Availability growth modeling and assessment

The reliability growth process, applied to a complex system under development, involves surfacing failure modes, analyzing the modes and their causes, and implementing corrective actions (fixes) to detected problems. In such a manner, the system reliability is grows and its configuration is going to be mature with respect to reliability. The conventional procedure of the Reliability growth implies evaluation of two principal parameters of the Non-Homogeneous Poison Process (NHPP) related to the failure rate only. In addition to the Reliability aspect, the Availability factor, and, as the result, the Availability growth (not only Reliability growth) is extremely important for the repairable Systems. Yet because the standard NHPP does not take into account the repair rate parameters, the practitioners are awaiting for a long time for an expanded procedure for the Availability Growth tracking. This paper suggests a model and a numerical method to evaluate these parameters, establishing consequently the Inherent Availability Growth model, i.e. considering only corrective maintenance times due to failures. The model can be further generalized for Operational and Achieved Availability by taking in account the preventive maintenance, administrative and logistics times as appropriate.