Reduction of Structural Vibration on Light Combat Helicopter

This paper addresses the vibration issues which were accosted during the initial flight testing of the Light combat helicopter (LCH), 5.8 T weight class Attack helicopter designed and developed by Hindustan Aeronautics limited. The first one was high canopy shake in lateral direction at main rotor n/rev frequency and secondly the helicopter vertical vibrations at high speeds. Series of structural optimization and stiffening, based on the finite element analysis resulted in knocking out the canopy shake. Further these structural modifications along with the changes in blade dynamic characteristics helped to budge the helicopter vertical vibrations outside the operating speed. These analysis details and results along with the ground test and flight test validation data are presented and discussed.