Sikorsky Aircraft Corporation’s two-seat S-52, the first helicopter to have all-metal rotor blades, first flew on 12 February 1947. Sikorsky developed a four-seat model and gave it the more powerful Franklin 0-425-1 engine. This model was first accepted first by the Marine Corps. It received the designation HO5S-1. It was designated HO5S-1 by the U.S. Navy and Marine Corp; HO5S-1G by the Coast Guard; and YH-18A by the Army.
The H05S-1 served as the Marine Corps’ primary medical evacuation helicopter in the final year of the Korean War. Able to carry wounded on internally-mounted litters with an attendant, it was an improvement over other light utility helicopters that required the wounded to ride outside of the fuselage while exposed to harsh conditions. The H05S featured an opening front bubble for easy access, a rear-mounted engine configured to maximize internal carrying capacity and offset rotor blade flapping hinges to improve control and stability, which made it ideal for night flying. A total of 93 were built including four Army YH-18’s.
Rotor diameter: 10.1 m (33 ft)
Length: 9.1 m (29 ft 9 in)
Height: 2.6 m (8 ft 7 in)
Weight, empty: 802 kg (1,768 Ib)
Weight, gross: 1,225 kg (2,700 lb)
Top speed: 185 km/h (115 mph)
Engine: Aircooled Motors, 0425-1, 245 hp
Manufacturer: Sikorsky Aircraft Div., United Aircraft Corp., Bridgeport, Conn., 1952
The Connecticut Air & Space Center is currently restoring 2 Sikorsky HO5S. One belongs to the Space Center and the other is on loan from the National Museum of the Marine Corps.