Monocopter

A monocopter or gyropter is a rotorcraft that uses a single rotating blade. The concept is similar to the whirling helicopter seeds that fall from some trees. The name gyropter is sometimes applied to monocopters in which the entire aircraft rotates about its center of mass as it flies. The name "monocopter" has also been applied to the personal jet pack constructed by Andreas Petzoldt.

The Gyroptère was designed in 1913–1914 by Alphonse Papin and Didier Rouilly in France, inspired by a maple seed. Papin and Rouilly obtained French patents 440,593 and 440,594 for their invention, and later obtained US patent 1,133,660 in 1915. The Gyroptère was characterized in the contemporary French journal La Nature in 1914 as "un boomerang géant" (a giant boomerang).

Papin and Rouilly's "Gyroptère" weighed 500 kg (1,100 lb) including the float on which it was mounted. It had a single hollow blade with an area of 12 square metres (130 sq ft), counterweighted by a fan driven by an 80 hp Le Rhone rotary engine spinning at 1,200 rpm, which produced an output of just over 7 cubic metres (250 cu ft) of air per second. The fan also propelled air through the hollow blade, from which it escaped through an L-shaped tube at a speed of 100 m/s (330 ft/s). Directional control was to be achieved by means of a small auxiliary tube through which some of the air was driven and which could be directed in whatever direction the pilot wished. The pilot's position was located at the centre of gravity between the blade and the fan.

Testing was delayed due to the outbreak of World War I and did not take place until 31 March 1915 on Lake Cercey on the Côte-d'Or. Due to the difficulty of balancing the craft, a rotor speed of only 47 rpm was achieved instead of the 60 rpm which had been calculated as necessary for takeoff. In addition, the rotary engine used was not powerful enough; it had originally been planned to use a 100 hp car engine, which proved unobtainable. Unfortunately, the aircraft became unstable and the pilot had to abandon it, after which it sank.

The Bölkow Bo 103 was an ultralight helicopter designed for reconnaissance and command-control purposes and constructed by Bölkow Entwicklungen KG in 1961 as part of a research order by the German Federal Ministry of Defense. It had a 6.66 m (21.9 ft) diameter monoblade rotor constructed of GRP in a single piece that incorporated its counterweight. A single prototype was built, but work was stopped in 1962 due to lack of interest on the part of the West German armed forces.

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