Direct Answer — When "Overhauled" and "Rebuilt" May Be Used
Both words are defined terms in 14 CFR §43.2, and a person may not apply them to a product unless the underlying work meets the stated standard. Under §43.2(a), a product may be described as overhauled only when it has been disassembled, cleaned, inspected, repaired as necessary, and reassembled using methods acceptable to the Administrator, and tested per approved standards and technical data. Under §43.2(b), a product may be described as rebuilt only when those same steps are done and it is tested to the same tolerances and limits as a new item, using new parts or used parts that conform to new-part tolerances or approved oversized/undersized dimensions.
The zero-time consequence flows from §91.421, not §43.2: the owner or operator may use a new maintenance record, without previous operating history, only for an engine rebuilt by the manufacturer or by an agency approved by the manufacturer. That new record must still carry forward each airworthiness-directive change and each specifically-requested service-bulletin change (§91.421(b)). An overhaul does not reset to zero, and a rebuild does not reset the AD clock — time since overhaul and current AD status both remain §91.417(a)(2) records the owner keeps.
Sources: 14 CFR §43.2, 14 CFR §91.421, 14 CFR §91.417 — eCFR.
In aviation maintenance, overhauled and rebuilt are not marketing adjectives — they are regulated descriptions with a defined standard behind each word. The standard lives in 14 CFR §43.2, titled Records of overhaul and rebuilding. The zero-time records consequence — the headline reason anyone cares which word applies — lives in 14 CFR §91.421. This article walks the two definitions, the zero-time authority, who actually gets to use each term, and where the work and the words get recorded. For the time-tracking mechanics that sit alongside this terminology, see engine and propeller overhaul time tracking records.
Why it matters for documentation: the value of an engine, the airworthiness status of an aircraft, and the integrity of an audit binder all turn on whether the word in the logbook matches the work behind it. Calling a part rebuilt when it was only overhauled is a §43.2(b) terminology problem because rebuilt carries a new-part tolerances-and-limits standard. Claiming zero time from an overhaul, rather than a manufacturer rebuild, is a §91.421 authority problem. Either error shows up the first time an FAA inspector reconciles the maintenance record against the airworthiness directive records. FAA civil penalties for recordkeeping and airworthiness violations under 49 U.S.C. §46301 reach $75,000 per violation (with a lower maximum of $1,875 per violation for an individual or small-business concern in certain cases) under 14 CFR §13.301 for violations occurring on or after December 30, 2024.
Overhauled vs Rebuilt — The §43.2 Standard, Word by Word
14 CFR §43.2 sets the floor for both terms. The steps are nearly identical on paper — disassemble, clean, inspect, repair as necessary, reassemble, test — but the test standard and the parts standard are what separate a rebuild from an overhaul, and that separation is what unlocks (or denies) a zero-time record.
Process & parts standard
Disassembled, cleaned, inspected, repaired as necessary, and reassembled using methods, techniques, and practices acceptable to the Administrator.
Test standard
Tested in accordance with approved standards and technical data, or standards and technical data acceptable to the Administrator developed and documented by a type-certificate / STC / part-21 approval holder.
Zero-time record?
No — overhaul does not authorize a new record without previous operating history. Time since overhaul continues.
Process & parts standard
Disassembled, cleaned, inspected, repaired as necessary, and reassembled, using either new parts or used parts that conform to new-part tolerances and limits or to approved oversized or undersized dimensions.
Test standard
Tested to the same tolerances and limits as a new item — the defining difference from overhaul.
Zero-time record?
Only for an engine rebuilt by the manufacturer or a manufacturer-approved agency, per §91.421 — and the new record must still carry forward AD and requested service-bulletin changes.
The decisive phrase is "to the same tolerances and limits as a new item"
Both definitions require disassembly, cleaning, inspection, repair as necessary, reassembly, and testing. What §43.2(b) adds for rebuilt is that the testing must be to the same tolerances and limits as a new item, and the parts must be new parts or used parts that conform to new-part tolerances and limits (or approved oversized/undersized dimensions). An overhaul restores serviceability to approved data; a rebuild restores it to new-part standards. The word you write has to match which standard the work actually met — and the rebuild standard is what supports the zero-time record discussed next.
The Zero-Time Record — §91.421, and What It Does and Doesn't Erase
The single most consequential thing about the word rebuilt is that, for an engine, it can support a brand-new maintenance record with no previous operating history. That authority lives in 14 CFR §91.421, not §43.2 — and it is tightly bounded.
§91.421(a) — Who may use a zero-time record
The owner or operator may use a new maintenance record, without previous operating history, for an aircraft engine rebuilt by the manufacturer or by an agency approved by the manufacturer. That is the entire authority for zero time — it is reserved to the manufacturer or a manufacturer-approved agency. A field overhaul, however thorough, does not produce a zero-time record.
§91.421(b) — What the new record must contain
Each manufacturer or agency that grants zero time to an engine rebuilt by it must enter in the new record: (1) a signed statement of the date the engine was rebuilt; (2) each change made as required by airworthiness directives; and (3) each change made in compliance with manufacturer's service bulletins, if the entry is specifically requested in that bulletin. The zero-time record is not a clean slate — it explicitly carries forward the AD and requested service-bulletin history.
§91.421(c) — The definition of a rebuilt engine
A rebuilt engine is a used engine that has been completely disassembled, inspected, repaired as necessary, reassembled, tested, and approved in the same manner and to the same tolerances and limits as a new engine with either new or used parts. This mirrors the §43.2(b) standard and ties the rebuild definition directly to new-engine tolerances and limits.
Zero time is not an airworthiness-directive reset
Zero time addresses the engine's time-in-service history for overhaul and life-tracking purposes — it does not erase or restart applicable airworthiness directives. In fact §91.421(b)(2) requires the AD changes to be entered into the new record. The owner or operator still maintains the current AD status under §91.417(a)(2), including the method of compliance, the AD number, and the revision date. Treating a fresh zero-time logbook as an AD reset is one of the fastest ways to fail an AD reconciliation.
Who May Use Each Term — and Why It Is Not Just Semantics
The §43.2 definitions describe processes; the §91.421 zero-time authority names a class of people. Putting them together:
"Overhauled"
A certificated mechanic with the appropriate ratings, or a Part 145 repair station within the scope of its ratings, can perform an overhaul and describe the product as overhauled when the §43.2(a) standard is met. The overhaul does not reset time to zero — time since overhaul keeps accumulating and stays in the §91.417(a)(2) records for items required to be overhauled on a specified time basis. See Part 145 repair station recordkeeping for how a shop documents that work.
"Rebuilt" + zero time
The §43.2(b) rebuilt standard describes a process, but the consequential zero-time record under §91.421 is reserved to the manufacturer or an agency approved by the manufacturer. In everyday practice, a zero-time engine record is a manufacturer (or manufacturer-approved-agency) product, accompanied by the §91.421(b) signed date statement, AD changes, and requested service-bulletin changes. If a record claims rebuilt-with-zero-time and the source is an ordinary field shop, that is the flag to investigate.
| Question | Overhauled | Rebuilt |
|---|---|---|
| Governing definition | §43.2(a) | §43.2(b); engine: §91.421(c) |
| Test standard | Approved standards & technical data | Same tolerances & limits as a new item |
| Parts standard | Repaired as necessary, approved data | New parts or used parts to new-part tolerances/limits (or approved over/undersize) |
| Zero-time record? | No | Engine only, by mfr or mfr-approved agency (§91.421) |
| AD clock reset? | No | No — AD changes carried into the new record |
| Recorded where | §43.9 entry; time-since-overhaul in §91.417(a)(2) | §43.9 entry; new record per §91.421(b) |
Note one section that is easy to confuse with §43.2: 14 CFR §43.10 is titled Disposition of life-limited aircraft parts and governs the tagging and disposition controls that keep a time-expired life-limited part out of the fleet — a different subject from the §43.2 terminology. The two intersect for life-limited parts records because a rebuild may install new or conforming used parts, but §43.10 is about disposition of the time-expired part, not about what the word rebuilt means.
Does the word in your logbook match the work behind it?
FileFlo classifies aviation maintenance documents against the governing CFR — including whether an engine record is an overhaul or a §91.421 zero-time rebuild, whether the §91.421(b) AD and service-bulletin entries are present, and whether time-since-overhaul is tracked for the §91.417(a)(2) records. See the full Aviation compliance coverage.
Where the Work — and the Words — Get Recorded
§43.2 governs the terminology; it is not itself the maintenance entry. The work behind the term is recorded under the ordinary maintenance-record rules, and a few sections have to line up:
§43.9 — The maintenance entry for the work
The entry for the overhaul or rebuild itself follows 14 CFR §43.9: a description of the work performed, the date of completion, the name of the person performing the work if different from the approver, and the signature, certificate number, and kind of certificate of the person approving the work for return to service. §43.9 covers maintenance, preventive maintenance, rebuilding, and alteration — but expressly not inspections under part 91, part 125, §135.411(a)(1), or §135.419, which are §43.11 entries.
§91.421(b) — The zero-time record (engine rebuild only)
For a manufacturer or manufacturer-approved-agency engine rebuild, the new record without previous operating history must carry the §91.421(b) elements: the signed date statement, each AD-required change, and each specifically-requested service-bulletin change. This is the document that justifies the zero-time figure on the engine.
§91.417(a)(2)(iii) — Time since overhaul, kept for the life of the aircraft
The owner or operator maintains the time since last overhaul of all items installed on the aircraft that are required to be overhauled on a specified time basis. After an overhaul that figure continues; after a zero-time rebuild the engine starts fresh, but the rest of the §91.417(a)(2) set — total time in service, life-limited parts status, current inspection status, current AD status, and copies of the FAA Form 337 for major alterations — remains the owner's continuing record. See Part 91 aircraft records requirements for the full §91.417 picture.
§43.5 — Approval for return to service
After maintenance, preventive maintenance, rebuilding, or alteration, no person may approve the product for return to service unless the §43.9 (or §43.11, as appropriate) entry has been made and the repair or alteration form furnished by the Administrator has been executed as prescribed. Overhaul and rebuild are return-to-service events: the term, the §43.9 entry, and the §43.5 approval all have to be consistent.
The terminology mistakes that become findings
- Calling an overhaul a rebuild. Rebuilt carries the §43.2(b) new-part tolerances-and-limits standard. If the work met only the overhaul standard, the word is wrong on its face.
- Claiming zero time from an overhaul. Zero time requires a §91.421 manufacturer (or approved-agency) rebuild, not an overhaul — no matter how complete the overhaul was.
- A zero-time record missing the §91.421(b) entries. No signed date statement, no AD changes, or no specifically-requested service-bulletin changes means the record is incomplete on its own terms.
- Treating zero time as an AD reset. The AD status is a §91.417(a)(2) record that survives a rebuild; §91.421(b)(2) carries the AD changes forward.
- A vague or missing time-since-overhaul figure for items required to be overhauled on a specified time basis under §91.417(a)(2)(iii).
Verify the current eCFR text before adopting any logbook stamp or record format. The words in the record have to match the standard the work actually met.
Related Part 43 / Part 91 records resources
- Engine & propeller overhaul time tracking — the TBO / time-since-overhaul mechanics behind the terms
- 14 CFR §43.9 — Maintenance record entry (how the overhaul / rebuild work is written up)
- Part 91 aircraft records — §91.417 maintenance + inspection record retention
- Airworthiness directive compliance records — what a zero-time record carries forward
- Life-limited parts records — §91.417(a)(2) status and §43.10 disposition
- PMA parts traceability & 8130-3 — the parts side of a rebuild
- FAA Form 337 — major repair / alteration records the owner keeps
- Aviation records retention schedule — how long to keep each record class
Where the Maintenance Is Done by Others — and the Proof Is Yours
The §43.2 standard and the §91.421 zero-time authority are obligations on the people performing and approving the work — the mechanic, the repair station, the manufacturer. FileFlo does not perform overhauls or rebuilds, hold a certificate, approve anything for return to service, or grant zero time. What it does is govern the documentary record — making sure the word in your file matches the standard, the §91.421(b) entries are present on a zero-time engine, and the supporting status records line up.
Term-to-record consistency
FileFlo classifies an engine or component record and surfaces whether it is documented as an overhaul or a §91.421 zero-time rebuild, and whether a zero-time record carries the §91.421(b) signed date statement, AD changes, and requested service-bulletin changes. It does not write the record or judge the work; it checks the document you uploaded against the rule so a terminology or completeness gap is caught before an FAA review.
Time-since-overhaul and the next-due picture
Tracking time since overhaul for items required to be overhauled on a specified time basis — and recognizing that a zero-time rebuild restarts the engine while the rest of the §91.417(a)(2) record continues — keeps the airworthiness window visible. Tie that to AD recurrence and overhaul time tracking so nothing slips between events.
The records an inspector reconciles
When a zero-time engine record meets the §91.417(a)(2) set — total time in service, life-limited parts status, current AD status, copies of the FAA Form 337 for major alterations — the reconciliation goes smoothly. FileFlo keeps that set indexed and current-status so the audit is not the moment the records are first assembled. For on-demand operators, the parallel set lives in Part 135 surveillance-audit preparation and CAMP maintenance recordkeeping.
Frequently Asked Questions
What is the difference between an "overhauled" and a "rebuilt" aircraft part under 14 CFR §43.2?
Both are defined-term claims you may not make casually. Under 14 CFR §43.2(a), no person may describe a product (an aircraft, airframe, aircraft engine, propeller, appliance, or component part) as overhauled unless, using methods, techniques, and practices acceptable to the Administrator, it has been disassembled, cleaned, inspected, repaired as necessary, and reassembled, and has been tested in accordance with approved standards and technical data (or standards and technical data acceptable to the Administrator that have been developed and documented by the holder of the type certificate, supplemental type certificate, or a material, part, process, or appliance approval under part 21). Under §43.2(b), no person may describe a product as rebuilt unless it has been disassembled, cleaned, inspected, repaired as necessary, reassembled, and tested to the same tolerances and limits as a NEW item, using either new parts or used parts that either conform to new-part tolerances and limits or to approved oversized or undersized dimensions. The practical line: overhaul restores a part to a serviceable condition per approved data; rebuild restores it to new-part tolerances and limits and is the only path that supports a zero-time record.
Who is allowed to describe an engine as "rebuilt" and grant it zero time?
For the purpose of using a new maintenance record without previous operating history (zero time), only the manufacturer or an agency approved by the manufacturer may do so. 14 CFR §91.421(a) provides that the owner or operator may use a new maintenance record, without previous operating history, for an aircraft engine rebuilt by the manufacturer or by an agency approved by the manufacturer. A general repair station or an A&P can perform an overhaul, and within §43.2(b) the rebuild definition itself describes a process rather than naming who may perform it — but the zero-time records authority in §91.421 is reserved to the manufacturer or a manufacturer-approved agency. So in everyday practice, when someone says a part was rebuilt and the times were reset to zero, that claim rests on §91.421 and belongs to the manufacturer or its approved agency, not to a typical field shop.
What does §91.421 require a manufacturer to put in the new zero-time engine record?
Under 14 CFR §91.421(b), each manufacturer or agency that grants zero time to an engine rebuilt by it must enter in the new record (1) a signed statement of the date the engine was rebuilt, (2) each change made as required by airworthiness directives, and (3) each change made in compliance with manufacturer's service bulletins, if the entry is specifically requested in that bulletin. Section 91.421(c) then defines a rebuilt engine as a used engine that has been completely disassembled, inspected, repaired as necessary, reassembled, tested, and approved in the same manner and to the same tolerances and limits as a new engine with either new or used parts. The zero-time record is not a blank slate that erases history — it carries forward the AD compliance and the service-bulletin changes the manufacturer made during the rebuild.
Does a zero-time rebuilt engine reset the airworthiness directive clock?
No. Zero time addresses the engine's time-in-service history for overhaul and life-tracking purposes; it does not erase or restart applicable airworthiness directives. 14 CFR §91.421(b)(2) expressly requires the manufacturer to enter each change made as required by airworthiness directives into the new record, precisely so that AD status carries forward. The owner or operator still maintains the current AD status as part of the §91.417(a)(2) records, including the method of compliance, the AD number, and the revision date. Treating a zero-time record as an AD reset is a recordkeeping error that an FAA inspector will catch on the very first AD reconciliation.
Can an overhaul reset an engine or propeller to zero time?
No. An overhaul restores a product to a serviceable condition in accordance with approved data, but it does not authorize a new record without previous operating history. Only a rebuild by the manufacturer or a manufacturer-approved agency supports zero time under 14 CFR §91.421. After an overhaul, the time in service continues to accumulate, and the record reflects time since overhaul rather than starting over. This is why the time-since-overhaul figure is one of the §91.417(a)(2) records the owner keeps for the life of the aircraft for items required to be overhauled on a specified time basis — overhaul is a milestone in a continuing history, not a fresh start.
Is §43.2 the same thing as §43.10? Both mention life and disposition.
No. They are distinct sections that are easy to conflate. 14 CFR §43.2 is titled Records of overhaul and rebuilding and governs when a person may DESCRIBE a product as overhauled or rebuilt. 14 CFR §43.10 is a separate section titled Disposition of life-limited aircraft parts and governs the tagging and disposition controls for parts that have reached a mandatory replacement limit so they are not returned to service. A rebuilt engine record under §91.421 and the life-limited parts disposition rules in §43.10 both touch part history, but they answer different questions: §43.2 is about the terminology and the standard behind the words overhauled and rebuilt; §43.10 is about preventing a time-expired life-limited part from getting back into the fleet.
Where does the overhaul or rebuild get recorded — §43.9 or somewhere else?
The maintenance entry for the work itself follows 14 CFR §43.9, which sets the content, form, and disposition of maintenance, preventive maintenance, rebuilding, and alteration records — a description of the work performed, the date of completion, the name of the person performing the work if different from the approver, and the signature, certificate number, and kind of certificate of the person approving the work for return to service. Separately, §43.2 controls whether the words overhauled or rebuilt may be used to describe the result, and for a manufacturer-rebuilt engine the zero-time record requirements live in §91.421(b). Note that §43.9 expressly does not cover inspection entries performed under part 91, part 125, §135.411(a)(1), or §135.419 — those are §43.11 entries. The approval for return to service after the work is governed by §43.5.
What recordkeeping mistakes around "overhauled" and "rebuilt" actually create findings?
The recurring ones are: using the word rebuilt on a part that was only overhauled (a §43.2(b) terminology problem because rebuilt carries a new-part tolerances-and-limits standard); claiming zero time on an overhaul rather than a manufacturer or manufacturer-approved-agency rebuild (a §91.421 authority problem); a zero-time record that omits the §91.421(b) AD changes or the specifically-requested service-bulletin changes; treating zero time as an AD reset; and a missing or vague time-since-overhaul figure in the §91.417(a)(2) records for items required to be overhauled on a specified time basis. FAA civil penalties for recordkeeping and airworthiness violations under 49 U.S.C. §46301 reach $75,000 per violation, with a lower maximum of $1,875 per violation for an individual or small-business concern in certain cases, per 14 CFR §13.301 for violations occurring on or after December 30, 2024. The records are the proof; the terminology has to match the work behind it.
Related Aviation Compliance Reading
Engine & Propeller Overhaul Time Tracking
TBO and time-since-overhaul mechanics behind the terms
14 CFR §43.9 Maintenance Record Entry
How the overhaul / rebuild work is written up
Life-Limited Parts Records (§43.10 disposition)
The distinct section §43.2 is often confused with
Part 91 Aircraft Records Requirements
§91.417 maintenance + inspection record retention
Annual / 100-Hour Inspection Scope
The Part 43 Appendix D inspection that reconciles these records
PMA Parts Traceability & 8130-3
The parts traceability side of a rebuild
Make sure "overhauled" and "rebuilt" mean what your records say
FileFlo is a compliance document intelligence platform that classifies aviation maintenance records against the governing CFR — distinguishing an overhaul from a §91.421 zero-time rebuild, checking for the §91.421(b) AD and service-bulletin entries, and tracking time-since-overhaul for the §91.417(a)(2) records. It flags missing record elements and generates an inspector-format audit binder on demand. It does not perform overhauls or rebuilds, hold a certificate, grant zero time, or replace your A&P, IA, or repair station. Starter $89/month · Professional $299/month · 5-day free trial, no credit card required.
Chad Griffith
Founder, FileFlo — compliance document intelligence
FileFlo helps operators classify, index, and prove their compliance documents are audit-ready. This article is a compliance-document perspective on 14 CFR §43.2 and §91.421 — it is not legal, airworthiness, or maintenance advice, and it does not replace an A&P mechanic, an IA, a repair station, or an FAA inspector. Always verify the current eCFR text for any regulatory decision.