This article is published in Aviation Week & Space Technology and is free to read until Aug 17, 2024. If you want to read more articles from this publication, please click the link to subscribe.
Ampaire is developing hybrid propulsion retrofits for small regional aircraft.
As the advanced air mobility industry makes continued strides toward type certification of the first electric vertical-takeoff-and-landing air taxis, skepticism is growing about the near-term commercial viability of the new vehicle class.
Many of the promises and projections made in investor presentations several years ago have since proved to be wildly optimistic. Timelines have shifted right, vehicle and operating costs have been revised higher, and in some cases, performance specs have shifted lower. All this is reflected by an investment scene that has all but dried up, with very little new money entering the industry from public or private capital markets.
- Following initial wave, investment dollars are scarce
- Hybrid, eCTOL concepts could overcome eVTOL drawbacks
The shifting market sentiment is reflected in the meager share prices of the electric vertical-takeoff-and-landing (eVTOL) makers that went public in 2021. Lilium and Vertical Aerospace—both of which face challenges to their financial runways—have been stuck in sub-dollar territory for months, down more than 90% from their initial public offering prices. Archer Aviation, Eve Air Mobility and Joby Aviation have fared somewhat better, trading in the $3-5 range as of late June, but in all cases investors are sitting on large paper losses.
As a result, few investors are willing to touch advanced air mobility (AAM) these days. While startups that already went public have had some success raising money from existing shareholders, the situation poses a serious challenge for multitudes of companies that missed the initial investment wave.
“The question in my mind is whether this market is going to overcorrect,” says Kevin Noertker, co-founder and CEO of hybrid propulsion developer Ampaire. “It’s disappointing. I’ve talked to many people who were excited about eVTOL, and now they won’t touch aviation. . . . My fear is that this heyday of funding and innovation, which the industry has seen over the last half-decade or so, could dry up if the industry plays its hand poorly.”
With market sentiment souring on eVTOLs, some industry players are hoping that attention could transfer to technologies like hybrid propulsion and electric conventional-takeoff-and-landing (eCTOL) vehicles, which could offer a more viable near-term business case. Hybrid propulsion can achieve a far superior range to battery-electric and enable true regional air mobility services. Similarly, eCTOLs can offer the noise and emissions reductions of eVTOLs but with a proven business case and lower hurdles in terms of airspace, infrastructure and regulations.
A key theme of the skepticism is the limited capabilities of existing batteries, as well as their slow rate of improvement. “When you start to do something commercial, there’s no way you can do it with electric [propulsion] only because the range will be too low,” says Jean Botti, co-founder and chief technical officer of French hybrid eVTOL startup VoltAero. “Are people really going to spend €5 or 6 million [$5.4 or 6.4 million] for an airplane that is going to carry them 50 km [31 mi.]? I think this is a very bad business proposition.”
Jean-Christophe Lambert, a former engineer involved with the Airbus E-Fan electric aircraft project who now heads Ascendance Flight Technologies, another French hybrid eVTOL startup, echoed those sentiments.
“We crossed the English Channel in 2015 with our [Airbus] E-Fan, and today in 2024 our batteries have only improved around 20% since then, so the rate of improvement is not even close to what we need,” Lambert says.
“One kg [2.2 lb.] of fuel is equivalent to 15-25 kg of batteries, so if you have 100 kg of fuel, you need 5 tons of batteries,” he says. “What is needed is a 2,500% increase in energy density, but we’re improving just 5% or so every few years. So it’s not just a matter of time—it will not happen any time soon. Batteries alone are not going to be a scalable way to decarbonize aviation.”
The challenges facing battery-electric aviation are myriad. Reserve requirements will eat into the already meager operational range of eVTOLs, further restricting their use case. Other issues such as operating in extremely hot temperatures—Archer and Joby plan to launch services next year in the United Arab Emirates—pose risks of battery degradation. Charging requires access to green electricity and dedicated infrastructure, which may not be available at smaller airports. And charging between trips adds to turnaround times, threatening promised utilization that urban air mobility business models depend on.
For those reasons, Manassas, Virginia-based Electra.aero has focused on developing a hybrid electric short-takeoff-and-landing (eSTOL) aircraft that requires minimal ground infrastructure and can perform useful regional missions up to 500 nm—double the 250-nm range promised by Eviation, which is developing an all-electric nine-passenger aircraft.
“If you use batteries only, you’ll find that the range you get is really compromised,” says J.P. Stewart, Electra’s vice president and general manager. “With a battery-only airplane, you’re talking 50-100 mi. in the upper end before the airplane starts getting egregiously complicated. But if you use the turbine-hybrid system, you can have one turbine that’s sized properly for cruise, and then use the batteries for the extra burst you need on takeoff and landing, or in an emergency situation if the turbine fails. . . . It’s far more efficient than relying solely on batteries.”
While a hybrid propulsion system does not have the same emissions and noise reductions as an all-electric aircraft, Stewart says the savings on both are still meaningful—with a 30% reduction in emissions over similarly sized conventional aircraft and “significant reductions” in noise levels. At the same time, he notes that operating costs are 70% lower than for eVTOL designs.
“We’re conservative in our philosophy,” Stewart says. “Building airplanes and building a market at the same time is high-risk. We’re not doing that. We’re starting with building the airplane for a known market, which has a capability that will facilitate future markets.”
In addition to a focus on hybrid propulsion, some startups are wondering whether eVTOL aircraft—including tiltrotor, multicopter and lift-plus-cruise designs—are too complex and costly to certify and maintain relative to more traditional aircraft concepts. Companies developing electric and hybrid eCTOLs, such as Eviation, Heart Aerospace and Electra.aero, among others, consider electrifying tube-and-wing aircraft using existing airport runways as a more expedited path to decarbonizing aviation.
Other startups, including Ampaire, Dovetail Electric Aviation and ZeroAvia, go further, focusing on developing propulsion systems to be retrofitted into existing small airplanes, a strategy intended to be lower-cost and more pragmatic than certifying a clean-sheet eCTOL.
Andre Borschberg, co-founder and executive chairman of H55, a Swiss startup that is developing electric powertrains for small regional airplanes and trainers, says eVTOL startups have downplayed the challenge of certifying an eVTOL aircraft, while at the same time losing focus on the criticality of achieving near-term commercialization to scale the industry.
“We are very selective with the groups we work with, favoring projects that have a chance to become certified quicker,” says Borschberg, whose company has partnered on initiatives to electrify the Bristell B23 trainer, Piper Archer, De Havilland Canada Dash 8 and De Havilland Canada Beaver.
“If I would rank them [in order of likelihood to commercialization], I would say first comes light aviation and fixed-wing aviation using existing designs—even if they’re not totally optimized,” Borschberg says. “Next would be new designs but still fixed-wing—for example, distributed propulsion eSTOL-type solutions—and lastly eVTOL, which will take much longer to get off the ground. This is how we think the industry will ultimately develop.”
Kevin Noertker of Ampaire, which is developing its hybrid powertrains for small regional aircraft like the Cessna Caravan, has a similarly skeptical assessment of the near-term market opportunity for eVTOLs.
“That’s why we’re focused on developing something nonspeculative,” he says. We’re not building a new airplane; we’re building a propulsion system. And rather than go fully electric or hydrogen, which has phenomenal infrastructure challenges and questionable economics, we’re going hybrid electric.”
But Noertker warns that growing disillusionment among investors means that even startups that are setting pragmatic goals will struggle to raise the cash needed to fund their programs.
“Billions of dollars were raised on the backs of either explicit or implicit commitments around the size of the market, the timeline and the economics,” he says. “Now we’re seeing the repercussions, and unfortunately, it’s affecting the entire industry.”
Related Content
