French aerospace giant Airbus had a promising electric aircraft project a few years ago, flying its E-Fan prototype across the English Channel in a highly publicised event.

Airbus was intending to put into production an electric light aircraft for training pilots but somewhere along the line, the manufacturer got cold feet and canned the project.

The two men championing the Airbus e-aircraft were technical chief Jean Botti and test pilot Didier Esteyne left Airbus to start their own project VoltAero, with Botti as CEO and Esteyne as Technical Director.

And they’ve been busy, taking a pragmatic approach by concentrating their efforts on a hybrid-electric aircraft and using an existing, if a bit old and unusual, airframe, a Cessna 336. They call it the Cassio.

VoltAero recently took part in the 2019 Nordic EV Summit in Oslo – Norway has already expressed its desire to ‘electrify’ its domestic air travel by the year 2040 and is a leader in the take-up of road electric vehicles (EV).

Botti took the opportunity to outline VoltAero’s vision.

“More than 190 projects have been announced worldwide for electric aircraft of all shapes and sizes,” he said.

“To be realistic, industry is in the kilowatt range for battery power today. In order to develop large electric aircraft such as regional airliners, power levels need to be in the megawatt range.”

He highlighted the technical and technological milestones that need to be achieved – and certified by airworthiness authorities – before electric aircraft can be significantly scaled up in size. These include increasing battery power densities, validating cooling techniques for batteries, developing of high-power connectors, as well as dealing with electromagnetic interference (EMI) and compatibility (EMC) issues.

“This is why VoltAero has sized the Cassio aircraft in the four-to-nine seat category, with a flight duration of at least 3.5 hours,” Botti explained, adding that Cassio will be well-tailored for such uses as point-to-point regional travel in commercial flights, for air taxi/charter companies, with private owners, as well as other utility-category applications.

VoltAero Cassio
VoltAero’s Cassio aircraft has two electric motors driving propellers on the wing. Plus, a hybrid unit mounted in the rear of the fuselage driving the rear prop.

Botti described the Cassio aircraft’s distributed hybrid-electric propulsion system. It’s ‘push-pull’ configuration composed of two wing-mounted electric motors to drive propellers in the forward-facing tractor (“puller”) position. Plus a ‘power module’ in the rear of the fuselage that combines an electric motor and thermal engine sharing the same shaft to a pusher (rear-facing) propeller.

Botti detailed the Cassio hybrid-electric propulsion system’s modes for the different phases of flight. They  begin with an electric-powered landing gear wheel for ground taxi; followed by use of the electric motor-driven propellers for takeoff and landing (ensuring high energy efficiency and low-noise operations at airports).

The aft fuselage power module’s thermal engine will turn the rear pusher propeller during cruise flight, also driving the associated electric motor as a generator to recharge the aircraft’s batteries.

“The hybrid-electric propulsion system for Cassio was designed from the start to be highly efficient and secure, which is reflected by our motto: ‘The power to fly safely,’” he added.

VoltAero Cassio
Jean Botto, right, at the Norway EV Summit, is CEO of VoltAero while Didier Esteyne, left, former test pilot at Airbus, is Technical Director.

Botti also underlined VoltAero’s prudent approach to development, testing and certification. It is using a flight demonstrator aircraft and ground-based ‘Iron Bird’ test rig to validate its hybrid-electric configuration.

This will reduce then risk for the Cassio configuration during its airworthiness certification and the subsequent application on a new-production airplane retaining the push-pull arrangement, and built using strong, lightweight composite materials.

Looking to Norway’s ambition of transitioning its air transport sector to electric power, Botti said the Cassio aircraft will be highly suitable for the country’s aviation infrastructure – a point that was confirmed during the Nordic EV Summit by Dag Falk-Petersen, the CEO of Avinor (which operates under the Norwegian Ministry of Transport and Communications, with responsibility for managing 44 state-owned airports).

Falk-Petersen explained that Norway offers a unique airport network and an established market for short-range flights with small aircraft. Additionally, Norway’s goals for the electrification of its air transport sector has broad support from the government, parliament and other stakeholders.

“Aircraft producers are looking for a market and a customer; and we have both!” he concluded.

VoltAero Cassio
VoltAero is well advanced with its Cassio project and hopes to fly the prototype this year.

First phase funding has been secured by VoltAero for the Cassio project, covering the development work, Iron Bird integration and flight test. Overall, the programme’s cost – taking it into production – is estimated at €70 million, with the additional funding to be raised in future financing rounds.


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