + revision and the applicable service bulletin actually used.
- §43.13(a) tools: calibration certificate on file for the test set, dated before the overhaul.
- §43.13(b) result: functional/operational check values captured, showing condition at least equal to original.
- §43.16 ALS: actuator life/interval status record updated — accumulated cycles, next-due, serial number.
- §43.9 entry: description, date, performer (when different), signature, certificate number, kind of certificate.
- §91.403(c): airworthiness status snapshot shows the item current as of the operating date.
An inspector can trace procedure → tools → result → ALS currency without leaving the record.
Unprovable — same work, broken chain
- §43.13(a) source: entry says "overhauled IAW manufacturer data" — no task, no revision; cannot show the current manual was used.
- §43.13(a) tools: no calibration record retrievable for the test set used.
- §43.13(b) result: no functional-check values recorded — at-least-equal-to-original is asserted, not shown.
- §43.16 ALS: actuator cycles not posted to the life-limit status; next-due unknown.
- §43.9 entry: signed and certificate number present.
- §91.403(c): no current airworthiness status snapshot — operator cannot demonstrate the item was complied with before flight.
The work might be fine. The record cannot prove it — and under §91.403(c) the aircraft's status is unknown.
"IAW manufacturer data" is not a reference to acceptable data
§43.9(a)(1) permits a description or a reference to data acceptable to the Administrator. A bare phrase like "in accordance with manufacturer data" identifies no specific document, task, or revision — so it does not let an inspector confirm the §43.13(a) current-manual requirement was met. The reference has to be specific enough (chapter/task and revision, SB number, work order that itself contains the procedure) that the source of the method is reconstructable from the record. This is precisely where FileFlo's document classification and revision tracking earn their keep: the entry points to a version-controlled document, not a vague phrase.
Can you prove the procedure, the result, and the ALS currency from the record alone?
FileFlo is the compliance document layer. It classifies aviation maintenance records and reference data against the governing CFR — §43.13(a) procedure references, §43.16 / §91.403(c) airworthiness-limitation status, life-limited-parts currency, and §91.417 retention — tracks expirations and next-due values, and assembles an inspector-format binder on demand. It does not perform maintenance, hold your certificate, or replace your inspection program. See the full Aviation compliance coverage.
Who These Rules Apply To — and Where the Record Risk Concentrates
§43.13 and §43.16 reach everyone authorized to perform maintenance under §43.3; §91.403(c) reaches every owner or operator. The way the documentation risk shows up differs by operation.
A&P Mechanics and IAs
The procedure-source risk is highest at the field level: an entry that asserts work was done "per manufacturer data" without identifying the task and revision cannot show the §43.13(a) current-manual requirement was met. ALS items demand particular care — under §43.16 they are performed per the ALS, not under the general "other acceptable methods" latitude of §43.13(a). Pair this with the §43.9 entry-content requirements and the §91.409 inspection framework.
Part 145 Repair Stations
Repair stations work to customer and manufacturer data at volume; the §43.13(a) risk is data control — making sure each job referenced the current ICA/SB revision, and that calibrated tooling records back up the §43.13(a) test-equipment requirement. The maintenance release and the §145.219 records have to make the procedure traceable. See the Part 145 audit binder and the repair station quality control manual.
Part 135 and Part 91 Operators
For the operator, §91.403(c) is a daily operating gate: every ALS item must be current before flight. A qualifying part 121/135 program can rely on §43.13(c) for the §43.13 method standard, but the ALS still flows through the approved program. Tie the airworthiness status to the broader §91 records set, the ARROW documents, and surveillance-audit preparation. For corporate flight departments, the same logic governs the flight-department record set.
Related Part 43 / airworthiness-limitations resources
- Life-Limited Parts Records — the ALS retirement-life status that §43.16 / §91.403(c) demand
- Airworthiness Directive Compliance Records — §39.7 and the §43.9 entries for AD work
- §43.9 Maintenance Record Entry Requirements — what the entry must contain
- ARROW Documents — the onboard airworthiness/registration set
- Aviation Records Retention Schedule — §91.417 life-of-aircraft vs 1-year records
- RVSM / Altimeter / Transponder Inspection Records — recurring tests, not ALS limits
- Operations Specifications (OpSpecs) — the approved alternatives §43.16 and §91.403(c) reference
- Part 135 CAMP Maintenance Recordkeeping — continuous airworthiness program records
Frequently Asked Questions
What does 14 CFR §43.13(a) require when performing maintenance?
14 CFR §43.13(a) requires each person performing maintenance, alteration, or preventive maintenance on an aircraft, engine, propeller, or appliance to use the methods, techniques, and practices prescribed in the current manufacturer's maintenance manual or Instructions for Continued Airworthiness (ICA) prepared by its manufacturer, or other methods, techniques, and practices acceptable to the Administrator, except as noted in §43.16. The person must also use the tools, equipment, and test apparatus necessary to assure completion of the work in accordance with accepted industry practices, and must use any special equipment or test apparatus recommended by the manufacturer (or its equivalent acceptable to the Administrator). In short: the rule sets the source of the procedure (the current manual or ICA) and the equipment standard for doing the work.
What is the difference between §43.13(a) and §43.13(b)?
They are two halves of the performance standard. §43.13(a) governs the method — which procedure you follow and which tools you use. §43.13(b) governs the result — it requires that the work be done so that the condition of the aircraft, engine, propeller, or appliance worked on is at least equal to its original or properly altered condition with regard to aerodynamic function, structural strength, resistance to vibration and deterioration, and other qualities affecting airworthiness. A technician can follow a procedure and still fail §43.13(b) if the finished condition is not at least equal to original or properly altered. Both must be satisfied, and the record is what later demonstrates that they were.
What is the Airworthiness Limitations Section (ALS) and why does §43.16 single it out?
The Airworthiness Limitations Section is the part of a manufacturer's maintenance manual or Instructions for Continued Airworthiness that contains the mandatory replacement times, inspection intervals, and related procedures the FAA approved as airworthiness limitations — most commonly the life limits on life-limited parts and certain mandatory structural inspections. §43.16 singles it out because the ALS is not merely guidance: under §43.16, each person performing an inspection or other maintenance specified in an ALS must perform it in accordance with that section, or in accordance with operations specifications approved by the Administrator under part 121 or 135, or an inspection program approved under §91.409(e). The general §43.13(a) latitude to use other acceptable methods does not extend to ALS items — that is exactly what the 'except as noted in §43.16' clause in §43.13(a) carves out.
What does §91.403(c) require of the operator regarding airworthiness limitations?
Per 14 CFR §91.403(c), no person may operate an aircraft for which a manufacturer's maintenance manual or instructions for continued airworthiness has been issued that contains an airworthiness limitations section unless the mandatory replacement times, inspection intervals, and related procedures specified in that section — or alternative inspection intervals and related procedures set forth in an operations specification approved under part 121 or 135, or in accordance with an inspection program approved under §91.409(e) — have been complied with. This is an operating prohibition aimed at the owner or operator, distinct from the §43.16 performance rule aimed at the person doing the maintenance. Read together: §43.16 controls how the ALS work is performed, and §91.403(c) prohibits flying the aircraft until that ALS work has been complied with.
Where do the Instructions for Continued Airworthiness (ICA) come from?
The ICA originate with the type-design holder. Under 14 CFR §21.50(b), the holder of a design approval must furnish at least one set of complete Instructions for Continued Airworthiness to the owner of each type aircraft, aircraft engine, or propeller upon its delivery, or upon issuance of the first standard airworthiness certificate for the affected aircraft, whichever occurs later — and must make any changes to those instructions available to affected persons. The ICA are where the Airworthiness Limitations Section lives, and §43.13(a) ties the performance of maintenance back to the ICA (and the current manufacturer's maintenance manual). FileFlo classifies and version-tracks these documents so the maintenance you perform references the current revision rather than a superseded one.
Does §43.13(c) mean a Part 135 operator can use its own maintenance manual instead of the manufacturer manual?
In specific circumstances, yes — as an acceptable means of compliance. Per §43.13(c), unless otherwise notified by the Administrator, the methods, techniques, and practices contained in the maintenance manual or the maintenance part of the manual of the holder of an air carrier or operating certificate under part 121 or 135 (and operators under part 129 holding operations specifications that require a continuous airworthiness maintenance and inspection program) constitute acceptable means of compliance with §43.13. So a qualifying Part 121 or 135 program can rely on its approved/accepted maintenance manual content. Important caveat: §43.13(c) addresses the §43.13 method standard. It does not relax §43.16 / §91.403(c) for Airworthiness Limitations items — those still must be performed per the ALS or per opspecs approved under part 121/135 or an inspection program under §91.409(e).
What records prove that maintenance was performed the way §43.13 and §43.16 require?
There is no single 'performance certificate.' Compliance is proven by an assembled record set: the §43.9 maintenance record entry (description or reference to acceptable data, date, performer name when different from the approver, and the approving person's signature, certificate number, and kind of certificate); the underlying reference data the entry points to (the AMM/ICA task, service bulletin, or work order that contains the actual procedure used); the life-limited-parts and ALS status records that demonstrate the §91.417(a)(2) life-of-aircraft items are current; and, for repair stations, the §145.219 records. The entry says what was done and who approved it; the referenced data and the ALS/life-limit status records demonstrate it was done to the right procedure and that mandatory limits were honored.
Are the 24-month §91.411 and §91.413 tests airworthiness limitations under §43.16?
No. The 24-calendar-month altimeter/static-system test under §91.411 and ATC transponder test under §91.413 are recurring operating-rule requirements, not airworthiness limitations in the §43.16 sense. The §43.16 / §91.403(c) airworthiness limitations are the mandatory replacement times, inspection intervals, and related procedures the FAA approved in the Airworthiness Limitations Section of the type design's ICA (for example, life-limited part retirement lives). It is worth tracking all of these together because they are commonly confused, but only the ALS items carry the §43.16 performance constraint and the §91.403(c) operating prohibition. A 24-month test interval is not a retention period and is not an ALS life limit.
Related Aviation Compliance Reading
§43.9 Maintenance Record Entry Requirements
The six data points every maintenance entry must carry
Life-Limited Parts Records Requirements
The ALS retirement lives that §43.16 makes mandatory
Airworthiness Directive Compliance Records
§39.7 + the §43.9 entries that document AD-mandated work
Part 91.409 Annual Inspection Requirements
Inspection programs and the §91.409(e) reference
Engine & Propeller Overhaul Time Tracking
Time/cycle records behind ALS and overhaul currency
FAA Form 337 Major Repair & Alteration Records
Life-of-aircraft documentation for major work
Prove your maintenance was performed the way Part 43 requires — before the inspector asks
FileFlo is a compliance document intelligence platform. It classifies aviation maintenance records and reference data against the governing CFR — §43.13(a) procedure and tooling references, §43.13(b) result evidence, §43.16 / §91.403(c) airworthiness-limitation status, life-limited-parts currency, and §91.417 retention clocks. It tracks next-due values, surfaces gaps weeks before a review, and generates inspector-format audit binders. It is the proof layer — it does not perform maintenance, hold your certificate, or replace your inspection program. Starter $89/month · Professional $299/month · 5-day free trial, no credit card required.