Research team's electric motor drive takes off in test flight on passenger hybrid electric plane

3/19/2023 University of Arkansas Office of University Relations

Prof. Nenad Miljkovic and a team funded by ARPA-E ran their first successful test flight of a passenger hybrid electric aircraft.

Written by University of Arkansas Office of University Relations

Engineering researchers at the University of Arkansas (U of A) achieved a major milestone Feb. 20 with the successful test flight of their electric motor drive on a hybrid electric aircraft. The project could lead to significant changes in the aeronautics industry and huge benefits to environmental quality.

Used primarily as air taxis in island regions and remote areas, small planes like the Cessna 337 have two gasoline-powered engines that perform the demanding tasks of air propulsion and acceleration, as well as lighter tasks such as taxiing, cruising and landing. These engines are notorious gas guzzlers.

For the past several years, researchers led by Alan Mantooth, Distinguished Professor of Electrical Engineering and executive director of the National Center for Reliable Electric Power Transmission (NCREPT) at the U of A, have engaged in an ambitious project to design and develop battery-powered motor drives that can be used in lieu of one of the gas-powered engines. The project was funded under the U.S. Department of Energy ARPA-E CIRCUITS program. ARPA-E is a U.S. government agency promoting and funding early stage research and development of advanced energy technologies.

The U of A researchers (Profs. Mantooth, David Huitink, Yue Zhao, Chris Farnell) designed a 250-kilowatt motor drive to power a rear electrical engine in the ARPA-E hybrid electric aircraft testbed built by Ampaire, Inc., an electrified aircraft company located in Southern California. The rear electrical engine in combination with a front gasoline-powered engine propels the hybrid electric aircraft during taxiing, takeoff, cruising and landing.

Nenad Miljkovic
Professor Nenad Miljkovic

University of Illinois researchers led by Prof. Nenad Miljkovic worked with the U of A researchers to accomplish simultaneous electrical-mechanical-thermal-control co-design of the motor drive. Expertise from Illinois was focused on thermal management design, while U of A researchers contributed expertise on electrical, mechanical and controls. Wolfspeed, a manufacturer of silicon-carbide semiconductors, contributed commercial power modules and integration expertise to the development of the electronic motor drive. Ampaire coached the academic-led team through the requirements to FAA-qualify the motor drive and validate its performance and reliability on a pathway to test flight. After roughly 1.5 years of ground tests and validations proving the technology, Ampaire successfully piloted the plane, powered by the research team’s inverter technology. The test flight occurred Feb. 20 at the Camarillo airport near Los Angeles, California.

“With recent refinements, we’ve managed to optimize design of the electrical-thermal-mechanical-control systems – in other words, all aspects of the motor drive are now simultaneously optimized,” Mantooth said. “This has major implications for the new and emerging era of electrification of transportation vehicles, whether they be planes, trains, automobiles, heavy equipment, ships or drones. We’re extremely excited about this work.”

The Ampaire hybrid aircraft with the U of A motor drive installed was displayed at the ARPA-E Energy Innovation Summit in Denver, Colorado, in 2022 and inspected by U.S. Secretary of Energy Jennifer Granholm. After extensive testing and evaluation, the test flight comes before the 2023 ARPA-E Energy Innovation Summit that will be held in Washington, D.C., March 22-24. Aided by the research team, Ampaire will conduct additional test flights and continue to collect data to improve future designs.

"The University of Arkansas electric motor drive was the first ARPA-E technology to be successfully tested in-flight on the ARPA-E hybrid electric aircraft testbed, and is a big accomplishment for ARPA-E and the CIRCUITS program” said Dr. Isik Kizilyalli, ARPA-E Associate Director for Technology, “Testing transformative electric aviation technologies on an aero-platform in actual flight environments enables validation of the technology in real world conditions, which will greatly accelerate the adoption of the technology. The U of A motor drive was the first of soon to be many ARPA-E-funded electric aviation technologies, such as circuit breakers, inverters, motors, power distribution systems, batteries, fuel cells and even high efficiency combustion engines (either directly or as a generator) that will be tested in-flight as the agency tackles the electrification of aircraft to bring us towards a more electrified future.”

The project was an outgrowth of collaborations established as part of the National Science Foundation Center for Power Optimization of Electro-Thermal Systems, or POETS. Based at the University of Illinois Urbana-Champaign, POETS focuses on increased electrification in all modes of mobility and transport.

As a top power electronics program worldwide, the U of A Power Group is a POETS partner, in which Prof. Mantooth serves as Deputy Director of the Center. In addition to motor drive design, U of A researchers contributed meaningful laboratory research and testing at NCREPT and the High Density Electronics Center, or HiDEC. NCREPT houses grid-scale, regenerative power electronic drives, circuit breakers, transformers and other equipment, while HiDEC provides a unique facility for creating integrated and packaged power modules that form the basis of power electronics components and the equipment for mechanical vibration testing and analysis.

About ARPA-E: The Department of Energy Advanced Research Projects Agency-Energy (ARPA-E) advances high-potential, high-impact energy technologies that are too early for private-sector investment. ARPA-E empowers America's energy researchers with funding, technical assistance, and market readiness.ARPA-E awardees are unique because they are developing entirely new ways to generate, store, and use energy. ARPA-E projects have the potential to radically improve U.S. economic prosperity, national security, and environmental well being.

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This story was published March 19, 2023.