Method for controlling a power plant of a rotorcraft comprising at least two turboshaft engines

A method for controlling at least a first turboshaft engine and a second turboshaft engine of a rotorcraft that set a common kinematic linkage in motion respectively via a first output kinematic linkage and a second output kinematic linkage, the first turboshaft engine having a first free turbine connected to the first output kinematic linkage, the rotorcraft having an output electric machine operating on request at least in electrical energy generator mode, the output electric machine in the electrical energy generator mode being driven by the first output kinematic linkage, the rotorcraft having an input electric machine operating on request at least in motor mode, the input electric machine being connected by an input kinematic linkage to a gas generator of the second turboshaft engine, and the input electric machine in the motor mode driving the input kinematic linkage to drive the second turboshaft engine,

• wherein the method comprises a phase with optimized specific fuel consumption comprising the following steps:
• supplying a first flow rate of fuel to the first turboshaft engine in order for the first turboshaft engine to generate a high power and to supply therefrom a first non-zero power to the common kinematic linkage, the high power being a sum of the first non-zero power and a remaining portion of the high power, the first flow rate of fuel being greater than an original flow rate of fuel supplied to the first turboshaft engine prior to an initiation of the phase with optimized specific fuel consumption, the original flow rate of fuel having been supplied to the first turboshaft engine in order for the first turboshaft engine to generate an original power and supply the original power to the common kinematic linkage prior to the initiation of the phase with optimized specific fuel consumption, the first non-zero power being equal to the original power, the output electric machine being inactive prior to the initiation of the phase with optimized specific fuel consumption;
• operating the output electric machine in the electrical energy generator mode in order for the output electric machine to take off the remaining portion of the high power and to generate therefrom electrical energy;
• and
• supplying a second flow rate of fuel to the second turboshaft engine and operating the input electric machine in the motor mode in order for the second turboshaft engine in conjunction with the input electric machine to supply a second non-zero power to the common kinematic linkage, the second flow rate of fuel being less than an initial flow rate of fuel supplied to the second turboshaft engine prior to the initiation of the phase with optimized specific fuel consumption, the initial flow rate of fuel having been supplied to the second turboshaft engine in order for the second turboshaft engine to generate an initial power and supply the initial power to the common kinematic linkage prior to the initiation of the phase with optimized specific fuel consumption, the second non-zero power being equal to the initial power, the input electric machine being inactive prior to the initiation of the phase with optimized specific fuel consumption.