SYSTEM AND METHOD OF OPERATING MULTI-ENGINE SYSTEM

A method of operating a multi-engine system of an helicopter includes the multi-engine system having a first turboshaft engine having a first shaft, a second turboshaft engine having a second shaft, a gearbox having a clutch system, and a range of rotation speeds defined as a placarded zone. The method generally has: rotating the first and second shafts at a flight rotation speed (NLF) above the placarded zone when clutched to a load; decreasing a rotation speed of the first shaft from the flight rotation speed (NLF) to a first idle rotation speed (NLHI) above the placarded zone; unclutching the first shaft from the load during the decreasing; 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 (NLLI) below the placarded zone, the simultaneously decreasing including clutching the first shaft to the load.