Power margin indicator device for a rotorcraft, an associated rotorcraft, and a corresponding method

A power margin indicator device constituting a first limitation indicator for a rotorcraft, for providing a pilot of the rotorcraft with information about a power margin available on at least one engine and a main power transmission gearbox of the rotorcraft as a function of flying conditions, the device comprising:

• input means for collecting input data corresponding to at least two distinct operating parameters of the at least one engine and of the main power transmission gearbox;
• calculation means connected to the input means, the calculation means serving:
• to calculate at least two power margins as a function firstly of respective values of the at least two operating parameters, and secondly of limitation values for at least one of the utilization ratings corresponding to a maximum takeoff power, a maximum continuous power, a maximum transient power, a thirty second one engine inoperative supercontingency power, a two minute one engine inoperative contingency power, and a one engine inoperative continuous contingency power for the at least one engine;
• to compare the at least two power margins in order to identify a limiting power margin as being the smallest of the at least two power margins;
• and
• to convert the limiting power margin into a collective pitch margin for the blades of a rotor of the rotorcraft;
• and
• display means presenting on a display screen the collective pitch margin represented on a scale graduated in collective pitch equivalents in a window of the display screen and an index representative of a current collective pitch of the blades of the rotor;
• wherein:
• the calculation means are configured to determine the following simultaneously for at least one of the utilization ratings corresponding to the maximum takeoff power, the maximum continuous power, the maximum transient power, the thirty second one engine inoperative supercontingency power, the two minute one engine inoperative contingency power, and the one engine inoperative continuous contingency power for the at least one engine:
• initially, a plurality of results corresponding to the collective pitch margin for the blades of the rotor for a plurality of values of the speed of rotation of the rotor, the plurality of values of the speed of rotation of the rotor forming a predetermined range of values for the speed of rotation of the rotor;
• and
• subsequently, a plurality of collective pitch limits obtained by summing the current collective pitch of the blades of the rotor with each of the results of the plurality of results;
• and
• the display means present at least one planar curve corresponding to the at least one of the utilization ratings corresponding to the maximum takeoff power, the maximum continuous power, the maximum transient power, the thirty second one engine inoperative supercontingency power, the two minute one engine inoperative contingency power, and the one engine inoperative continuous contingency power for the at least one engine, the at least one planar curve being representative of the plurality of collective pitch limits over the predetermined range of values for the speed of rotation of the rotor, the at least one planar curve being formed by a set of points presenting as abscissa value the speed of rotation of the rotor and as ordinate value a corresponding collective pitch limit, each of the at least one planar curves being capable of moving at least along an ordinate axis Y relative to the scale graduated in collective pitch equivalents and/or relative to the index representative of a current collective pitch of the blades of the rotor.