From Builder to Owner: Understanding Aircraft Maintenance Logs

TL;DR: Your airplane’s logbooks are more than paper—they’re proof. They certify your airworthiness, protect your wallet, and tell the story of your machine. Whether you fly a certified Cessna or a homebuilt Sling TSi, the same truth applies: if it’s not written, it didn’t happen. This post breaks down what the FAA actually requires, what good record-keeping looks like, and how to turn your logs from a regulatory chore into a mark of craftsmanship.

As my Sling TSi build moves steadily toward completion, my attention has started to shift from clecos and torque wrenches to what life will look like once the airplane is mine to operate. There’s a surprising amount to prepare for before that first flight: hangar space, insurance, maintenance planning—and, perhaps least glamorous of all, record-keeping.

Every airplane has two sets of wings: the metal ones that make it fly and the paper ones that keep it legal. While builders obsess over rivet patterns and avionics wiring, it’s the logbooks that quietly define whether an aircraft is airworthy, insurable, and ultimately saleable.

This post grew out of my own research into best practices for maintaining aircraft logs as I prepare to become a first-time owner. It’s meant to summarize what I’ve learned from FAA regulations, advisory circulars, and experienced owners—but it’s not a substitute for doing your own homework. Use it as a starting point to explore the rules that apply to your airplane, and confirm details with your A&P, DAR, or local FSDO when in doubt.

If you’d like to keep this information handy, I’ve created a Quick Reference Guide that distills all the key FAR citations, inspection requirements, and best-practice tips from this post into a single printable page.

Download Quick Reference Guide

Think of it as a preflight checklist for your airplane’s paperwork.

The Overlooked Heart of Airplane Ownership: Maintenance Logs

Before diving into regulations and acronyms, it helps to understand what these logs really are: the running ledger of your airplane’s mechanical life. They document every inspection, repair, and adjustment that keeps the aircraft legal and safe to fly. Whether you own a certified or an experimental aircraft, the same principle applies—your logbooks are the official evidence that the airplane is being maintained in accordance with the rules and is in a condition for safe operation.

The Legal Backbone

The starting point is clear and simple:

14 CFR § 91.403(a) — “The owner or operator of an aircraft is primarily responsible for maintaining that aircraft in an airworthy condition, including compliance with part 39 of this chapter.”

That single sentence transfers ultimate responsibility from the mechanic’s bench to the owner’s desk.

Mechanics perform the work, but the owner must ensure the required inspections are completed and documented. If it isn’t in the record, the FAA considers it not done.

The companion rule reinforces this:

§ 91.405(a) — “Each owner or operator shall ensure that maintenance personnel make appropriate entries in the aircraft maintenance records indicating the aircraft has been approved for return to service.”

So while you can delegate the wrench-turning, you can’t delegate the duty to make sure it’s written down.

The Safety Backbone

Aircraft logs are the machine’s medical chart. They tell the story that preflights can’t:

AD and service-bulletin compliance
Oil-analysis trends
Compression-check history
Repairs and replacements
Avionics upgrades and configuration changes

When a mechanic opens your airframe log, they aren’t just looking for ink—they’re looking for continuity. Gaps or cryptic one-liners force them to assume the worst.

The FARs quietly require this continuity by tying the act of returning an aircraft to service directly to record-keeping:

§ 43.9(a) — Each maintenance record must include “a description of the work performed, the date of completion, the name of the person performing the work, and the signature, certificate type, and certificate number of the person approving the work for return to service.”

Even if you never read Part 43 again, that sentence tells you exactly what every log entry must contain.

The Financial Backbone

From a buyer’s perspective, good logbooks are gold. Missing or damaged logs routinely cut resale value by 10–40 percent because they destroy confidence in the aircraft’s history.

The FARs make certain records permanent and transferable:

§ 91.417(b)(2) — “The owner or operator shall transfer the maintenance records required by paragraph (a)(2) … with the aircraft upon its sale.”

That means total time, life-limited part status, AD compliance, and inspection history must travel with the airplane forever. A tidy set of logs is therefore both a legal necessity and a financial safeguard.

Bottom Line

Maintenance logs are not bureaucratic clutter. They are:

Your proof of airworthiness
Your safety history
Your resale asset
Your compliance record
Your airplane’s autobiography

What Logbooks Does an Aircraft Need? Required Records vs. Actual Books

Here’s where regulation meets reality.

What the FARs Actually Require

The FAA requires records, not specific physical logbooks. The controlling rule is §91.417, which obliges the owner to keep:

(a)(1) records of maintenance, preventive maintenance, and alterations;
(a)(2) records of total time, life-limited parts, AD status, inspection status, and Form 337s; and
(b)(2) those permanent records must be transferred at sale.

Nothing in § 91.417 dictates how those records are formatted. They can live in bound books, typed sheets, or electronic files—as long as the information exists and is retrievable.

How the Aviation World Implements It

To make life easier, owners and mechanics separate these records into familiar books:

Logbook	Purpose	Typical Contents
Airframe Log	Core record for the airplane itself	Annual/Condition inspections, structural work, AD compliance, ELT entries, avionics installations, W&B changes
Engine Log	Follows the engine, not the airframe	Oil changes, compressions, magneto work, SB/AD compliance, overhaul data
Propeller Log	Required for props with maintenance intervals (e.g., constant-speed)	Blade inspections, governor service, overhaul data
Avionics Log (optional)	Tracks modern systems	Software updates, 91.411/413 tests, configuration sheets
Builder’s Log (E-AB)	Construction record, not maintenance	Photos, materials, methods—used for certification and resale background
Phase I Flight-Test Log (E-AB)	Required during initial test period	Flight cards, results, anomalies, corrective actions

Each serves the same underlying regulatory purpose: to preserve the information required by § 91.417 in an organized, traceable way.

Why Separate Books Matter

Continuity: mechanics and buyers can follow each component’s history.
Component portability: engines and props can change airframes but keep their life stories.
Resale value: missing an engine log often cuts price dramatically.
Ease of compliance: separate logs make AD tracking and inspection entries cleaner.

Legal vs. Practical Reality

Book Type	Legally Required (Info)	Practically Expected	Notes
Airframe	Yes	Always	Primary record
Engine	Yes	Always	Follows engine
Propeller	If maintenance interval	Usually	Essential for constant-speed
Avionics	No	Common	Helpful for modern panels
Builder (E-AB)	For certification	Valuable	Not a maintenance record
Flight-Test (E-AB)	Yes during Phase I	Historical	Proof of testing

In Plain English

The FAA cares what information you keep, not where you keep it.
The aviation community simply standardized “where” to make life easier.
If your records collectively show what § 91.417 demands—and do so legibly and chronologically—you’re legal, safe, and far more attractive to buyers.

Certified Aircraft: The Regulatory Spine

If Section 1 laid out why maintenance logs matter, this section explains what the rules actually say. For a standard-category (certified) airplane operated under Part 91, the framework comes primarily from 14 CFR Parts 43 and 91. Together they form the backbone of every log entry ever written in a Cessna, Piper, or Cirrus.

Owner Responsibility: § 91.403 and § 91.405

The FAA starts with a clear assignment of duty:

§ 91.403(a) — “The owner or operator of an aircraft is primarily responsible for maintaining that aircraft in an airworthy condition, including compliance with part 39 of this chapter.”

That means the owner must ensure:

Required inspections are performed on time, and
Maintenance is properly recorded.

Mechanics may do the work, but the owner is accountable for ensuring the work—and the paperwork—exist.

§ 91.405(a) — “Each owner or operator shall ensure that maintenance personnel make appropriate entries in the aircraft maintenance records indicating the aircraft has been approved for return to service.”

Those two lines alone summarize the legal relationship between you and your A&P.

What Must Be Recorded: § 91.417

Section 91.417 defines which maintenance records must exist, what they must include, and how long you must keep them. It divides records into two categories—short-term and permanent.

(a)(1) Short-Term Records

“Records of the maintenance, preventive maintenance, and alterations and records of the 100-hour, annual, progressive, and other required or approved inspections shall include—
(i) a description of the work performed;
(ii) the date of completion; and
(iii) the signature, kind of certificate, and certificate number of the person approving the aircraft for return to service.”

These are the day-to-day maintenance entries. They must be kept until the work is repeated or superseded, or for at least 1 year, whichever is longer.

(a)(2) Permanent Records

“The total time in service of the airframe, each engine, each propeller, and each rotor;
the current status of life-limited parts;
the time since last overhaul of items with required overhaul intervals;
the current inspection status;
the current status of applicable airworthiness directives (ADs); and
copies of major repair and alteration forms (FAA Form 337).”

These are your forever records. You must preserve them for the life of the aircraft and transfer them to the new owner at sale (§ 91.417 (b)(2)).

How Entries Must Be Written: § 43.9 and § 43.11

While § 91.417 tells you what records are needed, Part 43 tells you what each entry must contain.

Maintenance, Preventive Maintenance, and Alterations — § 43.9(a)

“Each person who maintains, performs preventive maintenance, rebuilds, or alters an aircraft, airframe, aircraft engine, propeller, appliance, or component part shall make an entry in the maintenance record of that equipment containing—
(1) a description of the work performed or reference to data acceptable to the Administrator;
(2) the date of completion;
(3) the name of the person performing the work; and*
(4) if the work is approved for return to service, the signature, certificate type, and certificate number of the person approving the work.”

That’s why every entry you see ends with a line like:

“Returned to service IAW Lycoming SB-632. John Doe, A&P 3456789.”

Inspections — § 43.11(a)

For required inspections—annual, 100-hour, transponder, altimeter/static, etc.—the rule adds a few extra items:

“Each person performing an inspection required by Part 91 shall make an entry including—
(1) the type of inspection and a brief description of its extent;
(2) the date;
(3) the aircraft total time in service;
(4) the signature, certificate type, and certificate number of the person approving or disapproving the aircraft for return to service; and*
(5) if approved, a statement that the aircraft is approved for return to service; if not, a statement that the aircraft is not approved and a list of discrepancies.”

Special Log Requirements

Several other rules add targeted record-keeping obligations:

Requirement	FAR Reference	What Must Be Logged
ELT Battery Replacement	§ 91.207(c)(1)	Record new battery expiration date in log and on ELT label
Altimeter / Static System Test	§ 91.411 + § 43.11	Record date, total time, and test statement
Transponder Test	§ 91.413 + § 43.11	Record same as above; valid 24 months
AD Compliance	§ 39.3 + § 91.417(a)(2)(v)	Show method, date, hours, and next due
Major Repairs / Alterations	§ 43 App. B + § 91.417(a)(2)(vi)	File and retain FAA Form 337

Together, these fill in the details of what inspectors and buyers expect to find in every logbook.

Retention and Transfer

Keep short-term records → for 1 year or until superseded (§ 91.417 (b)(1))
Keep permanent records → for the life of the aircraft (§ 91.417 (b)(2))
Transfer permanent records → to the new owner upon sale (§ 91.417 (b)(2))

If you ever lose them, there’s no regulatory “do-over”—only painstaking reconstruction through invoices and FAA records.

The Certified-Aircraft Summary

In practice, every certified-aircraft owner must be able to answer “yes” to five questions:

Do I understand that I’m responsible under § 91.403 for airworthiness and record-keeping?
Are all required inspections (annual, 100-hr, 91.411, 91.413) documented under § 43.11?
Are all maintenance entries compliant with § 43.9 and § 91.417?
Are ADs tracked, current, and clearly logged?
Can I produce the permanent records listed in § 91.417(a)(2) and transfer them if I sell the airplane?

If the answer to any of these is no, the airplane’s paperwork—and therefore its legal airworthiness—is incomplete.

Experimental Amateur-Built Aircraft: Freedom, Responsibility, and Record-Keeping

When a builder transitions from riveting aluminum to logging maintenance, the regulatory world shifts beneath their feet. Certified airplanes operate within a tight framework of type certificates, service manuals, and prescribed inspections. Experimental Amateur-Built (E-AB) airplanes, by contrast, live under a philosophy of freedom with accountability.

The FAA steps back from dictating how you maintain your aircraft and instead asks you to prove, through your own records, that it remains in a condition for safe operation.

From Type Certificate to Personal Responsibility

Certified airplanes are “born” under a type certificate that defines every rivet and cable. Your Sling TSi, like all E-ABs, has no such blueprint. You, the builder, are the manufacturer of record.

That distinction means airworthiness is no longer measured against a manufacturer’s design but against your Operating Limitations—the custom rulebook issued with your airworthiness certificate.

§ 91.403(a) — “The owner or operator of an aircraft is primarily responsible for maintaining that aircraft in an airworthy condition, including compliance with part 39 of this chapter.”

That responsibility never leaves you. The FAA simply gives you wider latitude to decide how to fulfill it.

The Legal Framework

Three regulatory pillars govern maintenance for experimentals:

Part 91 – still applies fully (§§ 91.403, 91.405, 91.417).
Part 43 – mostly does not apply. § 43.1(b) — “This part does not apply to any aircraft that has an experimental certificate unless the FAA has determined otherwise and described it in the operating limitations.”
Operating Limitations – issued per FAA Order 8130.2K (replacing 8130.2J), they carry the weight of regulation under § 91.9(a).

Together they replace the rigid rules of the certified world with a system tailored to your specific aircraft.

The Condition Inspection — The Experimental “Annual”

Instead of the annual inspection required by § 91.409(a), experimentals must undergo a Condition Inspection once every twelve calendar months.

Typical OpLim wording:
“No person may operate this aircraft unless within the preceding 12 calendar months it has had a condition inspection performed in accordance with the scope and detail of Appendix D to Part 43.”

The required logbook entry reads:

“I certify that this aircraft has been inspected on [date] in accordance with the scope and detail of Appendix D to Part 43 and was found to be in a condition for safe operation.”

Who may sign:

The Repairman Certificate holder for that specific aircraft (§ 65.104), or
Any A&P mechanic.
No Inspection Authorization (IA) is required.

This inspection is the heart of your ongoing airworthiness. It proves the airplane still meets the second half of the FAA’s definition: “in a condition for safe operation.”

Major Changes and Returning to Phase I

§ 21.93 defines a major change as one that “appreciably affects weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities.”

Your Operating Limitations (usually paragraph 13) require that after a major change you must:

Enter the aircraft into Phase I test status.
Conduct a minimum of 5 hours of flight testing.
Log the modification, test hours, and results.
Make a log entry declaring the aircraft “in a condition for safe operation.”

Common “major change” examples for a Sling TSi:

Propeller model change
Adding or removing a ballistic parachute
Engine or cooling-system modification
Major avionics rewiring or bus redesign

Until the post-test entry is complete, you’re legally back in Phase I—no passengers allowed.

Airworthiness Directives and Service Bulletins

§ 39.3 — “This part prescribes airworthiness directives that apply to aircraft, aircraft engines, propellers, and appliances.”

Because your airframe has no type certificate, airframe ADs do not apply.
However, ADs do apply to any type-certificated components installed in your aircraft:

Rotax 916iS engine: comply with any FAA ADs and all Rotax Service Instructions or Bulletins.
Airmaster propeller: comply with any prop-specific SBs or ADs.
Appliances such as transponders, ELTs, or magnetos: follow applicable ADs.

And § 91.417(a)(2)(v) still requires you to record:

“The current status of applicable airworthiness directives, including the method of compliance, the AD number, and when the next action is due.”

Treat these entries exactly as you would in a certified airplane.

Record-Keeping Requirements That Don’t Change

Even with Part 43 mostly exempt, § 91.417 still governs your documentation:

A. Maintenance Records — § 91.417(a)(1)

Description of work performed
Date of completion
Signature, certificate type, and number of person approving return to service
Keep these until superseded or at least one year.

B. Permanent Records — § 91.417(a)(2)

Total time on airframe, engine, and propeller
Life-limited-part status
Inspection status
Applicable AD status
Major repair/alteration documents
Results of 91.411/91.413 tests
Keep for the life of the aircraft and transfer at sale (§ 91.417 (b)(2)).

C. Other Required Entries

Requirement	FAR Reference	What to Record
ELT battery replacement	§ 91.207(c)(1)	New expiration date and installation date
Altimeter / Static system test	§ 91.411 + § 43.11	Date, total time, statement of approval
Transponder test	§ 91.413 + § 43.11	Same as above; valid 24 months
Condition Inspection	OpLims	Exact wording required

Keeping Experimental Logs Professionally

Although you’re not bound to § 43.9/43.11 formatting, using it demonstrates professionalism and consistency.
Write every entry with:

A clear description of work or reference to acceptable data.
Date of completion.
Signature and certificate number (if applicable).
Statement of return to service or safe condition.

Pair that with the best practices from Section 3—chronological order, digital backups, summaries—and your logs will stand shoulder-to-shoulder with those of any certified aircraft.

Certified vs Experimental at a Glance

Category	Certified Aircraft	Experimental Amateur-Built
Primary Authority	Parts 43 & 91	Part 91 + Operating Limitations
Part 43 Applicability	Fully applies	§ 43.1(b): mostly exempt (Appendix D for Condition Inspection)
Annual Inspection	Annual by IA (§ 91.409(a))	Condition Inspection (§ 91.409(e) + OpLims) by Repairman or A&P
Major Change Procedure	Log entry only	Return to Phase I (§ 21.93 + OpLims Para 13)
AD Applicability	All applicable ADs (§ 39.3)	Only for type-certificated engines/props/appliances
Record-Keeping Rule	§ 91.417	§ 91.417 (same requirements)
Who May Maintain	A&P / owner for preventive	Anyone except Condition Inspection sign-off
Airworthiness Standard	Conforms to type design & safe condition	Conforms to OpLims & safe condition

The Builder-Owner Mindset

The FAA’s experimental philosophy is simple: more freedom, more responsibility.
They trust that a person capable of building an airplane can also maintain it responsibly. Your logbooks are how you prove that trust is well-placed.

Every entry you write—from an oil change to a Condition Inspection—becomes part of a permanent record that defines the aircraft’s reliability, resale value, and your reputation as its builder.

Best Practices: Making Maintenance Logs Work for You

By now, we’ve covered what the FARs require. But “legal” and “useful” are not the same thing. You can technically satisfy § 91.417 with a shoebox of receipts and still make your mechanic—or a future buyer—miserable. Good record-keeping is what turns regulatory compliance into operational clarity and resale value.

These best practices apply equally to certified and experimental aircraft, and they form the habits that separate “bare-minimum paperwork” from a professionally maintained airplane.

Keep Logs Organized and Sequential

There’s no mandated format, but continuity matters enormously. Each logbook should tell a story in chronological order, without gaps or ambiguity.

Tips:

Use one entry per event (don’t bundle a year’s worth of oil changes into a single line).
Number or date each page consecutively.
Avoid stapling loose receipts into the middle of a bound log—tape or scan them neatly instead.
Never tear out pages; if you need to correct an entry, draw a single line through the error, write “VOID,” and initial it.

FAA Advisory Circular 43-9C encourages clear, legible, permanent entries and warns that “poorly written or incomplete records may render the aircraft unairworthy until verified.”

Store Originals Safely — and Digitize Everything

Paper fades, ink smears, and hangars flood. Once an original logbook is lost, it’s gone for good.

Best practice:

Keep originals at home in a cool, dry, fire-resistant location.
Scan or photograph every page after each entry.
Store digital copies in at least two places—cloud and local backup.
When flying away for maintenance, bring copies, not originals.

A digital archive is not a regulatory substitute, but it’s invaluable for insurance claims, pre-buy inspections, and peace of mind.

Use Standardized Entry Language

Even though the FARs don’t require specific phrases, consistent wording communicates professionalism and clarity.

Common, FAA-recognized patterns include:

Maintenance entry:

“Replaced left brake caliper O-ring IAW Cessna 172 Service Manual, Ch. 32-40-00. Operational check good. Returned to service. John Doe, A&P 3456789.”

Inspection entry:

“Annual inspection completed IAW 14 CFR Part 43 Appendix D. No defects noted. Total time 2,356.7 hrs. John Doe, IA 3456789.”

ELT entry:

“ELT battery replaced 11 Jan 2025. Next due Jan 2030. Entry per § 91.207(c)(1).”

Using standard phrasing ensures any mechanic—or FAA inspector—instantly understands what was done and under what authority.

Maintain a Quick-Reference Summary

A one-page summary at the front of each logbook saves everyone time.

Typical summary sheet items:

Category	Data Example
Airframe TT	1,245.6 hrs
Engine	215.4 SMOH (Lycoming O-360-A4M)
Propeller	215.4 SOH (Hartzell HC-C2YR)
Last Annual	02 May 2025
Next Due	31 May 2026
Last 91.411/413 Tests	12 Jan 2024 / due Jan 2026
ELT Battery Due	Jan 2028
AD List Reference	See attached spreadsheet

It’s not required by the FARs—but every savvy buyer expects it.

Track ADs and Service Bulletins Separately

§ 91.417(a)(2)(v) requires the status of all applicable Airworthiness Directives, including “the method of compliance, the AD number, and when the next action is due.”

Rather than burying this in the airframe log, create a simple table or spreadsheet:

AD No.	Applicability	Method of Compliance	Date	TTAF	Next Due	Reference
2020-26-16	Lycoming crankshaft	Complied via SB 632	05-2023	1,122.4	N/A	AF pg. 142

Also include Service Bulletins (SBs)—they may not be regulatory, but documenting them demonstrates proactive maintenance.

Include Supporting Documentation

Mechanics are legally required to make the entry, but owners benefit from keeping everything behind it:

Work orders and invoices
Parts tags and 8130-3 forms
STCs, field approvals, and 337s
Weight-and-balance revisions
Equipment lists
Test reports (oil analysis, compressions)

Organize these in a binder or digital folder labeled by year. The goal is that anyone reading your logs can immediately find the underlying proof.

Keep a Running “Squawk List” and Maintenance Plan

Even though not required, maintaining your own log of discrepancies makes annuals smoother. Track minor issues—sticking hinges, slow starter, GPS anomalies—and check them off as they’re fixed.

Pair this with a maintenance plan listing:

Next oil change
Next filter change
Upcoming ADs or SBs
Wear-item replacements

It’s far easier to stay ahead than to reconstruct forgotten details later.

Record Trends Over Time

Oil analysis, compressions, and borescope photos tell a long-term story. Store these chronologically and include them in the engine log or a supplemental binder. A graph of oil-analysis metals or compression readings over time instantly conveys engine health to a buyer or mechanic.

Label Everything Clearly

Simple but often overlooked:

Write “AIRFRAME LOGBOOK #1,” “ENGINE LOGBOOK #2,” etc., on each cover.
Include registration N-number and serial numbers inside the first page.
When a component is replaced (engine, prop), start a new log clearly marked “NEW ENGINE LOG – Installed TT = 0, TTAF = XXXX.”

Clear labeling avoids confusion and preserves traceability across ownership changes.

The Checklist for Organized Logs

Here’s a one-page reference you can literally tape inside your hangar cabinet:

Airframe, engine, and propeller logs up to date
Each entry legible, dated, and signed per § 43.9/43.11
AD spreadsheet current and cross-referenced
Summary sheet at front of each book
Digital scans backed up off-site
Work orders, 337s, and W&B revisions filed
Upcoming maintenance items tracked
Oil analysis and compressions logged
Logbooks stored safely away from the airplane

Why It’s Worth the Effort

Clean, comprehensive logs aren’t just paperwork—they’re currency.vThey simplify annuals, build trust with mechanics, reassure insurers, and add tangible resale value.
When the day comes to sell, organized records make your airplane look like it’s been cared for by an airline—even if it’s a two-seat taildragger.

Conclusion: The Logbook as a Legacy

Airplane ownership isn’t just about flying—it’s about stewardship. Every flight hour, oil change, and inspection you record adds another line to your aircraft’s biography. Whether your airplane rolled out of Wichita with a type certificate or out of Torrance with a builder’s signature, its maintenance logs are the living record of your judgment, care, and competence.

The FAA’s rules make the owner “primarily responsible” for airworthiness, but the best owners turn that obligation into pride. Clear, complete records don’t just keep inspectors happy—they make annuals smoother, strengthen resale value, and build confidence in everyone who touches the airplane, including your future self.

This post brings together what I’ve learned so far while researching how aircraft maintenance logs work—legally, practically, and philosophically—for both certified and experimental aircraft. As a soon-to-be new owner, I wanted a clear picture of what’s expected and why it matters. In a follow-up post, I’ll go deeper into the hands-on side of record-keeping for my Sling TSi—the specific tools, structure, and organization system I plan to use to manage digital and physical logs, track inspections, and keep the airplane’s documentation as modern and disciplined as its avionics. It’s where the builder truly becomes the historian.

Until then, remember: the ink in your logbooks is as much a part of the airplane as the rivets in its wings.