Sikorsky Aircraft Corporation
HO4S-3
The HO4S-3 is a variant of Sikorsky’s early helicopter series, developed in the late 1940s as the fourth production model of the H-19 Chickasaw family. First flown in 1949, the HO4S-3 entered service with the United States Air Force and Navy, where it fulfilled transport, rescue, and liaison duties during the early Cold War. Powered by a single 600‑horsepower Pratt & Whitney R-1340-40W radial engine, the machine could lift up to 2,600 pounds and carry up to ten troops or a comparable cargo load. Its three‑bladed main rotor, enclosed fuselage, and fully articulated controls gave it superior stability and ease of handling compared with contemporary piston‑engine helicopters. The aircraft featured a spacious cabin with wide side doors, a rear loading ramp, and optional amphibious floats for maritime operations. The HO4S-3’s reliability and versatility made it a workhorse in polar expeditions, humanitarian missions, and the Korean War, establishing a template for later utility helicopters. By demonstrating that a single‑engine rotorcraft could operate in harsh environments and perform multiple roles, the HO4S-3 helped cement Sikorsky’s reputation as a leader in vertical‑flight technology.