Plain English Meaning
A fresh logbook started from zero hours after an engine or component is rebuilt to like-new condition. The old logbook is kept on file, but time tracking starts over in the new one.
Full Definition
A new logbook started for an engine, propeller, or component that has been completely overhauled to factory-new tolerances and limits, allowing its operating time to be reset to zero. The original logbook is retained as a permanent record, and the zero-time logbook tracks all time and maintenance from the overhaul forward.
Context Anchor
Seen in aircraft maintenance records, especially when reviewing the history of a rebuilt engine or major component.
Derivation
Zero-time' refers to resetting the recorded operating time to zero. The term reflects the regulatory allowance — under specific conditions — to treat the overhauled item as if it had no prior service time for record-keeping purposes.
Why Pilots Care
Accurate zero-time records prevent missed mandatory overhauls or inspections that could lead to engine failure in flight.
Intuition Check
Do not assume “zero-time” means the engine or component has never existed or has never been used. It means its approved maintenance time record has been reset to 0 after a qualifying rebuild.
Example Sentence 1
After the manufacturer overhauled the engine to new limits, it was returned to service with a zero-time logbook.
Example Sentence 2
During the pre-purchase inspection, the buyer asked to see the zero-time logbook to verify the engine's maintenance status.