Swiss electric propulsion specialist H55 has reported progress in the development of a 200kWh aviation battery system for the RTX Hybrid-Electric Flight Demonstrator, as hybrid propulsion concepts move closer to commercial application in regional aircraft.
The demonstrator programme, led by Pratt & Whitney Canada and Collins Aerospace under RTX, aims to achieve up to 30% improvement in fuel efficiency through a hybrid-electric propulsion architecture.
The system combines a conventional thermal engine with a 1MW electric motor and H55’s energy storage system (ESS). The programme reached a key milestone in June 2025 with its first full-power ground test.
H55’s battery system designed for aviation certification
H55’s ESS has been developed specifically to meet aviation certification requirements, with a focus on safety, modularity and weight optimisation. The system is based on a battery architecture that has undergone testing aligned with European Union Aviation Safety Agency (EASA) requirements.
According to H55, the battery design has accumulated more than 2,000 flight hours across previous applications without incident, providing a validated baseline for integration into larger aircraft systems.
The ESS is modular in design, enabling flexible integration into aircraft structures and facilitating weight distribution—an important factor in aviation applications. The system is also intended to support scalability from smaller aircraft platforms to larger regional aircraft configurations.
Scaling electric propulsion for regional aviation
The hybrid-electric demonstrator is being developed on a modified De Havilland Canada Dash 8-100 platform and is expected to progress towards flight testing as integration continues.
The programme represents a step towards extending battery-electric propulsion technologies into the CS-25 (Part 25) category of regional transport aircraft, a segment where hybrid architectures are being explored to reduce fuel consumption and emissions.
H55’s technology originated from the Solar Impulse programme and has since been applied in a number of electric aircraft projects. The company said the current development builds on this experience to scale battery systems for higher-power applications.
Growing role of batteries in hybrid aviation
Hybrid-electric propulsion is being evaluated by aircraft manufacturers as a potential pathway to improve efficiency while maintaining operational flexibility. In such systems, batteries are used to supplement conventional engines, particularly during high-demand phases such as take-off and climb.
As these architectures develop, energy storage systems capable of meeting stringent aviation safety and certification requirements are expected to play a critical role.
The RTX demonstrator programme provides a platform for validating battery performance at regional aircraft scale, with potential implications for future commercial aircraft development.
