Case Study: Application of STPA in the development of a Fuel‐Cell Propulsion System

To mitigate the impact of climate change caused by aviation, several states have committed to achieving the Net Zero 2050 goal for flight operations. Meeting this ambitious target requires the aviation industry to significantly reduce its emissions output, driving the development of zero‐emission technologies such as electric or hydrogen propulsion systems. Project Fresson aims to demonstrate the feasibility of utilizing Hydrogen Fuel Cell technology to generate the electrical power necessary to drive an electric engine retrofitted onto a Britten‐Norman BN‐2B Islander aircraft. While these technologies hold great promise for decarbonizing aviation, they also introduce new challenges. The integration of hydrogen propulsion systems comes with increased complexity, as these systems involve multiple interconnected subsystems, each with their own behaviours and dynamics. This complexity amplifies the potential for emergent risks, particularly in critical operational scenarios. Addressing these challenges is essential to ensuring safe and effective deployment of novel technologies. This paper presents a case study on the application of System Theoretic Process Analysis (STPA) as a powerful methodology to address inherent challenges that arise when developing systems. By systematically identifying safety constraints and uncovering potential hazards, STPA enables the early detection of risks and emergent behaviours that may not be apparent through traditional safety processes. Unlike traditional approaches, STPA considers the system's concept of operations, and how interactions within as well as beyond its boundaries, may lead to unsafe conditions. The aim is to demonstrate how STPA enables early identification and implementation of mitigations against undesirable emergent behaviours. By doing so, it enables the definition of a comprehensive set of functional safety requirements that ensures the safe and efficient integration of hydrogen propulsion technologies, ultimately advancing their viability as a solution for sustainable aviation.