Annual vs 100-Hour vs Progressive vs Phase Inspections: Which Applies to Your Aircraft

Four inspection programs appear in FAR 91.409, and which one applies to your aircraft is decided by its category and how it is operated — not by what the owner would prefer. Getting the distinction right matters because the wrong program means the aircraft is not airworthy, regardless of how thoroughly it was inspected.

The four are the annual, the 100-hour, the progressive inspection, and the manufacturer or approved programs required for larger and turbine-powered aircraft. The full rule is in 14 CFR 91.409.

Annual inspection (FAR 91.409(a))

An annual inspection is required within the preceding 12 calendar months unless an exception in 91.409(c) applies. Calendar months matter: an inspection signed off in March is good through the last day of March the following year, not the anniversary of the date.

The inspection is performed under Part 43 and approved for return to service by a person authorized under 43.7 — in practice an A&P mechanic holding an Inspection Authorization, or an appropriately rated repair station or manufacturer. An A&P without an IA can perform the work, but cannot sign the annual off.

100-hour inspection (FAR 91.409(b))

A 100-hour inspection is required for aircraft carrying any person other than crew for hire, and for flight instruction for hire in an aircraft the instructor provides. That last condition is the one most often misread — it applies when the instructor supplies the aircraft, not when a student brings their own.

The 100-hour limit may be exceeded by up to 10 hours while en route to a place where the inspection can be done, and that extra time counts toward the next 100 hours. Flying 6 hours past the limit to reach a shop means the next inspection is due at 94 hours, not 100.

An annual satisfies the 100-hour requirement. The reverse is not true: a 100-hour does not count as an annual unless it is performed by someone authorized to perform annuals and entered as an annual. A certificated A&P mechanic can perform the 100-hour inspection without an Inspection Authorization.

Progressive inspection (FAR 91.409(d))

A progressive inspection spreads the inspection across the year instead of concentrating it in one event. The owner or operator submits a written request to the responsible FAA Flight Standards office and provides an IA mechanic, certificated airframe repair station or manufacturer to supervise or conduct it, a current inspection procedures manual, an inspection schedule, and adequate facilities and technical data.

The full aircraft must be inspected within each 12 calendar months. Aircraft on a progressive inspection are exempt from the annual and 100-hour requirements.

If the program is discontinued, the owner must notify Flight Standards in writing. The annual is then due within 12 calendar months of the last complete inspection under the program, and the 100-hour within 100 hours of it. A progressive inspection is best suited to high-utilization aircraft where annual downtime is costly — the administrative overhead only pays off when the aircraft flies enough to justify it.

Phase and manufacturer programs (FAR 91.409(e) and (f))

Large airplanes, multiengine turbojets (including the Cessna Citation line), multiengine turboprops and turbine-powered rotorcraft must use one of four programs and identify it in the maintenance records: a Part 121/135 continuous airworthiness inspection program, a Part 135 approved aircraft inspection program, the current inspection program recommended by the manufacturer, or an owner-developed program approved by the FAA. Manufacturer programs typically divide the work into phases scheduled by hours, cycles or calendar time.

Single-engine turboprops and single-engine jets are not listed in 91.409(e), so the annual — and the 100-hour, if used for hire — rules apply unless they are on a progressive inspection or a Part 135 program. This catches owners moving up from a piston into a single-engine turbine who expect a phase program and find the annual still applies.

Turbine engine inspections such as hot section inspections are scheduled by the engine manufacturer's maintenance data and vary by engine model and operation. Check the data for your specific engine rather than working from a figure quoted for a different variant.

What the logbook entry must show

Under FAR 43.11, the inspection entry records the type and extent of the inspection, the date, the aircraft's total time in service, and the signature, certificate number and kind of certificate of the person approving or disapproving return to service. If the aircraft is not approved, the owner receives a signed list of discrepancies. That list is the document that tells you what has to be addressed before the aircraft flies again.

Which program fits your aircraft

Inspections at Michigan Aviation

Michigan Aviation is FAA Part 145 repair station KL2R956K at Oakland County International Airport (KPTK) in Waterford, Michigan. Inspection work we perform:

• Annual, 100-hour, phase and pre-buy inspections
• Cirrus SR20, SR22 and SR22T 100-hour and annual inspections
• Cessna Citation CJ and Williams FJ44 maintenance

If you are not certain which program your aircraft falls under, bring the aircraft details and current inspection status and we will confirm the applicable program and scope before anything is booked.