On 8 Dec 41 Igor Sikorsky flew definitive version VS-300 helicopter. Incorporating predominant features used in modern helicopters-- collective pitch control with single main and tail rotors--was first helicopter in the world to incorporate them in a single airframe. VS-300 was company-financed helicopter for testing of various configurations such as single-rotor, 1-, 2-, and 3-blade main- and tail-rotor designs; 1- and 2- blade tail rotors; and 1- and 2-rotor longitudinal control designs. An outgrowth of 1939 appropriation ($300,000) under Dorsey Bill for research and development of rotary wing aircraft, XR-4 funded by government for $50,000. Additional $100,000 of United Aircraft Company money (parent of Vought-Sikorsky) added; development called VS-316. XR-4 design as originally proposed had 4 rotors--a main rotor and 2 laterally displaced horizontal control rotors for longitudinal control and a fourth rotor in the vertical plane for torque compensation and yaw or rudder action. Halfway into construction, VS-300 modified by removing 2 lateral control rotors, and cyclic pitch added to main rotor. Provided excellent lateral and longitudinal control (in VS-300), and VS-316 modified accordingly.