HO2S-1

The Sikorsky HO2S‑1 was the United States Navy’s first production amphibious helicopter, entering service in 1946 as the naval version of Sikorsky’s civilian S‑51. Developed in the immediate post‑World War II era, the HO2S‑1 demonstrated that rotary‑wing aircraft could operate from sea as readily as from land, a concept that reshaped naval aviation doctrine. Powered by a 1,050‑horse‑power Pratt & Whitney R‑985 radial engine, the machine featured a single main rotor, a co‑axial tail rotor, and a watertight, boat‑shaped hull that allowed it to land on and take off from open water. Its modest performance—maximum speed around 97 knots, range of roughly 210 nautical miles, and capacity for a pilot plus three to four passengers—was enough to fulfill a diverse set of missions, including rescue and personnel transport, anti‑submarine patrol, and aerial observation. The HO2S‑1’s rugged design, interchangeable undercarriage and floats, and its reliable powerplant earned a reputation for durability in harsh maritime environments. By proving the practicality of ship‑borne helicopter operations, the HO2S‑1 paved the way for later naval rotorcraft such as the H‑19 Chickasaw and the iconic SH‑3 Sea King, cementing Sikorsky’s role as a pioneering force in aviation history.