On the maximization of control power in low-speed flight for a BWB configuration

Abstract

The maximization of control power is considered for an aircraft with multiple control surfaces, which may be decoupled or coupled; the force and moment coefficients are specified by polynomials of the control surface deflections, of any degree not less than two. The optimal deflections, which maximize and minimize any force or moment coefficient are determined subject to constraints on the range of deflection of each control surface. The results are applied to a flying wing configuration to determine: (i/ii) the pitch trim, at the lowest drag for the fastest climb, and at the highest drag for the steepest descent; (iii) the maximum and minimum pitching moment and the associated range of trimmed c.g. positions for several engine configurations; (iv) the maximum and minimum yaw control power and the fraction needed to compensate an outboard engine failure for several propulsion configurations; (v) the maximum and minimum rolling moment and the strongest wake vortex which can be compensated. The optimal case of all control surfaces has significant advantages over using just one, e.g., the range of drag modulation with pitch trim is much wider and the maximum and minimum available control moments larger.