Imagine a “disc” weighing less than 16 kilograms that can instantaneously drag a 400-kilogram load — that is the disruptive breakthrough delivered by the axial flux motor. In recent years, whether it is air taxis (eVTOLs) shuttling above city skylines or industrial UAVs performing reconnaissance and logistics missions, the demands placed on propulsion systems have become almost impossibly stringent: minimal volume, minimal weight, and maximal thrust. Traditional motors falter when forced to satisfy all these requirements at once. A disc-shaped motor whose magnetic field flows along the axial direction is quietly emerging as the brightest powertrain star in the low-altitude economy. Below, we will examine this “explosively powerful” report card through the lens of axial flux motor rotor evolution and real-world test data comparisons.
The Essence of Propulsion Innovation: The Leap from “Radial” to “Axial”
To understand this revolution, we must first distinguish between two “electrification logics.” Traditional motors use a radial flux path, where the magnetic field flows perpendicular to the motor’s rotational axis, much like the blades of a water wheel spinning around a central shaft. An axial flux motor, in contrast, directs the magnetic field parallel to the rotational axis, with the stator and rotor arranged as parallel discs. This design dramatically shortens the magnetic circuit, thereby increasing the effective magnetic surface area and significantly boosting magnetic field utilization. At the same time, the flat architecture makes the entire motor resemble a disc, enabling the weight and axial length to be halved compared with a radial motor of equivalent power.
The axial flux motor rotor, as the direct converter of energy, determines the ultimate “physique” ceiling of the motor through its design. Currently, the industry is championing three main rotor topologies for aerospace propulsion:
YASA (Yokeless and Segmented Armature) Topology: This classic dual-rotor, single-stator structure discards the traditional iron-core “yoke” to substantially reduce weight and core losses, making it the preferred solution for aerospace applications pursuing low losses and high efficiency. Relevant studies have further quantified this advantage: the YASA topology performs best at minimizing core losses.
AFIR (Axial Flux Internal Rotor) Topology: Permanent magnets are mounted on the internal rotor, and the magnetic field flows axially from the outer stator to the inner rotor. This topology excels at achieving the highest torque density among all axial flux configurations and is particularly suitable for vertical-take-off-and-landing aircraft that demand “enough thrust to make a brick fly.”
Offset AFIR (Offset Axial Flux Internal Rotor) Topology: This design builds upon the AFIR by optimizing the relative positions of the stator and rotor. It sacrifices a portion of torque density in exchange for a much broader high-efficiency operating region, making it the optimal solution for long-endurance UAVs and hybrid eVTOLs oriented toward cruising.
Head-to-Head on Core Technical Metrics: The Axial Flux Motor Rotor Reverses the Landscape of Electric Drive with a “Dimensionality Reduction Strike”
Any technical hype is hollow without real-world test data. So how large is the measured gap between axial flux and radial flux motors on core metrics?
In torque density — the most critical “muscle” indicator — the axial flux motor rotor demonstrates overwhelming superiority. Its torque generation follows a more favorable geometric relationship — the stronger “cubic effect” — whereas traditional radial motors are limited to the “square effect.” It is precisely this fundamental difference that enables axial flux motors to typically deliver 30%–40% higher torque density for the same volume. For comparable diameters, the torque density can be up to four times that of a conventional solution, while the axial length can shrink to one-sixth.
In power density (power-to-weight ratio), the gap is even more striking. Traditional radial motors are constrained by the stacking of numerous silicon steel laminations and copper windings; top-tier mass-produced products mostly hover between 4 and 5 kW/kg, with very few exceptions managing to break through 16 kW/kg. In contrast, axial flux motors targeting aviation applications have already pushed this metric beyond 10 kW/kg and have been tested in real-world conditions at 6 kW/kg in a dual-motor coordinated configuration. In the supercar domain, YASA has even achieved a peak power-to-weight ratio as high as 59 kW/kg.
The difference in efficiency maps is equally impossible to ignore. Radial motors have a narrow efficiency “sweet spot”; once the operating point deviates, the efficiency curve drops sharply. The axial flux motor rotor, benefiting from a shorter flux path and lower iron losses, breaks through this limitation and maintains a high-efficiency coverage area above 90% across a wide range of speeds and torques.
Frontier Test Report Card: A Real-World Test of Fitness for the Skies
Much of the data above remains confined to laboratories and ground vehicles. What do actual aviation propulsion results look like? The real-world test data from the following leading companies provide the best answers.
Traxial: As a frontrunner in axial flux technology, Traxial delivered a “clean sweep” in joint tests with Punch Powertrain in May 2025. Its yokeless axial flux motor (AXF300), paired with a SiC controller, easily achieved a staggering peak power of 310 kW and continuous power of 270 kW on the test bench, with a maximum torque of 730 Nm. The performance remained stable throughout, with no failures or degradation.
CRRC Zhuzhou Electric Motor’s “Yufeng” T-Series: Representing China’s traditional high-end equipment excellence, this axial flux propulsion system boasts a motor efficiency of 95% and a controller efficiency of 98%. It delivers a continuous torque density of 10 Nm/kg and a peak torque density of 20 Nm/kg, with an axial dimension only one-half to one-third that of a conventional motor, perfectly meeting the direct-drive propulsion needs of eVTOLs and compound-wing UAVs.
Arctic Tern Power OW280we: Designed specifically for medium-to-large eVTOLs, this motor weighs only 15.6 kg yet can unleash a peak thrust of 400 kg, demonstrating an exceptionally high thrust-to-weight ratio. A proprietary forced-air cooling technology and IP66 protection rating ensure stable thrust even in severe environments such as heavy rain and high temperatures.
Emil Motors’ Magnet-Free Solution: As a forward-looking exploration, Emil Motors announced test results for a magnet-free axial flux induction motor in October 2025, achieving a peak torque of nearly 270 Nm and a rated speed of 7,000 RPM. Although the prototype’s upper limits were held back by protective measures, the test verified the engineering feasibility of breaking free from rare-earth dependence and enhancing high-temperature stability.
Facing the Challenges: The “Achilles’ Heel” of the Axial Flux Motor Rotor and the Path to Overcoming It
No technology is flawless. The inability to mass-produce axial flux motor rotors on a large scale stems from several fatal “Achilles’ heels.”
The first is the extremely high barrier of manufacturing precision. An air-gap deviation at the micron level can trigger severe vibration, noise, and even mechanical wear. The second is the thermal management challenge. The high specific power translates into enormous heat flux density, and the sandwiched disc structure results in very low thermal capacity. The permanent magnets on the rotor are highly susceptible to irreversible demagnetization from overheating. Finally, mass-production costs remain high. Due to the specialized composite materials and processes involved, manufacturing costs are typically 20%–50% higher than those of radial motors.
Nevertheless, these technical barriers are being tackled one by one. In thermal management, precision solutions based on embedded dual-loop water cooling have entered in-depth research. In manufacturing, soft magnetic composite (SMC) integral compression molding technology, guided by a 3D-printing mindset, is attempting to eliminate the headaches of ultra-high-precision assembly. At the top-level design, the industry consensus is shifting from “passive cooling” to an integrated “materials + structure + control” thermal management synergy, thus addressing reliability issues at the source.
Conclusion
As the low-altitude economy rushes toward the eve of a trillion-scale explosion, the axial flux motor rotor is undeniably becoming the core power unit for eVTOL and UAV propulsion systems. What it brings is not merely an increase in power figures, but a fundamental break from the traditional notion that “might demands mass.” It provides a genuinely reliable technological foundation for the efficient aerial road networks between future cities. In this extreme balancing act among volume, weight, thrust, and efficiency, that thin disc has already become the most powerful “heart” propelling us into the future.
