eVTOL vs EV Motors: Key Engineering Differences Explained
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<p>Electric motors power both electric vehicles (EVs) and electric vertical take-off and landing (eVTOL) aircraft, but their design priorities diverge significantly. Jon Wagner, former Tesla battery executive and now Joby Aviation's power train lead, explains how cost, mass, redundancy, and manufacturing strategies differ between the two industries. This Q&A breaks down the critical distinctions that make eVTOL motors unique.</p>
<h2 id="q1">1. How Do Cost and Mass Trade-Offs Differ Between eVTOL and EV Motors?</h2>
<p>In ground transportation, cost is the dominant factor engineers optimize for. Every component is evaluated with a strict budget, and mass savings are only pursued if they don't push the price too high. For eVTOL aircraft, the equation flips: reducing weight and improving efficiency justifies spending significantly more per part. As Jon Wagner notes, the trade-offs between cost and mass go much deeper in aviation. A lighter motor not only improves range and payload but also reduces structural requirements, creating a compounding benefit. This means eVTOL makers are willing to use expensive materials like cobalt-iron alloys (Permendur), which cost roughly ten times standard motor steel, solely for a small boost in performance. In contrast, an EV manufacturer would rarely approve such an expensive material unless it also cut costs elsewhere.</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&width=980" alt="eVTOL vs EV Motors: Key Engineering Differences Explained" 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>
<h2 id="q2">2. Are eVTOL and EV Motors Based on the Same Technology?</h2>
<p>Yes, at their core, both use similar electromagnetic principles—permanent magnet motors, induction motors, or wound-field designs. The fundamental failure modes are also alike. However, the application drives entirely different design responses. For an EV, a motor failure typically means pulling over safely; the system is not engineered for continued operation after a fault. For eVTOL, safe flight and landing are non-negotiable, so engineers must design redundancy into every critical component. The base motor technology is the same, but the surrounding architecture—redundant windings, multiple controllers, and distributed propulsion—diverges drastically. As Wagner puts it, the same core tech exists, but aviation requires a different mindset about risk and failure.</p>
<h2 id="q3">3. What Redundancy Do eVTOL Motors Have That EV Motors Lack?</h2>
<p>Redundancy is purposely designed into eVTOL drive systems, whereas in EVs it's typically a secondary benefit of all-wheel drive layouts. For example, Joby’s aircraft uses multiple motors and propellers so that if one motor fails, others can compensate. This is not an afterthought—it's a primary requirement for certification. In contrast, even dual-motor EVs rarely have independent power supplies or control circuits per motor; the system is optimized for cost and performance, not failure tolerance. Wagner points out that in ground transportation, you can simply pull over; in aviation, you must maintain flight. That drives full redundancy: separate batteries, motor controllers, and even physical separation to prevent a single fault from cascading.</p>
<h2 id="q4">4. How Does Joby's Manufacturing Approach Differ from Automotive?</h2>
<p>Automotive manufacturing often relies on a supply chain where each component—motor, inverter, gearbox—is designed and produced by different vendors. This creates interface boundaries that introduce inefficiencies, such as extra weight from connectors and housings, or suboptimal thermal management. Joby, like many eVTOL developers, takes an integrated approach: they design the entire powertrain in-house, optimizing across component boundaries. This reduces mass and improves efficiency, but it requires deep expertise in multiple domains. Wagner notes that in a mature industry like automotive, outsourcing works well for scale, but for aviation, integration yields critical performance gains that justify the extra engineering effort.</p><figure style="margin:20px 0"><img src="https://spectrum.ieee.org/media-library/image.png?id=65579658&width=1200&height=600&coordinates=0%2C50%2C0%2C51" alt="eVTOL vs EV Motors: Key Engineering Differences Explained" 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>
<h2 id="q5">5. Why Is Permendur Exciting for eVTOL but Not for EVs?</h2>
<p>Permendur, a cobalt-iron alloy, offers slightly better magnetic performance than standard electrical steel, which translates into higher efficiency or lighter weight for the same torque. However, it costs roughly ten times as much. In an EV, where every cent matters and weight is less critical, this cost premium is prohibitive. But in aviation, even a small mass reduction can significantly increase range or payload, making the material attractive. Wagner highlights this as a clear example: eVTOL makers will pay for a small performance improvement because it cascades into big operational benefits, while that same improvement in a car would never offset the expense.</p>
<h2 id="q6">6. How Does Safety Drive Different Design Choices for eVTOL Motors?</h2>
<p>Safety is the core differentiator. In an EV, a motor failure might strand you, but you can call for roadside assistance. For eVTOL, failure during flight is catastrophic, so design must ensure continued safe operation after any single point of failure. This leads to redundant windings, multiple independent controllers, and distributed propulsion. Wagner emphasizes that the mitigation in cars is to pull over; in aircraft, the mitigation is redundancy—not just in motors but also in batteries, power electronics, and cooling systems. This safety-driven philosophy permeates every aspect of eVTOL motor design, from material selection to thermal management to fault detection.</p>
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