Surf Air Mobility has committed to buying up to 150 Cessna Grand Caravan EX single-engine utility turboprop aircraft from Textron Aviation and plans to replace their Pratt & Whitney PT6 turbine engines with hybrid-electric propulsion systems beginning in 2024.

The provisional order announced on Tuesday is for 100 firm and 50 options for the Grand Caravan EX, with deliveries to begin in the second quarter of 2022. In a media statement issued by the private air transportation group, Surf Air Mobility said that the transaction is subject to it securing further financing.

For now, the deal does not appear to mark a direct initiative by the Textron group to offer hybrid- or electric propulsion alternatives to its piston- and turboprop-powered aircraft. Despite having recently formed a new eAviation electric aviation division earlier this year, the company seems content for customers like Surf Air and their partners to take a lead in the electrification process.

Surf Air Mobility plans to develop a hybrid-electric propulsion system and will seek an FAA supplemental type certificate (STC) to install the system in its Caravan fleet. The powertrain will use a turbo-generator to charge batteries that run an electric motor-driven propeller. Surf Air Mobility is still in discussions with manufacturers of electric motors, the turbo-generator, and batteries, according to Surf Air Mobility chairman and CEO Sudhin Shahani.

Earlier this year, Surf Air Mobility agreed to acquire hybrid-electric aircraft developer Ampaire and the California-based start-up will drive the technological development of the hybrid-electric Caravan STC. Ampaire has demonstrated the Electric EEL, a hybrid-electric conversion of a Cessna 337 Skymaster in which one of the airplane's two piston engines is replaced with an electric powerplant. Ampaire also had planned to develop hybrid-electric propulsion for the De Havilland Twin Otter and Grand Caravan. The company hasn’t applied to the FAA yet for the Caravan STC, but this should happen soon, Shahani said.

“We’re building on the work that Ampaire has been flying now for three years,” he said. “We’ve proven cost and emissions reductions a little over 30 percent. I'm replacing [the PT6] with a lighter combustion turbo-generator, where you get back some weight, and then adding the EPU [electronic power unit] and the battery pack, which work in series with the turbo-generator, and wrapping all of that with our proprietary control software.”

Ampaire's work to date puts it in a strong position to act as a systems integrator for the plan to convert the Caravans to hybrid-electric propulsion. Likely potential supplies of turbo-generators and electric motors might include companies such as Rolls-Royce, MagniX, and Safran.

The advantage of hybrid-electric technology is that the turbo-generator makes its own electricity to spin the electric motor and propeller, eliminating the need for charging stations at airports and also the time required to recharge. “We think that this is the biggest step one can make in the shortest amount of time towards decarbonization,” he said.

Shahani doesn’t anticipate any major hurdles and said that current battery technology will enable the hybrid-electric conversion. “What we're doing here is engineering, not science. It doesn't depend on any updates in battery technology that don't exist today.”

As the new Grand Caravan EXs come online next year, Surf Air Mobility says it will place them with one of its operating partners, from among the companies that have aircraft and flight availability listed on the Surf Air Mobility platform.

There are no plans to replace the Pilatus PC-12s currently operated for Surf Air’s membership charter service by Advanced Air because they are useful for longer flights, from 300 to 500 miles, while the hybrid-electric Caravan will serve routes from 50 to 250 miles. The idea is to fly a similar mission profile—with slightly shorter routes—as the Grand Caravan, providing transportation in a nine-seat configuration while cutting costs and emissions by 25 percent. “We see room to scale our platform,” he said, “and we see a regional air service more affordable to a much broader audience.”

“Hybrid-electric propulsion technology, deployed at scale for environmental and commercial benefits, is an important part of the future of travel,” said Textron Aviation president and CEO Ron Draper.

Surf Air Mobility has flirted with electric aircraft previously, after it bought Blackbird, a charter broker, in early 2020. Although Blackbird announced plans to purchase 110 Bye Aerospace electric eFlyer light airplanes, with plans to put them in charter service, Shahani said, “We don’t have any immediate plans or timelines for that. We’re focused on the eight-passenger, high-frequency scheduled service, and bringing the price point down in a scheduled service setting. It’s a multi-phased approach, and that’s our first move in electrification.”

After the STC is approved, Surf Air Mobility will offer the hybrid-electric upgrade to existing Grand Caravan owners at a price similar to the cost of overhauling the PT6 engine. “So it becomes an attractive option for them to switch over,” he said.

Rob Scholl, senior vice president at Textron eAviation, explained that the Surf Air Mobility order is not a deal with Textron Aviation’s nascent eAviation division. Rather, his role means that he works “across the entire Textron Aviation enterprise. I look for interesting opportunities, technologies, products, and partners to work with. While there's not really an eAviation division today, what I'm doing is working across the portfolio with all the products that we have from fixed-wing to vertical lift to the defense side at Textron Systems, to look at different opportunities. And this is a great example of what Textron can bring to market. This is an opportunity to showcase the combined expertise and technologies of both Textron Aviation and Surf Air Mobility. The outstanding capabilities and versatility of the Grand Caravan make it an ideal aircraft to take advantage of this new technology.”

Textron Aviation will help Surf Air Mobility with engineering and data to support the STC program. After FAA certification, Surf Air Mobility will seek certification outside the U.S., and Textron Aviation will help with sales and product support. “It’s an exciting opportunity to create new markets and reduce the carbon footprint of aviation,” Scholl said. “If you look at Textron Aviation, we have the largest fleet of fielded aircraft anywhere in the world, so the opportunity to take a new propulsion technology and find ways to integrate it into existing platforms allows us to make an impact not only with new aircraft. If we see opportunities to do other things with new designs, we would take a look at that as well."

In 2022, Surf Air Mobility aims to take delivery of 12 Grand Caravan EXs. “We expect to be able to ramp up based on demand,” Shahani said. There are no plans to add autonomous technology to fly the Caravans, he added. Passengers who fly in Surf Air Mobility aircraft expect to see pilots in the front seats. “Our missions are focused on the passengers. Autonomy may start in the cargo space.”

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