A control augmentation system for high aspect ratio aircraft has aileron/flaperon and throttle position sensors; spoiler and flap controls; a mode switch with manual, and landing modes; and a controller driving left and right spoiler and flap servos, the controller including at least one processor with memory containing firmware configured to: when the mode switch is in manual mode, drive both spoiler servos to a symmetrical position according to the spoiler control; when the mode switch is in landing mode, drive the left spoiler to a position dependent on aileron and throttle position, and the right spoiler to a position dependent on aileron and throttle position, the left and right spoiler positions differing whenever ailerons are not centered, and an average of spoiler positions is more fully deployed when the throttle position is at a low-power setting than when the throttle position is at a high-power setting.