Definition
An aircraft component that has a mandatory maximum operating life set by the manufacturer and approved by the regulatory authority, after which it must be removed from service and cannot be returned to use regardless of its apparent condition. The life limit may be expressed in flight hours, calendar time, operating cycles, or landings, and is tracked individually for each part.
Plain English
A part that has a fixed expiration -- once it has been used for the set amount of time or number of cycles, it must come off the aircraft and be discarded, even if it still looks fine.
Context Anchor
Seen in aircraft maintenance records, logbooks, inspection planning, and airworthiness-limitations sections for aircraft, engines, propellers, and some components.
Derivation
“Life” here means the approved service life of the part, not whether the part looks worn out. “Limited” means that service life has a fixed boundary that cannot be exceeded.
Why Pilots Care
Failure to replace a life-limited part can ground the aircraft, void insurance, or cause in-flight failure of critical systems.
Intuition Check
Do not assume a life-limited part can stay installed just because it looks good or still works. The limit is mandatory; reaching it means the part must be removed from service.
Example Sentence 1
The mechanic pulled the engine logbook to verify that none of the life-limited parts had exceeded their hour limits.
Example Sentence 2
During the annual inspection, the mechanic verified the remaining life on every life-limited part listed in the engine logbook.