In November 2023, the UK Civil Aviation Authority launched the Hydrogen Challenge to explore hydrogen as a zero-carbon emission aviation fuel. The challenge involves investigating the use of hydrogen in powertrain systems, airport infrastructure, and regulatory frameworks. Cranfield Aerospace Solutions (CAeS), in collaboration with Exeter Airport Consortium and ZeroAvia, was selected to participate in the Hydrogen Sandbox Challenge. CAeS is working on Project Fresson, which involves developing a hydrogen fuel cell powertrain for the Britten-Norman Islander aircraft. This project is based at the Cranfield University Centre for Aeronautics in Bedfordshire, UK. The Project Fresson team is led by Daqing Yang, a principal air vehicle design engineer, and Roger 'Dodge' Bailey, the chief test pilot. They are focused on replacing one of the Islander's engines with new hydrogen technology. The team aims to demonstrate the feasibility of using hydrogen as a power source for the Islander, addressing challenges such as heat management and aerodynamic performance. Collaboration between engineers, test pilots, and design teams is integral to the project's success. Alexander Purvis, an air vehicle design engineer at CAeS, works closely with Bailey in flight testing and assessing the aircraft's performance. The team encounters challenges due to the vintage nature of the Islander, including discrepancies in construction that require meticulous attention and modification. The focus of the testing is on the powerplant adaptation for hydrogen propulsion. Detailed testing and modification are essential to ensure the successful integration of the new powertrain system. The Project Fresson team is dedicated to overcoming technical challenges and validating the use of hydrogen in aviation, positioning the UK at the forefront of hydrogen-powered flight innovation.