Leonardo's studies of the flight of birds and the manner in which the principles of flight might be adapted, naturally and artificially, for human purposes are rich in scientific observation and imaginative power. The fascination of these farranging investigations resides in the analogy that Leonardo sought to establish between humans and natural creatures: birds, insects, and bats. He spent many unfruitful years, during his first stay in Milan (1486-90) and his second period in Florence (1505), experimenting with a flying machine. The attempt to support and move the human body in the air failed because, in the absence of an internal combustion engine, Leonardo could not create mechanisms of propulsion capable of providing the necessary upward lift. Nevertheless, based on his understanding of air currents, pressure, and resistance, he came up with designs for machines that anticipated the modern glider, parachute, and helicopter. Related to these studies were notes concerning the cosmos, later developed by Galileo.



  

Leonardo da Vinci, Study of a Large Wing with Manoeuvrable Tips, Codice Atlantico, Biblioteca Ambrosiana, Milan.
Leonardo was convinced that man could achieve his objective of flight only by imitating the natural movements of birds and other winged animals.

Leonardo da Vinci, Drawings and Notes on the Illumination of the Sun,
the Earth and the Moon,
Leicester Codex, 1506-08,
Bill Gates Collection, Seattle.

Leonardo da Vinci, Helical Airscrew, c.1487,
Manuscript B, Institut de France, Paris.
The airscrew may be regarded as the ancestor of the modern helicopter. The plan, long pursued by Leonardo, for a flying machine that used only human muscular energy failed because he did not manage to find a system of propulsion that corresponded to the supporting strength of the wings.