In the spring of 1941 a prototype helicopter designed by Igor Sikorsky was performing well enough to warrant a contract being awarded to the Vought-Sikorsky division of United Aircraft for the development of a two-seat version, designated the XR-4. XR-4 retained the single rotor of the VS-300 but had a covered fuselage, side-by-side seating and dual controls. The flying controls in the XR4 set the standard for all subsequent helicopters. The XR4 was re-engined in 1943 and called XR4C. Service trials with the YR-4A and YR-4B, including one from a tanker, resulted in the final variant, the R-4B.
The first flight of the new helicopter was made in January 1942, and 130 production examples were soon produced. The R-4 recorded two firsts: it accomplished the first helicopter landing aboard a ship, and the first rescue by a helicopter (April 23, 1944 in Burma - one YR-4 of new Air Commandos evacuated 4 persons from aircraft L-1, which crashed over Japan teritory - first helicopter´s combat engaging).
Twenty-five R-4s (under the designation HNS-1) were operated by the U.S. Navy and U.S.
Coast Guard, and 52 R-4s were operated by the British (under the designation Hoverfly I).
This aircraft was the first helicopter produced for the US Air Force, and the world's
first mass-produced helicopter. Four (probably) prototypes used Air Commandos in
|Primary function||Two-seat training and rescue helicopter|
|Manufacturer||Sikorsky Aircraft Division of United Aircraft Corporation|
|Powerplant||One Warner R-550 7-cylinder, fan-cooled, radial engine|
|Thrust||200 HP||149 kW|
|Length||35 ft 5 in||10.8 m|
|Height||12 ft 5 in||3.78 m|
|Weight||empty||2,020 lb||916 kg|
|max.||2,535 lb||1,150 kg|
|Speed||max.||81 mph||131 km/h|
|cruising||65 mph||104 km/h|
|Rate of climb||650 ft||198 m/min|
|Ceiling||8,000 ft||2,440 m|
|Range||230 miles||370 km|
|First flight||January 1942|
Source: David Hanson´s American Aircraft of World War II