Definition
A federally required inspection of an aircraft and its engine that must be completed every 100 hours of flight time when the aircraft is used for hire or for flight instruction provided by the aircraft owner. The inspection covers the same scope as an annual inspection but is tied to flight hours rather than the calendar. It must be performed and signed off by an appropriately certificated mechanic, and the aircraft cannot legally be operated for hire beyond the 100-hour limit until the inspection is completed.
Plain English
A required check-up that certain aircraft must have after every 100 hours of flying. It applies to planes used for paid flights or for flight training where the owner provides the airplane. A qualified mechanic does the inspection and signs the logbook before the aircraft can keep flying for those purposes.
Context Anchor
You will see this term in aircraft maintenance records, flight school scheduling, rental checkout paperwork, and FAA discussions of required inspections.
Derivation
Inspection comes from the Latin idea of “looking into” or “examining closely.” In aviation, it means more than a quick look; it is a required check of the aircraft’s condition by someone authorized to perform it. The “100-hour” part refers to aircraft operating time, not calendar time.
Why Pilots Care
It keeps the aircraft legal to fly in training and rental operations and directly affects availability of planes for student pilots.
Intuition Check
Do not read “100-hour” as 100 hours on the calendar or 100 hours in a pilot’s logbook. It means 100 hours of aircraft time in service. Also, it is not the same thing as an annual inspection, although an annual inspection can satisfy the 100-hour requirement for that interval.
Example Sentence 1
The flight school grounded the trainer because it had reached 100.2 hours since the last 100-hour inspection.
Example Sentence 2
The flight school grounded the trainer until the 100-hour inspection could be finished to stay within regulatory limits.