Vibration reduction of helicopter with trailing-edge flaps at various flying conditions

The aim of this study is to find the optimal torsional stiffness and trailing-edge flap locations of the helicopter rotor blade for minimum vibration and flap control power at flap lengths of 6% and 9% of the rotor-blade length. A three level orthogonal array based response surface method using polynomial functions is used to describe both vibration and flap control power. Pareto points minimizing hub vibration and flap control power are found at flap lengths of 6% and 9% of the rotor length. This study also explores the variation in rotor hub vibration and flap control power with flying conditions such as the advance ratio and the thrust-to-solidity ratio at the optimum design points. This gives a useful improved design with about a 60% decrease in hub vibration with a penalization of increased flap power at the normal flying regime of rotor-craft flight.