ACCORDING to historical records the earliest known drawings for an aerial machine that can be classified under the heading of helicopter were made in the fifteenth century by the world renowned Italian scientist and artist Leonardo da Vinci (1452–1519). Probably the Chinese had been making their helicopter toy for some considerable time before da Vinci commenced his experiments. This toy consisted of two feathers, joined together by means of a cork or soft wood boss, to form a crude type of propeller which was pushed up a threaded stick so that upon leaving the stick the propeller rotated at high speed and continued to screw itself up in the air. When the speed of rotation decreased the propeller slowly windmilled down to the ground. A similar toy is still being sold today.
Hay ward, L.H. (1952), "A Review of Helicopter Patents: A Lecture Presented to the Members of The Helicopter Association of Great Britain on Friday, January 18, 1952", Aircraft Engineering and Aerospace Technology, Vol. 24 No. 4, pp. 92-105. https://doi.org/10.1108/eb032147Download as .RIS
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