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 Russky Vityaz was crushed by an engine that fell off a single-seat Morane aircraft during a landing. Sikorsky decided not to repair the seriously damaged Russky Vityaz and began working on his next brainchild — the Ilya Muromets. Sikorsky Russky Vityaz The Sikorsky Russky Vityaz (), or Russian Knight, previously known as the Bolshoi Baltisky () "(The Great Baltic)" in its first four-engined version, was the first four-engine aircraft in the world, designed by Igor Sikorsky and built at the Russian Baltic Railroad Car Works ("Russo-Baltiiskyi Vagonnyi Zavod" or "R-BVZ") in Saint Petersburg in early 1913. Sikorsky conceived the S-21 design in