A parametric design study is numerically conducted for a helicopter primary control system with smart trailing-edge flaps. The swashplateless rotor design is implemented by modifying a production modern bearingless rotor through the use of plain flaps on the blades, and by replacing the pitch link to fixed system control system assembly with a root spring. A comprehensive rotorcraft analysis based on UMARC is carried out to obtain the numerical results for both the swashplateless rotor configuration and a conventional baseline. The predictions show that the blade pitch index angle is a key parameter in the reduction of flap deflections, and for the improvement of rotor performance. By lowering the blade root spring stiffness, and by positioning the spanwise location of the flap toward the blade tip, the control effectiveness of the trailing-edge flap is increased. A flap length of 18%R and flap chord ratio of 0.20, are found to generate an optimum design in terms of reducing actuation power while maintaining flap control authority. Blade aeroelastic stability predictions indicate that the swashplateless rotor has higher damping in the blade lag, flap, and torsional modes when compared with a conventional rotor for the most cases studied.
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