# Mean Downtime

Also found in: Acronyms.

## Mean Downtime

a value that characterizes the maintainability of a technical device. The mean downtime is equal to the mathematical expectation of the time required to restore the device to operational condition. It is the arithmetic mean of all the periods of idleness connected with the restoration to operational condition following an in-service failure. It depends on monitoring procedures, the accessibility of the device to examination, the possibility of disassembly, and the dependability of the device’s parts. One of the main indicators of the reliability of repairable devices, the mean downtime is reported in performance specifications.