Sikorsky H-34 Choctaw
The Sikorsky H-34 Choctaw, company designation S-58, is an American piston-engined military helicopter developed from the smaller S-55 (H-19 Chickasaw) and first flown on 8 March 1954. Designed for the U.S. Navy as the HSS-1 Seabat anti-submarine helicopter, it served the Marine Corps as the HUS-1 Seahorse transport, the Army as the Choctaw, and the Coast Guard and Air Force in rescue and VIP roles, carrying Presidents Eisenhower and Kennedy among others. Sikorsky built 1,821 of them before its production ended in January 1970; Sud-Aviation licence production in France and Westland's turbine-powered Wessex development in Britain brought the combined total to 2,340. Marine UH-34Ds went to South Vietnam with Operation Shufly in 1962, and the H-34 was the last piston-engined helicopter operated by the Marine Corps.
Why It Mattered
The H-34 mattered first as a submarine hunter: where the Navy's earlier S-55 had worked in hunter-killer pairs, one helicopter carrying the dipping sonar and the other the torpedo, the S-58 had the power to carry sonar and weapons in a single aircraft. The same reserve of power made it a useful transport for every American service: the cabin carried 16 troops, and the type flew in transport, search and rescue, anti-submarine and VIP roles. In July 1956 an HSS-1 set three world speed records over closed courses, the fastest at 141.9 mph over 100 kilometres. In Algeria, French helicopter transports that could insert troops into contested ground helped give birth to the modern tactics of airmobile warfare. In Vietnam it became the Marines' assault helicopter, and John Hax, who flew the UH-34D there with HMM-163 in 1965, remembered it as the last piston-engined military helicopter, a dinosaur whose one saving characteristic was reliability. Licence production in France, Great Britain and Italy carried the combined total past 2,300 aircraft.
Design Notes
Sikorsky developed the S-58 with company funds as a follow-on to the S-55; it was twice as powerful as the earlier helicopter and much more aerodynamic. A single Wright R-1820-84 Cyclone radial, rated at 1,525 hp for takeoff, sat inclined in the nose behind clamshell doors, its driveshaft rising behind the elevated cockpit to the main gearbox. The four-bladed main rotor was chosen because it produced lower blade loading than the S-55's three-blade rotor, so the blades could fly faster before stalling, and because it reduced vibration. Passenger cabin, fuel cells and cargo hook were stacked below the main rotor, a layout intended to make the helicopter insensitive to changes in center of gravity. The tail-dragger gear greatly reduced the turning radius on deck, and a manually folded main rotor and folding pylon let the helicopter fit aircraft carrier elevators. For the Navy's Seabat versions, dipping sonar paired with automatic stabilization equipment let a crew hold a hover over the sonar transducer at night and in low visibility, which the Sikorsky Historical Archives calls a giant step forward for anti-submarine warfare.
Operational History
Sikorsky received a Navy contract in June 1952 for four XHSS-1 prototypes, and test pilot Jimmy Viner flew the first of them on 8 March 1954. The production Seabat entered Navy service in August 1955, and the Navy ultimately received 385 Sikorsky Seabats. The Army took delivery of its first Choctaws in March 1955 and ultimately received 437 of them through 1965. A civil version was FAA-certified in August 1956, and airlines including Chicago Helicopter Airways, New York Airways and Sabena flew a 12-passenger configuration on scheduled services. The Marines began receiving their Seahorses in February 1957, some 600 in all, and the type became the Marine Corps' first armed and armored assault helicopter. France assembled its first H-34s from parts supplied by Sikorsky, then Sud-Aviation built a further 166 under licence for the French Navy and Air Force. In the Algerian War, French Air Force H-34s flew over 87,000 hours and helped evacuate more than 20,000 French soldiers, nearly 2,200 of them at night. Operation Shufly first sent Marine UH-34Ds to South Vietnam with HMM-362 in 1962. In Vietnam the Marines used the H-34 as a combat assault and transport helicopter and for medical evacuation, and trialled it as a gunship with the TK-1 kit of two M60C machine guns and two rocket pods. Reactions to the armed H-34s, nicknamed Stingers, were mixed, and they were soon replaced, though the kit informed the later TK-2 arming of the Marines' UH-1Es. South Vietnam's air force flew the H-34 as its primary helicopter until the UH-1 Huey replaced it. Sikorsky's Stratford plant made S-58s for the Navy, Marine Corps, Army and export customers until 1970, closing the piston-engined production run.
Afterlife
The Marines flew their last UH-34 on 3 September 1973, when Bureau Number 147191 was flown from Quantico to MCAS New River to be placed on static display. Air Force Reserve units flew 32 retired Navy Seabats as HH-34J rescue helicopters from 1971 to 1974, awaiting turbine-engined replacements. From 1970, Sikorsky remanufactured S-58s to the turbine-powered S-58T standard, and in 1981 the type certificate and support passed to California Helicopter International. The British derivative outlived the parent type in front-line service: Westland's turbine-powered Wessex, developed on the S-58 airframe, remained in RAF service until January 2003. Civilian H-34s long outlasted the military fleets: many retirees passed through storage at Davis-Monthan Air Force Base, while others went to work in civil transport and external cargo lift. The type remains in limited civil use today, and some aircraft have been restored and flown as warbirds. Many more are preserved statically, among them a UH-34D on display at the National Museum of the Marine Corps in Triangle, Virginia.