Research on Safety Analysis of Mode Transition of Flight Guidance System Based on STPA

In the process of automatic flight of civil aircraft,the mode transition of the flight guidance system is an important factor affecting safety and should be subject to a comprehensive safety analysis.Traditional safety analysis methods mainly focus on the failure factors of individual components,ignoring the safety issues arising from the nonlinear interactions between components.For this reason,this paper adopts the System Theory Process Analysis(STPA) method to conduct a systematic and complete analysis of the mode transition of the flight guidance system.Meanwhile,considering that there are parts in the STPA me-thod that require manual analysis,the formal model checking tool UPPAAL based on the theory of timed automata is introduced to model and verify the system,so as to ensure the correctness of the control structure diagram and identify the truly Unsafe Control Actions(UCA),thus avoiding the waste of resources.Finally,a standardized causal factor analysis framework is proposed to analyze the verified UCAs one by one.The example proves that the proposed method is effective for the safety analysis of aviation complex systems.