High performance reliability analysis of phased mission systems

Systems often operate over a set of time periods, known as phases, in which their reliability structure varies and many include both repairable and nonrepairable components. Success for such systems is defined as the completion of all phases, known as a phased mission, without failure. An example of such a system is an aircraft landing gear system during a flight. The Binary Decision Diagram (BDD) method provides the most efficient solution to the unreliability of non-repairable systems whilst for repairable systems Markov or other state-space based methods have been most widely applied. For systems containing both repairable and non-repairable components the repairable modelling methods are normally used, despite having far higher computational expense than the non-repairable methods, since only they are able to handle the dependencies involved. This paper introduces improvements to the BDD method for analysing non-repairable systems as well as an entirely new method that utilises a new modelling technique involving both BDD and Markov techniques.