VoltAero Hybrid-Electric Aircraft Makes Landmark Flight Fueled by Wine Waste

Royan, France-based VoltAero isn’t most aviation companies. The firm on Thursday announced it completed what it claims is an industry first. This week, it flew a hybrid-electric aircraft powered entirely by sustainable aviation fuel (SAF) from partner TotalEnergies Aviation—fuel derived from bioethanol produced from the waste created by French vineyards.

The flight took off from VoltAero’s development facility in Royan, using the company’s Cassio S testbed airplane—a modified Cessna 337 Skymaster—equipped with a proprietary hybrid-electric powertrain. It ran on TotalEnergies’ Excellium Racing 100 fuel, which since 2022 has been used in automobile competitions such as the 24 Hours of Le Mans endurance sports car race.

Compared to the fossil fuel equivalent, VoltAero said the vineyard-derived fuel can reduce carbon dioxide emissions by 65 percent over its entire lifecycle and that it will “significantly lower” operating costs. It’s certified as a 100 percent sustainable product according to a mass balance system applied by a voluntary, European Union-approved certification body.

“Based on initial results, we calculated a truly impressive CO2 reduction of approximately 80 percent while operating the Cassio powertrain in its electric-hybrid mode and with the internal combustion engine fueled by TotalEnergies’ Excellium Racing 100,” said Jean Botti, CEO and chief technology officer of VoltAero. “It underscores the opportunity for production Cassio aircraft to represent a major step closer to aviation’s decarbonization goals by replacing standard Avgas 100 high-octane fuel for aviation piston engines.”

The company added that its goal was to validate its powertrain with SAF, “thereby derisking airworthiness certification” for Cassio aircraft in development. It’s been testing hybrid-electric aircraft for years, starting in 2020 with the Cassio 1 testbed, which made two crossings of the English Channel the following year.

“This demonstration flight is part of our commitment to support players in the aviation sector for their decarbonization objectives,” said Joël Navaron, president of TotalEnergies. “More broadly, it demonstrates our desire to continue our research and development efforts to offer an alternative to aviation gasoline containing lead, thereby meeting the challenges of general aviation’s decarbonization.”

VoltAero was originally part of Airbus’s E-Fan project, which ran from 2014 to 2017. Botti previously served as CTO of Airbus and led the program’s research. But he asserted in a 2020 Q&A that on Cassio designs “there’s nothing carried over from the E-Fan apart from the knowledge gained from the years of working on E-Fan.”

Designed with a modular fuselage that can be reconfigured for a variety of use cases, VoltAero’s Cassio models are expected to be flown by regional commercial operations, air taxi and air charter companies, and private owners. They’ll also be used for utility services such as cargo or postal delivery and medical evacuations.

The company’s first production aircraft is the Cassio 330. It will be flown by a single pilot with space for four or five passengers and rely on 330 kilowatts of hybrid-electric propulsion power. VoltAero pulled back the curtain on the first Cassio 330 prototype at the Paris Air Show in June, and the firm expects to fly it for the first time this year.

At the tail end of Cassio 330 flight testing, the company will roll out a second prototype, which is expected to take off in the second quarter of 2024. The upcoming model will feature an avionics suite from Avidyne, including its Quantum 14-inch displays for single-pilot operations and advanced connectivity.

The 330 will eventually be joined by the Cassio 480, a six-seat version with 480 kilowatts of propulsion power. Further out is the Cassio 600, an even larger design for 10 to 12 passengers with—you guessed it—600 kilowatts of power. Both designs will be larger than the 330 and feature retractable landing gear.

All three models are expected to be built around an aluminum airframe, with a forward fixed canard and aft-set wings with twin booms to support the aircraft’s high-set horizontal tail. They’ll use electric motors in the aft fuselage-mounted hybrid propulsion unit to deliver fully electric power during taxi, takeoff, landing, and primary flight—so long as that distance is less than 93 sm (81 nm).

The Cassio family’s propulsion power unit is made by combining a 4-cylinder Kawasaki Motors thermal engine and a Safran ENGINeUS smart electric motor, with peak power ratings of 165 kilowatts and 180 kilowatts, respectively. It combines 300-kilowatt internal combustion engine power with a trio of 60-kilowatt electric motors for a total output of 480 kilowatts. French company Akira Technologies will lead the integration and validation of the unit.

Like other hybrid designs, the propulsion system’s hybrid feature will use the internal combustion engine as a range extender. The module will recharge the aircraft’s batteries during flight, and it can serve as a backup in case of an issue on the electric propulsion side. 

In full hybrid mode, Cassio 330 is expected to reduce emissions by 20 percent versus comparable aircraft. That jumps to 100 percent in full electric mode. Notably, the power requirement for ground charging VoltAero’s initial design is only 380 volts, which the company said is available at most airports.

Cassio 330 will have a flight duration of three and a half hours (which could rise to five with the range extender), a range of 800 sm (695 nm) and a cruise speed of 200 knots. It’ll be able to take off and land with less than 1,800 feet of runway. And with its 2.5 metric ton maximum takeoff weight, the aircraft is classified as a CS-23 normal-category airplane under European Union Aviation Safety Agency (EASA) regulations.

The first Cassio 330 models will be assembled at VoltAero’s “purpose built” facility at Rochefort Charente-Maritime Airport (LFDN) in France’s Nouvelle-Aquitaine region.

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