With 40-year-old airframes and innovation coming only to the cockpit, it seems like general aviation hasn’t seen substantial change in decades. Driven primarily by creative engineering in Europe, but now catching up in the United States, electric propulsion is at the threshold, and when it arrives, the shape of aviation as we know it will change.

It’s hard to overstate the benefits of electric propulsion. The electric motor has one moving part; the time to replacement (in lieu of overhaul) is considerably longer; and electric motors are cheaper to buy, cheaper to operate, easier to operate, lighter, require less maintenance, run quieter, and don’t have the power pulses that put strain on airframes and propellers. The one downside—and it’s a big one—is energy. Where do you find the energy to run the motor? The power density of fossil fuels is hard to beat.

With claims of Jetsons-like flying electric cars in the next five years and hybrid airliners soon after, it’s easy to be skeptical about the development of electric propulsion. Clearly, big claims like that are meant to promote excitement and spur investment, and shouldn’t be taken as true progress reports.

Yet real progress is happening. In Europe, Pipistrel’s Alpha Electro two-seat electric trainer has been certified and is flying. A program in California brought Pipistrels to the United States as part of a flight training test site, although training has to wait until the rules for certification change to allow electric propulsion in the Light Sport category. The Bye Aerospace Sun Flyer is years ahead of the competition among current development programs, and shows promise at making it through certification.

The Sun Flyer is a two-seat, 1,900-pound-gross weight, all-electric aircraft aimed at the training market. It’s the first project for the certified market from Bye Aerospace, which has previously found success making unmanned aircraft systems for military applications.

The Sun Flyer is meant to change the cost of learning to fly. Bye Aerospace promotes a total operating cost of $14 an hour, compared to more than $75 an hour for a Cessna 172. With the airplane projected to cost between $200,000 and $300,000, some simple math shows that training in an electric aircraft could chop the cost of learning to fly by as much as 50 percent, opening aviation up to tens of thousands more people.

Propulsion comes from a 90-kilowatt Siemens motor, equivalent to about 115 horsepower. This will result in roughly the same power-to-weight ratio as the Cessna 152. Seimens has quickly become the electric propulsion leader in development programs. The Sun Flyer’s motor is one of many projects the company is working on, with power applications ranging from 30 kilowatts (40 horsepower) to more than a megawatt. The motor Siemens developed for Extra Aircraft’s technology demonstrator had a 5:1 power-to-weight ratio, something piston engines can’t touch. And Siemens’ SP70D, to be used on the Sun Flyer, weighs only 26 kilograms (57 pounds).

Then there’s the batteries. Whereas the weight of fuel is an ever-changing variable that gives pilots an infinite range of potential loading options, battery weight is fixed. And the batteries will be heavy. Bye Aerospace is quoting 10 packs totaling 880 pounds. Thanks to lightweight construction materials, Bye is saying to expect a “crew weight” of 440 pounds. Even with such a light motor, the batteries will be dispersed both in the cowling and behind the cabin, indicating that their weight is a primary design consideration.

Relative newcomer EP Systems is providing the battery packs for the Sun Flyer. Part of what gave Bye Aerospace confidence to go with the California-based start-up was its work with NASA’s X–57 project, an all-electric test aircraft. It takes a Tecnam P2006T, strips the engines, and bolts on a new wing and a host of electric motors. EP Systems is the battery pack provider, and the batteries the company is providing to the Sun Flyer are similar.

Aside from weight, fire safety is a major consideration of carrying around hundreds of pounds of batteries. Teslas seem to be spontaneously combusting on the road, Boeing had fires on the 787, and earlier this year a Magnus eFusion electric aircraft crashed in Hungary with news reports saying fire may have been a cause.

Bye Aerospace CEO George Bye said the safety protocol around the batteries is threefold. First, you design a robust monitoring system. Then you incorporate a battery management unit that can isolate any problems—and finally, you build in physical containment. NASA said its tests of EP Systems’ batteries showed the fire mitigation system worked well enough to prevent and contain any potential fires, a key point in the battery testing process.

Pipistrel claims a 1.5-hour endurance on the Alpha Electro. Bye is claiming an endurance of more than three hours, and says that number is today’s reality with no technological leap or improvement required. “It’s not magic,” he said. The Sun Flyer’s current batteries are 260 watt-hours per kilogram, a number some speculate to be roughly equivalent to the latest batteries on a Tesla. Strung together, the packs produce 92 kilowatt-hours of energy, 73 kwh of which is usable when you factor in VFR reserves and other buckets we shouldn’t plan to dip into. That’s enough energy to run an average American home for more than two days. With battery technology improving at an average of 5 to 8 percent every year, it’s not hard to imagine a future where electric aircraft get well beyond the training market and enter the world of GA utility.

Bob Hepp, the owner of Aviation Adventures in northern Virginia and one of the first Sun Flyer position holders, is interested in how the Sun Flyer will help his flight school. Hepp paid a deposit of $10,000 each for his two Sun Flyers, a not insignificant amount for a private flight school. “I’ve been watching electric for a long time, knowing the issues with 100LL,” he said. “Ten years after Sun Flyer makes it to market there will be a dividing line between those that have electric airplanes and those that don’t. And those that don’t will be driven into bankruptcy because of the economics.”

Much of Hepp’s interest in electric is practical. Siemens isn’t releasing the motor replacement time yet, but 10,000 hours is emerging as an industry standard. Charging the airplane will cost significantly less than fueling it, with little to no impact on operations, and then there’s the maintenance benefits. “I never realized how much I hated oil,” Hepp said. With a large fleet of airplanes, at least one always seems to be undergoing an oil change. It’s expensive, messy, time consuming, and laborious. “I can’t wait to never have to deal with oil again.”

Electric propulsion is at a pivotal point. We don’t all have to get on the eVTOL bandwagon just yet, but electric trainers, electric family haulers, and electric aerobats are coming, and they represent a major change in how we will learn to fly, operate, and maintain airplanes.

Hepp said the manager of his local FBO told him he wants to be his first student when he gets a Sun Flyer. “And this is the guy who sells me my fuel.”

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Dogfight

Are electric aircraft a viable part of general aviation’s future?