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.
Plain English
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.'
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.