The use of a discrete event simulation to model the achievement of maintenance free operating time for aerospace systems

This paper describes a discrete event simulation model that allows a system designer to investigate the means and feasibility of meeting an operating period requirement. The model takes into account the system reliability, the proposed mission tasking and the maintenance support regime. The life of individual basic items may be modelled using any appropriate model, and may include the effect of mission-phase environmental factors. System reliability is modelled by state-space representations of system architecture, and is considered when calculating the effect of failures on system condition and mission capability. The maintenance regime is modelled from user-defined combinations of basic maintenance operations, and is influenced by imperfect diagnostics and prognostics. The simulation, although complex, is straightforward and timely for designers to use as an interactive "what-if" tool. The basic simulation output is the probability of achieving an operating period of a desired length. Comprehensive listing of particular simulation events is optional. The simulation also shows the effects of a scheduled repair policy, prognostic usage, repair management, etc. on operating success, thus permitting an interactive customer-designer dialog and truly optimum product design.