Siemens, Airbus and Rolls-Royce Team Up to Create a Hybrid-Electric Airplane
Siemens, Airbus, and Rolls-Royce's hybrid-electric airplane collaboration, announced in late 2017 under the E-Fan X programme, was one of the most ambitious partnerships in aviation history: three of the world's leading aerospace and engineering companies joining forces to develop a viable hybrid-electric propulsion system for commercial aircraft. The programme aimed to demonstrate that electric motors could replace conventional jet engines at meaningful power levels, paving the way for cleaner, quieter, and more efficient air travel.
Why Three Industry Giants Came Together
The electric mobility revolution had already transformed the automotive and marine sectors when Airbus, Rolls-Royce, and Siemens formalized their E-Fan X partnership. Aviation posed the greatest technical challenge: the power-to-weight requirements of flight are far more demanding than ground transport, and the energy density of batteries remained a limiting factor for anything beyond short-range, lightweight aircraft.
The partnership addressed this by targeting hybrid-electric propulsion rather than pure-electric flight. By combining gas turbine power with high-output electric motors, the consortium could achieve meaningful real-world testing at scale while establishing the engineering knowledge base for future all-electric programmes. Each partner contributed a distinct competency: Airbus handled overall systems integration; Rolls-Royce provided the turboshaft engine that would generate power for the electric motors; and Siemens supplied the two-megawatt electric motors, their power electronic control units, and the DC converters linking the systems together.
The E-Fan X Programme: What Was Actually Being Built
The E-Fan X testing platform was a British Aerospace 146 regional jet, a four-engine aircraft chosen for its existing propulsion architecture. The plan called for replacing one of the four gas turbine engines with a two-megawatt electric motor, representing a power level several times greater than any previously flight-tested electric propulsion system in a commercial aircraft context. As the programme matured and reliability was demonstrated, the intention was to progressively replace additional engines with their electric equivalents.
The two-megawatt target was significant. Siemens had been developing aircraft-grade electric motors since at least 2016, when the company partnered with Airbus and Pipistrel to fly the Cricri, a small twin-engine demonstrator using electric motors. The E-Fan X scaled that ambition dramatically, targeting motor outputs comparable to regional turboprops.
2016 Airbus, Siemens and Pipistrel Cricri electric aircraft demonstrator
Engineering Goals: Efficiency, Cost, and Environmental Impact
The three stated objectives of the E-Fan X programme were to improve efficiency, reduce operating costs, and lower the environmental impact of conventional aircraft propulsion. Electric motors operate with higher efficiency than gas turbines across a broad range of conditions, particularly at lower power settings such as taxi, climb, and cruise. Hybrid systems can leverage electric power precisely where it is most efficient and switch to gas turbine output where sustained high power is required, such as takeoff.
On the environmental side, the E-Fan X was explicitly positioned as a platform for learning how to decarbonize commercial aviation. The aviation sector is responsible for a significant share of global transport emissions, and hybrid-electric propulsion, even if it did not eliminate all fossil fuel use, offered a path toward meaningful reduction at scale.
A Foundation for the Next Generation of Sustainable Aviation
The E-Fan X programme was also described by its founders as a training ground for the next generation of aeronautical engineers and designers. The technical challenges of integrating high-voltage electrical systems into an aircraft, managing thermal loads, ensuring redundancy, and certifying novel propulsion architectures were all areas where aviation had limited institutional knowledge. Working through these challenges on a flying testbed built that knowledge base in a way that no laboratory programme could replicate.
The partnership ultimately laid important groundwork for the broader hybrid-electric aviation movement that followed, including regional aircraft programmes from multiple manufacturers and the growing eVTOL sector.
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