An optimal sparing model for the operational availability to approach the inherent availability

In an operating system, especially for the military, it is very desirable to achieve a high operational availability (A/sub O/). In fact, the optimal goal would be for the operational availability to approach or equal the inherent availability (A/sub I/). This could be accomplished by eliminating or reducing all time delays that keep the system down (nonoperational) and are not directly associated with the repair time (mean time to repair) of a failed item. The main culprit in keeping the system down is the availability of required spares. Therefore, if the logistic delay time due to the availability of spares is to be eliminated or reduced, the spares necessary to keep the system operational must be available at the location at all times. This, however, implies that the logistic delay time in the event of a system's failure, other than location delays, would be zero. Eliminating or reducing these delays requires an efficient and timely spares pipeline. An efficient and cost-effective way that this can be accomplished is to synchronize the spares pipeline with the system architecture and the fault-tolerant features. It is the goal for any system to be 100% available at the moment when it is required to accomplish a task. Therefore, an A/sub O/ optimization concept must be established. The maintenance and spare concept, in conjunction with an expert system using real-time computers as described in this paper, could make it possible to achieve the desired A/sub O/.