Under what condition may an engine be granted zero time by the manufacturer?

An engine can be granted zero time by the manufacturer specifically when it has been rebuilt. The term "zero time" indicates that the engine is considered to have no operational hours or cycles and is essentially treated as a brand-new engine from a maintenance perspective.

In the context of aviation maintenance, a rebuild involves extensive refurbishment of the engine, including replacing worn parts, and ensuring that it meets the original specifications set forth by the manufacturer. This process may involve reconditioning major components and replacing parts that are out of tolerance, thereby providing a high level of assurance regarding the engine's reliability and performance after the rebuild.

Rebuilding is distinct from both overhauling and remanufacturing. While an overhaul generally refers to disassembling the engine, inspecting, and repairing components as necessary to return it to service, this does not necessarily qualify it for zero time status unless specific criteria are met. Similarly, remanufacturing may involve rebuilding, but it may not always adhere to the same strict standards for zero time classification established by the manufacturer. Therefore, the condition that qualifies an engine for zero time primarily aligns with it being fully rebuilt.