Application of Discrete Time Time-Sequence Non-Static Fault Tree in Safety Assessment of Civil Aircraft Auxiliary Power System

The auxiliary power unit system(APS) is an important modern airborne system, whether in the field of civil aviation or military aircraft. According to the requirements of SAE ARP 4761, static and non-static fault tree analysis methods are often used for system level safety analysis. Non-static fault trees generally need to be transformed into isomorphic state space models to be solved, which lacks universality and computational complexity, making them unable to be widely used in the engineering field. This article proposes a discrete time Time-Sequence dynamic fault tree solution method and calculates a case study of its application in APS. The calculation results indicate that as the time division of discrete time tasks increases, the relative error of the calculation decreases. When the task time segment is greater than 10, the relative error is less than 0.5%, the calculation results meet the needs of engineering use, and the calculation amount is controlled within an acceptable range.