Advanced Air Mobility Interviews

Near-term Sustainability for Air Transport – Ampaire’s Hybrid-electric Aircraft

Near-term Sustainability for Air Transport – Ampaire’s Hybrid-electric Aircraft

Ampaire is a hybrid-electric propulsion manufacturer established in Hawthorne, California. In July 2022, its Electric EEL set a new benchmark for hybrid-electric aircraft, with a nonstop flight in the US of 1,135 miles.

Susan Ying thought she had retired. As a distinguished aerospace engineer by trade, Ying had spent much of her career with Boeing as a director for research and technology, before moving to Shanghai to work with the Commercial Aircraft Corporation of China (COMAC) on its ARJ21, C919 and C929.

Although she did not know it at the time, it was during her stay with Boeing that the seeds for her move to Ampaire were being sowed. As part of her role back then, Ying tried to recruit a young man from Stanford University, who decided to join Northrop-Grumman instead. Years later, a friend reintroduced the pair and that young man she once interviewed turned out to be Cory Combs, Co-Founder at Ampaire.

After listening to Combs talk through Ampaire’s vision and goals, she relished the opportunity to join what she describes in her own words as “this revolution” in aviation, not the next revolution.

“It’s way too exciting to be on the side lines watching this happen. I want to be in it, you know, roll up my sleeves and do it.”

The first revolution was powered flight, when the aviation pioneers stuck engines onto aircraft and had the ability to control where the aircraft went. The second was the jet engine, which revolutionized commercial air travel, making it possible to connect cities and countries flying faster, farther, and higher.

“This revolution right now, is that we are going to improve our flight so that it will be cleaner, greener, and quieter, and the best part is that it will be more affordable so that we can really connect all of the remote parts of the world,” says Ying.

Ampaire’s first aircraft is a modified Cessna 337 SkyMaster, which the company calls the Electric EEL. The 337 is unusual in that it employs a push – pull configuration for its engines, with one at the front of the fuselage, and one at the rear. Whilst this configuration is relatively uncommon, it helped the company convert the front engine to electric power first to act as a prototype “flying test bed”, whilst the rear engine remains in its original state.

Ampaire’s first commercial product involves a hybrid-electric powerplant that works similarly as some hybrid-electric cars being independent of the charging infrastructure. A traditional piston engine is joined on the shaft by an electric powertrain, all of which are capable of powering the aircraft. This is referred to as “integrated parallel” system architecture, different from that of the Electric EEL which is an “independent parallel” system architecture. 

According to Ying, Ampaire’s solution revolves around what she describes as “using electric where it makes the most impact.” For example, on take-off an engine must produce maximum power to speed up the aircraft to the point that it can lift off, then it must keep producing enough power to make the aircraft climb. To “energy optimise” for the whole mission, we use electric power appropriately as boost in take-off and climb to avoid the excess fuel required by the combustion engine, and minimise the electric and fuel usage for the cruise by a more efficiently sized combustion engine, which not only cuts down on fuel costs, but also cuts down on harmful emissions. Ampaire says that on a typical flight the fuel cost savings could be between 50 – 75%, depending on the length of the flight.

“The best part is that we can do that today. Once we have the certification in 2024, it could basically be introduced into service right away,” says Ying. “We don’t have to wait for a decade for a brand new airplane to be certificated.”

Since the EEL’s first flight in June 2019, the company has taken the opportunity to carry out several demonstration flights, almost at opposite ends of the earth. The first was in Hawaii, where the EEL flew from one side of Maui to the other in 15 minutes, a distance that Ying says would take at least a couple of hours by car.

The second took place in the Scottish Highlands, where the aircraft was used to connect the mainland to some of the smaller islands, with Ying saying that the aircraft would make commuting between different towns and islands possible, whereas before the trips would necessitate an overnight stay somewhere.

But the longest flight took place when Ampaire took the EEL to Oshkosh for the EAA AirVenture event. Having left the company’s Camarillo homebase for a short hop and night stop at Mojave, the aircraft departed the next day for Hayes, Kansas, with the 1,135nm-journey becoming the furthest that a hybrid-electric aircraft has flown to date.

The EEL should be viewed as just a technology demonstrator, a way of proving the technology can work, before scaling up to larger aircraft. The first of those will be the Cessna 208 Caravan, or, as Ampaire calls it, the Eco Caravan.

The Caravan, which first flew in 1982, is a single engine aircraft that can carry up to 1,436 kg of freight, or 13 passengers when in a passenger configuration, although with Ampaire the max seating is reduced to nine, and the payload to 1,133 kg. With more than 3,000 Cessna Caravans built, its operators appreciate its low acquisition and operating costs as well as its rugged design, which makes it ideal for connecting remote communities, whether it is carrying passengers or freight.

Ampaire announced the first orders for the Eco Caravan during the EAA AirVenture event where the EEL was being displayed. The order was placed by southwest USA-based air mobility company WingTips, which placed an initial firm order for five aircraft, as well as taking out options on a further 20 aircraft.

“Fuel saving is at least 50%, 50-70%, and once again, that depends on how you optimize that,” says Ying. “Operating costs will be reduced around 25% or so, of the total operating cost.”

That could just be the beginning though, as both companies say that they are looking into an agreement for a further 175 aircraft, which could come in stream as WingTips expands nationwide in the US. The two companies are also looking at larger aircraft, with the DHC-6 Twin Otter as the front runner. Ampaire has already been working on a hybrid engine for that aircraft, having originally won a USD$6.4 million grant from NASA for its research and development.

Although the company says it would be possible to work on smaller aircraft than the 337, Ying says the market for hybrid or electric general aviation aircraft is already getting crowded.

“Our goal is not going down small, its scaling up high. Because we believe that to really make a difference in terms of sustainability, we cannot stay at nine-passenger aircraft.”

What that looks like in the future could well depend on battery technology, both in capacity and physical size. It’s clear that Ampaire has 737 or A320 sized aircraft in its sights with the most pollutions due to the installed base.

“The immediate problem that we can solve is for regional air mobility,” says Ying, “we can go cleaner, greener, and quieter more affordably today!”