Electric Motor Drive Takes Off in Test Flight of Passenger Hybrid Electric Plane

Photo by Ampaire Inc.

U of A researchers collaborated with two private companies, Ampaire and the trademarked Wolfspeed, and the University of Illinois to develop an electric motor drive tested in flight on an hybrid electric aircraft.

Engineering researchers at the 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 by the U.S. Department of Energy/Advanced Research Projects Agency–Energy CIRCUITS program, or ARPA-E, a U.S. government agency promoting and funding early-stage research and development of advanced energy technologies.

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

Led by Nenad Miljkovic, professor of mechanical science and engineering, the University of Illinois researchers focused on thermal-management design, while the U of A researchers contributed expertise on electrical and mechanical and controls.

Wolfspeed, a trademarked 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 rigorous environmental testing requirements, derived from aerospace hardware standards and necessary to qualify and validate the motor drive's performance and reliability on a pathway to test flight. After roughly 18 months 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.

“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 hybrid aircraft was displayed at the ARPA-E Energy Innovation Summit in Denver 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 flying testbed capability, supported by ARPA-e, gives Ampaire a rapid test tool for evaluation of emerging technology in a relevant environment,” said Ed Lovelace, chief technology officer and vice president of engineering at Ampaire. “Successfully evaluated technologies have an opportunity to become part of Ampaire’s commercial electrified aviation product roadmap, providing greater capabilities.”

"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 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 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. Based at the University of Illinois Urbana-Champaign, the center 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 partner of the center, for which Mantooth serves as executive director. In addition to motor drive design, U of A researchers contributed meaningful laboratory research and testing at NCREPT and the university’s High Density Electronics Center. NCREPT houses grid-scale, regenerative power electronic drives, circuit breakers, transformers and other equipment, while High Density Electronics Center 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 the University of Arkansas: As Arkansas' flagship institution, the U of A provides an internationally competitive education in more than 200 academic programs. Founded in 1871, the U of A contributes more than $2.2 billion to Arkansas’ economy through the teaching of new knowledge and skills, entrepreneurship and job development, discovery through research and creative activity while also providing training for professional disciplines. The Carnegie Foundation classifies the U of A among the few U.S. colleges and universities with the highest level of research activity. U.S. News & World Report ranks the U of A among the top public universities in the nation. See how the U of A works to build a better world at Arkansas Research News.

About the University of Illinois, Urbana-Champaign: With our land-grant heritage as a foundation, the University of Illinois Urbana-Champaign pioneers innovative research that tackles global problems and expands the human experience. We are charged by our state to enhance the lives of citizens in Illinois, across the nation, and around the world through our leadership in learning, discovery, engagement, and economic development. Illinois is the lead institution of the POETS Center, which is focused on the integration of electrical and thermal power flows in tightly confined mobile environments. The goal of POETS is to increase power density in electrified mobility in three market segments: on highway, off highway, and aerospace.  The center supports roughly 25 faculty and 50 to 60 graduate students and post-docs across four institutions – Stanford, University of Arkansas, University of Illinois and Howard University.

About Ampaire: Los Angeles-based Ampaire was formed in 2016 with a mission to become the world's most-trusted developer of practical, compelling electric aircraft. The company is upgrading existing passenger aircraft to hybrid electric power–the quickest, most capital efficient approach to making commercial electric air travel a reality with available technology. Ampaire has scored a series of industry firsts since the 2019 maiden flight of its Electric EEL technology testbed aircraft, including the longest flight for a hybrid-electric aircraft--1,135 statute miles en-route from Los Angeles to Oshkosh, Wisconsin, and the largest hybrid electric aircraft ever flown with the Eco Caravan test flight in November 2022. For more information about Ampaire, visit www.ampaire.com.

About Wolfspeed: Wolfspeed (NYSE: WOLF) leads the market in the worldwide adoption of silicon carbide and GaN technologies. We provide industry-leading solutions for efficient energy consumption and a sustainable future. Wolfspeed’s product families include silicon carbide materials, power devices and RF devices targeted for various applications such as electric vehicles, fast charging, 5G, renewable energy and storage, and aerospace and defense. We unleash the power of possibilities through hard work, collaboration and a passion for innovation. Learn more at www.wolfspeed.com.

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.