1784: Model Helicopter with Twin Rotors

The French academician and naturalist Launoy in 1784 demonstrated to the French Academy a model helicopter based on the flying top and made by his mechanic colleague, Bienvenu. Though only a miniature, his helicopter performed in free flight and caused a sensation. At each end it had a rotor, each one bearing two blades of silk fabric on a wire frame. The rotors were spun in opposite directions by pulling on strings wound round them. Bienvenu had solved a problem that was to haunt designers of full-sized helicopters in 100 years' time - the problem of torque, that is the tendency for the machine's body to twist in the opposite direction to the blades.

Echoes of the Frenchmen's success reached England when George Cayley was a boy. He used their design as the basis of a model he made in 1796 when he was 23. He had adapted it by giving each rotor four blades. Each blade was a feather with a slight twist in it. Cayley saw clearly the central problem of the helicopter - that to fulfill its potential for taking off and landing vertically and for hovering, it had to produce enormous power in proportion to its engine weight.

1842: Steam for the Helicopter Is Not Enough

A colleague of Cayley's, W.H. Phillips, made a model helicopter in 1842 that demonstrated that the best engine then known, the steam-engine, could drive a helicopter through wing-tip jets. But despite its ingenuity, Phillips's steam boiler was too heavy. The Italian engineer Enrico Forlanini in 1877 produced a steam-engine weighing less than 8 lb to fly a model helicopter, but even this did not give enough power in relation to weight. Further advance had to wait until the petrol engine was fully developed.

1907: The First Manned Helicopters

In France Louis Breguet and Paul Cornu, both in 1907, succeeded in lifting a rotating-wing aircraft a couple of feet off the ground. Both machines were full size and powered by petrol engines. In each case the inventor was at the controls. Cornu was up for less than 30 seconds. Breguet's machine stayed up for about a minute but, with four rotors on outriggers, it was highly unstable and had to be held steady at the corners by helpers.

1919-1936: Cierva's Autogyro

The autogyro was to prove the key to solving the control and stability problems of rotating-wing flight. Juan de la Cierva, a Spaniard, sought safer flying through craft that would not stall even when the forward speed dropped. In 1919 he added a free-wheeling rotor to a standard aircraft with wings and a propeller. The rotor was not connected to the engine. It was the airflow caused by the aircraft's motion through the air that turned it. As the rotor turned in the airflow it gained lift. Once the craft was airborne, the rotor would continue turning in the airflow and giving lift; even with the engine switched off, the craft would make a slow but steep descent. This ability to turn by itself gave the machine the name autogyro.

In 1926 Cierva moved to Britain and in 1928 he piloted an autogyro from Croydon, near London, to Paris - the first Channel crossing by rotor craft - and in the 1930s 500 Cierva autogyros were built worldwide.

After Cierva's death in 1936, interest in rotor aircraft centred on the helicopter, but about 1960 Fairey Aviation and Wing Commander Ken Wallis in England took a new interest in autogyros. Wallis has made autogyros from 200 to 500 lb in weight.