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 VS-44 Sikorsky VS-44 The Sikorsky VS-44 was a large four-engined flying boat built in the United States in the early 1940s by Sikorsky Aircraft. The VS-44 was designed primarily for the transatlantic passenger market, with a capacity of 40+ passengers. Three units were produced: "Excalibur", "Excambian", and "Exeter". In the early 1930s, the primary mode of long-distance air travel over oceans was in flying boats, due to the ease of constructing docking facilities on shore without having to construct runways, and the possibility of malfunction forcing a sea landing. One flying boat designer was Russian immigrant Igor Sikorsky who had founded