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Markov model-based reliability and safety evaluation for aircraft maintenance-system optimization

Redundant aircraft systems are intended for operation under established flight missions and maintenance programs. Systems may have latent failures and their reliability may vary, depending on previously made scheduled checks and repairs. System failure modes are a basis for assessing failure effect on flight safety, and are determined by the components' failure modes and their sequence of occurrence. Using a model of Markov homogeneous process it is shown that probabilities of the aircraft system states can be presented as a product of two multipliers. The first of them depends on a components failure rate and flight duration under condition of serviceability of all the components at take-off. It may be determined by known methods using the Markov processes and Boolean logic. The other depends on the check and repair intervals for the components and system states, as well as the flight phase limits. The practical calculation formulae are presented. The proposed method presents a new practical approach for aircraft systems analysis and may be used for a wide range of complex systems with latent failures. The analytical model may be used for solving a number of practical tasks: redundancy optimization; determining check intervals; optimizing aircraft minimum equipment list, etc.-in order to minimize operation cost and ensure flight safety. Practical application of this technology to modern aircraft has shown good results.