The Future of Advanced Air Mobility

Net Zero Research and Development Projects Proliferate as Europe Chases a Clean Aviation Future

European Union (EU) efforts to achieve a net zero carbon future for aviation by 2050 are being stepped up with the launch of a flurry of research and development projects under the auspices of the Clean Aviation Joint Undertaking. Much of the work will focus on developing regional airliners to decarbonize short-haul flying, with prominent aerospace groups—including Honeywell, Collins Aerospace, Textron, Airbus, Rolls-Royce, and GE Aviation—playing key roles.

At the end of January, Honeywell confirmed that it is leading Project Newborn, working with 17 other partners from 10 European countries to develop a megawatt-cell hydrogen fuel cell propulsion system. Initially, the resulting technology is expected to be integrated into a demonstrator aircraft by Textron eAviation subsidiary Pipistrel, building on recently completed work under the Unifier19 project (see below). Honeywell said that the technology is intended for use with a variety of hybrid-electric, short-haul airliners. 

According to Honeywell Aerospace principal scientist Ondrej Kotaba, the Newborn technology is expected to first see a commercial application on a new 19-seater commuter aircraft. It could also be used for passenger- and cargo-carrying eVTOL vehicles and larger general aviation aircraft.

Other companies and organizations involved in the project include PowerCell, the Fraunhofer Institute, Aciturri, the University of Nottingham, Siemens Industrial Software, Test-Fuchs, Reaction Engines, CIRA, Customcells, Friedrich-Alexander-Universitaet Erlangen-Nuernberg, and the Katholieke Universiteit Leuven. Honeywell is providing equipment such as air management and control systems, with much of the work to be conducted from the U.S.-based group’s Technology Solutions R&D center in Brno, Czech Republic.

Honeywell is also leading Clean Aviation's TheMa4HERA project, whose name stands for Thermal Management for Hybrid Electric Regional Aircraft. This involves 24 European partners, including Collins subsidiary Nord Micro, which together will devise new approaches for controlling the temperatures of aircraft equipment other than the propulsion system. 

According to Honeywell, this project will develop advanced thermal management components and architectures for next-generation narrowbody aircraft, including those with hybrid-electric propulsion systems. Separately, in 2022, Honeywell started testing a one-megawatt turbogenerator.

HECATE Seeks Quantum Leap in Electric Power Distribution

Last month, Collins announced that it is coordinating the development of a high-voltage electric power distribution program under the Clean Aviation HECATE project. Engines and electronics group Safran is acting as technical coordinator with Diehl Aerospace, Airbus Defence and Space, and Leonardo, and multiple European universities are also involved. The project, whose acronym stands for Hybrid-Electric Regional Aircraft Distribution Technologies, is backed by almost $44 million in EU and UK government funding.

According to Collins, the introduction of hybrid-electric propulsion systems powerful enough for regional airliners will require a quantum leap in high-voltage power distribution. This is because electrical power ratings are expected to increase from hundreds of kilowatts on today’s aircraft to megawatt levels.

According to Todd Spierling, Collins’s principal technical fellow for electrification, the new-generation hybrid-electric powertrains will have to produce higher levels of electrical power to support both the propulsion system and the secondary power needs of other aircraft systems. “They will have to process a lot of high-voltage power and so it’s going to take a very different approach to power distribution and management,” he explained to FutureFlight. “As power levels go up, things become more critical and there is more potential for damage, so that you have to be able to instantaneously implement protections.”

Marc Holme, senior director of Collins’s electric power systems organization, explained that the group’s expertise in this field builds on contributions to major airliner programs such as Boeing’s 787, which he said “is the most electrified commercial aircraft flying.” Collins is also involved in the regional hybrid-electric flight demonstrator program led by engine-maker Pratt & Whitney.

The HECATE partners are addressing this challenge by pursuing a goal of ground testing the power distribution system for a 500- kW-plus hybrid-electric powertrain to technology readiness level five by 2025. They will conduct simulated high-altitude performance tests at Manchester University’s Aerospace HV facility.

Collins will coordinate its contributions from the group’s Applied Research and Technology Organization in Cork, Ireland, supported by other facilities in the UK and Germany. It is developing key elements, including power conversion and secondary distribution technologies.

Safran is providing primary power distribution equipment and cabling. Thales and Diehl Aerospace are working on new power electronics, system control, and energy management technology.

Could an Electric Miniliner Transform Regional Air Links?

One of the EU-backed research and development efforts in which Pipistrel has played a leading role is the Unifier19 project to evaluate options for developing zero-emissions regional airliners. “The key purpose of this project was to improve the quality of people’s lives by providing cost-efficient and sustainable air mobility solutions over short and very short routes,” Pipistrel Vertical Solutions aerodynamics engineer David Eržen told FutureFlight.

The Slovenia-based company, which Textron eAviation acquired in 2022, worked with European universities Politecnnico di Milano and TU Delft on two potential applications for an electric 19-seat aircraft conceptually referred to as the Miniliner. In work concluded at the end of 2022, they explored how this might be used to feed passengers from local airfields that don’t currently have scheduled air services to larger hub airports, and also to provide point-to-point flights between smaller cities.

According to Eržen, such an aircraft could be economically viable on routes as short as just 100 to 200 kilometers (up to 125 miles), providing a green alternative to cars and especially in the absence of workable rail links. Pipistrel believes the aircraft it has in mind could access more than half of Europe's 3,000 small airfields–many of which have only grass runways–and require just 800 to 1,000 meters to land and take off.

Pipistrel Vertical Solutions head of research Blaž Močan explained that under the Unifier19 model, the aircraft concept has sufficient range capability so that there wouldn’t necessarily have to be infrastructure for battery recharging or hydrogen refueling at all the airfields served. He envisages a network of hub bases from which Miniliners would operate multiple sectors.

The prospect of a viable electric commuter aircraft could reshape the debate around environmentally sustainable public transportation options. This is especially true in countries like France and Norway, where governments are moving to ban domestic flights. Eržen added that research suggests that the electric aircraft could be between 10 and 20 dBA quieter than current turboprop regional airliners.

With the conceptual phase of Unifier19 now complete, Pipistrel and multiple other partners will step up work on the technology building blocks for the propulsion system for such aircraft. This will be a hydrogen-electric powertrain using fuel cells.

The work all falls under the broad remit of the EU’s Clean Aviation Joint Undertaking, which is seeking to meet goals established under the Paris Accord for zero carbon emissions by 2050. The latest round of projects started in January 2023, and Pipistrel is a technical partner in five of them and a project coordinator in two, including four demonstrators fueled by liquid hydrogen that could lead to a family of aircraft, ranging in size from light trainers to delivery drones and airliners.

Newborn, which is the largest of these five projects, is expected to deliver a powertrain system fit for the commercial aviation sector that could result in it being integrated with a hybrid-electric regional airliner as part of the HERA project. However, the technology could also be applied to general aviation aircraft.

Močan confirmed that Pipistrel has already had discussions with prospective operators of these aircraft. The Clean Aviation timeline calls for the technology to be ready for ground demonstrations in 2026, followed by flight testing in 2030.

This month, Clean Aviation will be launching a second call for project proposals. Through a combination of public and private funding, more than €1.8 billion is being invested in projects aimed at achieving the goal of net zero carbon emissions from aviation by 2050.

Other Clean Aviation projects include HEART and AMBER, under which Rolls-Royce Deutschland and GE Avio are, respectively, working on multi-megawatt hybrid electric propulsion systems. Both of these companies are also working on direct combustion of hydrogen under the CAVENDISH and HYDEA programs.