AAM Spotlight: Ben Tigner, Overair

Spun off from Karem Aircraft in 2020, Overair is a California-based startup looking to develop and certify a piloted, five-passenger eVTOL air taxi. Dubbed Butterfly, the aircraft is notable for its four 20-ft.-dia. propellers, which the company says offer superior performance and less noise than competing designs. In a recent conversation with the AAM Report, CEO Ben Tigner discussed Overair’s heritage and the Butterfly’s unique design. A partial transcript follows:

AAM Report: How does the company benefit from its legacy as a spinoff from Karem Aircraft?

Tigner: At Karem Aircraft, we spent the last couple of decades working collaboratively with the Army and other military organizations to develop vertical lift propulsion technology. At that time, we had in mind certain military objectives that were aligned with low-noise signature and highly efficient use of energy and power for lower-cost, future-generation vertical lift aircraft. But as the world of eVTOL started becoming a thing, we realized the technology we had was exactly what was needed to enable this new UAM [urban air mobility] application, and so we decided to spin off as a separate company specifically focused on using that technology for civilian application. That technology basically imbues us with the ability to engineer much larger-sized propellers than other people in the industry. 

What is the benefit of using larger propellers?

If you are able to engineer very large propellers, that allows you to push more air, which in turn allows you to generate thrust using less power and making less noise. A sort of intuitive example is to compare the amount of air throughput of a hair dryer versus a ceiling fan. The hair dryer pushes air through a very small propeller, essentially, and it’s pretty noisy. A ceiling fan actually generates the same amount of thrust but it takes a lot less power and it makes a whole lot less noise. That’s because the propeller blades of the ceiling fan move much slower through the air than the little fan inside the hair dryer. It’s the same thing with eVTOLs that use small propellers versus big propellers that turn slower. But it takes more sophisticated technology to be able to do that, and that’s what we have by virtue of being a spinoff from Karem Aircraft.

Why did Overair build and test its full-scale propulsion system before the prototype aircraft was assembled?

Doing the propulsion system test first was a key part of our strategy that puts us on a more efficient path to certification. From the beginning, our focus was never on trying to get an aircraft in the sky as quickly as possible. That’s because we knew this was uncharted territory for the FAA, and so we wanted to focus on getting the ground rules established and well understood before we really started engineering the vehicle in detail. That approach leads to a smaller number of iterations where we have to build hardware, test it, find out what its flaws are, and then re-engineer it under a new set of certification rules. With programs like this, there is always a certain amount of iteration involved, but our strategy was designed to minimize the amount of iteration and therefore minimize the total cost of getting through the program.

What is the status of the prototype aircraft?

That is our next major step. Now that we have full confidence that the propellers do what we designed them to do, we can start putting four of them on a full-scale vehicle, which is what we’re working on right now. Most of the large structural parts of the first prototype are now in existence, and we’re working busily away in our shop beginning to assemble them into a complete airplane. We expect to have the airplane done by around the end of this year and have a first flight shortly thereafter.

When do you expect the Butterfly to be certified?

We don’t expect to be the first company certified, but we will be in the first wave of companies, and that’s partly because our efficient certification path benefits from having other folks who went before us sort of clear the path ahead. We won’t be the first out of the gate, but I expect us to be in that early pack around the 2025-2026 time frame. Keep in mind, when it comes to passenger service and UAM, I do expect there will be some time lag between certification and actually developing methods of smoothly operating fleets of these vehicles. But for applications that don’t involve human safety, I think there will be opportunities to begin operating shortly after certification.