A unique four-engine aircraft has begun flight testing of technologies that could be used in future application of electrical propulsion systems on helicopters, drones and other platforms.
This low-cost testbed is a French Cri-Cri ultra-light aircraft that has been modified for all-electric propulsion – with its two piston engines (typically rated at 9-15 horsepower) replaced by four brushless electrical motors, each powered by a high energy-density Lithium polymer battery.
The all-electric Cri-Cri is fitted with four electric motors, each powered by a high energy-density Lithium Polymer battery, and will be performing aerobatic manoeuvres as part of its flight test programme.
The electric-powered Cri-Cri made its maiden flight late last month in the French city of Royan, and was brought to Le Bourget Airport near Paris this week for its first public demonstration. Its development is the result of a collaboration involving EADS Innovation Works, Aero Composites Saintonge and the Green Cri-Cri Association.
“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,” explained Emmanuel Joubert, the head of propulsion systems at EADS Innovation Works.
This photo shows the all-electric Cri-Cri following its first public demonstration flight at Le Bourget Airport on 2 September. The propellers on its four electric motors are clearly visible as pilot Didier Esteyne taxis after landing on Runway 03.
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 – providing an excellent baseline for EADS Innovation Works’ future design of propulsion systems, he added.
The four Lithium Polymer batteries currently installed on the Cri-Cri testbed provide a combined power total of 22 kW., which is sufficient for takeoff, climb and normal flight, as well as for the planned aerobatic manoeuvres that will be performed later in the test programme.
Developed in a collaboration effort involving EADS Innovation Works, Aero Composites Saintonge and the Green Cri-Cri Association, the all-electric Cri-Cri currently has a flight autonomy of about 20-30 minutes – which is the limit based on currently-available battery technology.
“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.”
The Cri-Cri is one of the world’s smallest piloted aircraft, with a wingspan of 4.9 metres and a fuselage length of 3.9 metres. As part of the Cri-Cri testbed’s modification for its all-electric propulsion, lightweight composite structures were introduced to reduce the airframe’s weight in compensation for the Lithium Polymer batteries’ additional weight.