Biophysics of Bird Flight^ 



By August Raspet 



[With 2 plates] 



There is no doubt that modern mechanical flight owes its inspiration 

 to observations of birds in flight by early philosophers and scientists 

 as well as by interested laymen. The earliest living "flying machine" 

 is dated about 150 million years ago. This was the pterodactyl of geo- 

 logic times. In contrast, manmade flying machines are only 57 years 

 old. You can see from this contrast of eras that we may look for new 

 knowledge of flight from a study of this age-old concept of bird flight. 



In Greek mj^hology, the story of Daedalus and Icarus is well 

 known. Daedalus designed and built, supposedly, two flying ma- 

 chines, covered with feathers, using a stnicture of wax t-o support 

 them. Tliis was really a mythical imitation of bird flight. There was 

 no application of real knowledge of the mechanism of bird flight, 

 merely an imitation, in form, but not in function. But, of course, not 

 having this knowledge, we, even today, cannot duplicate bird flight 

 in the sense of straight imitation on a scale such that a man can fly as 

 a bird does, by his own muscle power. 



The first known flying machine constructed on bird-flight concepts 

 was Da Vinci's well-known invention. About 1505, Da Vinci test- 

 flew this machine, using a test pilot, as is common practice today. 

 The results are indicated in Da Vinci's notebooks by the fact that after 

 this test flight there was no more mention of flying. There is rumor 

 that the test pilot broke his leg. The test pilot, in this case, was one 

 of Da Vinci's household servants (pi. 1) . 



It was Lilienthal [1]^ who also imitated bird flight, even to the point 

 of using such small stabilizing tail surfaces that his machme was only 

 marginally stable. But we must remember that it was also Lilienthal 

 who, by this bird imitation, proved Newton, Kirchhoff, and Helmholtz 

 to be wrong in their concept that lift is generated by a downward de- 



» Reprinted by permission from Science, vol. 132, No. 3421, July 22, 1960. 



'The author, at the time of his death on Apr. 27, 1960, was head of the Aerophyslcs 

 Department of the Engineering and Industrial Research Station, Mississippi State Uni- 

 versity, State College. 



• Numbers In brackets refer to list of references and notes at end of article. 



40.") 



