Model Based Safety Analysis (MBSA) Tool for Avionics Systems Evaluation

Model-Based Safety Analysis (MBSA) is an approach in which the design and safety engineers share a common system model created using a model-based development process. MBSA intends to act as a bridge between design engineers and safety engineers reducing the time required to verify the safety of a new designed system. The system model can consist of the failure behavior exclusively or along with the physical behavior of the system and components. MBSA can be built upon qualitative methods (Boolean formalisms such as fault trees or event trees) or quantitative methods (Transition systems such as Markov chains and Petri nets). Our work is based on developing a new Object-Oriented tool utilizing the MBSA approach. The tool utilizes various algorithms such as directional traverse algorithms, Constraint Satisfaction Problems (CSP) Back-tracking algorithms and Markov chains. The tool output is a definition of minimum cut sets (failure combinations which cause the total failure of the system). Unfortunately, most of the MBSA tools are applied and evaluated upon more mechanical systems with such components as pumps and valves. The aircraft avionics systems are not always considered during the development phase. In this paper, a new library of avionics systems' components - such as data buses or sensors - is built according to various standards. The library is then used to model various types of related assemblies from a subsystem such as a specific transmission system to a complete hierarchy of an avionics system. The tool is then will be evaluated according to the output failure modes or combinations. The results are compared to the failure combinations extracted from the classical safety analysis methods. The results will show if the developed tool can be considered as a decent replacement of the classical safety analysis methods.