Rotor blade servo flap to cut helicopter vibration

Eurocopter will test the first full-scale rotor blade equipped with an active servo flap next year. The Franco-German company hopes the latest generation of blades will help reduce external noise and vibration and improve performance.

Eurocopter will test the first full-scale rotor blade equipped with an active servo flap next year. The Franco-German company, which has introduced a range of new technologies to the helicopter over the last 10 years, hopes the latest generation of blades will help reduce external noise and vibration and improve performance.

Helicopters experience excessive vibration due to the aerodynamic loading from moving rotor blades. This causes noise and fatigue, which can reduce the life of the aircraft. To counter the vibration, Eurocopter has designed a rotor blade with an active servo flap fitted to the trailing edge.

The flap can be used to actively cancel out the aerodynamic loads. if successful this could make the aircraft easier to handle and give overall better performance, said Michel Polychroniadis, Eurocopter’s research programme director.

‘We have not only the capacity to reduce noise but also to reduce vibrations and improve performance,’ he said.

Blades with flaps have been investigated for some time by the aerospace industry, but this will be the first to be subject to a full flight test. The blade will be fitted to a twin-engine EC135 that is designed for manoeuvrability and low noise levels.

Active servo flaps could also be used to alter the blade’s pitch, allowing the mechanical complexity of the rotor hub to be improved.

The technology is being investigated alongside active engine control, which will enable the pilot to change the rotational speed of the blades depending on the flight conditions. Eurocopter hopes these other improvements will cut the helicopter’s external noise levels to between seven and nine dB below present limits set by the International Civil Aviation Organisation. The company believes its concept of the ‘neighbourly’ helicopter will prove a market winner as more customers demand less environmentally unfriendly aircraft.

Other plans include advanced blade geometry where the tips are swept back. This offers lower noise in descent and will be tested on a demonstrator helicopter in two years’ time, said Polychroniadis.

On the web