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.
Plain English
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.
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.