3.2 Inspections, Airworthiness Directives, and Preventive Maintenance

An airworthiness certificate is not a lifetime hall pass. 14 CFR 91.403(a) makes the owner or operator primarily responsible for maintaining the aircraft in an airworthy condition, including compliance with part 39 Airworthiness Directives. 91.409 then sets the inspection clock that PAR tests constantly. Calendar-month math matters: “within the preceding 12 calendar months” runs to the last day of the 12th month, not to the anniversary hour on the tach.

Annual inspection — 91.409(a)

Except as provided in 91.409(c), no person may operate an aircraft unless, within the preceding 12 calendar months, it has had an annual inspection in accordance with part 43 and has been approved for return to service by a person authorized by 43.7 — or an inspection for issuance of an airworthiness certificate under part 21. An annual completed on March 10, 2026 is good through March 31, 2027. On April 1, 2027 the airplane is not legal to fly as PIC until another annual (or a qualifying part 21 airworthiness inspection) is signed off.

Who may sign an annual is narrower than “any mechanic.” An annual must be performed and returned to service by a person authorized to perform annual inspections — in general-aviation practice, a mechanic with Inspection Authorization (IA) under 65.95, or another person 43.7 actually authorizes for that inspection. A 100-hour inspection performed by an A&P who does not hold an IA cannot be substituted for the annual unless it is performed by a person authorized to perform annuals and is entered as an “annual” inspection in the required maintenance records. 91.409(a) states that rule in so many words.

100-hour inspection — 91.409(b), and the rental trap

The 100-hour is not “every rental airplane, always.” 91.409(b) has two triggers: (1) operating an aircraft carrying any person (other than a crewmember) for hire, and (2) giving flight instruction for hire in an aircraft which that person provides. If either trigger is met, the aircraft must have received an annual or 100-hour inspection within the preceding 100 hours of time in service (or a part 21 airworthiness-certificate inspection).

A flight school that provides the 172 and charges for dual given in that 172 is in the second box. That airplane needs both a current annual and a 100-hour program. An annual satisfies the 100-hour requirement because 91.409(b) expressly accepts “an annual or 100-hour inspection.” The reverse is not true unless the 100-hour was done by someone authorized to perform annuals and logged as an annual.

A private pilot who rents the same 172 for a personal weekend trip, carrying friends who are not being carried for hire, is not automatically in 91.409(b). The renter is not carrying persons for hire, and the renter is not giving flight instruction for hire in an airplane the renter provides. The airplane still needs a current annual. Many school airplanes need the 100-hour anyway because the school also uses them for dual. Read the logs and ask how the airplane is used; do not assume every rental is a 100-hour airplane, and do not assume a school 172 can skip the 100-hour.

The 10-hour overrun is tightly limited. “The 100-hour limitation may be exceeded by not more than 10 hours while en route to reach a place where the inspection can be done.” The excess time used to reach that place must be included in computing the next 100 hours. It is not a 10-hour slush fund for local pattern work.

PAR scenario: the school 172 you will use for dual is two hours past 100 hours since the last 100-hour/annual, and you are sitting at the home airport. You may not depart for a local lesson. The two-hour overrun is not “while en route to a place where the inspection can be done.” If you were already away from home and flying to the shop that will do the inspection, you could use up to 10 hours to get there, and those hours would count against the next 100. Sitting on the ramp two hours overdue is a no-go.

ELT, transponder, and pitot-static

91.207(d) requires each required ELT to be inspected within 12 calendar months after the last inspection for proper installation, battery corrosion, operation of the controls and crash sensor, and a sufficient signal from the antenna. Independently, 91.207(c) requires ELT batteries to be replaced or recharged when the transmitter has been in use for more than 1 cumulative hour, or when 50 percent of their useful life (or, for rechargeable batteries, 50 percent of their useful life of charge) has expired. The new expiration date must be marked on the transmitter and entered in the aircraft maintenance record. 91.207 also lists operation exceptions (training entirely within a 50-nautical-mile radius, airplanes equipped to carry not more than one person, temporary removal up to 90 days with a log entry and “ELT not installed” placard, and others). Do not skip the inspection just because last year’s annual sticker is still in the window.

91.413: no person may use an ATC transponder specified in 91.215(a), 121.345(c), or 135.143(c) unless, within the preceding 24 calendar months, it has been tested and inspected and found to comply with part 43 appendix F. After installation or maintenance that could introduce data-correspondence error, the integrated system must also meet part 43 appendix E paragraph (c).

91.411 is an IFR-in-controlled-airspace rule, not a day-VFR airworthiness rule. No person may operate an airplane or helicopter in controlled airspace under IFR unless, within the preceding 24 calendar months, each static pressure system, each altimeter instrument, and each automatic pressure altitude reporting system has been tested and inspected to part 43 appendices E and F. Opening the static system (except using a drain or alternate-static valve) also requires a retest. A VFR private pilot still needs to know the interval because the written exam asks it and because many training airplanes are flown IFR by other renters.

Airworthiness Directives are mandatory

Part 39 Airworthiness Directives have the force of regulation. 91.403(a) puts AD compliance on the owner or operator. An AD may be one-time or recurring. Recurring ADs have their own hour or calendar intervals that do not reset just because an annual was signed. Before you accept a rental, look at the AD compliance record in the logs — not only the last annual entry. An overdue AD makes the airplane unairworthy even if every inspection sticker looks fresh. 91.403(c) also requires compliance with the Airworthiness Limitations section of the manufacturer’s maintenance manual or instructions for continued airworthiness when one has been issued.

Preventive maintenance a private pilot may do

43.3(g) allows the holder of a pilot certificate issued under part 61 (except a sport pilot, who is limited to light-sport aircraft the pilot owns or operates) to perform preventive maintenance on any aircraft owned or operated by that pilot that is not used under part 121, 129, or 135. 43.7(f) lets a person holding at least a private pilot certificate approve that aircraft for return to service after performing that preventive maintenance. The work is limited to the tasks in part 43 Appendix A(c), and only if the work does not involve complex assembly operations.

Appendix A(c) is a closed list. Classic private-pilot jobs on that list include removing/installing/repairing landing-gear tires; servicing shock struts and wheel bearings; lubrication that does not require disassembly beyond nonstructural covers; replenishing hydraulic fluid; replacing safety belts, position-light bulbs, spark plugs, prefabricated fuel lines, and batteries; and cleaning or replacing fuel and oil strainers or filter elements. Engine oil-and-filter service is taught as preventive maintenance when it stays inside those listed tasks — lubrication under (c)(6) and oil strainer/filter replacement under (c)(23) — and does not become a complex assembly job. The appendix does not use the phrase “oil change” as its own numbered line, so do not invent a special exception. Anything not on the list (magneto internal work, cylinder removal, fabric recover, structural repair) is maintenance or a repair for an A&P or repair station.

After the work, 43.9 requires a maintenance-record entry with a description of the work (or a reference to acceptable data), the date of completion, and the signature, certificate number, and kind of certificate of the person approving the work. That signature is the return-to-service for the work performed. A private pilot may not sign off someone else’s maintenance.

Progressive inspection exists in 91.409(d) as an approved alternative: the owner or operator requests it from the responsible Flight Standards office and must still complete a full inspection of the aircraft within each 12 calendar months. Most PAR training airplanes are on the annual/100-hour system, not a progressive program. If a logbook says “progressive,” treat it as official only when the 91.409(d) paperwork is actually in place.

Special Airworthiness Information Bulletins are not ADs

ACS element PA.I.B.K1c pairs Airworthiness Directives with Special Airworthiness Information Bulletins (SAIBs), and the test wants you to know they are different animals.

The practical distinction: an uncomplied-with applicable AD makes the airplane unairworthy, and 91.7 then prohibits the flight. An SAIB that you have not acted on does not. A wise owner still reads them, because an SAIB is often the FAA's first public notice of a problem that later becomes an AD.