Definition
A complete disassembly, inspection, repair as necessary, reassembly, and testing of an aircraft engine, performed in accordance with the manufacturer's specifications and approved data. During a major overhaul, the engine is restored to limits and tolerances specified by the manufacturer, with parts replaced or reconditioned as required to bring the engine back to a serviceable, like-new condition.
Plain English
Taking an engine completely apart, checking every part, fixing or replacing what's worn or damaged, putting it back together, and testing it to make sure it runs to the manufacturer's standards.
Context Anchor
Seen in aircraft engine maintenance records, logbooks, and discussions about engine condition, cost, and time between overhauls.
Derivation
Overhaul' comes from the nautical term meaning to haul rigging apart for inspection — literally to 'haul over' and examine. 'Major' distinguishes it from minor or top overhauls, which involve only partial work. Together it signals the most thorough level of engine restoration short of building a new one.
Why Pilots Care
A major overhaul resets engine condition, affects airworthiness, operating costs, and the aircraft's value and remaining service life.
Intuition Check
Do not read “major overhaul” as simply “a big repair.” In aircraft engine maintenance, it means a complete, structured process of taking the engine apart, inspecting it, repairing it as needed, reassembling it, and testing it.
Example Sentence 1
The aircraft's logbook showed 200 hours since the last major overhaul, leaving plenty of time before the next one was due.
Example Sentence 2
All clearances and parts replaced during the major overhaul were recorded before the engine was returned to service.