Sikorsky Aircraft Corporation
HO4S-1
The Sikorsky HO4S‑1 was an early single‑engine, single‑rotor utility helicopter developed by Sikorsky Aircraft Corporation in the mid‑1940s to meet the United States Navy’s need for a versatile ship‑borne observation and rescue platform. Originating from the successful R‑4 series, the HO4S‑1 incorporated a more powerful 250‑hp Franklin engine, a larger three‑bladed main rotor, and an enlarged cabin that could accommodate two crew members and up to 250 lb of cargo or a stretcher patient. First flown in 1945, the type entered limited service in 1946, operating from aircraft carriers, destroyer escorts, and shore stations. Its robust airframe and simplified controls made it well suited for operations in harsh maritime environments, while the optional pontoons enabled water landings for rescue missions. Although only a few dozen were built, the HO4S‑1 demonstrated the practicality of ship‑board helicopters and paved the way for more capable Sikorsky models such as the H‑19 Chickasaw. The aircraft’s contribution to naval aviation doctrine, particularly in search‑and‑rescue and anti‑submarine support, marked a turning point, establishing helicopters as indispensable assets in modern naval fleets.