Flight milestones and lessons learned from X-plane programs
By Phillip Ansell and Virginia Stouffer|December 2023
The Electrified Aircraft Technology Technical Committee supports the integration of electrified aircraft systems through the design, evaluation and application of key technologies, including components for propulsion, actuation, safety, airworthiness and thermal management.
NASA announced in June that it would halt development of its X-57 Maxwell demonstrator and in September concluded the program, aside from closedown work. Although this campaign had no flight tests, the agency said it served an instrumental role in advancing aircraft electrification. Researchers received a wealth of information from the integration of the fully electric propulsion system of this X-plane concept. Much of this information became an active component of the ongoing NASA Electrified Powertrain Flight Demonstration project. In July, program leads GE Aerospace of Ohio and magniX of Washington unveiled the livery of their EPFD test aircraft, which could fly as early as 2025.
Electric vertical takeoff and landing aircraft reached several milestones toward certification this year. In June, Joby Aviation of California received an FAA Special Airworthiness Certificate, allowing the company to begin flight tests with its pre-production air taxi to inform equipment qualifications required in certification for commercial flight. Joby plans to begin passenger service in 2025. Joby also secured an additional $55 million in funding from Department of Defense in April, and in September delivered an air taxi to Edwards Air Force Base in California for testing. Another California air taxi developer, Archer Aviation, received a Special Airworthiness Certificate for its Midnight air taxi and began testing in August. Archer announced a Defense Department contract worth up to $142 million in July.
Also in July, FAA released “Modernization of Special Airworthiness Certification,” a notice of proposed rulemaking to redefine the light sport aircraft category. The current rule limits aircraft weight to 1,320 pounds (599 kilograms). FAA instead proposed performance-based measures, allowing aircraft that are almost two and a half times bigger, with a doubling of potential airspeed, and removing the single reciprocating engine requirement for any number and type of propulsors so that both electric and powered lift could be included. The requirements would allow for non-paying passengers to be carried, or for cargo and surveillance work.
Hydrogen-electric aircraft power systems made significant leaps this year. In January, California-based ZeroAvia flight tested its modified Dornier 228 testbed aircraft. The company replaced one turboprop engine of the configuration with a hybrid fuel cell/battery powertrain. In March, Universal Hydrogen of California flew a modified De Havilland Canada Dash 8 aircraft, which also had one turboprop engine replaced with a hydrogen-electric powertrain.
Several electrified aircraft configurations demonstrated progress at the Paris Air Show in June. French company VoltAero displayed its Cassio 330 hybrid- electric aircraft, scheduled to make its first flight this year. Known for its fully electric propulsion design, Eviation of Washington secured letters of intent for 50 aircraft during the show. New entrant Aura Aero of France secured multiple memorandums of understanding with operators to acquire its hybrid-electric aircraft configuration. SolarStratos of Switzerland also debuted its solar-electric aircraft concept, which the company intends to fly at high altitudes to acquire scientific data of the Earth’s atmosphere and climate.
New academic programs for electrified aircraft were established under NASA’s University Leadership Initiative program. In March, the Carbonless Electric Aviation, or CLEAN, project was awarded to Tennessee Technological University under ULI Round 6. This project focuses on the development of solid oxide fuel cell systems coupled with combustion-driven turbogenerators to produce electricity from ammonia. The Center for High Efficiency Electrical Technologies for Aircraft project at the University of Illinois, Urbana Champaign was awarded a $4 million Phase II grant to continue work in developing prototypes of hydrogen-electric aircraft technologies for future zero-emissions systems. A ULI team led by Ohio State University completed a five-year NASA-funded effort on electrified propulsion technologies. This campaign concluded this year with a test at the NASA Electric Aircraft Testbed in Ohio, where the team attempted to run at full power and prove that the power electronics worked under altitude conditions.
Contributor: Amy Jankovsky