The SH-3 Sea King (company designation S-61) is a twin-engined anti-submarine warfare (ASW) helicopter designed and manufactured by the American Company Sikorsky. Designed to combine the hunter/ killer functions in one airframe, the Sikorsky HSS-2 was the subject of a US Navy contract awarded on 23 September 1957. This called for an all-weather anti-submarine helicopter with dunking sonar' equipment and able to carry up to 381 kg of offensive weapons. The S-61 design had watertight hull, retractable landing gear in the stabilizing floats, and was powered bytwo General Electric T58 turboshaft engines driving a five-blade main rotor. The prototype flew on 11 March 1959 and seven YHSS-2 trials aircraft followed; the type became redesignated SH-3 in September 1959. The initial production version, the SH-3A Sea King, began to reach Fleet squadrons in September 1961 and later conversions included the HH-3A VIP transport flown by the Executive Flight Detachment, Washington. The essentially similar CH-124 was supplied to Canada while the Royal Norwegian air force acquired S-61A helicopters without ASW equipment for rescue duties, and the Royal Malaysian air force acquired S-61A-4 Nuri helicopters equipped to carry 31 troops or operate in the SAR (Search And Rescue) role.