466
P. Liu
Fig. 7.26 The flapping aircraft designed by Da Vinci
Fig. 7.27 American astronomer and flight pioneer Langley’s (Samuel Pierpont, 1834–
1906) glider
Vinci. George Kelly also conducted extensive research on bird flight, estimating the relationship between speed, wing area and lift by observing the
bird’s wing area, weight and speed. In his famous treatise “On Aerial Navigation” published in 1809, he put forward a very important conclusion, “The
man-made aircraft should consider the propulsion power and the lift surface
separately, and do not consider the trust and lift together”. This judgment
P. Liu
Fig. 7.26 The flapping aircraft designed by Da Vinci
Fig. 7.27 American astronomer and flight pioneer Langley’s (Samuel Pierpont, 1834–
1906) glider
Vinci. George Kelly also conducted extensive research on bird flight, estimating the relationship between speed, wing area and lift by observing the
bird’s wing area, weight and speed. In his famous treatise “On Aerial Navigation” published in 1809, he put forward a very important conclusion, “The
man-made aircraft should consider the propulsion power and the lift surface
separately, and do not consider the trust and lift together”. This judgment