Redefining air transportation.
​One milestone at time.

Fall 2021 -- Propulsion System Testing, Southern California

Our mantra

Our end goal is unambiguous - give life to a new form of electric aerial mobility that is safe, sustainable, and equitable. These sort of opportunities don't come around often, and thousands of moving pieces must come together to make this a reality. We've been laying the ground work for this journey for the past three decades and know how to roll-up our sleeves and get it done. Since 2018 we've been hard at work bringing Butterfly into existence. Come see where we are in this journey.

Design Origins | Butterfly

Butterfly is designed based on decades of technology development with stakeholders such as the US Department of Defense and NASA to produce the most advanced flight vehicles in the world. Butterfly applies this technology to the commercial market, providing the right vehicle for advanced aerial mobility (AAM).

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TR-36 Single rotor test stand. An advanced, larger version of the propulsion technology powering Butterfly, which was developed for the US Department of Defense Future Vertical Lift Program. 

Mobile propulsion testing

An inside look at Overair’s Optimum Speed Propulsion System

The core of Butterfly’s unique performance advantages

Mobile propulsion testing: This is Butterfly’s full-scale propulsion testbed, sitting on a 50,000-pound truck. Much like a wind tunnel, we use a mobile testbed to simulate real-world conditions of Butterfly’s future flights.

Perfecting our propulsion system early on in Butterfly’s development is the most efficient path to commercialization. Through this testing, we’re able to verify our design choices for FAA certification and prepare Butterfly for production.

As the heart of Butterfly’s design, and by far the most challenging aspect of Butterfly’s development, this propulsion testing is a tremendous milestone for the Overair team. With this achievement, Overair is poised to certify and commercialize Butterfly during the mid-2020s.

20-foot diameter propellers

An inside look at Overair’s Optimum Speed Propulsion System

The core of Butterfly’s unique performance advantages

20-foot diameter propellers: By far the largest propellers on any EVTOL, our propellers spin very slowly, requiring less energy and minimizing noise.

Our large propellers will automatically vary how fast they spin in vertical flight (for takeoff and landing) and forward flight (for cruise), like a dimmer knob rather than an on/off light switch. In fact, they will spin half as fast once Butterfly is flying forward – this is a breakthrough for vertical flight aircraft. By using the “optimum speed” for each phase of flight, Butterfly uses less battery power, leaving extra margins for safety and performance in tough weather, as well as range and payload.

Advanced blade design

An inside look at Overair’s Optimum Speed Propulsion System

The core of Butterfly’s unique performance advantages

Advanced blade design: This is a different kind of propulsion with very large propellers that spin much slower than other designs. The shapes of the blades and their tips have been crafted by some of the world’s leading aerodynamic minds, and the results point to one thing: Butterfly will be the quietest EVTOL. Compare the noise made by a ceiling fan to a hair dryer – the hair dryer is loud because the blades of its small fan need to turn much faster, while the ceiling fan pushes just as much air while making almost no sound. Butterfly is in a class of its own.

Individual blade control (“IBC”)

An inside look at Overair’s Optimum Speed Propulsion System

The core of Butterfly’s unique performance advantages

Individual blade control (“IBC”): Butterfly uses a cutting-edge control scheme that has been 15 years in the making. IBC allows us to vary the angle of each propeller blade as it spins. This variation controls the aircraft’s movement in vertical flight.

Unique to Butterfly, IBC will make Butterfly's ride quality much smoother than existing helicopters. IBC also reduces maintenance costs by reducing the forces imposed on the airplane’s parts.

Vectored thrust configuration

An inside look at Overair’s Optimum Speed Propulsion System

The core of Butterfly’s unique performance advantages

Vectored thrust configuration: Butterfly will redirect (“vector”) its propellers’ thrust in all three flight modes: vertical flight, forward flight and the angled transition between them. Our propulsion rig tests our propellers in all three of these flight modes. Butterfly’s vectored thrust design is the most efficient of any aircraft type that can take off and land vertically, like a helicopter, and fly forward efficiently with wings, like an airplane.

Together with its large diameter propellers, Butterfly’s vectored thrust design provides its high payload, all-weather performance and quiet flight capability.

Direct-drive electric motors

An inside look at Overair’s Optimum Speed Propulsion System

The core of Butterfly’s unique performance advantages

Direct-drive electric motors: Butterfly’s all-electric motors will be powered by battery cells that are generally available today and produce zero carbon emissions. With no gearbox and very few moving parts, Butterfly’s motors are safer, quieter, more efficient and cheaper to operate than existing aircraft engines.

Active data collection

An inside look at Overair’s Optimum Speed Propulsion System

The core of Butterfly’s unique performance advantages

Active data collection: By equipping our test rig with telemetry antennas, we’re able to stream thousands of data points per second from hundreds of sensors all over the propulsion system. These sensors measure aeroelastic forces and help us expand our testing envelope. The data is streamed directly from the test rig to engineers at Overair headquarters.

 

 Butterfly Development

A thoughtful approach that puts early emphasis on propulsion development.

Certification-Driven Design

Guided by safety and the ultimate finish line.

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Agile Development​

Technical risk paid down early and often.

Coming soon- Full-scale Flight Vehicle

Having already flown two sub-scale versions of Butterfly and currently putting propulsion system through the ringer on the ground, the next step in our journey is the most exciting yet.

Bringing a world of possibilities closer to home

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Butterfly

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