SYSTEM AND METHOD OF OPERATING MULTI-ENGINE SYSTEM

A method of operating a multi-engine system of an helicopter (100) 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 shaft at a flight rotation speed (NLF) when clutched and rotating the second shaft at a first idle rotation speed (NLHI) when unclutched, the first idle rotation speed (NLHI) above the placarded zone; decreasing a rotation speed of the first shaft from the flight rotation speed (NLF) to a given rotation speed within the placarded zone; decreasing a rotation speed of the second shaft to the given rotation speed; clutching the second shaft; and decreasing the rotation speeds of the first and second shafts to a second idle rotation speed (NLLI) below the placarded zone.