Patent ID: 9725164
Date: 2017-08-08
CPC Classifications: B64C,G05D,Y02T

Claim:
1. A method for a rotorcraft, the rotorcraft extending longitudinally along a first anteroposterior plane (P1) separating a first side from a second side of the rotorcraft, the rotorcraft including a main rotor, an auxiliary rotor, and a power plant configured to drive the main rotor and the auxiliary rotor in rotation, wherein the auxiliary rotor is configured to exert lateral thrust in order to control yaw movement of the rotorcraft, the lateral thrust being directed towards the second side in order to counter torque generated by the main rotor on a fuselage of the rotorcraft, the rotorcraft further including a tail fin extending in elevation, wherein the tail fin is provided at least in part with a deflectable airfoil, wherein the airfoil is configured to generate transverse lift as a function of a deflection angle of the airfoil, wherein the airfoil has a trailing edge, wherein the deflection angle of the airfoil is at 0° when the trailing edge is present in a second plane (P2), wherein the deflection angle of the airfoil is negative relative to the second plane (P2) when the trailing edge is directed towards the second side, wherein the deflection angle of the airfoil is positive relative to the second plane (P2) when the trailing edge is directed towards the first side, wherein the deflection angle of the airfoil is controllable at least as a function of a current value of a speed parameter (V) of the rotorcraft and of a current value of a power parameter (W) of the power plant so as to enable the auxiliary rotor to be operated at a predetermined operating point in order to satisfy at least one of a performance target for the rotorcraft and an acoustic target for the auxiliary rotor, the method comprising: receiving a first power threshold (W1) and a second power threshold (W2), wherein the second power threshold (W2) is greater than the first power threshold (W1); receiving a first speed threshold (V1), a second speed threshold (V2), a third speed threshold (V3), and a fourth speed threshold (V4), wherein the second speed threshold (V2) is greater than the first speed threshold (V1) which is greater than the fourth speed threshold (V4) which is greater than the third speed threshold (V3); controlling the deflection angle of the airfoil to reach a first zone (Z1) for which the deflection angle of the airfoil is at a maximum positive threshold angle (δmax) relative to the second plane (P2), the first zone (Z1) being reached by the deflection angle of the airfoil when the current value of the speed parameter (V) of the rotorcraft is lower than the third speed threshold (V3); controlling the deflection angle of the airfoil to reach a second zone (Z2) for which the deflection angle of the airfoil is at the maximum positive threshold angle (δmax) relative to the second plane (P2), the second zone (Z2) being reached by the deflection angle of the airfoil when the current value of the speed parameter (V) of the rotorcraft is greater than the fourth speed threshold (V4) and lesser than the first speed threshold (V1) and the current value of the power parameter (W) of the power plant is greater than the second power threshold (W2); controlling the deflection angle of the airfoil to reach a third zone (Z3) for which the deflection angle of the airfoil is substantially 0° relative to the second plane (P2), the third zone (Z3) being reached by the deflection angle of the airfoil when the current value of the speed parameter (V) of the rotorcraft is greater than the second speed threshold (V2) and the current value of the power parameter (W) of the power plant is greater than the second power threshold (W2); and controlling the deflection angle of the airfoil to reach a fourth zone (Z4) for which the deflection angle of the airfoil is at the minimum negative threshold angle (δmin) relative to the second plane (P2), the fourth zone (Z4) being reached by the deflection angle of the airfoil when the current value of the speed parameter (V) of the rotorcraft is greater than the fourth speed threshold (V4) and the current value of the power parameter (W) of the power plant is lower than the first power threshold (W1).