Method of optimizing the noise generated in flight by a rotorcraft

1. A method of optimizing noise generated by a hybrid power plant of a rotorcraft during a flight phase, the hybrid power plant being provided with at least one engine and with at least one electric machine;

wherein the method includes the following steps:

a determination step for determining a required power to be delivered by the hybrid power plant for the flight phase; and

a distribution step for distributing the required power between the engine(s) and the electric machine(s) as a function of a target noise level, of the required power for the flight phase, and of a model for a noise generated by the engine(s) depending on an operating parameter of the engine(s);

wherein the distribution step includes the following sub-steps:

a first determination sub-step for determining a main power to be delivered by the engine(s) so that the engine(s) generate(s) a sound level less than or equal to the target noise level, the main power being determined as a function of the target noise level and of the model for the noise generated by the engine(s); and

a second determination sub-step for determining a first supplementary power to be delivered by the electric machine(s) so that the hybrid power plant delivers the required power; and

when the first supplementary power is less than or equal to an available power of the electric machine(s), the distribution step includes the following sub-steps:

a first control sub-step for causing the electric machine(s) to deliver the first supplementary power; and

a second control sub-step for causing the engine(s) to deliver the main power; and

when the first supplementary power is greater than the available power, the distribution step includes the following sub-steps:

a third control sub-step for causing the electric machine(s) to deliver a reduced first supplementary power that is equal to the available power; and

a fourth control sub-step for causing the engine(s) to deliver an increase main power so that the hybrid power plant delivers the required power.

2. The method according to claim 1 ,

wherein the available power is equal to a maximum power that the electric machine(s) can deliver without damaging the electric machine(s).

3. The method according to claim 1 ,

wherein the available power is calculated as a function of a quantity of electrical energy available in at least one electrical energy source powering the electric machine(s) and of a duration for which the quantity of electrical energy can be used until the electrical energy available in the electrical energy source(s) is exhausted.

4. The method according to claim 1 ,

wherein the target noise level is a function of the environment overflown by the rotorcraft and/or of a height of flight of the rotorcraft relative to the ground of the overflown environment.

5. The method according to claim 1 ,

wherein the method includes an inhibition step for inhibiting the distribution step for distributing the required power when, during the flight phase, the engine(s) is/are not a predominant noise source.

6. The method according to claim 5 ,

wherein the flight phase, in which the engine(s) is/are not the predominant noise source, is a level cruising flight phase or an approach flight phase.

7. The method according to claim 1 ,

wherein the operating parameter of the engine(s) is a speed of rotation of the engine(s), an operating temperature of the engine(s) or a torque delivered by the engine(s).

8. The method according to claim 1 ,

wherein, when each engine of the at least one engine is a turboshaft engine comprising a gas generator and a free turbine, the operating parameter of the engine is a speed of rotation of the gas generator, a temperature of gases at an outlet of a combustion chamber of the gas generator, or a torque delivered by the free turbine or by the gas generator.