High Quality Content by WIKIPEDIA articles! The Sikorsky R-4 was a two-place helicopter designed by Igor Sikorsky with a single, three-bladed main rotor and powered by a radial engine. The R-4 was the world's first mass-produced helicopter and the first helicopter to enter service with the United States Army Air Forces, Navy, and Coast Guard, as well as for the United Kingdom's Royal Air Force and Royal Navy. The VS-316, was developed from the famous experimental VS-300 helicopter, invented by Igor Sikorsky and publicly demonstrated in 1940. The VS-316 was designated the XR-4, under the United States Army Air Forces' series for "Rotorcraft". The XR-4 made its initial flight on 13 January 1942 and was accepted by the Army on 30 May 1942. The XR-4 exceeded all the previous helicopter endurance, altitude and airspeed records that had been set before it.

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