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EP-4191041-B1 - SYSTEM AND METHOD OF OPERATING MULTI-ENGINE SYSTEM

EP4191041B1EP 4191041 B1EP4191041 B1EP 4191041B1EP-4191041-B1

Inventors

  • Beauchesne-Martel, Philippe
  • DE LUSSY, GAETAN
  • HEBERT, Jeremie
  • COUTU, DANIEL

Dates

Publication Date
20260513
Application Date
20221202

Claims (11)

  1. A method of operating a multi-engine system (105) of an helicopter (100), the multi-engine system (105) having a first turboshaft engine (102) having a first shaft (154), a second turboshaft engine (104) having a second shaft (154), and a gearbox (150) having a clutch system (152) clutching at least one of the first shaft (154) and the second shaft (154) to a load (107) of the helicopter (100), the first and second shafts (154) having a range of rotation speeds defined as a placarded zone, the method comprising: rotating the first and second shafts (154) at a first idle rotation speed (NL LI ) below the placarded zone when the first and second shafts (154) are clutched to the load (107); increasing a rotation speed of the first shaft (154) from the first idle rotation speed (NL LI ) to a flight rotation speed (NL F ), the flight rotation speed (NL F ) above the placarded zone; unclutching the second shaft (154) from the load (107) during the increasing the rotation speed of the first shaft (154); and increasing a rotation speed of the second shaft (154) to a second idle rotation speed (NL HI ) when the second shaft (154) is unclutched from the load (107), the second idle rotation speed (NL HI ) above the placarded zone and below the flight rotation speed (NL F ).
  2. A system for operating a multi-engine system (105) of an helicopter (100), the multi-engine system (105) having a first turboshaft engine (102) having a first shaft (154), a second turboshaft engine (104) having a second shaft (154), and a gearbox (150) having a clutch system (152) clutching at least one of the first shaft (154) and the second shaft (154) to a common load (107) of the helicopter (100), the first and second shafts (154) having a range of rotation speeds defined as a placarded zone, the system comprising: a processing unit (1002); and a non-transitory storage medium (1004) having stored thereon program code (1008) executable by the processing unit (1002) for: rotating the first and second shafts (154) at a first idle rotation speed (NL LI ) below the placarded zone when the first and second shafts (154) are clutched to the load (107); increasing a rotation speed of the first shaft (154) from the first idle rotation speed (NL LI ) to a flight rotation speed (NL F ) above the placarded zone; unclutching the second shaft (154) from the load (107) during the increasing the rotation speed of the first shaft (154); and increasing a rotation speed of the second shaft (154) to a second idle rotation speed (NL HI ) when the second shaft (154) is unclutched from the load (107), the second idle rotation speed (NL HI ) above the placarded zone and below the flight rotation speed (NL F ).
  3. The method or system of claim 1 or 2, wherein the increasing a rotation speed of the first shaft (154) includes increasing a fuel flow to a first combustor section (16) of the first turboshaft engine (102), and the increasing the rotation speed of the second shaft (154) includes increasing a fuel flow to a second combustor section (16) of the second turboshaft engine (104).
  4. The method or system of any preceding claim, wherein the increasing the rotation speed of the second shaft (154) is simultaneous to the increasing the rotation speed of the first shaft (154).
  5. The method or system of any preceding claim, wherein the increasing the rotation speed of the first shaft (154) is performed progressively and in accordance with a first linear increase rate (r1).
  6. The method or system of claim 5, wherein the increasing the rotation speed of the second shaft (154) is performed progressively and in accordance with a second linear increase rate (r2), the first linear increase rate (r1) steeper than the second linear increase rate (r2).
  7. The method or system of claim 6, wherein the first linear increase rate (r1) is twice the second linear increase rate (r2).
  8. The method or system of claim 6 or 7, wherein a difference between the first linear increase rate (r1) and the second linear increase rate (r2) causes the unclutching.
  9. The method of any preceding claim, further comprising performing the method upon receiving a command to operate the first turboshaft engine (102) in a flight regime and maintain the second turboshaft engine (104) in an idle regime.
  10. The system of any of claims 2 to 8, configured to execute said programming code (1008) upon receiving a command to operate the first turboshaft engine (102) in a flight regime and maintain the second turboshaft engine (104) in an idle regime.
  11. The method or system of any preceding claim, wherein the increasing the rotation speed of the second shaft (154) is performed upon detecting that the second shaft (154) has unclutched from the load (107).

Description

TECHNICAL FIELD The present disclosure (invention) generally relates to multi-engine systems for aircraft and more particularly to methods and systems of operating such systems. BACKGROUND OF THE ART Helicopters are often provided with at least two turboshaft engines. Typically, the turboshaft engines are coupled to a main rotor via a common reduction gearbox having a clutch system. The turboshaft engines may have undesirable dynamic vibrations modes that can be excited when a shaft rotates at speeds within a range of rotation speeds referred to as a placarded zone. In some embodiments, helicopters are provided with dedicated systems for decelerating a given one of the turboshaft engines when it's shaft is unclutched from the main rotor and free to rotate at rotation speeds within the placarded zone. For instance, in some of these dedicated systems, vanes within the given turboshaft engine are actuated from a low resistance position to a high resistance position thereby decelerating the rotation speed of the shaft below the placarded zone, thereby avoiding unwanted vibrations. Although existing systems for decelerating turboshaft engines below the placarded zone are satisfactory to a certain degree, there remains room for improvement. US 2018/187604 A1 relates to an assistance device for a free-turbine engine of an aircraft having at least two free-turbine engines. US 2013/199198 A1 relates to a method of automatically regulating an aircraft power plant, to a device, and to an aircraft. SUMMARY In one aspect, there is provided a method of operating a multi-engine system of an helicopter, the multi-engine system having a first turboshaft engine having a first shaft, a second turboshaft engine having a second shaft, and a gearbox having a clutch system clutching at least one of the first shaft and the second shaft to a load of the helicopter, the first and second shafts having a range of rotation speeds defined as a placarded zone, the method comprising: rotating the first and second shafts at a first idle rotation speed below the placarded zone when the first and second shafts are clutched to the load; increasing a rotation speed of the first shaft from the first idle rotation speed to a flight rotation speed, the flight rotation speed above the placarded zone; unclutching the second shaft from the load during the increasing the rotation speed of the first shaft; and increasing a rotation speed of the second shaft to a second idle rotation speed when the second shaft is unclutched from the load, the second idle rotation speed above the placarded zone and below the flight rotation speed. In another aspect, there is provided a system for operating a multi-engine system of an helicopter, the multi-engine system having a first turboshaft engine having a first shaft, a second turboshaft engine having a second shaft, and a gearbox having a clutch system clutching at least one of the first shaft and the second shaft to a common load of the helicopter, the first and second shafts having a range of rotation speeds defined as a placarded zone, the system comprising: a processing unit; and a non-transitory storage medium having stored thereon program code executable by the processing unit for: rotating the first and second shafts at a first idle rotation speed below the placarded zone when the first and second shafts are clutched to the load; increasing a rotation speed of the first shaft from the first idle rotation speed to a flight rotation speed above the placarded zone; unclutching the second shaft from the load during the increasing the rotation speed of the first shaft; and increasing a rotation speed of the second shaft to a second idle rotation speed when the second shaft is unclutched from the load, the second idle rotation speed above the placarded zone and below the flight rotation speed. DESCRIPTION OF THE DRAWINGS Reference is now made to the accompanying figures in which: Fig. 1 is a cross-sectional view of an example turboshaft engine of the aircraft in accordance with an illustrative embodiment;Fig. 2A is a schematic view of a multi-engine aircraft, in accordance with one or more embodiments;Fig. 2B is a schematic diagram of an exemplary multi-engine system for the aircraft of Fig. 2A, showing axial cross-sectional views of two gas turbine engines, in accordance with an illustrative embodiment;Fig. 3 is a block diagram of an example architecture for operating a multi-engine aircraft, in accordance with an illustrative embodiment;Fig. 4 is a flow chart of a method of operating a multi-engine aircraft in a first run-up phase, in accordance with one or more embodiments;Fig. 5 is a graph showing commanded engine regime, fuel supply rate and rotation speed as a function of time during the run-up phase of Fig. 4, in accordance with one or more embodiments;Fig. 5A is a graph showing rotation speed of a second shaft as a function of rotation speed of a first shaft, in accordance with an illustrative embodiment