Measurement of the actual versus predicted uptime of a system
Operational availabilityinsystems engineering is a measurement of how long a system has been available to use when compared with how long it should have been available to be used.
Operational availability is a management concept that evaluates the following.[1]
Diagnostic down time
Criticality
Fault isolation down time
Logistics delay down time
Corrective maintenance down time
Any failed item that is not corrected will induce operational failure. is used to evaluate that risk. Operational failure is unacceptable in any situation where the following can occur.
Capital equipment loss
Injury or loss of life
Sustained failure to accomplish mission
In military acquisition, operational availability is used as one of the Key Performance Parameters in requirements documents, to form the basis for decision support analyses.[2]
Aircraft systems, ship systems, missile systems, and space systems have a large number of failure modes that must be addressed with limited resources.
Formal reliability modeling during development is required to prioritize resource allocation before operation begins. Estimated failure rates and logistics delay are used to identify the number of forward positioned spare parts required to avoid excessive down time. This is also used to justify the expense associated with redundancy.
Formal availability measurement is used during operation to prioritize management decisions involving upgrade resource allocation, manpower allocation, and spare parts planning.
Operational availability is used to evaluate the following performance characteristic.
For a system that is expected to be available constantly, the below operational availability figures translate to the system being unavailable for approximately the following lengths of time (when all outages during a year are added together):
The following data is collected for maintenance actions while in operation to prioritize corrective funding.