Definition
Components installed on a certificated aircraft to substitute for original or previously installed parts. To be legally installed, replacement parts must meet FAA approval requirements — typically through a Parts Manufacturer Approval (PMA), Technical Standard Order (TSO) authorization, production under a type or production certificate, or other FAA-approved process — and must be appropriate for the specific aircraft make and model.
Plain English
Parts used to replace worn, broken, or removed parts on an aircraft. They have to be FAA-approved and correct for that aircraft, not just any part that physically fits.
Context Anchor
Seen when discussing aircraft maintenance, inspections, FAA oversight, and whether an aircraft remains safe and legal to operate.
Derivation
Replacement comes from “replace,” meaning to put something back in the place of something else. That helps here because the part is not just an extra item; it is taking the place of a part that was already part of the aircraft.
Why Pilots Care
Using unapproved replacement parts can invalidate the aircraft's airworthiness certificate and create serious safety risks during flight.
Intuition Check
Do not assume “replacement parts” means any part that looks the same or can be made to fit. In aviation, the replacement part must be suitable and permitted for that aircraft.
Example Sentence 1
The mechanic ordered FAA-approved replacement parts for the brake assembly before returning the aircraft to service.
Example Sentence 2
Before flight, the owner verified that all replacement parts installed during the annual inspection carried proper documentation.