H-34 Choctaw

The Sikorsky H-34 Choctaw (company designation S-58) is an American piston-engined utility helicopter. It was originally designed for US Navy anti-submarine warfare and entered service in 1954. The armed forces of 25 countries operated it, and it saw combat in Algeria, Vietnam, the Dominican Republic, Nicaragua and the Six-Day War. It was the last piston-engined helicopter in US Marine Corps service. Including licence production, 2,340 were built between 1953 and 1970.

Development

Sikorsky developed the S-58 as a lengthened, more powerful version of the S-55 (H-19 Chickasaw). The US Navy placed a contract in 1952, and the aircraft first flew on 8 March 1954. The Navy designated it HSS-1 Seabat in the ASW role and HUS-1 Seahorse in the utility role. The Army ordered it in 1955 as the H-34 Choctaw, and the Marine Corps followed in 1957. In 1962 these designations became SH-34, UH-34 and CH-34.

In France, Sud-Aviation assembled US-supplied kits and built a further 166 under licence. In the UK, Westland developed the turboshaft-powered Wessex from 1958. Sikorsky ended production in 1968 after building 1,821.

Design

The S-58 kept the S-55's nose-mounted radial engine, with the drive shaft passing through a cockpit set above the cargo compartment, but adopted tail-dragger landing gear. Military versions use a 1,525 hp Wright R-1820-84 Cyclone, giving a maximum speed of 122 mph (196 km/h) and a range of 190 mi (310 km). Transport versions carry 12 to 16 troops or eight stretchers.

The civil S-58T conversion was certified in April 1971. It uses two Pratt & Whitney Canada PT6T-3 Twin-Pac turboshafts, which raise full-power altitude from 700 ft to 6,000 ft and allow continued flight after an engine failure.

Armament

USMC H-34s were among the first helicopter gunships trialled in Vietnam. They were fitted with the Temporary Kit-1 (TK-1), consisting of two M60C machine guns and two 19-shot 2.75 in rocket pods. These "Stingers" were quickly phased out, but the TK-1 formed the basis of a follow-on armament kit for USMC UH-1Es.

Operational History

In the Algerian War, French Air Force helicopters, including the H-34, flew over 190,000 hours and evacuated more than 20,000 combatants. Their combined use of armed and transport helicopters produced early airmobile tactics.

The US Army did not deploy its H-34s to Vietnam, but Marine Corps crews requested the type by name for its reliability. The RVNAF 219th Squadron used H-34s to insert MACV-SOG teams into Laos.

Israeli S-58s carried troops and evacuated wounded at the Battle of Karameh on 21 March 1968. In 1961 an H-34 had to release the flooded Mercury capsule Liberty Bell 7, which sank. The last USMC flight took place on 3 September 1973. Civil S-58Ts later flew scheduled passenger services in New York.

Variants

• HSS-1 Seabat (SH-34G): US Navy anti-submarine production model, with 215 built.
• HSS-1N Seabat (SH-34J): Night and bad-weather ASW version with improved avionics and autopilot, with 167 built.
• HUS-1 Seahorse (UH-34D): US Marine Corps utility transport, with 462 built.
• H-34A (CH-34A): US Army version powered by the R-1820-84, with 359 built.
• S-58T: Civil conversion with twin PT6T-3 Twin-Pac turboshafts and a nose cowling with twin rectangular intakes.