All-electric stunt aircraft to test novel propulsion systems

A four-engine all-electric acrobatic plane has made its first public demonstration flight at Le Bourget Airport near Paris.

The modified French Cri-Cri ultra-light aircraft will serve as a low-cost testbed for technologies that could be used in future application of electrical propulsion systems on helicopters, drones and other platforms. Its development is the result of a collaboration involving EADS Innovation Works, Aero Composites Saintonge and the Green Cri-Cri Association.

The aircraft's two piston engines (typically rated at 9-15 horsepower) have been replaced by four brushless electrical motors with counter-rotating propellers, each powered by a high energy-density lithium polymer battery. As part of the modification programme, composite structures were introduced to reduce the airframe's weight in compensation for the additional battery weight.

Following the flight on 2 September, pilot Didier Esteyne said the aircraft flew "very smoothly, much more quietly than a plane with conventional propulsion".

Acrobatic manoeuvres will form part of the flight-test programme. "But we are still at the beginning and have a lot to learn," said Esteyne. "We are allowed to start aerobatic manoeuvres only after five hours of flight and 15 landings."

Emmanuel Joubert, head of propulsion systems at EADS Innovation Works, added: "With the Cri-Cri testbed, we now have a highly innovative system for in-flight evaluations of electric propulsion system components, including batteries, power management controllers and sensors."

In addition, EADS Innovation Works has developed new simulation modelling that will be compared with data gathered during the Cri-Cri flights. This will enable the simulation models to be calibrated against actual flight test results.

The four lithium polymer batteries provide a combined power total of 22kW, which is sufficient for take-off, climb and normal flight, as well as for the planned aerobatic manoeuvres that will be performed later in the test programme.

At present, the all-electric Cri-Cri has a flight autonomy of about 20-30 minutes. "We hope to extend this flight time with better energy management, along with aerodynamic improvements – but there always will be limitations with today's electric technology," Joubert said. "Even in the future, we don't expect large aircraft such as the A380 to use electric propulsion, but there are logical applications such as the hybrid propulsion concept that EADS has been evaluating for helicopters."

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