Two recommendations for the acquisition and growth of reliable systems

Abstract

This paper presents two recommendations for improving the acquisition and growth of reliable systems that support the intent of DoDI 5000.02 and ANSI/GEIA-STD-0009: ● During the proposal evaluation and selection process, use a metric based on a Historical Observed Reliability Ratio (HOR-R, pronounced “horror”) of the potential supplier's predicted or assessed reliability measure to its observed field reliability value. ◯ Consistent HOR-R values of less than or equal to 1.0 provide confidence that the supplier has a repeatable process for translating its prediction/assessment methodology of choice into correlated field experience that meets or is better than the reliability requirement, representing limited reliability and life cycle cost risk to the customer. ◯ HOR-R values greater than 1.0 indicate potential risk to the customer, in that the supplier has not demonstrated an ability to achieve reliability requirements in the field based on its prediction/assessment techniques, implying increased reliability and life cycle cost risk. ◯ Inability of a supplier to provide any HOR-R value based on past performance represents an unknown level of reliability and life cycle cost risk to the customer. ◯ Any reliability prediction or assessment technique can be used, e.g., empirical handbooks, physics-of-failure (PoF), etc., since the effectiveness of the metric is not based on the ability of the approach to generate a “suitable” number. ◯ The metric can be applied to requirements based on Mean Time Between Failure (MTBF), Mean Time to Failure (MTTF), Reliability (R(t)), Operational Availability (Ao), etc. ● Extend the definition of reliability growth A-Mode and B-Mode failures [1, 2] to include classifications of “Unanticipated Failure Mode” and “Unexpected Failure Mode”. ◯ The larger the percent contribution of Unanticipated Failure Modes to Total Failure Modes, the less robust the Design for Reliability (DFR) process is in proactively identifying failure modes prior to testing. Corrective action is based on an evaluation of current DFR analyses, modeling and simulation processes to improve their ability to identify failure modes. ◯ The larger the percent contribution of Unexpected Failure Modes to Total Failure Modes, the less effective the DFR process is in mitigating known failure modes. Corrective action is to improve reliability design practices, rules, procedures, etc., to more effectively mitigate identified failure modes prior to test. These two recommendations, and the corrective actions they initiate, provide benchmarks to improve both the effectiveness of acquisitions in reliability and life cycle cost risk avoidance, and the ability of DFR activities to proactively identify and mitigate failure modes prior to their more costly discovery during testing or field use.