Missing a maintenance due date doesn't just mean an awkward conversation with your mechanic. An aircraft that's past its annual, transponder check or a recurring AD isn't legal to fly, and an insurer may question a claim on it. The fix is simple: know every item that comes due, what it's measured in, and when it's next due.
This guide covers what a typical piston airplane flown under Part 91 needs to track. Your aircraft may have more (type-specific inspections, life-limited parts, operator programs), so check with your A&P/IA.
The recurring items
Annual inspection
Required every 12 calendar months by 14 CFR 91.409(a). Calendar months means it runs to the end of the month: an annual signed off on March 3 is good until March 31 of the following year. It must be done by an A&P with Inspection Authorization (IA).
100-hour inspection
Required by 91.409(b) if the aircraft carries people for hire or is provided by you for flight instruction for hire. It's measured in time in service, which most operators track with the tach. You may overfly it by up to 10 hours to reach a place where it can be done, but those hours count against the next interval. An annual also counts as a 100-hour. More in annual vs 100-hour inspection.
ELT
Under 91.207, the emergency locator transmitter must be inspected every 12 calendar months, and its battery replaced when it has been used for more than one cumulative hour or when 50% of its useful life has passed. The battery's replacement date should be marked on the outside of the transmitter.
Transponder
91.413 requires the transponder (and its altitude reporting) to have been tested within the preceding 24 calendar months to use it.
Altimeter and static system
91.411 requires the altimeter, static system and automatic altitude reporting to have been tested within 24 calendar months to fly IFR in controlled airspace. Many VFR-only owners do it alongside the transponder check anyway.
Airworthiness Directives
ADs are mandatory. Some are one-time; others recur every so many hours, calendar months, landings or cycles. Each recurring AD is its own due item, often with a different interval from anything else on the airplane. See how owners track AD compliance.
Oil changes and manufacturer items
Oil change intervals, propeller overhauls and engine time between overhaul (TBO) come from the manufacturer. For most Part 91 operations they aren't regulatory limits, but most owners track them as if they were, and an insurer or buyer will ask about them.
What each item is measured in
Every due item is measured in one of four ways, and many need more than one ("every 12 months or 100 hours, whichever comes first"):
- Calendar date: annual, ELT, transponder, pitot-static.
- Tach or time in service: 100-hour, oil changes, many recurring ADs, engine time.
- Landings: some landing gear and brake ADs and inspections.
- Cycles: mostly turbine and pressurized aircraft.
The common mistake is tracking dates in one place and hours in another. Anything measured in hours or landings needs the meter readings from every flight, so your tracking is only as good as your flight records. See Hobbs vs tach time for which meter to use.
What your records must show
14 CFR 91.417(a)(2) requires the owner to keep records showing:
- total time in service of the airframe, each engine, each propeller and each rotor
- the current status of life-limited parts
- time since the last overhaul of items that are overhauled on a specified time basis
- the current inspection status, including time since the last required inspection
- the current status of applicable ADs, including the method of compliance, the AD number and revision date, and for recurring ADs, when the next action is due
- copies of major alteration forms (FAA Form 337)
These records transfer with the aircraft when you sell it. Individual maintenance entries (91.417(a)(1)) are kept until the work is repeated or superseded, or for one year.
How to track it without missing anything
- List every item once, with its interval and what it's measured in. Start from your last annual's paperwork and the AD list for your airframe, engine, propeller and appliances.
- Record meter readings at every flight, tach and Hobbs, start and end. Without them, hour-based items drift.
- Count landings if any item depends on them.
- Set reminders ahead of time: 30 days or 10 hours is a common warning window. A shop may need weeks of notice.
- Ground the aircraft when something is overdue, especially if other people fly it. A partner or renter can't be expected to check your spreadsheet.
- Keep the signed entries with the tracking, so when an item is done, its next due date is recalculated from the actual sign-off.
Frequently asked questions
What maintenance records does an aircraft owner have to keep?
Under 14 CFR 91.417, the owner keeps records of maintenance and inspections, plus the current status of total time in service, life-limited parts, overhauls, inspections and ADs. The status records transfer with the aircraft when it's sold.
Can I fly past my annual inspection?
No. An aircraft past its annual isn't airworthy for flight. If you need to move it to a shop, you need a special flight permit (ferry permit) from your local Flight Standards District Office (FSDO).
Does a private airplane need a 100-hour inspection?
Only if it carries people for hire or is provided for flight instruction for hire. A privately flown airplane needs the annual, not the 100-hour, though many owners follow the 100-hour items as good practice.
What's the easiest way to track aircraft maintenance?
Use one place for every item and every flight's meter readings, so hour-based items update themselves, and set reminders well before each due date. Aircraft maintenance tracking software does this automatically; a spreadsheet works if you update it after every flight.