The Hidden Tradeoffs Powering Joby’s eVTOL Motors

Electric vehicles, whether they’re cars on the road or electric vertical take-off and landing (eVTOL) aircraft, are built around similar electric motors. But there are vital differences including component costs, mass, and redundancy.

Jon Wagner spent five years as the senior director of battery engineering for Tesla before joining California-based eVTOL developer Joby Aviation in 2017. He spoke with IEEE Spectrum about how engineering differs between cars and aircraft.

How do eVTOL motors differ from car motors?

Jon Wagner: In general, ground transportation has a different focus on cost versus mass. You know, would you be willing to spend more on the parts in order to save a certain amount of mass? The trade-offs end on the ground vehicle and at a certain point the cost is dominant, whereas with aviation, the trade-offs between cost and mass go a lot deeper. And so for certain solutions eVTOL makers are willing to spend more money in order to enable either lighter weight or greater efficiency.

The other key difference is related to safety. In essence, we’re dealing with the same motor technologies for ground transportation and aviation right now, so the failure modes are similar. But of course, with aviation we have the desire for continued safe flight and landing, and that drives what you do in the design to mitigate those failures if they were to occur. In many cases in ground transportation, the mitigation for a failure is to pull over safely to the side of the road. In aviation, the mitigation is redundancy, because there’s not an option to pull over.

Is redundancy designed into EV motors?

Wagner: Typically, redundancy is not designed into electric vehicle drive systems solely for the purpose of redundancy. There are some cars now that have all-wheel drive—so there’s a motor on the front, a motor on the back—so as a secondary feature you get the redundancy. But it wasn’t done with the primary intent of having redundancy.

How does Joby’s eVTOL manufacturing compare to EV manufacturing?

Wagner: The most efficient way to run a large-scale engineering effort in a mature industry, such as automotive, is to break your system up into pieces that can be outsourced to suppliers who are going to do a really good job on each piece. The downside is that when you break a problem up into three pieces, you now have interface boundaries between each of these pieces, and those always create inefficiencies. We were able to design highly integrated solutions without taking that manufacturing penalty.

Are there any materials you’re really excited about?

Wagner: Permendur [a cobalt-iron alloy] typically costs in the neighborhood of 10 times as much as traditional motor steel. That’s significant, and it’s often not used in ground transportation because of that cost. It comes with small improvements in performance, but enough that for aviation it’s quite interesting.

Will electric aircraft catch on like ground EVs?

Wagner: I’ve always wanted to be a very forward thinker with respect to power-train. However, one of the things I’ve learned over the years is that power-train development has to come with a very healthy dose of patience. Developing a whole new type of power-train is a big endeavor, but it’s one that I’m very confident the aviation industry will undertake. We’re certainly undertaking it here at Joby, and we’ll see that broaden, I’m sure, with time.

This article appears in the May 2026 print issue as “Jon Wagner.”