US 11,674,456 B1
System and method of operating multi-engine system
Philippe Beauchesne-Martel, Brossard (CA); Gaetan De Lussy, Montréal (CA); Jeremie Hebert, Napierville (CA); and Daniel Coutu, Longueuil (CA)
Assigned to PRATT & WHITNEY CANADA CORP., Longueuil (CA)
Filed by PRATT & WHITNEY CANADA CORP., Longueuil (CA)
Filed on Dec. 2, 2021, as Appl. No. 17/540,574.
Int. Cl. F02C 9/42 (2006.01); F02C 7/36 (2006.01)
CPC F02C 9/42 (2013.01) [F02C 7/36 (2013.01); F05D 2220/329 (2013.01); F05D 2260/4023 (2013.01); F05D 2270/023 (2013.01); F05D 2270/304 (2013.01)] 17 Claims
OG exemplary drawing
 
1. 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 flight rotation speed above the placarded zone when the first and second shafts are clutched to the load;
decreasing a rotation speed of the first shaft from the flight rotation speed to a first idle rotation speed above the placarded zone;
unclutching the first shaft from the load during the decreasing the rotation speed of the first shaft; and
subsequently to the decreasing and the unclutching, simultaneously decreasing the rotation speeds of the first shaft and of the second shaft to a second idle rotation speed below the placarded zone, the simultaneously decreasing including clutching the first shaft to the load.