Three-dimensional, Unsteady-lift Problems in High-speed Flight Basic Concepts

The problem of the build-u of lift on two- and three-dimensional wings flying at high speeds is discussed as a boundary-value problem for the classical wave equation. Kirchhoff's formula is applied so that the analysis is reduced, just as in the steady state, to an investigation of sources and doublets. Some simple applications of this method are considered, including the determination of the starting lift of a three-dimensional wing and the potential functions for some types of unsteady vortex motion.