Sikorsky HO3S

The Sikorsky HO3S first flew in 1946. It employed a Pratt & Whitney R-985-AN-5 radial piston engine, had a top speed of ~105 mph (169 km/h), and a range of ~275 miles (443 km). The HO3S could carry 1–2 crew, and two stretchers.

The HO3S-1 was among the first to be regularly deployed on Navy ships, often from cruisers and battleships for rescue and utility missions.

It supported Marine landings and operated from amphibious assault ships, performing reconnaissance, casualty evacuation, and liaison missions.

It was one of the first helicopters to conduct combat medevac missions, using litters mounted externally or in the small cabin. The HO3S-1 was extensively used during the Korean War for Search and Rescue (SAR) missions, extracting downed pilots from enemy territory.

The HO3S was one of the earliest production helicopters to use a fully articulated main rotor, which significantly improved handling and paved the way for modern rotorcraft design.

The HO3S-1 also served as a primary trainer for Navy and Marine Corps helicopter pilots in the late 1940s and early 1950s.