Aircraft Maintenance Calendar: What to Track and When

Every general aviation aircraft has a set of recurring inspections and checks the FAA requires. Miss the right one and you ground the airplane. This post is the working calendar.

1. Annual inspection (FAR 91.409(a))

Required every 12 calendar months for every non-commercial aircraft. An IA (Inspection Authorized mechanic) signs it off. The aircraft is grounded if the annual is overdue. No flying it to the shop for the inspection unless you've a ferry permit.

2. 100-hour inspection (FAR 91.409(b))

Required every 100 flight hours for aircraft used for hire: flight school, rental, paid instruction. Not required for private operation. Can be combined with the annual if timing works out.

3. ELT: Emergency Locator Transmitter (FAR 91.207)

Inspected annually. Battery replaced when cumulative use exceeds 1 hour or at 50% of useful life, whichever comes first. For 406 MHz ELTs, battery life is typically 5-6 years.

4. Transponder test (FAR 91.413)

Required every 24 calendar months. Without a current transponder test, the transponder isn't legal for use in most controlled airspace.

5. Pitot-static / altimeter (FAR 91.411)

Required every 24 calendar months for IFR operations. Tests static system, altimeter, and automatic altitude reporting. If you fly IFR, this is a grounding item; if you fly VFR only, you can defer it but many shops combine it with the transponder test regardless.

6. VOR check (FAR 91.171)

Required every 30 days for IFR VOR operations, but this one is pilot-performed and logged. Not a shop event. Track it because forgetting to log it disqualifies the VOR from IFR use.

7. Airworthiness Directives (ADs)

Recurring or one-time inspections and modifications mandated by the FAA for a specific airframe, engine, prop, or component. Check the FAA AD database (or your maintenance-tracking system) for new ADs every annual, and whenever the FAA publishes a new airworthiness alert for your model.

8. Component time-in-service trackers

Not regulatory, but operationally critical:

• Engine time since overhaul (TSMOH): against the manufacturer's TBO.
• Prop time since overhaul: usually 2000 hours or 5-6 years.
• Oil change interval: typically 50 flight hours or 4 calendar months.
• Spark plug cleaning: every 100 hours is typical.
• Hose inspection: engine rubber goods have finite calendar lives independent of hours.

9. Document + compliance items

• Registration: renewed every 7 years; the FAA mails reminders, but the responsibility is yours.
• Insurance: typically annual, with proof-of-insurance required on the aircraft.
• Airworthiness certificate: no expiration, but must be on board.
• Logbook archival: keep logbooks (airframe, engine, prop) in a safe place off the aircraft; scan and back up.