Patent ID: 9676490
Date: 2017-06-13
CPC Classifications: B64D,F02C,F05D

Claim:
1. A method of assisting the piloting of a multi-engined rotorcraft in the event of a failure of one of the main engines of a power plant of the rotorcraft, referred to as an engine-failure situation, the power plant delivering the mechanical power needed at least for driving rotation of at least one main rotor of the rotorcraft providing the rotorcraft at least with lift, the main rotor, outside an engine-failure situation, being driven by the power plant in compliance with applying a speed setpoint, referred to as the NR setpoint, of variable value that is calculated by a flight control unit depending on the current flight conditions of the rotorcraft so as to lie in a range of NR setpoint values that are proportional to the value of a predefined nominal speed for driving the main rotor, the flight control unit supplying the NR setpoint to a regulator unit for regulating the individual operation of each of the main engines for driving the main rotor at a speed, referred to as the NR speed, in compliance with applying the NR setpoint, the regulator unit applying various regulation ratings to the individual operation of each of the main engines depending on the current flight state of the rotorcraft, including: in a current flight state of the rotorcraft that is outside an engine-failure situation, first regulation ratings, referred to as AEO ratings, defining a maximum authorized rating for each of the main engines for respective predefined durations at each of the AEO ratings; in a current flight state of the rotorcraft that is an engine-failure situation, second regulation ratings, referred to as OEI ratings, defining a contingency rating authorized for at least one of the main engines remaining operational for respective predefined durations corresponding to each of the OEI ratings; and the rotorcraft being fitted with a unit, referred to as a display unit, using a display screen for displaying at least one value relating to the mechanical power margin that is authorized for use by the pilot, referred to as the authorized margin, which value is deduced by calculation means depending on at least the current regulation rating of the main engines while taking account at least of limit criteria identifying the operating states of the main engines; wherein, outside an engine-failure situation, the value displayed by the screen relating to the authorized margin, then referred to as the limited margin, is the value of the authorized margin after a predefined value, referred to as the safety margin, has been subtracted therefrom by a computer, on condition at least of driving the main rotor at an NR speed, referred to as “low” speed, under the control of the flight control unit and identified as being below a predefined speed threshold for driving the main rotor, referred to as the NR speed threshold, such that in an engine-failure situation and in the event that, prior to the engine-failure situation, the rotorcraft was operating at a drive NR speed for the main rotor below the NR speed threshold, the pilot of the rotorcraft has a mechanical power reserve making it easier for the pilot to take action on the behavior of the rotorcraft in order to re-establish control quickly over its progress, while avoiding any significant drop in the number of revolutions per second in the rotation of the main rotor.