HO4S-3G

The Sikorsky HO4S‑3G is a commercial variant of the iconic S‑51 amphibious helicopter, produced by Sikorsky Aircraft Corporation in the early 1950s. Derived from the military HO4S (also known as the R‑4) that first flew in 1942, the HO4S‑3G incorporated a more powerful 450‑horse‑power Pratt & Whitney R‑985-AN-1 radial engine, an enlarged cabin, and reinforced rotor blades to improve lift capacity and stability on water. First delivered to civilian operators in 1951, the aircraft quickly became a workhorse for offshore oil exploration, coastal fire‑fighting, and passenger transport in regions lacking runway infrastructure. Its distinctive three‑bladed main rotor and boat‑shaped hull allowed seamless transition between land and sea, setting a standard for future amphibious rotorcraft. Over 200 units were built, and the model remained in service well into the 1970s, proving its durability and versatility. The HO4S‑3G’s blend of rugged simplicity, reliable power, and dual‑mission capability cemented its place in aviation history as a pioneering bridge between wartime rotorcraft technology and modern commercial helicopter operations. Today several surviving examples are displayed in aviation museums, where they serve as tangible reminders of the early era of amphibious helicopter innovation.

Sikorsky Aircraft Corporation

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