Bird flight and airplane flight

Research was based on a series of mechanical, electrical, and cinematographic instruments developed to measure various features of air current behavior as well as bird and airplane flight. Investigation of rising obstruction and thermal currents led to a theory of bird flight, especially of the gliding and soaring types. It was shown how a knowledge of bird flight can be applied to glider and ultimately motorized aircraft construction. The instruments and methods used in studying stress in airplanes and in comparing the lift to drag ratios of airplanes and birds are described.