Trimming Dual Control Rotors For Optimum Performance

Certain advanced rotor concepts, in addition to the conventional collective and first harmonic control inputs, feature a secondary control input to alter the loading distribution, thereby improving performance. Trimming such a rotor requires selecting primary and secondary control input settings to achi eve specified trim forces at the most favorable trade-off of performance parameters. Trade-off optimization using typical aeroelastic rotor analyses directly is prohibitively expensive. The paper discusses and illustrates an indirect approach using response surface analysis. Results of a limited number of aeroelastic analysis cases are used to develop a simple mathematical model of rotor responses of interest. Optimization is performed with the simple model, and the final selection of controls confirmed by the main rotor analysis program.