What is the difference between an annual and a 100-hour inspection?
Updated · Wingman AeroCare, KFNL
Short answer: An annual and a 100-hour inspection cover the same scope and detail (14 CFR Part 43 Appendix D). The differences are who can sign them and when they are required: every aircraft needs an annual every 12 calendar months, signed by an A&P with Inspection Authorization (IA); a 100-hour is required only for aircraft used for hire or for flight instruction in an aircraft provided by the instructor, and any A&P mechanic can sign it. An annual counts as a 100-hour, but a 100-hour never counts as an annual.
Side-by-side comparison
| Annual inspection | 100-hour inspection | |
|---|---|---|
| Rule | 14 CFR 91.409(a) | 14 CFR 91.409(b) |
| Who needs it | Every aircraft operated under Part 91 standard inspection rules | Aircraft carrying any person (other than a crewmember) for hire, or used for flight instruction for hire in an aircraft provided by the instructor |
| Interval | Within the preceding 12 calendar months | Within the preceding 100 hours of time in service |
| Scope | At least Part 43 Appendix D | At least Part 43 Appendix D (same) |
| Who can perform and sign | A&P with Inspection Authorization (14 CFR 65.95), an appropriately rated repair station, or the manufacturer | Any A&P mechanic (14 CFR 65.85 and 65.87), or an appropriately rated repair station |
| Substitutes for the other? | Yes, an annual satisfies the 100-hour | No |
| Grace period | None | Up to 10 hours, only to reach a place where the inspection can be done |
If the scope is the same, why do both exist?
The annual exists so every aircraft gets a thorough inspection at least once a year, signed by a mechanic with the additional authority of an IA. The 100-hour exists because aircraft used commercially (flight school aircraft, rentals used for instruction, aircraft carrying people for hire) can accumulate a lot of hours in a year, and the FAA wants them inspected more often than once every 12 months.
Because the checklist is the same (14 CFR 43.15(c)(1) requires both to include at least Appendix D), a well-run 100-hour is just as thorough as an annual. The only difference in the work is the signature.
Who needs a 100-hour inspection?
Under 14 CFR 91.409(b), you need a 100-hour if the aircraft:
- Carries any person, other than a crewmember, for hire; or
- Is provided by the person giving flight instruction for hire.
Practical examples: a flight school's trainer, a rental aircraft used for instruction, or an aircraft leased to a flight school. If you own your airplane and fly it yourself, or you hire an independent instructor to teach you in your own airplane, you generally need only the annual.
How does the 10-hour allowance work?
14 CFR 91.409(b) allows the 100-hour limit to be exceeded by up to 10 hours, but only while the aircraft is en route to reach a place where the inspection can be done. It is not a general grace period. The excess time counts against the next 100 hours: if the inspection is done at 105 hours, the next one is due 95 hours later.
There is no equivalent allowance for the annual. If the annual expires, the aircraft cannot be flown without a special flight permit. See can I fly with an expired annual.
Can a 100-hour and an annual be done at the same time?
Yes. Many for-hire aircraft time their schedule so that one of the 100-hour inspections each year is done as an annual by an IA. That single inspection resets both the 12-calendar-month annual clock and the 100-hour clock. Some operators instead use a progressive inspection program under 14 CFR 91.409(d), which spreads the work over smaller, more frequent visits; that requires an FAA-approved program and is mostly used by higher-utilization fleets.
How Wingman handles it
At Wingman AeroCare, annual inspections are performed and signed off by an A&P mechanic holding Inspection Authorization, and 100-hour inspections by a certificated A&P, under 14 CFR Part 43. Typical turnaround is 3-5 business days for a 100-hour and 4-7 business days for an annual, assuming no major findings and parts availability. If you operate a training or rental aircraft in Northern Colorado, see our 100-hour inspection service or our annual inspections, and contact us to plan your schedule.