Fault Tree Analysis Primer

Book excerpt: One of the most valuable root-cause analysis tools in the system safety toolbox is fault tree analysis (FTA). A fault tree (FT) is a graphical diagram that uses logic gates to model the various combinations of failures, faults, errors and normal events involved in causing a specified undesired event to occur. The graphical model can be translated into a mathematical model in order to compute failure probabilities and system importance measures. A FT can model all aspects of a system, including hardware, software, human actions and the environment. FTs are employed to evaluate large complex and dynamic systems, in order to understand and prevent potential safety and reliability problems. Using the rigorous and structured methodology of FT construction allows the systems analyst to model the unique combinations of fault events that can cause an UE to occur. This book provides an overview of the FTA process; it describes the symbols, terms, construction methodology and mathematics of FTA.