This paper aims to find a robust optimal design for twin trailing-edge flap for helicopter vibration reduction for various flying conditions with minimum flap power requirement. The objective is to find the optimum length and locations of twin trailing-edge flaps to minimize hub vibration in the helicopter with minimum flap power requirement and to evaluate the robustness of these optimum at various flying conditions such as advance ratio and thrust to solidity ratio. Polynomial response surface metamodels is used to approximate the hub vibration and flap power objective functions for optimization. Firstly, a single objective optimization minimizing hub vibration alone is carried out without considering the flap power requirement. A multi-objective optimization minimizing vibration and flap power is also carried out to explore the possibility of a compromise design of trailing-edge flaps. This optimization finds the robust optimal length and locations of twin trailing-edge flaps with the objective of minimizing hub vibration for various flying conditions. Result shows that a flap length of 9 percentage of the rotor is the optimum giving 55 percentage reduction in hub vibration compared to the baseline values. The corresponding inboard and outboard flap positions are 0.61R and 0.87R respectively. The robustness of these design solution with flying conditions such as advance ratio and thrust to solidity ratio are also explored.
