Collins and P&W Unveil Hybrid-Electric Propulsion Systems

Collins Aerospace has completed the preliminary design for a new 1-MW electric motor that will serve as a key component of the new Regional Hybrid-Electric Flight Demonstrator under development by its Raytheon group sister company Pratt & Whitney (P&W). The aircraft engine maker plans to start ground testing with the Collins motor later this year in preparation for the start of flight testing in 2024 in Montreal.

The demonstrator program, based on plans to reduce carbon emissions from regional aircraft, forms part of a wider spectrum of work on new propulsion technology within the Raytheon group. The efforts could eventually result in larger hybrid-electric powertrains for narrowbody airliners carrying 220 passengers on 3,000 nm sectors, delivering at least a 30 percent cut in emissions.

Also this week at the Farnborough International Airshow, P&W and Collins are announcing the launch of the STEP-Tech demonstrator program. They aim to start ground testing the system in late 2022.

Based at the Raytheon Technologies Research Center in East Hartford, Connecticut, the project centers on the development of a 100- to 500-kW high voltage distributed turboelectric hybrid-electric propulsion system. Initial plans call for the system to apply to smaller eVTOL aircraft and uncrewed air vehicles, but the companies said they can scale up the technology to a 1-MW power rating for larger applications.

The STEP-Tech unit consists of a scalable turbogenerator, batteries, and a power management system, as well as propulsor units. The partners completed proof of concept studies earlier this year.

The new 1-MW electric motor on display in Farnborough (Raytheon Pavilion C631) builds on the power generation and distribution systems for Boeing’s 787 widebody airliner program produced by the legacy Hamilton Sunstrand business that became part of Collins Aerospace after the merger of UTC Aerospace and Rockwell Collins. Collins’s Solihull facility in the UK makes the new units and plans to soon deliver them to P&W for integration with one of its existing aircraft engines.

According to Collins vice president for power and controls Bill Dolan, each 1-MW motor will deliver a fourfold improvement in power density compared with current electric motor technology. Initial testing has been conducted by the University of Nottingham, where in June engineers achieved 400-kW power outputs in ground runs. Collins intends to do further electric motor development work at its new electric power systems laboratory in Rockford, Illinois, which it calls The Grid and plans to open in 2023.

At some point, P&W wants to evaluate the electric motor operating in tandem with its Geared Turbofan engine. It is also considering options for integrating the Regional Hybrid-Electric Flight Demonstrator and the STEP-Tech unit with a new aircraft engine.

Frank Preli, Pratt & Whitney’s vice president for propulsion and material technologies, said during a pre-airshow press briefing that the Raytheon group partners are evaluating a sliding scale of hybrid-electric applications, from a “mild” basis under which only 5 percent of power is electrical to 50 percent or more. He predicted that both parallel and integrated hybrid-electric propulsion systems could become available for new air transport applications starting in the mid-2030s.

Preli noted that the company sees regional airliners as the early adopters of the new propulsion technology, with anticipated 30 percent energy savings from the start. He said that the Raytheon subsidiaries have entered contracts with several major aircraft manufacturers and expect to make available certifiable propulsion systems for new Boeing or Airbus single-aisle aircraft. They expect a further reduction of carbon emissions by enabling the turbogenerator element of the new powertrains to run on sustainable aviation fuel.

According to Juan de Bedout, Raytheon’s vice president for aerospace technology, the group sees as imperative accelerated efforts to reduce carbon from flights with emissions from air transport, which scientists expect to more than double in the coming years and rise from around 2 percent of global emissions to 18 percent. Last year, Raytheon signed on to the Air Transport Action Group’s commitment to achieving net-zero emissions by 2050.

The U.S.-based group, which employs about 58,000 engineers worldwide, feels that the motor-generator and power management capability of Collins is a strong match for P&W’s expertise in developing new turboprops and turbofans. The companies already collaborate on a related project funded by the Canadian and Quebec governments to evaluate hybrid-electric propulsion on a De Havilland Dash 8-100 turboprop aircraft in partnership with battery specialist H55.

Rival aircraft engine makers Rolls-Royce and Honeywell are also working on 1-MW-class hybrid-electric propulsion systems. Safran is developing electric propulsion systems of up to around 600 kW power output.