THE RS.360 was conceived in the mid 60's as a turboshaft engine, for helicopter application and operation in the 1970's. It is one of three engines in the Anglo‐French Helicopter Agreement ratified in 1967. This agreement covered three helicopters — a medium, the SNIAS Puma with Turmo IIIC4 engines, a SNIAS LOH Gazelle with Astazou IIIN and a utility helicopter, the Westland Lynx. The RS.360 was chosen as the power plant for this helicopter and the design has been closely tailored to suit this aircraft. It is of modern design, but using ‘state of the art’ technology with the objective of providing a reliable, easily maintained power plant with particular emphasis on multi‐engine applications. A two spool gas generator layout was chosen for overall mechanical simplicity and to provide a good acceleration characteristic over the whole speed range. This arrangement eliminated the need for air blow‐off or sophisticated variable geometry. An important feature of the engine is the use of a modular concept permitting the replacement of major assemblies without the need for sophisticated equipment. Inherent in the design is the potential for adequate power growth. Provision has been made for extensive condition monitoring facilities in addition to normal flight requirements, ie intrascope access, magnetic chip detectors and SOAP.