Method of optimising a faired anti-torque rotor with minimum acoustic disturbance for a rotorcraft, in particular a helicopter, and faired anti-torque rotor thus obtained

摘要

The method involves selecting a lower limit frequency of preset one-third octave band centered on a center frequency. Perceived frequency of sound is established by assigning a multiplicative coefficient, while considering Doppler Effect. Parameters relative to a diameter of a multi-blade ducted tail rotor i.e. Fenestron(RTM: shrouded tail rotor), given number of blades and to a tangential speed in end of the blades are selected such that the perceived frequency of sound is equal to specific equation or lower than the lower limit frequency. The equation comprises parameters such as multiplicative coefficient, tangential speed, number of blades, and diameter of the rotor. An independent claim is also included for an acoustically optimized anti-torque device for a noise certificated rotorcraft.