The First Successful Helicopters

In 1936, a helicopter flown in Germany became the forerunner of the modern helicopter. The Focke-Achgelis FW-61

THE CONVERTIPLANE

A variation on the helicopter princi­ple is the convertiplane. This concept dates back to the autogiro of the 1920s. A convertiplane is capable of vertical takeoff and landing (VTOL) using rotary-wing flight, but then switches to normal layout for for­ward flight at speeds matching those of conventional airplanes. The idea was demonstrated in 1957 by the British Rotodyne, a helicopter-like airliner with wings and engines for normal flight. An example of a modern convertiplane is the tilt-wing CV-22 Osprey.

had two rotors mounted on outriggers (metal frames) on either side of the fuselage. This aircraft could take off and land vertically, it could hover, and it could fly at 76 miles per hour (122 kilo­meters per hour) during flights of over an hour in duration.

Igor Sikorsky, who had left Russia in 1919 and had become a U. S. citizen, was still busy working on ideas for heli­copters. In 1940, his new helicopter, the VS-300, made its first flight without being tethered to the ground. It was a

BELL HELICOPTERS

The Bell Aircraft Corporation was founded by American Lawrence Bell (1894-1956). The company made its name with airplanes, such as the record-breaking X-1, but became equally famous for helicopters, start­ing with the Bell Model 47 (1945). This small, bubble-nosed whirlybird stayed in production until 1973 and was used by armed forces all over the world. Its original piston engine gave the Model 47 a top speed of 105 miles per hour (169 kilometers per hour).

small, single-seat machine with a single rotor. The VS-300 was followed in 1942 by the XR-4, the first military helicopter to be put into production. A small number of XR-4s were flown by Allied forces during World War II (1939-1945). In 1943, an XR-4 became the first heli­copter to take off from a ship.