Extension of hazard and safety analysis techniques to address problems of hierarchical scale

Hazard analysis techniques are evolving to deal with the complexity of modern aerospace systems. However, a problem still arises in assessing complex systems using classical safety analysis techniques and linking the results back to the functional hazard assessment. The problem arises from the scale and complexity of systems, and the difficulty of relating the analysis results across the design hierarchy. This paper shows one way to address the problem by relating functional failure analysis, hazard and operability studies, failure mode and effects analysis and fault tree analysis to each other, integrating them into a new hybrid technique, and applying it to systems that are described hierarchically. The technique is called FLASH (failure logic for analysis of system hierarchies). It has been applied and tested on a fault-tolerant computer-based braking system