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
Sikorsky S-3 early in December. The S-3 made its last flight on December 13, 1910 when at an altitude of 90 feet the engines distributor shifted to a retarded position and lost power. The aircraft landed hard on a frozen pond, broke through the ice and sank causing serious damage. The S-3 was salvaged and some parts including the engine were used in the construction of the S-4. Sikorsky S-3 The Sikorsky S-3 was an early Russian single seat biplane design by Igor Sikorsky. Work on the machine started in July 1910 and was completed in late November. The S-3 was a