Flight Experience Makes Pipistrel An Electric Aviation Leader
Barely 20 years ago, Pipistrel was a virtual unknown in the aviation industry, a tiny Slovenian manufacturer of small ultralight aircraft. In June, the privately held company entered the history books when it received the first internationally recognized type certificate for an electric aircraft.
European Union Aviation Safety Agency (EASA) certification for the Velis Electro two-seat trainer—and its in-house-developed electric engine and battery system—was not the first aviation milestone for Pipistrel. In 2007, its one-off, dual-fuselage Taurus G4 won NASA’s Green Flight Challenge; the battery-powered four-seater exceeded the equivalent of 400 mpg per passenger.
Pipistrel followed up in 2014 with the WattsUp, a proof-of-concept electric trainer that started its journey toward the Velis Electro. Along the way, German aerospace center DLR modified the Taurus G4 into the Hy4, which in 2016 became the first four-seater to fly on hydrogen fuel-cell propulsion. That same year, Pipistrel ground-tested a 200-kW serial hybrid-electric power train.
All this experience proved invaluable in gaining EASA approval for not only the Velis Electro but also a complete licensing, operating and maintenance ecosystem around the aircraft that allows buyers to begin training immediately. “We ship the airplane with the charger as well,” notes Tine Tomazic, Pipistrel group chief technology officer.
“Why do we do it?” he asks, referring to electric propulsion. The answer is cost: The energy cost of flying the Velis Electro is just €0.9 ($1.06) per hour. That compares with $40-60 per hour in avgas to fly a popular piston-powered trainer such as the Cessna 172. Factoring in battery replacement takes the Velis Electro to €17 per hour, but even its total operating cost of €33 per hour is a fraction of the $150-200 per hour for a 172.
Pipistrel has learned much by bringing the Velis Electro to market and hopes its EASA certification “will create good precedents for other applicants in the pipeline,” Tomazic says. One key has been Pipistrel’s electrified flight experience back to the two-seat Taurus Electro of 2007. “How to do it? Fly, fly and fly more,” he says.
In ground testing on an iron bird, all elements of the power train operate at the same electrical potential because the system is connected to the Earth. “When you fly, there’s no cable to the ground,” Tomazic says. “Almost by definition, the components will be floating in voltage. If you don’t make sure they all operate at the same potential, you may see interesting things going on.”
Other issues relate to electromagnetic interference and cable routing and can range from “some interesting ringing and singing in the radios” to spurious cockpit indications from the air data computers, he says. “You learn a lot about the placement of AC cables between the power electronics and the motor, because those are kilowatt-level antennas—very exciting things,” Tomazic notes.
The most popular misconception about electric aircraft that Pipistrel has encountered? That an aircraft needs 4-hr. flight endurance to be useful, far beyond the capability of today’s batteries. The Velis Electro can fly a 50-min. traffic-pattern training mission. “Just because you can fly for half an hour or an hour doesn’t render this aircraft useless,” Tomazic says. “It could be very useful.”
Pipistrel is not stopping at the Velis Electro. The company is leading Europe’s Mahepa project, which is developing a hybrid-electric propulsion architecture using modular components. This will fly with fuel cells in the Hy4, and batteries and a combustion engine in the Panthera. Under Mahepa, Pipistrel is studying scaling the system up to a 19-seat commuter aircraft.
The company also has announced its next aircraft: It is an electric vertical-takeoff-and-landing (eVTOL) type and a departure from the more than 2,000 light aircraft it has built to date. But it is not an urban air taxi for Uber, as expected. It is the Nuuva family of hybrid-electric unmanned cargo aircraft. With a 1,700-kg (3,750-lb.) maximum takeoff weight and 13.2-m (43.3-ft.) span, the V300 is designed to carry a 300-kg payload 300 km (185 mi.) at 165 kt. The 6-m-span, 100-kg V20 will carry up to 16 kg.
The company slowed work on its Uber design to accelerate development of the unmanned cargo aircraft, arguing regulatory and other constraints could delay entry into service of eVTOL air taxis to 2028. The V300 is planned to enter service in 2023, but deliveries of the V20 could begin as early as 2021. Pipistrel says the simple, reliable Nuuva will be able to operate from standard helipads at a fraction of the cost of a helicopter.