Helicopters in the USAF
Historically, man based his early efforts to fly primarily on rotary-wing aircraft. However, he used a fixed-wing aircraft for his first successful flight, that of Orville Wright at Kitty Hawk. Although aviation made marked advancements in fixed-wing aircraft in the decades following the Wright brothers first flight, another 35 years passed before the demonstration of a practical, successful flight with a helicopter.
The U.S. Army first became interested in rotary-wing aircraft in 1918 when the Air Service investigated the Peter Cooper Hewitt helicopter design. Although the Army never contracted for a flying model, Hewitt demonstrated his long-term interest in aeronautics by constructing a helicopter. While this craft demonstrated vertical lift-off, the helicopter proved to be unstable and difficult to control. Several other inventors had the same problems in obtaining a controllable aircraft and the Army never ordered any designs.
It took another 13 years before the Kellett Autogyro Corporation produced the first Air Corps helicopter, the YG-1 (which was an autogyro). The Air Corps conducted service trails of the YG-1 but never ordered any production models.
In 1937 the Focke-Achaelis helicopter remained in flight for more than one hour, successfully demonstrating practical flight capabilities. Spurred by this German success, the Congress passed the Dorsey Bill in 1938, which appropriated $2 million dollars for rotary-wing aircraft development. The Platt-Lepage Aircraft Company produced an experimental counter-rotating, twin-rotor helicopter that the Air Corps designated the XR-1. While the XR-1 flew successfully in July 1940, the Army only bought one experimental model.
In 1941 the Air Corps awarded Igor Sikorsky a contract for one experimental single-rotor helicopter. This helicopter, the XR-4, emerged from the status of experimental development to that of a full-fledged flying craft. On May 1942, the XR-4 completed a flight from Stratford, Connecticut, to Dayton, Ohio, a distance of 761 miles. The R-4 became the first full-production helicopter for the U.S. Army Air Forces (USAAF). It had a 180-hp engine with the top speed of 75 mph and a range of 130 miles. In 1943 it underwent rigorous trails under arctic conditions in Alaska and hot, humid weather in Burma. Ultimately the USAAF took delivery of a total of 132 R-4 helicopters.R4