Patent ID: 6671590
Filing Date: 2003-12-30
Classification: B64C

Abstract:
A method for reducing noise generated by rotating blades of a tiltrotor aircraft, said method comprising the steps of:transmitting at least one higher harmonic control signal for input to at least one swashplate control actuator associated with at least one swashplate of a tiltrotor aircraft; producing at said at least one swashplate control actuator a sinusoidal oscillation of N cycles per rotor revolution in a non-rotating frame of reference associated with said at least one swashplate control actuator; producing sinusoidal rotor-blade pitch oscillations of said rotating blades at four cycles per rotor revolution in a rotating frame of reference associated with said rotating blades in response to input of said at least one higher harmonic control signal to said at least one swashplate control actuator to thereby reduce noise associated with said rotating blades of said tiltrotor aircraft; and controlling the phase associated with said rotor-blade pitch oscillations of said rotating blades associated with said tiltrotor aircraft utilizing said at least one swashplate under the control of said at least one swashplate control actuator, wherein the phase of said rotor-blade pitch oscillations yields a minimum 4/rev component of rotor-blade pitch angle at a rotor-blade azimuth angle within a range from 60 degrees up to and including 90 degrees.