The Sikorsky H-34 was an American military helicopter family derived from the company’s S-58 design. Versions served in transport, anti-submarine and other utility roles. The different service names included Choctaw, Seabat and Seahorse.[1]Sikorsky S-58Igor I. Sikorsky Historical Archives · sikorskyarchives.com · Accessed 2026-09-13Open source details[2]H-34 Seabat/SeahorseNational Naval Aviation Museum · history.navy.mil · Accessed 2026-09-13Open source details
Development from the S-55
Sikorsky developed the S-58 as a larger and more powerful successor to the S-55. The first aircraft flew on 8 March 1954 after a Navy contract placed in 1952. Army orders followed in 1955, and Marine Corps service entry followed in February 1957.[3]Marines and Helicopters 1946–1962United States Marine Corps · usmcu.edu · Accessed 2026-09-13Open source details Different military requirements produced several versions of the same underlying design.[1]Sikorsky S-58Igor I. Sikorsky Historical Archives · sikorskyarchives.com · Accessed 2026-09-13Open source details
Naval anti-submarine duties
The Navy’s HSS, later redesignated SH-34, carried sonar equipment and could employ homing torpedoes. Aircraft operated in hunter-killer teams, dividing the tasks of locating and attacking a submarine contact. The Seabat name is associated with this anti-submarine branch, whose installed equipment distinguished it from the troop-carrying versions.[2]H-34 Seabat/SeahorseNational Naval Aviation Museum · history.navy.mil · Accessed 2026-09-13Open source details
Marine transport service
The HUS, subsequently UH-34, served as the Seahorse transport. The Marine Corps acquired more than six hundred and used it as a principal helicopter assault transport during the early Vietnam War. Its cabin carried substantially more troops than the preceding medium transport helicopter, allowing each aircraft to contribute a larger lift capacity to a formation.[2]H-34 Seabat/SeahorseNational Naval Aviation Museum · history.navy.mil · Accessed 2026-09-13Open source details
Civil production and turbine conversions
The S-58 also gained civil certification and carried passengers for helicopter airlines including operators in Chicago, New York and Los Angeles. Utility operators used it for construction and petroleum-industry work. Sikorsky later offered the S-58T conversion, replacing the original radial engine with a twin-turbine installation approved in 1971. That development extended the family into new commercial work, while the military H-34 designation continued to identify its earlier service variants.[1]Sikorsky S-58Igor I. Sikorsky Historical Archives · sikorskyarchives.com · Accessed 2026-09-13Open source details