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EP-4739895-A1 - METHOD FOR CONTROLLING AN AIRCRAFT PROPULSION SYSTEM HAVING TURBOSHAFT ENGINES OPERATING IN PARALLEL AND CAPABLE OF BEING PLACED ON STANDBY, AND CORRESPONDING AIRCRAFT

EP4739895A1EP 4739895 A1EP4739895 A1EP 4739895A1EP-4739895-A1

Abstract

Method for controlling an aircraft propulsion system (S), comprising a rotor (R), a first turboshaft engine (M 1 ) and a second turboshaft engine (M 2 ), and at least one electric starter coupled to each turboshaft engine; the propulsion system being designed to have a nominal mode in which the two turboshaft engines drive the rotor and air is bled/electricity is tapped from the two turboshaft engines, and an eco mode in which only the first turboshaft engine drives the rotor, the second turboshaft engine being in standby mode, and the air being bled/electricity being tapped only from the first turboshaft engine, the rotor having a setpoint speed in the two modes, the method comprising: - with the propulsion system in nominal mode, verifying compatibility between aircraft operating parameters and the eco mode; - if compatible and if a command to switch to an eco mode is received, stopping the bleeding of air/tapping of electricity from the second turboshaft engine and verifying compatibility between operating parameters of the first turboshaft engine and the eco mode; - if compatible, idling the second turboshaft engine so that its output shaft has a speed lower than that of the rotor; - verifying correct operation of the starter of the second turboshaft engine; - if correct, placing the second turboshaft engine in standby mode by interrupting a supply of fuel to the second turboshaft engine in order to switch to the eco mode.

Inventors

  • MERCIER-CALVAIRAC, FABIEN
  • LEMAY, DAVID
  • BEDRINE, OLIVIER

Assignees

  • Safran Helicopter Engines

Dates

Publication Date
20260513
Application Date
20240618

Claims (10)

  1. 1. Method for controlling an aircraft propulsion system (S), comprising a rotor (R), at least a first turbine engine (Mi) and a second turbine engine (M2) which have output shafts (X S i, X S 2) connected to said rotor via a main gearbox (BTP) and which are respectively controlled by a first regulation computer (Ci) and a second regulation computer (C2) connected to each other by a digital link (L) and both connected to avionics (A), and at least one electric starter coupled to each turbine engine; the propulsion system being arranged to have a nominal mode in which the two turbine engines drive the rotor and air/electricity sampling is carried out on the two turbine engines, and an eco mode in which only the first turbine engine drives the rotor, the second turbine engine being on standby, and the air/electricity sampling is carried out only on the first turbine engine, the rotor having a set speed in both modes; characterized in that the method comprises: - while the propulsion system is in nominal mode, verification of compatibility of aircraft operating parameters with eco mode; - if so and in the event of receipt of an order to switch to eco mode, stopping the air/electricity samples taken from the second turboshaft engine and checking the compatibility of the operating parameters of the first turboshaft engine with eco mode; - if so, idling the second turboshaft engine so that its output shaft has a lower speed than that of the rotor; - checking the correct operation of the starter of the second turboshaft engine; - if so, putting the second turbo engine on standby by interrupting a fuel supply to the second turbo engine to switch to eco mode.
  2. 2. Method according to claim 1, in which the verification of the compatibility of the flight conditions with the eco mode comprises a first verification by each computer that the turbine engine associated with it has an internal operation compatible with the eco mode and a second verification by the avionics that the aircraft has operating parameters compatible with the eco mode.
  3. 3. Method according to claim 1 or 2, in which the idling of the second turbine engine comprises a misalignment of the two turbine engines to bring the first turbine engine to a power level close to that required in eco mode and a verification that the rotor maintains the set speed.
  4. 4. The method of claim 3, wherein idling the second turbine engine comprises controlling the second turbine engine to bring it into a zero-power thermal stabilization regime.
  5. 5. The method of claim 4, wherein idling the second turbine engine comprises checking the operating margins of the first turbine engine.
  6. 6. Method according to any one of the preceding claims, in which, the starter being coupled to the second turbine engine via a freewheel, the verification of the correct operation of the starter of the second turbine engine comprises an activation of the starter up to a predetermined speed then a regulation of the starter speed up to a standby mode speed.
  7. 7. The method of claim 6, wherein the standby mode regime is equal to approximately 10% of the nominal regime of the second turboshaft engine.
  8. 8. Method according to any one of claims 1 to 5, in which, the starter being coupled to the second turbine engine in direct drive, the verification of the correct operation of the starter of the second turbine engine comprises an activation of the starter of the second turbine engine to drive the second turbine engine in rotation and a verification that the second turbine engine has operating parameters showing a representative evolution of a generation of power by said starter.
  9. 9. A method according to any preceding claim, wherein placing the second turbine engine on standby comprises restoring the fuel supply to the second turbine engine and activating the starter, checking for a temperature rise in the second turbine engine and, if so, interrupting the fuel supply to the second turbine engine to switch to eco mode.
  10. 10. Aircraft comprising a propulsion system (S) comprising a rotor (R), at least a first turboshaft engine (Mi) and a second turboshaft engine (Mi) which have output shafts (Xsi, Xsi) connected to said rotor via a main gearbox (BTP) and which are respectively controlled by a first regulation computer (Ci) and a second regulation computer (Ci) connected to each other by a digital link and both connected to avionics A, and at least one electric starter coupled to each turboshaft engine; the avionics being arranged to implement the control method according to any one of the preceding claims to switch the propulsion system from a nominal mode in which the two turboshaft engines drive the rotor and air/electricity sampling is carried out on both turbo engines, to an eco mode in which only the first turbo engine drives the rotor, the second turbo engine being on standby, and the air/electricity samples are taken only from the first turbo engine, the rotor having a set speed in both modes.

Description

METHOD FOR CONTROLLING AN AIRCRAFT PROPULSION SYSTEM HAVING TURBOENGINES OPERATING IN PARALLEL AND CAPABLE OF BEING PLACED ON STANDBY AND CORRESPONDING AIRCRAFT DESCRIPTION The present invention relates to the propulsion of aircraft. BACKGROUND OF THE INVENTION A helicopter is an aircraft conventionally equipped with a main rotor driving a rotating wing to provide its lift and propulsion. In order to rotate the main rotor, it is known to equip the helicopter with two turboshaft engines operating in parallel at generally similar speeds. Each of the turboshaft engines is designed to be oversized so as to be able to provide, in the event of failure of the other turboshaft engine, sufficient power to allow the helicopter to continue its flight and land in safe conditions. When the helicopter is in cruise flight, the turboshaft engines operate at low power levels, which results in a particularly high specific consumption CS (defined as the ratio between the hourly fuel consumption by the combustion chamber of the turboshaft engine and the power supplied by this turboshaft engine) and therefore excess fuel consumption. In order to reduce the fuel consumption of the helicopter, it was proposed, in cruise flight situation, to put one of the turboshaft engines on standby and to operate this flight phase with the other turboshaft engine which then operates at a higher speed and therefore benefits from a lower specific consumption CS. Such a mode of operation of turbo engines is called for this reason "economy mode" or "eco mode". SUBJECT OF THE INVENTION The invention therefore aims to propose a method for controlling the propulsion system of an aircraft, which is more fuel-efficient while operating safely. SUMMARY OF THE INVENTION The use of the eco mode must not weaken the operational safety of the helicopter, but it is also necessary to be able to return the propulsion system to nominal mode reliably. According to the invention, the use of the eco mode is based on an automatic control system which assists the crew and implements a verification strategy in order, before putting one of the turbine engines into standby, to detect latent failures of the propulsion system on the one hand and to guarantee the subsequent restart of the dormant turbine engine on the other hand. For this purpose, a method according to claim 1 is proposed. Thus, the method of the invention makes it possible not only to determine whether the transition of the propulsion system from nominal mode to eco mode can be done without endangering the aircraft but also whether the propulsion system can be returned to nominal mode. The invention also relates to an aircraft implementing this method. Other characteristics and advantages of the invention will emerge from reading the following description of particular non-limiting embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS Reference will be made to the attached drawings, including: [Fig. 1] Figure 1 is a schematic view of a propulsion system of a twin-engine helicopter; [Fig. 2] Figure 2 is a schematic view of one of the engines of the propulsion system illustrated in Figure 1; [Fig. 3] Figure 3 is a flowchart illustrating the steps of the method of controlling the propulsion system illustrated in Figure 1; [Fig. 4] Figure 4 is a block diagram illustrating the sequence of verification steps in this process. DETAILED DESCRIPTION OF THE INVENTION With reference to FIG. 1, a helicopter comprises a propulsion system S comprising a main rotor R on which blades P are fixed, providing lift and propulsion for the helicopter. The rotor R is rotated by a first turboshaft engine Mi and a second turboshaft engine M2, each having an output shaft Xsi, Xs2 connected to said rotor R via a main gearbox MGB. The first turboshaft engine Mi and the second turboshaft engine M2 operate in parallel and are respectively controlled by a first control computer Ci and a second control computer C2. Such control computers are commonly called FADEC (from the English acronym “Full Authority Digital Engine Control”) and have a structure known per se. The first computer Ci and the second computer C2 communicate with each other via a digital link called intercomputer L and are connected to avionics A of the helicopter in particular to ensure the control of the turboshaft engines and in particular the functions of automatic start, protection against overheating, protection against overtorque, protection against surge, protection against flameout, and management of the service life of the first turboshaft engine Mi and the second turboshaft engine M2 . Each of the first Mi turboshaft engine and the second Mi turboshaft engine is designed to be oversized so as to be able to provide, in the event of failure of the other, first Mi turboshaft engine and second M2 turboshaft engine, sufficient power to allow the helicopter to continue its flight and land in safe conditions. The first turbine engine Mi and the second turbi