The Sikorsky S-61L and S-61N are civil variants of the SH-3 Sea King military helicopter. They were developed and produced by the American helicopter manufacturer Sikorsky Aircraft . The commercial version of the Sea King was developed during the late 1950s.

The S-61 (HSS-2) was Sikorsky’s first model to employ a main transmission capable of providing almost 100- to-1 reduction ratio needed for the turbo shaft engine’s high, 20,000 rpm, output speed. Prior MGBs had reduction ratios of only 10 or 12- to-one reflecting the much lower output speeds of piston engines.

The Sikorsky S-61 is a twin-engined helicopter originally designed as an embarked anti-submarine warfare (ASW) aircraft with the military designation of SH-3 Sea King. Was the first helicopter to combine the roles of Hunter and Killer in an unique airframe.

The Sikorsky S-61R is a twin-engine helicopter used in transport or search and rescue roles. A developed version of the S-61 (the SH-3 Sea King), the S-61R was also built under license by Agusta as the AS-61R.

The Sikorsky S-61R is a developed version of the S-61/SH-3 Sea King Model designed as a twin-engine rotorcraft utilized in transport and search and rescue operations. The aircraft was created under license by Agusta as the AS-61R.

The Sikorsky S-61 Sea King is an amphibious twin-engined medium ASW (anti-submarine-warfare) and multi-purpose helicopter produced by the American manufacturer Sikorsky Aircraft. Variants of the S-61 are the commercial S-61L & S-61N and the S-61R (CH-3C/E Sea King, HH-3E Jolly Green Giant and HH-3F Pelican).

The S-61/H-3, developed from the U.S. Navy HSS-2 Sea King antisubmarine helicopter, was designed to fulfill a 1957 U.S. Navy requirement for an antisubmarine helicop­ter. Originally designated the HSS‑2, which was changed in 1962 to SH‑3, the Sea King entered U.S. Navy service in 1961.

The S-61 design had watertight, hull-retractable landing gear in the stabilising floats, and was powered by two General Electric T58 turboshaft engines driving a five-bladed main rotor. The prototype flew on 11 March 1959 and seven YHSS-2 trials aircraft followed; the type was redesignated SH-3 in September 1959.

The Sikorsky S61N and S61L are based on SH3/S61A/B Sea King series originally developed in the late 1950s. They are two of the most widely used airliner and oil rig support helicopters built.

2 x General Electric CT58-140 turboshafts, 1,120 kW each. Medium-lift transport/utility helicopter. The Sikorsky S-61L and S-61N are civil variants of the successful SH-3 Sea King helicopter.