European OEMs partner to study environmentally friendly helos

Aviation International News » December 2007
November 29, 2007, 6:15 AM

Archrivals AgustaWestland and Eurocopter will join forces on a major environmental research program that will include integration technology demonstrators (ITDs) for a greener helicopter. The project–part of the larger E1.6 billion ($2.2 billion) Clean Sky Joint Technology Initiative–is expected to yield innovations such as smart blades for the main rotor and electric drive for the tail rotor. The project is funded in part by the European Commission.

As part of the Green Rotorcraft ITD program, the companies will study an “intelligent” main rotor blade that incorporates an active control system for mechanical and fluid dynamics. It can use movable tabs or flaps–actuated by piezo-electric components or smart materials–an AgustaWestland spokesman told AIN. Sensors installed on the blade supply the required data.

Two loops could be installed on a blade. The first one, to control vibration, could use a smart spring close to the root of the blade. The second, to control noise, could use active shape control at the blade tip to counter the local vortex. Each loop includes a sensor array, an adaptive controller and the actuator.

The partners are also exploring how to drive the tail rotor electrically, and independently of the main rotor. The result would be a reduction in the number of mechanical connections. There would no longer be a tail-rotor shaft and intermediate gearboxes. The availability of a suitable electric motor, with a practicable power-to-weight ratio, is critical to the project’s success.

Research engineers are also eyeing conformable fairings to reduce drag. “The most significant contribution to rotorcraft drag is from both bluff bodies–such as the rotor head and the undercarriage–and aerodynamic interactions,” the spokesman told AIN. On the rotor head, a conformable fairing would change its shape according to the flight conditions. This would optimize aerodynamics. “We would still guarantee safety and maintainability requirements,” he added.

He also pointed out that total drag depends on the combined interactions between components, rather than on the performance of a single element, so better integration can improve performance. Eurocopter and AgustaWestland will study how the main rotor wake affects the fuselage flow field.

The companies will also study specific aspects of the tiltrotor, such as wing design, flow control for rotor-wing interaction and reduced rotor-head drag in cruise. They will also assess the impact of the tilt angle on acoustic signature during approach.
As a continuation of research programs Friendcopter and Optimal, the Green Rotorcraft ITD will study environmentally friendly flight paths, the goal being to reduce noise and fuel consumption. Researchers will also focus on satellite navigation, among other tools.

The European Council of Ministers is expected to adopt the project formally this month. The European Commission has approved the JTI as part of its seventh framework program for research; now the state ministers must vote on the initiative.

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