The Future of Advanced Air Mobility

Axial-Flux Motors Can Deliver the Power Density Aviation Needs, Says Automotive Spin-off

Electric propulsion startup Evolito is accelerating efforts to power new aircraft with axial-flux technology that it claims will deliver motors with exceptional power density suitable for a variety of fixed-wing and VTOL applications.

The UK-based company was spun out from a company called YASA in July 2021 to harness aerospace intellectual property from the company before its automotive activities were acquired by car-making giant Mercedes-Benz. Evolito is now backed by venture capital groups B-Flexion and Oxford Science Enterprises.

YASA—which stands for Yokeless and Segmented Armature—achieved prominence in aviation circles through its involvement in Rolls-Royce’s Spirit of Innovation project. The company provided three of its motors and controllers for the convert NXT Next kitplane that last year set a trio of world records by becoming the world’s fastest all-electric aircraft, logging a top speed of 345.4 mph, smashing the previous record by 132 mph. Also involved in that project was UK-based battery manufacturer Electroflight, which was subsequently acquired by Evolito in July 2022.

Evolito CEO Chris Harris, who until September led YASA, told FutureFlight his 100-strong team will now focus its efforts on offering electric propulsion units (EPUs) with combined motors, gearboxes, and controllers for new eVTOLs. It also plans to provide motors and inverters for new and converted fixed-wing aircraft seating up to 19 passengers.

“The beauty of this approach is that we are building on 10- to 12-years of development and industrialization by YASA and so we’re already able to ship some units in particular configurations [to aviation customers],” he explained.

Evolito’s EPUs and individual motors are scalable in configuration and their power ratings can be progressively increased by stacking units together to increase from around 125 kW into the megawatt class.

According to Harris, YASA’s background in automotive electric propulsion since 2012 has given Evolito an aptitude for combining high-production volumes, with resulting lower costs, with the quality standards needed to meet aerospace safety requirements. In addition to Mercedes-Benz, Yasa has supplied motors and controllers to high-profile automakers such as Ferrari.

The company’s axial-flux motor architecture is flat by contrast with oblong-shaped radial motors. Harris said this approach has delivered “best in class power and torque density” that is very suitable for powering more efficient and environmentally sustainable aircraft that require smaller and more lightweight propulsion systems to meet net-zero carbon objectives.

Evolito says its axial-flux motors deliver superior torque density and brake horsepower.
Evolito said its axial-flux motors deliver superior torque density and brake horsepower. (Graphic: Evolito)

According to Evolito, its axial flux motors are around one-third the size and weight of comparable radial motors, with 30 percent greater power density. The stators, which contain the electromagnetic circuits, contain about half as much iron as is found in other axial-flux motors, which Evolito says results in an overall increase in torque density of around 20 percent.

The YASA 750 motors used for the Spirit of Innovation record-breaking flights provided total available peak torque of 2,370 Newton meters, peak power of 600 kW, and 822 bhp.