Birnbaum and criticality measures of component contribution to the failure of phased missions

This paper develops measures, which identify the contribution to system failure when the system operates a phased mission. The measures developed are the equivalent of Birnbaum's measure of importance and the criticality measure of importance in a conventional analysis. It is assumed that during the mission the system components cannot be repaired. In the determination of the importance measures, the contribution to phase failure is considered in two aspects: failure during the phase (in-phase importance) and failure on transition to a phase (transition importance). Component importance measures indicate the contribution to phase and overall mission unreliability.