The Future of Advanced Air Mobility

Bristow Evaluates Overair's Butterfly eVTOL for Advanced Air Mobility Plans

Helicopter operator Bristow this week launched a collaboration with a fourth aircraft manufacturer in the advanced air mobility sector. Under a memorandum of understanding signed on December 16, the Houston-based transportation group said it has “preordered” between 20 and 50 of Overair’s Butterfly eVTOL aircraft, a model that is expected to complete FAA type certification in 2025.

The announcement also said that Bristow will provide the California-based start-up with guidance on matters including vehicle design considerations, key performance parameters, flight planning best practices, flight operations data sharing, and health monitoring strategies, configuration and maintenance protocols, infrastructure, and ground support operations. It will also contribute to promoting the launch of eVTOL commercial operations.

At face value, the agreement with Overair seems similar to other recent agreements that Bristow has reached with Embraer’s Eve Urban Air Mobility, Vertical Aerospace, and Electra Aero. All of these also involved collaborative work and provisional commitments to add up to 250 of these companies' eVTOL and eSTOL aircraft to its fleet.

The exact commercial terms of these sales agreements remain unclear. During an investor’s call on November 4, Bristow CEO Chris Bradshaw explained that “at this stage in the development of the advanced air mobility industry, we are not making any firm capital commitments.”

This seems to imply that no deposits have been paid for any of the conditional purchases and that the operator has yet to make final decisions as to which of the various aircraft it may end up using. In its announcement, Overair stated that “of the vehicles Bristow is currently considering, Butterfly is the only aircraft with a vectored thrust configuration.”

Bristow, which has more than 70 years of experience in rotorcraft operations, is seeking to diversify its business model. With AOCs in multiple countries around the world, the group considers itself well-positioned to pursue new AAM applications, including logistics flights, cargo deliveries, and search-and-rescue missions. The company is also keen to support multiple eVTOL manufacturers and other operators with services such as aircraft maintenance and crew training.

“Our collaboration facilitates expansion into new high-density geographic markets with sustainable, innovative, and efficient vertical lift and aerial transport services,” said Bradshaw, commenting on the new agreement with Overair. “As the global leader in vertical lift, Bristow’s operational expertise and efficiency, supported by the trust and confidence of our customers, can safely bring eVTOL aircraft into the market.”

The Butterfly is expected to be able to carry five passengers on trips of over 100 miles and at speeds of around 200 mph. This might make it suitable for some of Bristow’s offshore support services, carrying oil and gas workers to platforms in locations such as the Gulf of Mexico and the North Sea.

According to Overair, the aircraft's low-noise and high payload and range performance are based on the patented Optimum Speed Propulsion system developed over the past couple of decades through a sequence of rotorcraft and drone designs developed by Overair founder Abe Karem. Its four large tilting propellers spin slowly in hover and even slower during cruise flight, which the company says results in reduced power consumption that boosts payload, as well as safety margins for operating in challenging environmental conditions. The high aspect ratio wings have full-span flaps to support low stall speeds.

Overair, which recently doubled the size of its Santa Ana headquarters, aims to start flight testing an initial technical demonstrator during 2022, followed by a full-scale prototype in 2023. It has already started ground testing a full-scale propulsion system, including the 20-foot-diameter rotor system. It is also working with prospective suppliers and partners to agree on how they will contribute to the program.

“Bristow’s decades of vertical lift experience will greatly enhance Butterfly’s path to commercialization,” said Overair CEO Ben Tigner. “Their operating insight, combined with our development and execution of the Butterfly program, will position Butterfly to serve Bristow on high-density routes.”