Elements of the SHARCS (Smart Hybrid Active Rotor Control System) Hybrid Control concept are demonstrated via two sets of whirl tower tests. Hybrid Control stands for combining a flow control (such as an Actively Controlled Flap or Active Twist Rotor) and of a structural (or stiffness) control device on a helicopter blade. A Hybrid Control system promises to reduce vibration and noise on helicopters simultaneously as well as to improve the efficiency of the flow control device. For the structural control system, a unique and entirely original Active Pitch Link has been developed at Carleton University, which is capable of dynamically controlling the torsional stiffness of a blade. Design, prototyping, static and whirl tower testing of this device is presented in the paper. A second set of whirl tower tests of an Active Twist Rotor equipped with a range of springs instead of the conventional pitch link, demonstrates that the Active Pitch Link shall indeed be capable of lowering the torsional stiffness of the blade. For these tests, the modal parameters of the blade were evaluated via a novel "Output-Only" method, which represents the first application of such methodology for rotary-wing applications.
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