- Hybrid-electric propulsion is set to reshape general aviation.
- Global test programs are driving the maturation of key hybrid propulsion systems.
- Hybrid propulsion for general aviation aeroplanes could be a reality, sooner than we think.
Hybrid-electric propulsion is expected to transform general aviation and private aircraft, with several new technologies expected to mature by the end of the decade. According to various estimates, an aircraft powered in flight with a hybrid-electric configuration using several energy sources in flight (either in tandem or alternately) could deliver up to a 5% reduction in fuel consumption as compared to a standard flight. At the present moment, the main sources of energy considered for hybrid-electric propulsion are batteries or fuel cells that convert hydrogen into electricity.
Several industry OEMs are pursuing test and development of different forms of hybrid-electric technologies, that could mature sufficiently to power production aircraft in the next decade. Some of the important programmes include the EcoPulse hybrid-propulsion aircraft demonstrator, which was designed and developed jointly by Airbus, Daher and Safran; RTX’s hybrid-electric Scalable Turboelectric Powertrain Technology (STEP-Tech) programme; GE and NASA, which are developing a hybrid electric demonstrator engine, etc.
EcoPulse Advances Hybrid-Electric
The EcoPulse programme was first announced at the 2019 Le Bourget Paris Air Show with a Daher TBM 900 Turboprop aircraft to be modified to not only evaluate the potential benefits of distributed hybrid-electric propulsion but also explore the possibility of integrating certain related technology bricks into future aircraft. The programme tested an important potential future hybrid-electric approach using distributed propulsion systems, which work by breaking down thrust generation between multiple small engines located along the wings.
The crucial flight test campaign was conducted from November 2023 to July 2024, over a period of eight months, during which 50 test flights were performed, accumulating approximately 100 flight hours. Daher provided the demonstrator aircraft, Airbus Defence and Space contributed the 800-volt, high-energy-density battery that was used to power the propulsion system, while Safran was put in charge of developing the distributed hybrid-electric propulsion system, which would feature six wing-mounted e-propellers. Airbus’ high-energy-density battery, which was capable of delivering 350 kilowatts of electricity, powered all six e-propellors in flight. The flight control computer system and aerodynamic and acoustic integration of the distributed-propulsion system was undertaken by Airbus as well. Daher was tasked with integrating Airbus and Safran’s modifications into the airframe. It also handled all flight and airworthiness testing.
Speaking this January, Jean-Baptiste Manchette, Airbus’ Head of Propulsion of Tomorrow, said, “The battery is one of the key parts of hybridisation, and the way to master how to design, manufacture and clear it for flight is really important for us.” Over the course of the EcoPulse project, the battery control models were successfully validated during flight testing, and it was proved that a battery of such power could be safely integrated into an aircraft and flown without compromising any safety standards.
Since larger batteries, like those used in the automotive industry, are too heavy and bulky for use on aircraft and standard aircraft battery technology is focused on low-voltage, low-energy-density batteries that are used to start the Auxiliary Power Unit (APU) or during emergencies, a customised lithium-ion battery was designed entirely in-house by Airbus Defence and Space. “Usually, on a light aircraft, we use a 28-volt battery. On a commercial aircraft, we use 115-volt AC as the standard. What we are using here [on EcoPulse] is 800 volts [DC], and that is a completely different story,” said Christophe Robin, Head of Aircraft Design at Daher.
“This EcoPulse campaign allows us to advance certain hybrid-electric technologies, such as high-voltage batteries, and integrate them into future aircraft, helicopters, and air mobility solutions,” said Jean-Baptiste. “With distributed electric propulsion, we achieved our goal of modelling flight physics and energy management at the aircraft level, key elements for shaping the next generation of aircraft.” Daher and Safran are now teaming up on a joint project, while Airbus and Safran are working together to explore the feasibility of open fan engines through the RISE demonstrator.
Hybrid-Electric Powerplant Development
GE Aerospace (GE) and NASA are working together to further the development of hybrid electric engines. In June 2024, GE announced that it was developing a hybrid electric demonstrator engine with NASA that would embed electric motors/generators in a high-bypass commercial turbofan to supplement power during different phases of operation. “Together with NASA, GE Aerospace is doing critical research and development that could help make hybrid electric commercial flight possible,” said Arjan Hegeman, general manager of future of flight technologies at GE Aerospace. Engine performance will be optimised by embedded electric motors/generators as they will create a system that can work with or without energy storage, like batteries.
As part of the programme, GE is modifying a Passport engine with hybrid electric components for testing through NASA’s Hybrid Thermally Efficient Core (HyTEC) project. This is one of several efforts that are underway at GE Aerospace to mature technologies for more electric aircraft engines. It is being advanced as part of the CFM International Revolutionary Innovation for Sustainable Engines (RISE) programme. This could help accelerate the introduction of hybrid electric technologies for commercial aviation prior to energy storage solutions being fully matured.
GE Aerospace has also collaborated with NASA to mature an integrated, megawatt (MW)-class hybrid electric propulsion system. This is being done as part of the Electrified Powertrain Flight Demonstration (EPFD) programme. Being undertaken in collaboration with Boeing, using a modified Saab 340B aircraft and GE Aerospace’s CT7 engines, ground and flight tests of the hybrid electric system are planned within this decade,
GE had undertaken the ground test of an electric motor-driven propeller in 2016, and in 2022, GE Aerospace completed the world’s first test of a MW-class and multi-kilovolt (kV) hybrid electric propulsion system in altitude conditions up to 45,000 feet that simulated single-aisle commercial flight at NASA’s Electric Aircraft Testbed.
Scalable Technology
RTX is continuing work on its hybrid-electric STEP-Tech demonstrator, for which it had announced a significant milestone in July 2024 when the company successfully validated sustained operation of the thermal engine, electrical generator, battery system and propulsors to demonstrate energy transfer between these components through the high-voltage electrical network. In October 2024, Collins Aerospace announced that it had completed prototype development of a solid-state power controller and power distribution panel as part of the SWITCH project, supported by the European Union’s Clean Aviation Joint Undertaking (Clean Aviation). “Hybrid-electric aircraft are an integral part of the aviation industry’s drive to achieve net-zero carbon emissions by 2050, yet without new, safe high-voltage power distribution systems, they will not fly,” said Tino Schuldt, general manager for Collins’ Nördlingen facility.
“The hybrid-electric propulsion solution is one of the key features offered by the SWITCH consortium to reach the CO2 reduction target of our programme for short-medium range aircraft,” said Pierre Durel, project officer for SWITCH. “We are excited to see tangible technology bricks becoming available, representing the significant efforts made by the team to deliver critical items needed to run the ground test demonstrator by the end of Phase 1.” Being developed as a modular demonstrator programme, STEP-Tech is prototyping future distributed propulsion concepts in the 100-500kW class, with the capability to scale to 1MW and beyond. These concepts could have application for a range of next-generation platforms, including advanced air mobility vehicles, high-speed electric Vertical Take-Off and Landing aircraft and blended wing body aircraft.
Pratt & Whitney Canada and Collins Aerospace are also supporting the development of a hybrid-electric propulsion system for Airbus Helicopters’ PioneerLab technology demonstrator, which is based on a twin-engine H145 helicopter. This programme will seek to demonstrate the potential of combined hybrid-electric propulsion as well as aerodynamic improvements to enable up to 30% improved fuel efficiency and reduced CO2 emissions compared to a conventionally powered aircraft. A Pratt & Whitney Canada PW210 engine derivative linked with two Collins Aerospace 250 kW electric motors and controllers through a common gearbox will replace the helicopter’s existing engines. Test flights of the hybrid-electric propulsion system are targeted to begin in 2027 at Airbus Helicopters’ site in Donauwörth, Germany.
HAL Eyes Zero-Emission Dornier 228
Hindustan Aeronautics Ltd (HAL) had entered into a development collaboration with UK-based firm Zero Avia in November 2021 for a hydrogen-electric powertrain capable of flying the 19 seat Dornier 228 aircraft up to 500 NM. HAL was to work with ZeroAvia to develop a Supplemental Type Certificate (STC) to allow retrofit of existing airframes for both Indian military and worldwide operators. HAL also had plans to help ZeroAvia to certify a Hydrogen-Electric Dornier 228 as well.
At the time it was announced that HAL also intended to build a new aircraft with additional FAA approval, designated Hindustan-228, that could also create the opportunity to incorporate ZeroAvia’s ZA600 zero-emission engines. At the time, plans called for HAL and ZeroAvia engineers to integrate ZeroAvia’s ZA600 hydrogen-electric powertrain into the Dornier 228 airframe.
ZeroAvia has extensively tested a ZA600 hydrogen-electric engine prototype aboard a Dornier 228 aircraft at its UK base and it also has an engineering partnership with Textron Aviation, with whom it is looking to secure a supplemental type certificate for the Cessna Grand Caravan as the launch airframe for the ZA600.
ZeroAvia had announced in February 2025 that it had as reached a consensus on the Certification Basis relating to its 600kW electric propulsion system (EPS) with the Federal Aviation Administration (FAA). The company stated that it had received a G-1 Issue Paper (stage 2) and formally confirmed agreement with its contents. The G-1 represents a key milestone on the journey towards final certification of the company’s EPS with the U.S. regulator and also on its path to certifying its first full hydrogen-electric powertrain (of which the EPS is a core system) with the UK Civil Aviation Authority, Zero Avia had stated. “While hydrogen-electric is the future for the majority of commercial routes in existence today, advances in electric propulsion technology and novel aircraft design are opening up an exciting range of new shorter range, electric air mobility applications. Certifying and selling our 600kW electric propulsion system helps ZeroAvia expand our addressable market and increase our impact in pursuit of a clean future of flight,” ZeroAvia, Founder and CEO, Val Miftakhov said.
The company has nearly 3000 orders for full powertrains and components. ZeroAvia’s 600kW EPS combines the company’s proprietary inverter and electric motor technology and the system comprises four ZeroAvia 200kW continuous power bidirectional inverters converting DC power to AC to supply ZeroAvia’s direct drive motor, capable of 2,200 rpm.
Timely Technology
It is quite clear that while hybrid-electric propulsion is quite some time way for larger commercial jetliners, it has an obvious and far reaching potential, when it comes to smaller generational aviation, private aircraft and regional transport aircraft. Significant efforts are being expended in the development of hybrid-electric powertrains and the creation of required synergies for their greater adoption in aviation. The maturity of these technologies in the coming years, along with the commencement of prototype flight testing, will generate sufficient data to inform all-new clean sheet designs and inform future certification standards as well. All going well, we could see aircraft with hybrid-electric powerplants sooner than planned.
