Definition
The section of Title 14 of the Code of Federal Regulations that establishes inspection requirements for civil aircraft operated under Part 91, including the annual inspection requirement and, for aircraft carrying persons for hire or used for flight instruction for hire, the 100-hour inspection requirement. It also describes alternative inspection programs available to certain aircraft, such as progressive inspections and approved manufacturer or AAIP programs.
Plain English
This is the federal rule that says when an airplane must be inspected to remain legal to fly. Most aircraft need an inspection at least once a year, and aircraft used for hire or for paid flight training need another inspection every 100 hours of flight time.
Context Anchor
Seen in aircraft maintenance records, inspection planning, aircraft rental or training operations, and discussions about whether an aircraft is legal to operate.
Derivation
14 CFR means Title 14 of the Code of Federal Regulations, the volume covering aeronautics and space. Part 91 covers general operating and flight rules for civil aircraft. Section 91.409 is the specific paragraph within that part that deals with inspections.
Why Pilots Care
Compliance keeps the aircraft legally airworthy; skipping the required inspections can ground the plane, void insurance, and create safety risks.
Intuition Check
Do not read this as the inspection itself. It is the regulation that tells when certain inspections are required.
Example Sentence 1
Before signing off the aircraft for the flight school, the mechanic confirmed the 100-hour inspection required by 14 CFR part 91, section 91.409 had been completed and logged.
Example Sentence 2
The flight school logged the 100-hour inspection to satisfy 14 CFR part 91, section 91.409 for its rental aircraft.