Plain English Meaning
An engine that has been taken fully apart, restored to like-new condition with parts that meet new-engine specifications, and given a fresh logbook that starts its time back at zero. Only the original manufacturer (or someone they authorize) is allowed to do this and call it 'rebuilt.'
Full Definition
A used aircraft engine that has been completely disassembled, inspected, repaired as necessary, reassembled, tested, and approved in the same manner and to the same tolerances and limits as a new engine using either new parts or used parts that conform to new-part tolerances and limits. Under FAA regulations (14 CFR 91.421), a rebuilt engine receives a zero-time logbook, meaning its operating history is reset and a new maintenance record is started. Only the engine manufacturer, or an agency approved by the manufacturer, may rebuild an engine and issue zero-time records.
Context Anchor
You may see this term in engine logbooks, maintenance records, aircraft sale listings, or discussions about an engine’s history.
Why Pilots Care
A rebuilt engine is typically returned to zero-time status with full TBO remaining, directly affecting purchase price, insurance, and future maintenance planning.
Intuition Check
Do not assume “rebuilt” just means someone fixed the engine after a problem. In this FAA maintenance sense, it means the engine was restored and tested to new-engine limits.
Example Sentence 1
The aircraft's logbook showed a rebuilt engine installed last year, so the engine time was recorded as zero even though the airframe had over 4,000 hours.
Example Sentence 2
The buyer required proof that the engine had been rebuilt by an approved facility before completing the purchase.