Joby Aviation is taking a different approach to building electric aircraft motors: rather than pursuing exotic new technologies, the company is focusing on smart integration of proven solutions and in-house manufacturing to achieve the efficiency, weight, and reliability needed for commercial air taxis. Jon Wagner, who led battery engineering at Tesla before joining Joby in 2017, explained that this philosophy of integration over invention has become central to how the company designs its powertrain for the S4 eVTOL (electric vertical takeoff and landing) aircraft now undergoing Federal Aviation Administration certification .

How Does Joby's Direct-Drive Motor Design Work?

At the heart of Joby's eVTOL is a direct-drive electric motor that spins the propellers at relatively low speeds to reduce noise. This design choice creates a specific engineering challenge: slow-spinning propellers require enormous torque, so Joby built a large-diameter motor to deliver the high torque density needed. The motor uses a magnet ring that rotates around a stationary stator made of copper coils and magnetic steel .

What makes this design particularly clever is its redundancy. The stator is divided into two separate sets of coils, each powered by its own inverter and battery. This means if one system fails, the aircraft can still operate on the backup. Tying everything together is a thermal management system that keeps the motor cool while minimizing weight, a critical factor for aircraft that must carry passengers efficiently .

"The original concept was that the more times you go through the process, each time you can identify improvements or problems that need to be addressed. And if you have a very good system for going through that iterative process quickly and at a low cost, then you can take risk, because if it fails, you just go again," explained Jon Wagner, former senior director of battery engineering at Tesla and now powertrain chief at Joby Aviation.

Jon Wagner, Powertrain Chief at Joby Aviation

Why Does In-House Manufacturing Give Joby an Advantage?

Joby's decision to build its motors in-house rather than outsourcing to suppliers represents a fundamental shift in how the company approaches engineering. In mature industries like automotive manufacturing, companies typically break complex systems into pieces and hand them off to specialized suppliers. This works well when the supply chain is established and everyone knows exactly what they need .

But in the emerging eVTOL industry, there is no mature supply chain. By keeping motor development in-house, Joby can design highly integrated solutions without the inefficiencies that come from interface boundaries between different suppliers. Wagner noted that when you break a problem into separate pieces, those connection points between pieces always create complexity, add weight, or introduce reliability concerns .

• Integration Benefits: Joby achieves the mass and performance advantages of a highly integrated solution by designing and manufacturing motors in-house, avoiding the penalties that would come from outsourcing to multiple suppliers.
• Manufacturability First: The company architected manufacturability into the entire motor concept from the start, treating it as a fundamental requirement rather than an afterthought in the design process.
• Supply Chain Flexibility: Without relying on external suppliers for critical components, Joby can iterate quickly and make design changes without waiting for suppliers to adapt their production processes.

What About Superconducting Motors and Future Technologies?

The aviation industry has shown considerable interest in exotic motor technologies, including superconducting coils and carbon nanotube materials that could theoretically reduce energy losses. However, Joby is not actively pursuing these approaches for its current aircraft .

The reason is practical: Joby's current direct-drive motors already achieve efficiency levels in the low to mid-90 percent range. The potential gains from superconducting technology would be modest, while the engineering challenges would be substantial. Superconducting motors must be kept extremely cold to maintain their special properties, and if the cooling system fails, the motor essentially becomes useless. For a commercial aircraft where reliability is paramount, this risk-reward calculation does not favor the technology .

Wagner noted that superconducting motors might make more sense at much larger scales, such as in motors rated for one to ten megawatts. At those power levels, even a five percent efficiency gain would translate to significant energy savings. But for Joby's current aircraft operating in the hundreds of kilowatts range, proven direct-drive technology remains the better choice .

How Is Joby Balancing Innovation With Certification Requirements?

As Joby moves toward FAA certification, the company faces a tension between pursuing new technologies and maintaining the stability needed for regulatory approval. The company set out more than a decade ago to build an aircraft that would shift transportation away from fossil fuels, and batteries remain the best available solution for that goal .

This philosophy of pragmatism over cutting-edge experimentation reflects a broader lesson from Joby's development process. The company uses what it calls a "design, build, and test" methodology, cycling through rapid iterations to identify problems and improvements. This approach has been applied to nearly every component of the S4, not just the powertrain. By embracing iteration and learning from failures quickly, Joby has been able to take calculated risks without betting the entire program on unproven technologies .

For potential passengers and investors watching the eVTOL industry, Joby's approach suggests that the path to commercial air taxis may not require revolutionary breakthroughs in materials science or physics. Instead, it may depend on engineering excellence in integrating existing technologies, manufacturing discipline, and the willingness to iterate until a design is reliable enough to carry people safely through the sky.