This paper examines a number of the methods available for producing high lift as required by today's STOL aircraft and compares these methods on the basis of maximum lift coefficient.
Most of the efforts to generate additional lift are directed toward providing favorable conditions for the boundary layer to prevent flow separation or to increase the projected wing area. Ideally a high lift system should make maximum use of both of these possibilities.
High lift coefficients are well within the current state-of-the-art and have been so demonstrated by numbers of research aircraft. However, the resulting problems of control criteria and handling qualities requirements still present an obstacle to the increased utilization of high lift systems.