For aircraft subject to the ordinary rules, annual inspections follow a calendar requirement and 100-hour inspections apply to specified operations. Confirm the aircraft program, authority and records.
Annual and 100-hour inspections use different triggers
For an aircraft subject to the ordinary provisions of 14 CFR 91.409(a) and (b), an annual inspection follows a calendar requirement, while a 100-hour requirement applies to the operations specified in paragraph (b). They are related inspections, but a buyer should determine the aircraft's actual operating and inspection program before making a calendar. “Private,” “commercial” or “rental” alone is not a complete legal analysis.
The controlling text is 14 CFR91.409: inspections and applicable exceptions. This guide focuses on common type-certificated general aviation airplanes. The rule includes exceptions and other inspection programs, including certain aircraft with special certificates and aircraft maintained under specified approved programs. A turboprop, experimental aircraft or different operation should not inherit a piston-owner checklist without professional review. Use the regulation and the aircraft's program to establish applicability first.
What the calendar requirement actually says
Paragraph (a), subject to its exceptions, requires the relevant annual inspection and return-to-service approval, or the specified airworthiness-certificate inspection, within the preceding 12 calendar months. An annual is not simply an oil change, a service appointment or a payment to the shop. The inspection and required approval must be properly accomplished and recorded. Booking a slot before expiry does not itself extend the aircraft's inspection status.
Calendar months matter. If a qualifying annual is completed in October, the ordinary 12-calendar-month framework runs through the end of the following October, subject to the actual rule and aircraft circumstances. It does not expire exactly 365 days after the mechanic's signature. Other obligations can become due earlier. An outstanding AD, life limit or discrepancy is not suspended because the annual calendar remains current.
For purchase planning, record the completion date, inspection type, approving person and supporting entry. Then identify the expected next calendar deadline. Do not infer that deadline from an advertisement saying “fresh annual” without reading the entry. Our annual inspection cost guide explains how the inspection scope and findings translate into a cash plan.
When the 100-hour requirement applies
Paragraph (b) addresses carrying a person other than a crewmember for hire and giving flight instruction for hire in an aircraft that the person providing instruction also provides. Subject to the exceptions, the aircraft must have received the specified qualifying inspection and approval within the preceding 100 hours of time in service. The wording is more precise than “every aircraft making money needs a 100-hour.”
A personally owned airplane used only for an owner's ordinary personal flying does not acquire a paragraph (b) requirement solely from accumulating 100 hours. Conversely, naming an arrangement “private” does not decide whether its actual conduct falls within the provision. Review who supplies the airplane, who supplies instruction, who is carried and what compensation arrangements exist. Unusual leases or instructional arrangements need an aircraft-specific answer from an appropriate professional or FAA office.
An owner also needs to distinguish the 100-hour inspection interval from separate hourly tasks. An AD can require a recurring action on an aircraft that does not need paragraph (b) inspections. A component's own interval may use different units or a different clock. Removing the 100-hour inspection from a personal-use budget therefore does not eliminate all hourly maintenance obligations.
Scope overlaps, but authority and records still matter
14 CFR Part 43 Appendix D: inspection scope sets out applicable items for annual and 100-hour inspections. It covers systems and structures such as the fuselage, cabin, engine, landing gear, wings, empennage, propeller and installed equipment. This shared scope does not mean every airplane takes the same labor hours, or that every optional purchase investigation automatically forms part of an annual. Equipment, access and aircraft-specific instructions still affect the work.
Certificate privileges determine who may perform and approve the work. A mechanic's inspection authorization includes annual inspection privileges under 14 CFR 65.95: inspection authorization privileges. 14 CFR 43.7: return-to-service authority also identifies other authorized certificate holders within their applicable privileges. A suitably authorized repair station or manufacturer is not the same legal category as an individual A&P mechanic. Confirm the actual signatory and authority for the planned task instead of assuming every shop employee can approve an annual.
Under 14 CFR 43.11: inspection entries and discrepancies, the record identifies inspection type and extent, date, aircraft total time, signature and certificate information, with the applicable approval or disapproval statement. If the result is a signed discrepancy list rather than approval, the calendar entry alone does not show that all required corrective work has been completed. Ask for the subsequent documented disposition before treating the airplane as ready for delivery.
When one inspection can satisfy another requirement
Section 91.409(b) recognizes an annual or a 100-hour inspection for its interval. An appropriately completed annual can therefore satisfy the applicable 100-hour inspection requirement. The reverse requires care: paragraph (a) says an inspection performed under paragraph (b) cannot substitute for the annual unless it is performed by a person authorized to perform annual inspections and entered as an annual in the required records.
This is why a seller's statement that “the inspections are the same anyway” is incomplete. The equipment may receive overlapping inspection attention, but the required authority, designation and entry still control. Ask the shop before the work starts whether it is conducting and documenting an annual, a 100-hour or a different program event. A buyer should not plan to rename a completed entry after the fact to cure a calendar problem.
The ten-hour provision is narrowly framed
The 100-hour limitation can be exceeded by no more than ten hours while en route to a place where the inspection can be done. Section 91.409(b) requires the excess time used for that purpose to count in computing the next 100 hours. This is not an automatic 110-hour service interval, a general extension for busy schedules or an extension of an annual's calendar deadline.
Consider an invented scheduling example for an aircraft to which paragraph (b) applies. The last qualifying inspection was at 1,200 hours of time in service. The ordinary next threshold is 1,300. If a permitted en-route movement results in inspection at 1,304, four excess hours count toward the next interval, leaving the next ordinary threshold at 1,400, not 1,404. Whether any proposed movement qualifies must be determined from the actual rule and circumstances.
Changing a spreadsheet due field to 1,404 would conceal those four hours rather than solve the problem. Record the previous threshold, actual completion time and treatment of any excess separately. This example illustrates the arithmetic only. It is not permission to fly an aircraft with an expired inspection, unairworthy condition or another unmet requirement.
Build an inspection-control sheet before purchase
| Field | Evidence to retain | Decision it supports |
|---|---|---|
| Applicable program | Certificate, operation and governing inspection provisions | Whether the ordinary annual and 100-hour framework applies |
| Calendar event | Inspection entry and actual approval outcome | Next calendar deadline and delivery feasibility |
| Hourly event | Time-in-service basis, last event and next threshold | Hours available for the intended operation |
| Separate obligations | AD, life-limit and component schedules | Tasks that can become due before either inspection |
| Open findings | Discrepancy list and corrective-work records | Whether further work, cash or transport planning is needed |
Give every row an evidence date and a responsible reviewer. A status sheet prepared for a pre-buy may be stale after demonstration flights or several weeks of fleet operation. Request updated time and maintenance events before closing, and agree who maintains the sheet between inspection and delivery. The sheet organizes the evidence; it does not replace signed records or the owner's airworthiness responsibilities.
Budget and schedule around the actual operation
For a higher-utilization aircraft, map expected hours against calendar deadlines and shop access. An inspection may occur before the next annual date because the applicable hourly interval arrives first. Compare the cost of the inspection itself with likely discrepancies, travel, repositioning and lost use. Do not multiply a generic annual price by an assumed number of inspections and call it a provider quote.
For personal ownership, preserve a separate allowance for recurring tasks even when paragraph (b) does not apply. A recent annual is a useful documented event, not a warranty against an expensive first-year finding. Coordinate the pre-buy inspection, records review and delivery plan, including the actual condition when the buyer takes possession. Financing approval does not determine inspection compliance.
Inspection questions
Do I need a 100-hour inspection for personal flying?
Ordinary personal flying alone does not trigger section 91.409(b). Confirm the aircraft's actual certification, operation and inspection program, and keep separate AD and component obligations current. Paid instruction and aircraft-supply arrangements need review against the specific rule rather than a general label.
Is the scope different?
Part 43 Appendix D describes applicable items for both annual and 100-hour inspections. Their triggers, authority and record requirements still matter. Additional model-specific work or a purchase investigation should be identified in the shop's written scope instead of assumed included.
Who performs these inspections?
Appropriately authorized maintenance personnel or organizations perform and approve the work within their certificate privileges. An individual mechanic's annual authority commonly involves inspection authorization, while other authorized certificate holders have their own rules. Confirm who signs, the authority used and the inspection designation recorded.