The Hidden Tradeoffs Powering Joby’s eVTOL Motors

Electric vehicles, whether on-road vehicles or electric vertical take-off and landing (eVTOL) aircraft, are built around the same electric motors. But there are important differences that include component cost, size, and repeatability.

Jon Wagner spent five years as Tesla’s senior director of battery engineering before joining California-based eVTOL developer Joby Aviation in 2017. He talked to IEEE Spectrum about how engineering differs between cars and airplanes.

How are eVTOL motors different from car motors?

Jon Wagner: In general, ground transportation has a different focus on cost versus weight. You know, would you be willing to use more parts to save a certain amount of weight? The trade-off is limited to low-end vehicles and at some point the cost becomes high, and in aviation, the trade-off between cost and mass is much deeper. And for some solutions eVTOL manufacturers are willing to spend more money to enable lighter weight or greater efficiency.

Another important difference is related to security. In short, we are dealing with the same vehicle technology for ground transportation and aviation right now, so the failure modes are the same. However, with an airplane we want to continue to fly safely and land, and that drive you do in the design to minimize that failure if possible. In many ground transportation situations, the reduction of failure to pull safely to the side of the road. In aviation, downsizing is repetitive, because there is no option to go back.

Is redundancy built into EV motors?

Wagner: Typically, reusability is not designed for electric vehicle drive systems for reusability. There are some cars now that are all-wheel drive—so there’s an engine in the front, an engine in the back—so that as a secondary feature you get repeatability. But it was not done with the original intention of wanting to redo the work.

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

Wagner: The most efficient way to use a large engineering effort in a mature industry, such as automotive, is to break your system into pieces that can be outsourced to suppliers who will do a really good job on each piece. The downside is that if you split the problem into three pieces, now you have communication constraints between these pieces, and those always create inefficiencies. We were able to design highly integrated solutions without taking that productivity penalty.

Is there anything really exciting?

Wagner: Permendur [a cobalt-iron alloy] It usually costs around 10 times more than traditional motor steel. That’s important, and it’s usually not used for ground transportation because of that cost. It comes with a small improvement in performance, but enough that in aviation it is quite interesting.

Will electric planes catch on like low-end EVs?

Wagner: I’ve always wanted to be the most forward thinking person in terms of power train. However, one of the things I’ve learned over the years is that powertrain development should come with a very healthy dose of endurance. Building a new type of power train is a huge undertaking, but hopefully the aviation industry will do it. We certainly do here at Joby, and we’ll see it expand, I’m sure, over time.

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