Power margin indicator for a rotary wing aircraft, particularly a helicopter

A power margin indicator for a rotary wing aircraft, particularly a helicopter, comprising at least one main lift and forward travel rotor, said indicator, which is intended to provide information about the power margin available on at least one engine and one gearbox of said aircraft, comprising:

• acquisition means which determine the values of parameters for the control of the engine and the gearbox;
• calculation means which, on the basis of said values of the control parameters received from said acquisition means and of limit values regarding these control parameters for various engine speeds, determine for each of said engine speeds a power margin, each of said power margins being determined for the corresponding engine speed with respect to a first limit which corresponds to the first of the limit values which would be reached by one of the control parameters if the power were to vary;
• and
• display means which display said first limits on a display screen for at least some of said speeds, which first limits are represented on a scale graduated in collective pitch equivalents and capable of scrolling past a fixed pointer which indicates the current collective pitch, the difference in terms of collective pitch between said pointer and one of said first limits being representative of the corresponding power margin,
• wherein said acquisition means determine the values of said rotor speed, and wherein said calculation means take account of said rotor speed values and of at least one rotor speed set point value to determine, regardless of the flight configuration, at least one power margin which is such that when the rotor speed drops below said set point value the corresponding first limit which is displayed by the display means indicates to the pilot of the aircraft that he should reduce the collective pitch until the rotor speed returns to said set point value.