Sikorsky S-61
Twin-turbine anti-submarine helicopter family designed and built by Sikorsky Aircraft under the company designation S-61, spanning the U.S. Navy's SH-3 Sea King (originally HSS-2), the presidential VH-3s, the civil S-61L and S-61N airliners, and license-built Sea Kings from Westland in the United Kingdom, Agusta in Italy and Mitsubishi in Japan, plus Canadian assembly from Sikorsky kits. First flown in 1959, it combined submarine detection and attack in one aircraft, recovered Mercury, Gemini and Apollo crews after splashdown, carried U.S. presidents, and remains in service in several countries more than six decades later.
Why It Mattered
The S-61 mattered because it put submarine hunting and submarine killing in a single aircraft, work the U.S. Navy had previously divided between two helicopter types. Sikorsky received a Navy contract in December 1957 to develop it as a complete weapon system, with the sensors, weapons and avionics to hunt submarines included from the start. The requirement came from the growing Soviet submarine threat of the Cold War, and the new helicopter was expected to search out and destroy submarines at night and in bad weather. Twin turboshaft power made that practical, giving crews performance and engine-out safety that the piston-engined sub-hunters before it could not match. From that single design came presidential transports, astronaut-recovery aircraft, civil airliners and license-built Sea Kings in Britain, Italy and Japan.
Design Notes
Sikorsky gave the S-61 a boat hull, so it could land on water and float, gaining overwater safety without inflatable floats. Two General Electric T58 turboshafts drove a five-bladed main rotor that folded automatically for shipboard stowage. Retractable gear sat in stabilizing sponsons to cut drag, and refined automatic stabilization equipment made the low sonar-dipping hover more reliable at night. Power grew as the family developed: the S-61B paired 1,250-shp T58-GE-8 engines, and the SH-3D that flew in July 1965 used 1,400-shp T58-GE-10s with an uprated gearbox and more fuel. For civil work the S-61L stretched the cabin for passengers and freight and dropped the stabilizing floats, while the amphibious S-61N kept them for overwater flying.
Operational History
The first of seven prototypes flew for thirty minutes on 11 March 1959, with Sikorsky test pilots Robert Decker and Francis Yirrell at the controls. Navy deliveries began to Helicopter Anti-Submarine Squadron 1 in June 1961, and that September the type was cleared for fleet anti-submarine duty, quickly pushing the piston-engined Seabat out of the ASW squadrons. Stratford built 255 SH-3As for the U.S. Navy and kept the naval Sea King line open for twenty years, with export aircraft following the domestic production. In Vietnam, Sea Kings flew combat search and rescue from carriers and small-deck ships, and in 1967 the Navy fielded ten armored HH-3A 'Big Mothers' built for the rescue mission. Navy Sea Kings were also the astronaut-recovery helicopters of the space program, retrieving Mercury, Gemini and Apollo capsules from the ocean after splashdown. A presidential role began in January 1962 with plans for eight VH-3As to carry the President; eleven VH-3Ds replaced them in 1975, and the Marines took sole responsibility for presidential helicopters in 1976. License production and exports widened the family further: Canada received four Connecticut-built aircraft and assembled thirty-seven more from Sikorsky kits, and Japan ultimately took delivery of 185 Sea Kings. Westland's first British-built Sea King flew in May 1969, and Agusta delivered its first Italian-built aircraft the same year, with follow-on orders stretching deliveries to 1987. The civil line ran in parallel: the S-61L first flew in November 1961 and the S-61N in August 1962, and 119 civil aircraft were built in all, working as airliners and offshore oil-support helicopters. In 1967 two Air Force HH-3Es, stretched derivatives of the design, made the first nonstop helicopter crossing of the Atlantic, flying from New York to the Paris Air Show in just under thirty-one hours with nine in-flight refuelings.
Afterlife
The U.S. Navy retired its last Sea King in December 2009, fifty years after the first flight; the Sikorsky Historical Archives calls it the longest-serving helicopter in U.S. Navy history. Canada flew its Sea Kings until December 2018, and Royal Navy Sea Kings officially retired the same year, though two British aircraft still fly under contract training German Navy pilots. The presidential VH-3Ds remain in service until their VH-92 replacement reaches full operational capability, so part of the family is still on front-line duty. Sea Kings also continue in government and military roles in India, Ukraine and elsewhere, and Argentina's navy flies Carson-modernized S-61Ts. Preservation is under way at the same time: a restored SH-3A joined the Patuxent River Naval Air Museum in 2015, and the VH-3A that carried Nixon from the White House on his resignation in 1974 is being restored again for the Nixon Library, where it is due back on indoor display in 2028.