Method of optimizing the performance of an aircraft, a device, and an aircraft

A method of optimizing the performance of an aircraft having a rotary wing driven by a power plant comprising at least one turbine engine, each turbine engine having a gas generator and a turbine assembly comprising at least one turbine, the method comprising:

• during a definition step (STP1), the manufacturer defining a minimum first performance level (LEND) of the aircraft and a maximum second performance level (HEND) of the aircraft;
• and
• during a health check step (STP2), performing at least one health check of each turbine engine by:
• determining a current power delivered by each turbine engine;
• measuring a current speed of rotation (Ng) and a current temperature (TET, T45) of the gas at said turbine assembly;
• determining a first power margin between said current power and a first minimum power defined by the manufacturer for guaranteeing said first performance level at said current speed of rotation (Ng);
• and
• determining a second power margin between said current power and a second minimum power defined by the manufacturer for guaranteeing said first performance level at said current temperature (TET, T45);
• and
• during an evaluation step (STP3), comparing each power margin with a first threshold (SH1, SH2), a target performance level being the second performance level when the first and second power margins of each engine are respectively greater than or equal to a first high threshold (SH1) and a second high threshold (SH2), said target performance level being the first performance level when the first power margin of an engine is less than the first high threshold and/or when the second power margin of an engine is less than the second high threshold;
• and
• displaying the target performance level, with the aircraft being piloted in flight in compliance with the target performance level established before the flight.