time between overhaul

A time period specified by the manufacturer of an aircraft engine as the maximum length of time the engine should be run between overhauls without normal wear causing parts of the engine to be worn beyond safe limits. TBO depends upon the engine being operated properly and maintained in accordance with the engine manufacturer's recommendations. The overhaul of an engine when it reaches its TBO hours is not mandatory except for certain commercial operators that have this requirement written into their operations manual.