Work on an even more successful design, a large and powerful twin engine amphibious hull antisubmarine helicopter for the U.S. Navy, began in the late 1950s. Unlike previous rotary wing subchasers, the new Sikorsky S61 design combined the hunter, equipped with dipping sonar, and the killer, equipped with homing torpedoes, into a single machine rather than a team of two. To save space, the tail pylon and the five blades of main rotor could be powerfolded; the S61 could also operate on one engine if need be.
The combination of advances introduced in the S61, Sikorsky's first turbine powered helicopter, fully justified the use of terms like new generation or breakthrough. The prototype of the S61B, known to the U.S. Navy as the "Sea King", flew for the first time on 11 March 1959. Deliveries of the Sea King production model to the Navy began in September 1961; in June 1962, the type was redesignated SH3. The SH3A broke a number of world speed records over fixed distances shortly after its introduction. The proof of its versatility, its reliability and its performance lies in fact that the S61 Sea King remained in production until the 1980s.
A whole family of related machines was produced for both military and civilian operators, with various fuselages and in amphibious and non amphibious versions with folding and non folding rotor blades. The non amphibious 28 seat S61L for civilian operators, which entered service with Los Angeles Airways in January 1962, was in fact the world's first real helicopter airliner; the fully amphibious S61N followed soon after.
A simple listing of the S61s military roles is also impressive. They were used for antisubmarine warfare; minesweeping; troop, VIP and assault transport; search and rescue/combat rescue; and logistical support.
The U.S. Department of Defense was the main customer, as before, but the U.S. Air Force, the U.S. Navy and the Coast Guard all use it. Two HH3E Jolly Green Giants of the U.S. Air Force's Aerospace Rescue and Recovery Service performed the first nonstop helicopter crossing of the North Atlantic. They left New York on 31 May 1967 for the Paris Airshow and arrived the following day after nine in-flight refuelings. The S61 family was built by Sikorsky, and Agusta in Italy, Mitsubishi in Japan, and Westland in Great Britain, which also developed the Commando troop transport version.
To this day, the Sea King remains the most widely used amphibious helicopter in the world; it is in use in the armed forces of at least 17 countries. At one point, Okanagan Helicopters Ltd. of British Columbia, one of the world's major helicopter operators, owned seven S61Ls and S61Ns as part of its fleet.
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Revised: June 30, 2010