French developer VoltAero has unveiled a significant redesign of its Cassio 330 hybrid-electric aircraft, dropping the distinctive twin-boom tail and single pusher propeller of its previous iteration on certification concerns in favour of a more conventional configuration.
In its latest and, the company insists, final guise, the four-passenger Cassio 330 is now powered by a pair of pusher-configured fuselage-mounted electric motors and gains a conventional T-tail arrangement. The fuselage has also been extended by 60cm (23in) to accommodate the modifications.
In addition, the aircraft switches to a series rather than parallel hybrid powertrain using battery packs arrayed on either side of the fuselage.
During taxi, take-off and initial flight phases, the Cassio 330 operates on all-electric propulsion, while the thermal engine recharges the batteries during cruise flight as a range extender.
VoltAero founder and chief executive Jean Botti says the design changes were instituted after certification discussions with the European Union Aviation Safety Agency (EASA).
“EASA asked how we would guarantee the stability of the aircraft in case of a blade detaching and hitting the boom or the vertical tail. It would have been very difficult to prove.”
Removing the twin-boom structure and high-set horizonal tail also reduces the loading on the wing, he says, and makes the aircraft easier to manufacture.
Although some will see a strong resemblance between the new Cassio 330 and the Piaggio P180 twin-turboprop, Botti says he took inspiration from the E-Fan – a light aircraft demonstrator project he led during his stint as Airbus chief technology officer.
Although using twin propellers rather than ducted fans, Botti says the design principles are the same.
“Since we had to find a solution, we went back to the E-Fan; look at the position of the fans, it is exactly where we will put the electric motors.”
Botti says the move to two electric motors – and the design of the motors themselves – offers a degree of redundancy not seen on the earlier iteration.
Conversely, however, one element of redundancy has been lost: the switch to a series hybrid powertrain means the aircraft can no longer be powered solely by the thermal engine.
The change to the overall propulsion architecture will also require different components to be used.
VoltAero had planned to use a 150kW Kawasaki Motors Ninja motorcycle engine in the previous version of the powertrain, but Botti says with the thermal engine now required to act as a generator, the power output of the unit needs to increase.
“We are contemplating a different thermal engine from Kawasaki that will be more powerful,” says Botti.
On top of which, the developer is also considering uprating the electric motors as the current 125kW Safran ENGINeUS 100 units “are not enough for us”. Safran plans to offer the ENGINeUS 100 with a range of outputs running up to 180kW.
VoltAero maintains the design changes will not affect its plans for certification, now set for 2027, arguing that although some time will be lost in the short-term, it will avoid any costly delays due to last-minute alterations needed later in the process.
However, Botti says the first Cassio prototype to fly in at the beginning of 2026 is likely to be powered by thermal engines only, probably twin Rotax 916s, as a risk-reduction exercise.
“It will be a good first test – it will allow us to completely explore the flight domain, do all the validation of the structure and make any changes we need. Once this is done, we can step to the hybrid.”
VoltAero will be showcasing a full-size mock-up of the new Cassio 330 at Paris, while its Cassio S demonstrator – a modified Cessna 337 – will be performing in the daily flying display.
