The present invention relates to a method for reducing the blade-vortex interaction noise of rotary wings. According to the invention: at least one value .PSI.o of the azimuth of the blades (1) is determined, for which value said blades shed tip vortices giving rise to a peak intensity of noise; a trailing edge flap (2) is disposed on each blade (1), the former generating an auxiliary vortex (11), parallel to the tip vortex (10) and attached to a blade section (8) lying between the blade section (7) around which the speed circulation is a maximum and the tip section (3) of said blade; and a deflection is applied to each of said flaps (2) such that, for said value .PSI.o, the speed circulation around said blade section (8) is a specified fraction of the maximum speed circulation.

A hub mounted actuation system for providing control of a portion of a rotor blade, such as a flap, on a rotorcraft. The rotor blade is attached to a rotor shaft that rotates with respect to an airframe. The hub mounted actuation system includes a stationary support mounted to the airframe and a rotary support attached to the rotor shaft for concomitant rotation therewith. At least one hub actuator rotates in combination with the rotor blade and includes a piston which is slidable within a housing. The piston and housing define a pressure chamber within the actuator which contains a fluid to be pressurized. A displacement control device is disposed between the stationary support and the rotary support for controlling movement of the piston within the housing. A linkage connects the hub actuator to the portion of the blade to be controlled. The linkage is adapted to displace the blade portion as a function of the movement of the piston within the housing.

A rotor blade arrangement includes a rotor blade with a hollow blade chamber therein, and a flap module removably arranged and secured in the blade chamber. The flap module includes a module housing received in the blade chamber, an actuator arranged in the housing, a flap pivotably arranged at an edge of the housing, and a power transmission linkage connecting the actuator to the flap. The module housing is inserted through an opening into the blade chamber, so that the flap protrudes and forms a continuation of the aerodynamic contour of the blade. The flap may be a trailing edge flap at the trailing edge or a leading edge nose flap at the leading edge of the blade. The flap module does not change the center of gravity of the blade. The entire flap module can be easily removed from the blade for adjustment, inspection, maintenance, repair or replacement.

An active control device for reducing blade-vortex interactions (BVI) noise generated by a rotorcraft, such as a helicopter, comprises a trailing edge flap located near the tip of each of the rotorcraft's rotor blades. The flap may be actuated in any conventional way, and is scheduled to be actuated to a deflected position during rotation of the rotor blade through predetermined regions of the rotor azimuth, and is further scheduled to be actuated to a retracted position through the remaining regions of the rotor azimuth. Through the careful azimuth-dependent deployment and retraction of the flap over the rotor disk, blade tip vortices which are the primary source for BVI noise are (a) made weaker and (b) pushed farther away from the rotor disk (that is, larger blade-vortex separation distances are achieved).

A helicopter rotor blade includes a main airfoil body (12) and a movable control flap (3) incorporated in the trailing edge profile of the airfoil body. The flap (3) is movably connected to the main airfoil body (12) by a flexibly bendable junction element (4), and is actuated by a piezoelectric actuator unit (5) via a push/pull rod (6) and a lever arm (7), whereby the control flap is deflected relative to the main airfoil body. The junction element (4) is preferably a continuous integral fiber-reinforced composite component having a flexible bending portion (42) with a reduced thickness in comparison to the adjoining portions, whereby the reinforcing fibers extend continuously through the joint in the direction of the connection between the main airfoil body and the flap.