An artist’s rendering of Bye Aerospace’s planned eight-seat electric airplane, the eFlyer 800.
At first glance, the new electric airplane that George Bye is developing looks boring compared to the futuristic flying cars and cargo drones that other electric aviation startups are working on. But if he’s right, his conventionally styled airplane could have a smoother, quicker path to market and be just as disruptive.
The eight-seat, twin-propeller plane, dubbed the eFlyer 800, which Denver-based Bye Aerospace is revealing details of first with Forbes, resembles a sleeker version of a Beechcraft King Air, the top-selling twin turboprop made by Textron. That’s no accident: Bye is designing the eFlyer 800 to be a replacement for nine-seat versions of that venerable workhorse, with comparable performance in all respects but range, and a similar price (the King Air 260 goes for above $6 million), but with under one-fifth the operating costs.
The 64-year-old former U.S. Air Force pilot and electric aviation pioneer says the eFlyer 800’s radically reduced costs, courtesy of the lower price of electricity compared to aviation fuel and the smaller maintenance requirements of electric motors, will open up new possibilities for fleet owners, including using the plane for air taxi service on routes that aren’t currently economical, as well as for on-demand cargo delivery, where he envisions the plane potentially replacing trucks for some legs of Amazon-style rapid delivery operations. “Electric aircraft can cover distances at less cost than a truck without any carbon dioxide emissions, and with much less noise, they can operate at night over high-density urban environments like L.A.,” he says.
Powered by lithium-sulfur batteries being developed by Oxis Energy, a U.K. startup that says it’s achieved a leap in energy density over conventional lithium-ion cells, Bye says the eFlyer 800 will have a maximum range of 500 nautical miles at a cruising speed of 320 mph. That would be less than a third the range of a King Air 260, but Bye argues that’s more than enough for the needs of the vast majority of turboprop operators.
He may be right: The average flight for a business turboprop over the past 12 months was 1.2 hours, according to data compiled by JetNet, which pencils out to somewhere in the range of 240 nautical miles, aviation consultant Rolland Vincent estimates.
Helping improve the design’s range is aerodynamic efficiency that Bye says is twice that of turboprops by virtue of the greater simplicity of electric propulsion systems: without fuel tanks, Bye was able to design thinner wings, and without protruding engine air intakes and exhaust nozzles, the propeller mounts are smaller.
Bye believes he can bring the plane to market somewhere between late 2024 and 2026, aided by the familiarity to regulators of its classic airframe design and the building blocks he’s already put in place for the eFlyer 800 with the smaller aircraft that he’s been developing since he founded his company in 2014.
With $29.7 million in funding, according to Pitchbook, and 50 employees, Bye Aerospace is currently assembling the first production version of a two-seat electric airplane, the eFlyer 2, which is designed to be used as a low-cost trainer for student pilots. Bye expects it to win safety approval from the FAA by the end of 2022, which should make it the first passenger aircraft designed around electric propulsion to be certified in the U.S. (Pipistrel has certified a smaller two-seat electric airplane in Europe under less stringent light sport aircraft standards.) Bye has also been developing a four-seat version. He’s taken deposits for 716 orders of the two planes, and he says he has launch customers for the eFlyer 800 that he’ll reveal soon.
George Bye stands in front of a prototype of the eFlyer 2.
The eFlyer 800 is based on the same systems that Bye developed for those planes and a supplier network that includes French aerospace conglomerate Safran, which is providing the electric motors.
Most important among Bye’s suppliers to the 800’s prospects is battery maker Oxis and whether it can meet its goals in developing a more power-packed and less fire-prone battery chemistry than standard lithium-ion. Current batteries contain 14 times less usable energy by weight than aviation fuel, and Bye needs a planeload of power to achieve the range his design needs: 750 kilowatt hours, ten times a Tesla battery.
Oxis CEO Huw Hampson-Jones told Forbes that last year his company fielded a lithium-sulfur battery in a UAV flight-tested in the U.S. that contained 473 watt-hours per kilogram of energy at the cell level, roughly 70% more than the best Li-on automotive batteries. Because sulfur is effective as a fire retardant for the highly flammable lithium in the battery, when the cells are assembled into packs, they require less heavy shielding to prevent thermal runaway than Li-on batteries— Hampson-Jones says Oxis’ packs are 60% lighter.
Bye’s plans for the eFlyer 800 are based on the assumption that it will have battery cells containing 550 wh/kg in energy; Oxis says it will achieve that by 2023.
In most cases, Bye says the plane likely won’t have to spend more than 30 minutes recharging on the ground. The plane’s batteries could recharge by as much as 15% during descent, when the propeller will act as a windmill, turning backward.
One of the biggest problems that researchers have been trying to overcome with lithium-sulfur is that the lithium metal anode degrades quickly and the batteries are toast after a few score discharge-recharge cycles. But Hampson-Jones says Oxis has developed a method to improve longevity that’s allowed the development of cells that have achieved “several hundreds” of cycles. Oxis is promising Bye cells that will be good for 800 cycles, which Bye says would mean its battery packs could last five to ten years before requiring replacement.
Paradoxically, the lower maintenance needed by electric airplanes could be a problem for their makers, and a deterrent to investors, says Vincent. Some of the highest profit margins in aviation are in aftermarket parts and service. “If the engines are as bulletproof and maintenance costs as low as they say, where do the [aircraft makers] and the engine companies make their money?” he asks.
Bye acknowledges that aftermarket revenue will be much lower compared to conventional aircraft programs.
One area where maintenance might be needed is the fuselage and wings, which will be made of carbon composites, a material that is lighter than aluminum but harder to fix if the plane gets banged up flying into some of the rougher dirt airstrips that turboprops frequent. That issue could be one of several that leads “old, stodgy” King Air operators “to look down their long noses at this,” says Vincent, and make it more of a city-to-city plane.
Bye thinks he could sell upward of 10,000 eFlyer 800s, including replacing some of the oldest models in the King Air fleet, which first came out in 1964. Meeting that goal may hinge on the plane’s low operating costs creating new uses and demand: There were a little over 3,000 eight- to ten-seat airplanes built over the past decade, and Forecast International projects that roughly 3,400 will be sold over the next ten years.
Vincent concurs. “I think the challenge and opportunity is to go after a different demographic, a new entrepreneurial type who wants to start up a business, who maybe they’re not even in the industry now,” he says.
To succeed it’s going to take Bye hundreds of millions of dollars and likely decades of work to establish a broader family of aircraft in the face of incumbent plane makers that are starting to seriously look at electrification.
But Vincent thinks Bye is on to something. “He’s got some great concepts. It’s to stay with it and continue against the headwinds—he knows it better than anybody.”
In my 14 years at Forbes I’ve helped direct our coverage of everything from Asia to autos and healthcare to housing. Right now I help manage our breaking news team and
In my 14 years at Forbes I’ve helped direct our coverage of everything from Asia to autos and healthcare to housing. Right now I help manage our breaking news team and write about aerospace and defense. Send tips to jbogaisky[at]forbes.com