Angus Batey Ampaire completes trial flights with hybrid-electric testbed on regional airline route in Scotland.
Angus Batey
Ampaire’s Electric EEL—a modified Cessna 337—arriving at Kirkwall Airport in the Orkney Islands on Aug. 12. Credit: Angus Batey/AW&ST
While many across the aviation industry are looking for step-change solutions to meet global emissions-reduction targets, California startup Ampaire is taking what it believes to be a more pragmatic approach. There are things that can be done today to bridge the gap to zero-emission flight—one of which, the company contends, is operationally representative testing.
“There are a lot of people with vision, but it’s about executing on that vision and doing real, meaningful things,” says cofounder and CEO Kevin Noertker.
To this end, Ampaire has built a testbed aircraft it calls the Electric EEL, a Cessna 337 Skymaster with the forward of its two centerline-mounted combustion engines replaced by an electric motor. A large fairing under the fuselage has been added to carry batteries. The aircraft made its first flight in June 2019 and last year completed a series of trials in Hawaii.
Noertker has come to Kirkwall Airport, in the Orkney Islands off the north coast of Scotland, for another set of representative route test flights. The EEL completed several flights between Kirkwall and Wick John O’ Groats Airport, around 60 km (40 mi.) away on the mainland. The flights involved the aircraft’s first operations over open water. The EEL has moved on to demonstration flights between Exeter and Cornwall Newquay airports in England with Ampaire’s partners under the 2Zero project.
The choice of Orkney to follow Hawaii was logical, Noertker says. “One of the real strong similarities we see is that in these regions, aviation matters,” he says. “It’s critical for these communities—it’s how people get on and off these islands, how you bridge the gap between two geographically separated areas. It’s how you get mail and send packages. It’s how tourists come on. It’s how people go to hospitals when they need to go to a major hospital. These are literally lifelines for communities. And what we see is a consistency in how people think about aviation and its importance to their local communities.”
And in carrying out flights on real-world routes with this level of importance to those who live and work near them, Ampaire has learned several important lessons.
“This is about providing essential services for everyday people,” Noertker says. “It’s not just about us in isolation doing something. It’s about the whole ecosystem—bringing together the airports, airlines, infrastructure, local government, community and the airplane. When you pull all that together, you can do something really big.”
To this end, the company has joined a 13-strong consortium in a project called SATE (Sustainable Aviation Test Environment) led by Highlands and Islands Airports Ltd. (HIAL), the state-funded operator of 11 remote airports. The Electric EEL flight program is the first project to be delivered under SATE’s auspices, and Noertker says it is only through such integrated programs that pragmatic development goals can be set and achieved.
“In most of these regions it’s challenging to get the right type of power, or enough power to charge the planes initially,” he says. “If we required it all to be charged with charging stations on the ground, then very few airports would actually be able to receive these planes in the near term.”
Hybrid powertrains therefore represent not just a useful means of achieving some significant emission reductions in the near term but are likely to be needed in some regions for a significant period. Noertker notes that Toyota’s hybrid-electric car, the Prius—the first mass-produced partially electrified road vehicle—is still being sold, despite having been in production for nearly 25 years.
The Ampaire Electric EEL departing Kirkwall Airport, Orkney, on Aug. 12. Credit: Angus Batey/AW&ST
“The Prius has a combustion engine and an electric system combined into what’s called a series hybrid,” he says. “That means no charging infrastructure is required. Hybrid [cars] still outsell fully electric, even though for many people, fully electric makes sense and works great. In aviation you’ll see [something] similar. Of course, it’s a steppingstone toward getting that charging infrastructure in place for future variants of the planes. But by being hybrid-electric that is charge-sustaining, where you don’t need to plug in, you can fly anywhere. And being able to fly anywhere means that we can in fact help quite a few more communities than we would otherwise be able to.”
There are other considerations that point to a hybrid-electric system’s medium-term commercial viability. While visiting for the test program, Susan Ying, Ampaire’s senior vice president of global partnerships, was a passenger on one of local operator Loganair’s Britten-Norman Islanders as it flew a scheduled circular service connecting Kirkwall with Sanday and Stronsay, two other islands in the Orkneys.
“Each flight was 5-7 min., and ground turnaround is only a few minutes,” she says. “If you have an all-electric airplane right now, you pull in and want to charge; that takes more than an hour—so that’s not doable with short interisland routes. But with a hybrid, you can do it right now.”
The right-hand side of the standard Cessna 337 instrument panel has been replaced by equipment to control and monitor the electric engine in the aircraft’s nose. Credit: Angus Batey/AW&ST
While the modified Skymaster is not a representative commercial platform, the flights Ampaire completed between Wick and Kirkwall demonstrated the viability of the hybrid-electric concept for current operations, according to Justin Gillen, Ampaire’s test pilot.
“We’ve been flying Wick to Kirkwall and back, and the design profile is to do that mission twice a day,” he says. “It’s about 20 min. of air time. We’d planned to do it four times per day—eight flights—and we can do that without significant recharging.”
Flights took place under voluntary company restrictions of daytime operations and not flying in visible moisture. Weather conditions during the Orkney deployment meant the aircraft was only able to fly on three days, but the team completed multiple flights each day flying was possible.
“In this configuration, the airplane uses roughly 30% less gas than the baseline Skymaster,” Gillen says. “The whole point is to demonstrate that we can operate this route more economically than the original airplane, using today’s technology.”
Economics will play a vital role in the development of the technology. Loganair operates two Islanders from Kirkwall on the interisland routes under a PSO (public service obligation) contract with the Orkney Islands Council. The contract also connects the islands of Eday, North Ronaldsay, Westray and Papa Westray with Kirkwall and was renewed in April for four years.
The routes are heavily subsidized, and while decarbonization was not mandated under the new contract, both Loganair and the council expect the certainty it provides will give the operator time and capacity to explore options. Hybrid-electric propulsion systems not only offer reduced emissions but also lower operating and maintenance costs. This in turn offers greater flexibility for operators.
“If all the short routes—or even the medium-size routes—are doable with 30-70% more efficient operating cost, you can imagine that the route structures will potentially change from hubs with spokes to point-to-point,” says Ying. “The future of flying may be a totally different topology than for current operations. It really opens up a new way of flying—not just cleaner but much more affordable for people.”
Ampaire’s long-term aspiration remains the creation of a fully electric aircraft, but hybrid aircraft mean the company can have a viable product line on sale relatively quickly. In 2019, the company secured a contract with NASA to explore the feasibility of installing serial hybrid-electric propulsion in the de Havilland Canada DHC6 Twin Otter. Surf Air Mobility, a commuter airline based in Los Angeles, entered into an agreement to acquire Ampaire in February; in July, Surf Air placed an order for up to 150 Cessna Grand Caravan EX aircraft from Textron Aviation, with plans to convert them to hybrid-electric configuration.
“The hybrid system that goes into the Caravan is very similar to the hybrid system intended for the Twin Otter,” Noertker says. “We’re able to have quite a bit of overlapping work between the two. The Caravan is right now our core focus as a launch product. Strategically, that makes a lot of sense. However, the Twin Otter, the Britten-Norman Islander and a few other planes will all be hybrid-electric someday. It’s just a question of when do we bring them to market?”
With only one engine, the Caravan would not be suitable for overwater interisland routes such as Wick to Kirkwall, Ying points out. But Ampaire’s involvement in SATE means there is scope for the company to return to Orkney for further flight trials with a suitable aircraft.
“The next meaningful step [would be when] we can actually get passengers flying hybrid-electric—maybe on Loganair flights,” Noertker says. “We could see it happening as early as 2024 or 2025 with our launch product.”
