Drag reduction on aircraft configurations with adaptive lifting surfaces

An approach, applicable to multiple-lifting-surface fixed-wing aircraft operating at subcritical Mach numbers, is presented for minimizing induced and profile drag with a constraint on the pitching moment. The approach allows the designer to select surface incidence, twist, and flap angles as variables for the optimization. The numerical formulation uses superposition to construct the spanwise lift distribution from basic and additional loadings, and decomposes the flap-angle distributions for each surface into mean and variation distributions. Together, these elements enable the solution of the problem using semi-analytical methods that also provide insight. Results are presented for a three surface aircraft which highlights low drag possibilities with positive static margins, presents the trade-offs between induced and profile drag, and provides insight into the aerodynamics of multiple lifting surface configurations.