Performance measurements of a soaring bird

Abstract

The history of aviation is intimately connected with the bird flight studies of early researchers.  Early efforts in bird flight research were confined to a close observation of the birds. There is no doubt that an understanding of soaring flight should precede attempts at understanding the more complicated flapping flight. Soaring enthusiasts might have profited considerably in their development of the art and science of soaring flight had they maintained a closer liaison with the bird flight students. The present study began in 1945 with an experiment in which a bird was trained by Mr. George F. Carter to carry a miniature barograph and recording anemometer. It was hoped to measure the performance of the bird as it glided between upcurrents.  Further, with a research sailplane it will be possible to accurately investigate the flight of birds near their stalling lift coefficient. This paper is intended to show how powerful a research tool the sailplane becomes when applied to bird flight studies. The results reported while precise as measurements to +/- 5 % may not be truly representative of the static aerodynamics of the bird. It may after all be extracting energy from the atmospheric turbulence. If it is found by measurements in still air that a good portion of the energy for the bird's flight comes from this source then it will have been established that dynamic soaring is really practiced by birds and that man must learn from them the mechanism.