Safe Architecture Design of Flight Control System for eVTOL

Advanced flight control system, aviation battery and motor technologies are driving the rapid development of eVTOL to offer possibilities for Urban Air Mobility. The safety and airworthiness of eVTOL aircraft and systems are the critical issues to be considered in eVTOL design process. Regarding to the flight control system, its complexity of design and interfaces with other airborne systems require detailed safety assessment through the development process. Based on SAE ARP4754A, a forward architecture design process with comprehensive safety assessment is introduced to achieve complete safety and hazard analysis. The new features of flight control system for eVTOL are described to start function capture and architecture design. Model-based system engineering method is applied to establish the functional architecture in a traceable way. SFHA and STPA methods are applied in a complementary way to identify the potential safety risk caused by failure and unsafe control action. PSSA with FTA assists to allocate safety requirements and modify the architecture of flight control system. Through the practice of safety-oriented architecture design of flight control system for eVTOL, safety requirements are identified, and related modifications and design are implemented to optimize the system architecture design. Comparing to the safety assessment method with only ARP4761 methods, the combination of ARP4761 and STPA will extend the perspective to deal with potential unsafety issues. Hazards caused by random failure and incorrected control are all tackled. The work of this paper can serve as a useful reference for the system safety assessment and architecture design for eVTOL and airborne systems.