Abstract: A method of monitoring a power transmission system of an aircraft, the aircraft including at least one main rotor driven in rotation by a rotor mast and an auxiliary unit having an auxiliary rotor. Control means control the auxiliary rotor. A power relationship is determined providing a first reduced power parameter of the auxiliary unit as a function of a position (POS) of the control means. A setpoint limit is set for a second power parameter for the rotor mast. A current position (POSACTU) of the control means is determined and a calculated value (Vcal) is also determined at least by applying the current position (POSACTU) to the power relationship. A limit value that is not to be exceeded by a power plant is determined, with the limit value being equal to the sum at least of the setpoint limit plus the calculated value.

Abstract: A flight instrument that displays the rotational speed of a main rotor of a rotary-wing aircraft, with the flight instrument including display means, a first indicator of a setpoint for the rotational speed of the main rotor, a second indicator of the first current value of the rotational speed of the main rotor, and third and fourth indicators of the limit values of the rotational speed. The setpoint for the rotational speed of the main rotor is variable and the first indicator is stationary on the display means, with the second, third and fourth indicators being movable in relation to the first indicator.

Abstract: A method during which a current position of a pilot control is determined, an equivalent position is determined that the pilot control needs to reach following a control transition in order to avoid modifying the actuator, and at least one mismatch is determined between the equivalent position and the current position. As from a transition, a target is determined for controlling the actuator by giving a corrected value to at least one position variable in a post-transition piloting relationship, the corrected value being determined as a function of the mismatch and of the current position of the pilot control. So long as the mismatch is not zero, the value of the mismatch in the relationship is reduced in proportion to the movement of the pilot control as the pilot control comes closer to the equivalent position.

Abstract: A method of assisting the piloting of a multi-engined rotorcraft in the event of an engine failure. A main rotor of the rotorcraft is driven at a variable NR speed under the control of a control unit. Calculation means identify an authorized margin of mechanical power usable by the pilot depending on a rating for regulating the operation of each of the engines under the control of a regulator unit. Outside an engine-failure situation, and providing the main rotor is being driven at a low NR speed, the mechanical power margin that is usable by the pilot and that is displayed on a screen, is in fact a limited margin of a value less than the authorized margin. Under such conditions, and in an engine-failure situation, the mechanical power reserve that is actually available enables the pilot to counter rapidly the sudden drop in the NR speed of rotation of the main rotor as induced by the engine failure.

Abstract: A method of driving a rotorcraft rotor (1, 2) at variable controlled speeds. Starting from a required speed (Nr), a setpoint for total power (Pt) is calculated while taking account of an anticipated power (Pf) to be delivered by the power plant (3) for driving the main rotor (1) at the required speed (Nr), and while taking account of a power surplus (S) relating to progressive power needs to be delivered from a current power (Pc) for driving the main rotor (1) at a current speed (V) of rotation to an anticipated power (Pf) for driving the main rotor (1) at the required speed (Nr). By way of example, account may be taken at least of the acceleration or conversely of the deceleration of the main rotor (1) between the current speed (V) and the required speed (Nr), or indeed account may be taken of the flight circumstance of the rotorcraft 30 determining the calculated required speed (Nr).

Abstract: A method of regulating the speed of rotation of at least one main rotor of a multi-engined rotorcraft, which rotor is driven at variable speed. In the event of a failure of one of the main engines of the rotorcraft, a control unit generates an NR setpoint that is not less than the nominal drive speed (NRnom) of the main rotor. Thereafter, a calculator acts iteratively to determine a target speed (NRobj) for driving the main rotor to obtain stabilized lift of the rotorcraft by balancing between the torque developed by the main rotor and the rate of increase of its drive speed. The autopilot then causes the pitch of the blades of the main rotor to vary so as to obtain the iteratively calculated target speed (NRobj) until stabilized lift of the rotorcraft is obtained.

Abstract: A method of driving a rotorcraft rotor (1, 2) at variable controlled speeds. Starting from a required speed (Nr), a setpoint for total power (Pt) is calculated while taking account of an anticipated power (Pf) to be delivered by the power plant (3) for driving the main rotor (1) at the required speed (Nr), and while taking account of a power surplus (S) relating to progressive power needs to be delivered from a current power (Pc) for driving the main rotor (1) at a current speed (V) of rotation to an anticipated power (Pf) for driving the main rotor (1) at the required speed (Nr). By way of example, account may be taken at least of the acceleration or conversely of the deceleration of the main rotor (1) between the current speed (V) and the required speed (Nr), or indeed account may be taken of the flight circumstance of the rotorcraft determining the calculated required speed (Nr).

Abstract: A method of driving a rotorcraft rotor (1, 2) at variable controlled speeds. Starting from a required speed (Nr), a setpoint for total power (Pt) is calculated while taking account of an anticipated power (Pf) to be delivered by the power plant (3) for driving the main rotor (1) at the required speed (Nr), and while taking account of a power surplus (S) relating to progressive power needs to be delivered from a current power (Pc) for driving the main rotor (1) at a current speed (V) of rotation to an anticipated power (Pf) for driving the main rotor (1) at the required speed (Nr). By way of example, account may be taken at least of the acceleration or conversely of the deceleration of the main rotor (1) between the current speed (V) and the required speed (Nr), or indeed account may be taken of the flight circumstance of the rotorcraft determining the calculated required speed (Nr).