ABSTRACTFour helicopters carrying destroyers are being built for the Canadian Armed Forces incorporating an advanced all gas turbine COGOG propulsion system supplied by United Aircraft of Canada Limited. The propulsion system installation described herein comprises two shaft lines, each with a Pratt & Whitney Aircraft FT4A‐2 main engine and a Pratt & Whitney Aircraft FT12A‐3 cruise engine, a reduction gearbox, propeller shaft and bearings, and a push rod actuated controllable pitch propeller.The associated ancillary systems, controls and monitoring instrumentation are described with comments on the underlying objectives and design philosophy.