Annual and Progressive Inspections and Part 43 Appendix D
The calendar and hour rules
Section 91.409(a) forbids operation unless the aircraft has had an annual inspection within the preceding 12 calendar months. Because the rule is written in calendar months, an inspection performed any day in January 2025 satisfies the requirement through January 31, 2026. The 100-hour inspection applies to aircraft carrying persons other than crew for hire, and to flight instruction for hire; it may be exceeded by up to 10 hours only to reach a place where the inspection can be done, and that excess carries forward into the next interval.
Progressive inspections
An approved progressive program distributes the same scope of inspection over numbered phases. It must be FAA-approved, use checklists, and complete a full cycle within 12 calendar months (and within 100 hours where the 100-hour rule applies). An IA may perform or supervise progressive inspections.
Appendix D scope and detail
Appendix D sets the minimum. Before work begins, inspection plates, access doors, fairings, and cowling are opened or removed. The inspection then covers the fuselage and hull, cabin and cockpit, engine and nacelle, landing gear, wing and center section, empennage, propeller group, engines, and appliances, and includes verification that required placards, markings, and documents are present and current. The checklist may be more detailed than Appendix D; it may never be less.
Traps
A clean airframe is not an inspection; the aircraft must be opened up enough to see. An annual does not substitute for a 100-hour, or the reverse, when both rules apply. Discrepancies must be corrected and the correction inspected before an airworthiness approval is signed, and inoperative equipment must be handled under the applicable operating rule rather than informally deferred.
Rule of thumb
Annual due date equals the last day of the twelfth month after the month of inspection.