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-35 Sikorsky S-35 The Sikorsky S-35 was an American twin-engined sesquiplane transport later modified to use three-engines. It was designed and built by the Sikorsky Manufacturing Company for an attempt by Rene Fonck on a non-stop Atlantic crossing for the Orteig Prize. It was destroyed in the attempt. The S-35 was designed as a twin-engined transport with a range. During 1926 Rene Fonck, a French First World War fighter ace, was looking for a multi-engine aircraft to enter a competition to be the first to fly non-stop from New York to Paris. The prize was $25,000, offered by Raymond Orteig. Fonck