Beyond the Road: How eVTOL Aircraft Motors Differ from Electric Car Motors

<p>Electric vehicles and electric vertical take-off and landing (eVTOL) aircraft both rely on similar electric motor technology, yet the demands of aviation force engineers to make fundamentally different trade-offs. While electric cars optimize for cost and mass within the constraints of road travel, eVTOL designs prioritize weight, efficiency, and redundancy to ensure safe flight. Insights from Jon Wagner, formerly of Tesla and now leading power train and electronics at Joby Aviation, reveal the critical engineering distinctions that set these two applications apart. This article explores the key differences in cost vs. mass, safety redundancy, manufacturing integration, and advanced materials.</p> <h2 id="cost-mass">Cost vs. Mass: The Fundamental Trade-Off</h2> <p>In ground transportation, the cost of components often dominates engineering decisions. Manufacturers seek to save a few dollars per part, even if it means adding a kilogram of mass. For electric cars, a slightly heavier motor or battery is acceptable because the vehicle still operates within road regulations and performance targets. Wagner explains that the trade-off between cost and mass in automotive is heavily skewed toward cost minimization: 'You would be willing to spend more on parts to save a certain amount of mass only up to a point.'</p><figure style="margin:20px 0"><img src="https://spectrum.ieee.org/media-library/a-man-stands-in-a-busy-open-plan-office-environment.png?id=65579658&amp;width=980" alt="Beyond the Road: How eVTOL Aircraft Motors Differ from Electric Car Motors" style="width:100%;height:auto;border-radius:8px" loading="lazy"><figcaption style="font-size:12px;color:#666;margin-top:5px">Source: spectrum.ieee.org</figcaption></figure> <p>In aviation, however, every kilogram matters. Additional weight reduces payload capacity, range, and flight efficiency. eVTOL developers are therefore willing to spend significantly more—sometimes ten times as much—on components that shave off even small amounts of mass. This shift changes the entire design philosophy. For example, lighter materials like composites and specialized alloys become viable candidates, even if they are prohibitively expensive for cars. The cost premium is justified by the direct operational benefits: lighter aircraft can carry more passengers or fly farther on the same battery charge.</p> <h2 id="safety-redundancy">Safety and Redundancy: A Matter of Failure Mitigation</h2> <p>The fundamental motor technologies for EVs and eVTOL are similar, meaning they share the same potential failure modes—such as bearing wear, winding shorts, or controller faults. But the response to a failure is vastly different. In an electric car, if the motor fails, the driver can simply pull over to the side of the road. This 'fail-safe' approach is acceptable because the risk to life is limited.</p> <p>In aviation, pulling over is not an option. An eVTOL operating at altitude requires <strong>continued safe flight and landing</strong> after any single failure. To achieve this, engineers design redundancy into the propulsion system. Wagner notes that 'the mitigation for a failure is redundancy, because there’s not an option to pull over.' This means multiple motors, controllers, and power sources must be distributed so that if one unit fails, the others can still maintain flight.</p> <h3 id="redundancy-evs">Redundancy in EVs vs. eVTOL</h3> <p>Some electric cars do have redundant motors—for instance, all-wheel-drive models with separate motors on front and rear axles. However, Wagner emphasizes that this redundancy is a secondary benefit, not a primary design goal. 'It wasn’t done with the primary intent of having redundancy,' he says. In eVTOL, redundancy is a core requirement from the start. Every component is selected and arranged to ensure that a single failure does not lead to catastrophic loss of control. This drives the use of multiple independent motor units, fault-tolerant wiring, and duplication of sensors and controllers.</p> <h2 id="manufacturing">Manufacturing Approaches: Integration vs. Outsourcing</h2> <p>Automotive manufacturing has evolved into a highly efficient, modular system. Car makers often break the powertrain into separate subsystems—motor, inverter, gearbox—and source each from specialized suppliers. This approach reduces cost and leverages economies of scale. However, as Wagner points out, 'when you break a problem up into three pieces, you now have interface boundaries between each of these pieces, and those always create inefficiencies.'</p><figure style="margin:20px 0"><img src="https://spectrum.ieee.org/media-library/image.png?id=65579658&amp;width=1200&amp;height=600&amp;coordinates=0%2C50%2C0%2C51" alt="Beyond the Road: How eVTOL Aircraft Motors Differ from Electric Car Motors" style="width:100%;height:auto;border-radius:8px" loading="lazy"><figcaption style="font-size:12px;color:#666;margin-top:5px">Source: spectrum.ieee.org</figcaption></figure> <p>For eVTOL, Joby Aviation takes a different path: <strong>highly integrated design and manufacturing</strong>. By controlling the entire development cycle—from motor windings to control software—they eliminate interface losses and optimize the system as a whole. This integration allows them to achieve better power density, thermal management, and reliability, even though it is less efficient from a pure manufacturing cost perspective. Wagner says they were able to 'design highly integrated solutions without taking that manufacturing penalty' by focusing on the unique requirements of flight.</p> <h2 id="materials">Materials Innovation: The Promise of Permendur</h2> <p>Advanced materials are a key enabler for eVTOL performance. One example is <strong>Permendur</strong>, a cobalt-iron alloy that offers superior magnetic properties compared to standard electrical steel. Wagner explains that Permendur costs roughly ten times more than traditional motor steel—a price that is prohibitive for ground vehicles. 'It comes with small improvements in performance, but enough that for aviation it’s quite interesting.'</p> <p>These small improvements translate into higher efficiency and lighter weight, which directly benefit flight duration and payload. Other advanced materials—such as high-temperature composite insulators and lightweight structural metals—are similarly being explored to push the boundaries of what eVTOL motors can achieve. While the cost is high, the return in flight performance justifies the investment.</p> <h2 id="conclusion">Conclusion</h2> <p>The differences between eVTOL and electric car motors are profound, rooted in the fundamental requirements of each domain. Cost dominates automotive design; mass and safety dominate aviation. Redundancy is a nice-to-have in cars but a must-have in aircraft. Manufacturing strategies diverge accordingly, with eVTOL favoring integration over outsourcing. And materials like Permendur highlight how aviation is willing to pay a premium for marginal gains that would never make sense for a road vehicle. As eVTOL technology matures, these engineering choices will continue to shape the future of urban air mobility.</p>