Generalized cost functions of avionics breakdown maintenance strategy

In this study, the generalized cost functions are proposed for choosing the optimal option of breakdown maintenance strategy of avionics systems. A mathematical model of avionics line replaceable unit (LRU) is developed. The model considers the main characteristics of the preflight checks and continuous testing of the LRU using built-in test equipment (BITE) in-flight. The equation for the mean time between unscheduled removals (MTBUR) is derived for an arbitrary and exponential distribution of time to failure. The cost functions are determined as the total operating costs separately for the warranty and post warranty period of operation. Different options of single-level, two-level and three-level maintenance are mathematically modeled and numerically analyzed for the warranty and post-warranty period of operation. The proposed analytical expressions take into account the trustworthiness of BITE, periodicity of preflight testing, cost of different maintenance operations, permanent and intermittent failure rate of LRUs and some other parameters. Numerical examples are included to illustrate the main features of the proposed mathematical models.