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 XP2S Sikorsky XP2S The Sikorsky XP2S was an American biplane patrol flying boat developed for the United States Navy during the early 1930s. After selling a small quantity of PS / RS patrol / transport amphibians to the Navy, Sikorsky (then a division of United Aircraft Corporation) endeavoured to interest the service in a patrol flying boat. Having received a development contract in mid-1930, Sikorsky delivered a complete aircraft for testing in June 1932. The XP2S-1, as the prototype was designated, was a two-bay, equal-span biplane of mixed construction. Its two R-1340 Wasp radial engines were mounted in a single nacelle