Development of a Metrics Framework for Real-time System-Wide Safety Assurance

Abstract

Real-time System-wide Safety Assurance (RSSA) is one of six strategic thrusts defined by NASA's Aeronautics Research Mission Directorate to articulate its vision for the future of aviation, and to drive research efforts in the near future. A framework of metrics is developed as part of work supporting the definition of an RSSA research roadmap. The bases for metric development are an RSSA descriptive model outlining the system architecture at a conceptual level, a review of previous safety metrics used to measure the impact of NASA research, and the delineation of challenges and opportunities stemming from unique systemic features in RSSA. The metrics are structured in a three-tier hierarchy that mirrors the functional decomposition of RSSA. Among them, mid-level metrics are novel and significantly distinct from prior aviation safety measures. Top-level metrics circumvent notable challenges associated with the current use of aggregate accident statistics, whereas low-level metrics are adopted from a broad review of the state of the art. All metrics are defined and discussed in detail. Qualitative validation indicates the framework meets its purpose and successfully addresses salient challenges. Aspects for further improvement and requisite future work are discussed.