The power module for VoltAero's Cassio production aircraft is undergoing flight testing on the Cassio 1 testbed, marking another step in the company's development of a series production hybrid-electric aircraft family for regional transportation that will accommodate four to 10 seats, with flight ranges of up to 1,200 km and cruise speeds of 200 kts.

Cassio 1 made its maiden flight, equipped with the power module, on 11 October from VoltAero's Royan-Médis airport home base in southwest France, followed by two additional in-flight evaluations over the following two days.

The proprietary power module is installed in an aft-fuselage pusher position, and combines three 60 kw high-performance electric motors arranged in a triangular ‘barrel’ configuration, with a 370 hp internal combustion engine.

This configuration of the power module prefigures the full-up powertrain for VoltAero's largest production Cassio aircraft version, the 10-seat Cassio 600, which is to deliver a total hybrid-electric power of 600 Kw (800 hp), enabling the 200 kt cruise (360 km/hr). “The startup of power module flight testing represents a true milestone for hybrid-electric aviation, and it keeps us on track toward our goal of having initial Cassio production aircraft entering service during late 2022 or early 2023,” explains Jean Botti, VoltAero's CEO and chief technology officer.

In regular operation, the power module's electric motors will be used for low-noise takeoffs and landings, with the internal combustion engine serving as a range extender and for recharging the Cassio's batteries while aloft. With VoltAero's unique patented series/parallel hybrid design, the power module can operate in modes from full electric to full hybrid, depending on the customer mission profile and range requirement.

Additionally, as both the electric motors and internal combustion engine are linked to a common shaft that drives a five-blade pusher propeller, the ability for each to operate independently provides a high level of propulsion safety, with one source acting as a backup in case of a problem or failure of the other.

VoltAero technical director and test pilot Didier Esteyne, who was at the controls of Cassio 1 for the flight tests, said he was impressed by the power module's operation. “I felt very comfortable with its performance from the first takeoff,” he comments. “The power module provides a real propulsive 'kick,' and I look forward to opening the aircraft's flight envelope.”