H55 battery architecture anchors RTX hybrid-electric propulsion demonstrator

SION, Switzerland - H55 in Sion, Switzerland, announced continued progress in developing its 200-kilowatt-hour energy storage system for the RTX Hybrid-Electric Flight Demonstrator, following the program’s first full-power system test in June 2025.

The demonstrator, led by RTX in Arlington, Va., through its subsidiaries Pratt & Whitney Canada in Longueuil, Quebec, and Collins Aerospace in Charlotte, N.C., aims to achieve up to a 30 percent improvement in fuel efficiency for regional aircraft. The hybrid-electric propulsion architecture combines an advanced thermal engine, a 1-megawatt electric motor, and H55’s battery system.

Pratt & Whitney Canada built on H55’s battery architecture and safety mechanisms as a certifiable foundation for the propulsion system. H55’s energy storage system, validated through extensive flight operations, established the compliance and safety baseline that enabled the program to advance.

Commenting on the partnership, H55 CEO Rob Solomon said, "There's a meaningful distinction between being selected as a component supplier and being chosen as a certification foundation. Pratt & Whitney Canada didn't just purchase our batteries. They built their demonstrator's compliance baseline on an architecture that H55 has already flown for more than 2,000 hours without incident and validated through EASA test campaigns. That's what eight years of disciplined certification work makes possible: when a program at regional aircraft scale needs to move fast, they reach for the system that's already proven. This milestone, the first full-power ground test of a hybrid-electric propulsion system at this scale, belongs to the entire team."

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H55’s energy storage system is designed to meet aviation certification requirements, featuring a lightweight, modular architecture that enables flexible integration and weight distribution. The system is based on a cell architecture that has completed European Union Aviation Safety Agency test campaigns.

The technology builds on H55’s broader experience in electric propulsion, including safety validation campaigns for battery modules to support the certification of next-generation propulsion systems.

H55 CTO and co-founder Sébastien Demont said, "This integration milestone represents a defining moment for H55 and for electric aviation as a whole. The certifiable battery architecture we developed for CS23 aircraft has proven its scalability: the same cell-level safety philosophy, the same engineering discipline, is now powering a battery system at the heart of a CS25 hybrid-electric demonstrator alongside Pratt & Whitney Canada. We are not adapting a concept, we are scaling a proven, validated platform. This is what it means to build technology that is certifiable by design."

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H55 traces its origins to the Solar Impulse project, which demonstrated long-duration electric flight. The company has since developed and flown multiple electric aircraft platforms, building operational experience that informs its current propulsion system designs.

Moving forward

The RTX Hybrid-Electric Flight Demonstrator is progressing toward aircraft integration and flight testing aboard a modified De Havilland Canada Dash 8-100. The program is intended to validate hybrid-electric propulsion at the regional aircraft scale and extend H55’s technology into the Part 25 and CS-25 transport category.

Expanding into the regional aircraft segment significantly increases the addressable market for H55’s propulsion technology, as aircraft manufacturers evaluate hybrid-electric systems to improve efficiency and reduce emissions.

Solomon added, "Programs like this allow us to demonstrate that the same certifiable battery architecture developed for smaller aircraft can scale toward the regional aviation market. That transition represents a major step in unlocking the commercial potential of electric propulsion."

As hybrid-electric aircraft move toward entry into service, energy storage systems are expected to become a critical lifecycle component of aircraft operations.