V.

History of the Helicopter

Inventors and engineers perfected the design of the helicopter gradually, over many years. Original inspiration came from objects like an ancient Chinese top, which rose upward when spun rapidly. One of the earliest inventors to design a helicopter was Leonardo da Vinci. In one of his notebooks from 1480, he illustrated a model helicopter driven by a clockwork motor. His notes imply that the model flew, but, from his sketch, an antitorque device is not apparent.

One of the first mechanical devices actually to hover was the Bréguet-Richet Gyroplane No. 1, designed by French aircraft pioneer Louis Charles Bréguet. It first flew in France on September 29, 1907, piloted by one of Bréguet’s engineers. Lifted by four rotors 8 m (26 ft) in diameter, this fragile craft hovered about 0.6m (2 ft) off the ground for a minute while being restrained by four men holding on to the frame. Without a control system, it was far from being a practical helicopter, but it demonstrated that it was possible to lift a person vertically by means of powered rotors.

On November 13, 1907, Frenchman Paul Cornu became the first person in history to rise vertically in powered flight, completely unrestrained from any support. The Cornu helicopter used two rotors attached to each end of a skeletal frame and was powered by a 24-horsepower engine. Although Cornu achieved a historic first, the controls of his machine were completely inadequate, and the craft never developed into a practical helicopter.

Spanish engineer Juan de la Cierva paved the way for the development of a successful helicopter, but never built a helicopter himself. Cierva developed the autogiro, which resembles the helicopter but which uses an unpowered rotor. The rotor autorotates, or autogyrates, as the autogiro is pulled through the air by a separate propeller. The turning rotor provides lift much like an aircraft wing. In January 1923, Cierva successfully flew his C.4 autogiro, which incorporated articulated rotor blades. This allowed the blades to flap freely up and down in response to the unsteady aerodynamic forces that arise in forward flight. The articulated rotor was the technical breakthrough that led others to develop the successful helicopter. Cierva might have eventually done so himself, but he died in an airplane crash in December 1936.

Germany made rapid strides in helicopter development in the 1930s and 1940s. The FA-61, designed by Heinrich Focke, flew for the first time on June 26, 1936. The FA-61 was the first practical design for a maneuverable helicopter. In 1937, as a propaganda stunt for the Nazi regime, the renowned female pilot Hanna Reitsch flew the FA-61 inside the city of Berlin’s Deutschlandhalle sports arena. Another German helicopter, the FL-282 Kolibri, was used by the German navy during World War II (1939-1945). It could fly at 140 km/h (90 mph) and reach an altitude of 4,000 m (13,000 ft) with a payload of 360 kg (800 lb). It was the first helicopter design produced in quantity, but only a few became operational before the war ended.

Igor Sikorsky, a Russian-born American aeronautical engineer, flew the first successful single main rotor helicopter, the VS-300, in 1939. He flew the final version of his VS-300 helicopter in 1941. Unlike previous helicopter designs, the VS-300 was the first helicopter to use a tail rotor to counteract the torque of the main rotor. This represented a major accomplishment that has been copied by the majority of helicopter designs built since. Sikorsky’s research and development of the VS-300 led to the R4, the first American helicopter built in large quantities.

During the 1990s, aeronautical engineers applied radar-evading stealth technology to the design of certain military helicopters (see Stealth Aircraft). The first helicopter to incorporate this technology was the U.S. Army’s RAH-66 Comanche, developed jointly by the Boeing Company and Sikorsky Aircraft Corporation. The fuselage is shaped to reduce the helicopter’s visibility to enemy radar, and weapons are carried internally to further reduce the helicopter’s detection by radar. The Comanche is also designed to radiate less heat than other helicopters in order to evade infrared (heat-seeing) detectors.

See also Aviation; Military Aviation.