Sikorsky R-4 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 States Coast Guard and the United Kingdom's Royal Air Force and Royal Navy. In U.S. Navy and U.S. Coast Guard service, the helicopter was known as the Sikorsky HNS-1. In British service, it was known as the Hoverfly. The VS-316 was developed from the famous experimental VS-300 helicopter,
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