THE TEST RESULTS OF AVR (ACTIVE VIBRATION REDUCTION) SYSTEM

A new method, Active Vibration Reduction (AVR) system, of actuating the main gearbox has been considered and the way to apply it to helicopters lighter than the medium weight class has been studied. In this method, the helicopter vibrations in longitudinal and lateral direction are treated separately, and hydraulic actuators are installed to excite the natural vibration modes in each direction. To reduce the required power, the strut support system of the main gearbox is optimized so that the helicopter has the minimum addition of response for the rotor hub vibratory forces and has the maximum response for the excitation forces generated by the hydraulic actuators. This concept has been confirmed by the analytical simulation, a test using a small skeleton model, the Rig tests and the flight tests using BK117 helicopter. It has been shown by these analysis and tests that this system has a strong potential to reduce the helicopter vibration.