Developing a subsystem reliability growth program

This paper presents an overview and a discussion of the methodology used in the AMSAA Subsystem Reliability Growth Planning Model (SSPLAN). SSPLAN is used to develop subsystem reliability growth planning curves that, with a specified probability, demonstrate a system mean time between failure (MTBF) objective with a specified level of confidence. The model uniquely determines the subsystem growth test times either by minimizing reliability testing costs or by using a specified allocation of the system-level failure intensity among the individual subsystems. SSPLAN provides a means to develop subsystem testing plans which will cost effectively demonstrate a system MTBF goal prior to system-level testing. Although additional failure modes will likely appear during system integration, a structured subsystem testing program will eliminate or reduce many failure mechanisms, and result in less system-level testing, since the initial system MTBF will be increased. The model can also serve as a means for prime contractors to integrate the reliability growth activities of their subcontractors. The model is currently under consideration as a management tool for structuring a reliability subsystem test program for two major Army weapon systems