Sikorsky R-4 end of the boom near the tail rotor while others had it positioned at the midpoint of the boom. Additionally, some had short "stub" exhaust pipes from the engine while others had a much longer one which extended vertically and then aft above the main landing gear struts. 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
Igor Sikorsky first flight on May 13, 1913. In recognition for his accomplishment, he was awarded an honorary degree in engineering from Saint Petersburg Polytechnical Institute in 1914. Sikorsky took the experience from building the Russky Vityaz to develop the S-22 "Ilya Muromets" airliner. Due to outbreak of World War I, he redesigned it as the world's first four-engined bomber, for which he was decorated with the Order of St. Vladimir. After World War I, Igor Sikorsky briefly became an engineer for the French forces in Russia, during the Russian Civil War. Seeing little opportunity for himself as an aircraft designer in