Why airplanes fly: The Strong Programme and the theory of lift

When the Wright brothers made their first controlled flight in 1903, no scientific theory could explain why their airplane should fly. In technical terms, the phenomena that needed explanation was lift, the upward vertical forces on an airplane in steady flight. Existing theories of fluid motion either predicted no lift at all or values for lift that were far lower than those achieved in practice. This scientific anomaly became an embarrassment after 1908, when the Wright brothers demonstrated their improved Flyer throughout Europe. With the Wrights’ demonstrations and Louis Bleriot’s 1909 flight across the English Channel, European militaries began investing heavily in aviation research and experimentation, highlighting the inadequacy of existing theories of lift. This is the ‘‘enigma of the airfoil’’ that Bloor seeks to explain in his book. To do so he gives his readers a detailed technical history of the development of airfoil theory, a central achievement of modern aerodynamics. But the enigma he seeks to explain goes beyond the theory of lift itself. Bloor also provides a careful comparative analysis of the two main schools of aerodynamic theory in the early 20th century, one British and the other German. The puzzle he examines here is well known in the history of aerodynamics, the British ‘‘failure’’ to embrace the circulation theory of lift pioneered by German-speaking academic engineers. As a founder of the Strong Programme in the sociology of scientific knowledge, Bloor rejects using social factors to explain only the British failure and not the German success. In doing so, he provides penetrating insights into different modes of reasoning involved in the application of mathematical theory to technological practice.