Smartflyer

The company is called Smartflyer, and its SF-1 prototype is the brainchild of former Swiss air force pilot Rolf Stuber. For decades, he’d been pondering the potential of an aircraft with an electric powerplant, but at the time there was no such aircraft on the market.

So, in 2016 he asked himself, “Why don’t I just build one?”

Eight years later, he introduced his new baby to the world.

The prototype, registered as HB-SXE, looks like a stretched-out four-seat, high-wing, tricycle-gear, single-engine piston aircraft, with one major difference: The propeller is on the empennage, not on the nose.

Stuber, now Smartflyer’s chief executive officer and head of design, explains that it made more sense to put the three-blade prop at the back because of the aerodynamics involved.

“The electric motor is about five times lighter than a conventional combustion engine, and therefore we had new possibilities to think about where the thrust should come from,” he said. “We thought it would be best to put the propeller in the back because the accelerated air mass can flow away freely and is not blocked by the broad fuselage cross-section if the prop were at the front.”

In that way, the aircraft can achieve 25 percent higher efficiency over a traditional configuration, he said.

SF-1 is aimed at the civilian trainer market and will be available in three different versions: pure electric, with an endurance of about 2.5 hours; hybrid-electric with a range-extender (which in the prototype is a Rotax 914, with a 21-gallon fuel tank); and eventually, a fuel cell variant. Smartflyer says it’s possible to swap out the nose cone (containing the modular energy source) in 15 minutes, without prior technical knowledge.

That “plug-and-fly” concept Stuber envisages will allow flight schools to purchase the components—for example two electric motors and one range-extender for every airframe—and mount them onto the aircraft according to what kind of flight lesson is planned: pure battery power for pounding the pattern, and the hybrid variant for cross-country flights of up to 432 nautical miles. Carbon dioxide emissions and operating costs could be as low as half of that of conventional trainer aircraft, not to mention the significantly lower noise profile.

Stuber says the aircraft was designed from the ground up for the electric motor, rather than simply replacing a combustion engine with an electric motor.The design “has the potential to become the best training aircraft for the civilian market.”—Rolf Stuber

SF-1’s cruise speed is targeted at 120 knots, and it has a maximum takeoff weight of 3,086 pounds. The four-seater’s takeoff power is 160 kilowatts, which translates into about 215 horsepower.

“We think pilots will love the aircraft, because it’s an aircraft built by pilots and for pilots,” Stuber said, adding that the design “has the potential to become the best training aircraft for the civilian market.”

The composite fuselage—laminated and created in the autoclave as one single finished piece—was manufactured by Aerolite, which specializes in lightweight aircraft interiors for medical missions.

Smartflyer is based in Selzach, a village about 30 miles north of Switzerland’s capital, Berne. The aircraft’s ground and flight-testing phase, due to launch in mid-2025, will take place at a military airfield in Payerne, halfway between Lausanne and Berne, provided Stuber finds the resources.

Financial support for Smartflyer initially came from a government fund bankrolled by aviation fuel taxes, in addition to Swiss investment company Invero and other smaller investors. What comes next though, is unclear. The firm is on the hunt for fresh capital to complete its testing phase, and an industrial partner to help with EASA certification (targeted for 2030) and series production. SF-1’s maiden sortie is scheduled for the fall of 2025.

“The project is an adventure, and it remains an adventure,” Stuber said.

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