Sikorsky R-4 Sikorsky R-4 The Sikorsky R-4 is a two-seat 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 large-scale mass-produced helicopter and the first helicopter used by the United States Army Air Forces, the United States Navy, the United States Coast Guard and the United Kingdom's Royal Air Force and Royal Navy. In U.S. Navy and U.S. Coast Guard service, the helicopter was known as the Sikorsky HNS-1. In British service, it was known as the Hoverfly. The VS-316 was developed from the famous experimental VS-300 helicopter,
Sikorsky S-28 was approved. The French ordered five examples and preparations were made to start construction, but the order was cancelled when World War I ended and no S-28s were completed. Sikorsky S-28 The Sikorsky S-28 was a proposed four engine biplane bomber aircraft designed by Igor Sikorsky to be built in France during World War I. Sikorsky moved to France in March 1918 and soon met with officers of the "Armée de l'Air" who asked him to design an aircraft capable of carrying a new 1,000 kg (2,200 lb) bomb. Although the aircraft was initially designed to be powered by two