Helicopter

A helicopter is an aircraft that is lifted and propelled by one or more horizontal rotors, each rotor consisting of two or more rotor blades. Helicopters are classified as rotorcraft or rotary-wing aircraft to distinguish them from fixed-wing aircraft because the helicopter derives its source of lift from the rotor blades rotating around a mast. The word 'helicopter' is adapted from the French hélicoptère, coined by Gustave de Ponton d'Amecourt in 1861. It is linked to the Greek words helix/helik- (ἕλικ-) = "spiral" or "turning" and pteron (πτερόν) = "wing".^[1][2]

As an aircraft, the primary advantages of the helicopter are due to the rotor blades that revolve through the air, providing lift without requiring the aircraft to move forward. This creates the ability for the helicopter to take off and land vertically without the need for runways. For this reason, helicopters are often used in congested or isolated areas where fixed-wing aircraft are not able to take off or land. The lift from the rotor also allows the helicopter to hover in one area and to do so more efficiently than other forms of vertical takeoff and landing (VTOL) aircraft, allowing it to accomplish tasks that fixed-wing aircraft are unable to perform.

Although helicopters were developed and built during the first half-century of flight, some even reaching limited production, it was not until 1942 that a helicopter designed by Igor Sikorsky reached full-scale production,^[3] with 131 aircraft built.^[4] Even though most previous designs used more than one main rotor, it was the single main rotor with antitorque tail rotor configuration of this design that would come to be recognized worldwide as the helicopter.

History

Since 400 AD, Chinese children have played with bamboo flying tops. This toy made its way to Europe and is depicted in a 1463 European painting.^[5] Pao Phu Tau (抱朴子) was a 4th-century book in China reported to describe some of the ideas inherent to rotary wing aircraft:^[6]

“

Someone asked the master about the principles of mounting to dangerous heights and traveling into the vast inane. The Master said, "Some have made flying cars with wood from the inner part of the jujube tree, using ox-leather [straps] fastened to returning blades so as to set the machine in motion."[7]

”

Leonardo da Vinci conceived a machine that could be described as an "aerial screw".^[8] He wrote that he made small flying models ^[9] but could not stop the rotor from making the whole craft rotate. Later machines would more closely resemble the ancient bamboo flying top, with spinning wings rather than screws.

In July 1754, Mikhail Lomonosov showed the Russian Academy of Sciences a small coaxial rotor powered by a wound-up spring, intended to lift meteorological instruments.^[9]

In 1783, Christian de Launoy, and his mechanic, Bienvenu, made a model pair of counter-rotating rotors (not coaxial) using turkey's flight feathers as rotor blades, and in 1784 demonstrated it to the French Academy of Sciences.^[9]

In 1861, the word "helicopter" was coined by Gustave de Ponton d'Amécourt,^[9] a French inventor who demonstrated a small steam-powered model.

From 1860 to 1880, many small helicopter models were designed and made.^[9] These included Alphonse Pénaud's model coaxial rotors, powered by twisted rubber bands (1870). Enrico Forlanini's unmanned helicopter was powered by a steam engine. It was the first of its type that rose to a height of 13 meters, where it remained for some 20 seconds, after a vertical take-off from a park in Milan (1877). Emmanuel Dieuaide's design featured counter-rotating rotors and was steam-powered through a hose from a boiler on the ground (1877). Melikoff designed a "man carrier," but it was almost certainly not built (1877). Dandrieux's design had counter-rotating rotors and a 7.7-pound (3.5-kilogram) steam engine. It rose more than 40 feet (12 m) and flew for 20 seconds (circa 1878).

In the 1880s, Thomas Edison experimented with small helicopter models in the USA. First he used a guncotton-powered engine, but it caused damage by explosions, and tests were ended. Next he used an electric motor. His tests showed that a large rotor with low blade area was needed.

Ján Bahýľ, a Slovak inventor, developed a model helicopter powered by an internal combustion engine, that in 1901 reached a height of 0.5 meters. On 5 May 1905, his helicopter reached four meters in altitude and flew for over 1,500 meters.^[10]