14 September 2012
An active main rotor blade control system using EADS Innovation Works-developed piezoelectric actuators will be further evaluated in a new series of airborne tests, confirming their full potential to significantly reduce helicopter noise and dramatically decrease in-flight vibrations.
These actuators are part of the Blue Pulse™ control system developed in cooperation with Eurocopter. Blue Pulse uses multiple flap modules on the helicopter rotor blades’ trailing edges, which are actuated at the appropriate frequencies by the actuators located inside the blades themselves.
EADS Innovation Works selected piezoceramic technology for the actuators, using a stack of several thin ceramic wafers. Piezoceramics react by a change in length when stimulated by an electrical current – a result of their specific crystalline structure. Although the ensuing movement is very small, the pizeo-actuators function very quickly and are able to generate relatively large forces.
The actuators are able to sustain very high centrifugal forces of up to 800 g. Based on the electric load applied, they enable low- and high-frequency motions of the flaps by extending and compressing, according to the electric load applied.
On each rotor blade, the actuators are integrated into a carbon-fibre housing called the flap module. This housing turns the actuators’ relatively small movements from a spanwise to a chordwise (rearward) direction, increasing it significantly. Two tension rods connect the actuator to the flap, which is hinged and can deflect up or down by several degrees.
Two piezoceramic actuators are fitted into each flap module. Up to three modules were incorporated on each rotor blade during initial flight testing, with the final Blue Pulse configuration expected to require fewer modules.
Very good results in terms of noise reduction and vibration decrease were seen during the initial Blue Pulse flight tests, performed on a Eurocopter EC145. Using a Step 1 configuration with modified – but otherwise standard – rotor blades, these evaluations demonstrated great reductions of peak noise.
Flight testing in 2012 is expected to validate the full potential for noise and vibration reduction, applying an improved Step 2 configuration that incorporates optimised flap drives in a more advanced Blue Pulse system.
In addition to the resulting smoother and more comfortable ride for passengers, the Blue Pulse active main rotor blade control system may contribute to a lifetime extension of onboard components such as electronics by providing an improved operational environment for the sensitive equipment.
Frank Hermle, a research engineer at EADS Innovation Works, explains the operation of a Blue Pulse flap module, which is displayed in EADS’ pavilion at the ILA Berlin Air Show. The module contains two of the EADS Innovation Works-developed piezoelectric actuators.