Sikorsky R4 - the world's first production helicopter
The idea of the helicopter has been around since Leonardo da Vinci drew his famous airscrew machine in 1480, but it wasn't until the Second World War that the first production helicopter went into military service with the US Navy. Designed by legendary Russian American aviation pioneer Igor Sikorsky, the R4 (or 'Hoverfly' in the UK) was part of a sequence of Sikorsky aircraft that emerged from earlier test models - notably the VS-300 - that were recognisably of the single main rotor with anti-torque tail rotor configuration. In 1943 the R4 was to become the most important forerunner of all civil and military rotary wing aircraft now flying around the world.
According to the Smithsonian National Space and Air Museum, the R4 led the way for the large-scale introduction of more advanced rotorcraft into military and civilian service, while representing the culmination of Sikorsky's endeavours to create a practical helicopter.
Although its effect on the war was marginal, the aircraft helped to formalise training procedures that were to become standard in rotary winged operations the world over. The main advantages of helicopters were vertical take-off and landing, the ability to hover for extended periods and good handling characteristics at low speeds. This made them ideal for transportation, search and rescue and fire-fighting - areas to which most fixed-wing aircraft are unsuited.
As with most modern helicopters the R4 has a single main rotor, which in its early design phases created the biggest challenge facing Sikorsky: that of counteracting the torque created by the main rotor mounted horizontally on top of the aircraft. To do this, he built in a smaller single anti-torque rotor mounted vertically at the tail (although he had experimented with as many as three tail rotors simultaneously mounted at various angles). As well as countering torque, the rear rotor allowed the pilot to pivot the aircraft using foot controls. Despite the idea of anti-torque rotors having been in existence since 1912, and despite the fact that in the 1930s many aviation commentators thought the idea unworkable, the rotor format of the R4 has become a standard.
The R4 was first used in combat in May 1944. In a letter to a friend, Colonel Philip G Cochran, commanding officer of the 1st Air Commando Group, wrote: "Today the 'egg-beater' went into action and the damn thing acted like it had good sense." The 'egg-beater' was used primarily for rescue in harsh terrains such as Burma and Alaska. Total production reached 131 units before the R4 was replaced by other Sikorsky models such as the R5 and the R6. A total of 400 Sikorsky helicopters were used during the war.
Although Sikorsky is not generally credited with inventing any new solutions to the problems of controlling a helicopter in flight, he is regarded as the person who improved and made the helicopter practical and successful.
As for the man himself, although his name is often linked to the invention of the helicopter this was an accolade he was always careful to deny. That honour arguably goes to a French inventor called Gustave de Ponton d'Am'court, who demonstrated a small, steam-powered model as far back at the 18th century. Other contenders include the Breguet brothers' 1907 Gyroplane and in the same year an eponymous counter-rotating aircraft by Paul Cornu which was the first piloted helicopter.
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