Abstract: Based on the platform of blended wing body tailless configuration, to solve the problem of decreasing pitching control efficiency at high angles of attack for basic longitudinal control surfaces including canard elevator and tail elevator, the new concept of lower surface spoiler is put forward and the effectiveness and auxiliary function for pitching control at high angles of attack is analyzed with numerical simulation method. The influences of the parameters such as lower surface spoiler's height, deflection angle, and relative position when combined with tail elevator are studied. The design law, flow mechanism and action principle to afford nose-down pitching moment increment are put forward. The results show that lower surface spoiler can support tailless configuration as a high-efficiency longitudinal control effecter. With the single use of lower surface spoiler, the maximal nose down pitching moment can be obtained to balance 10? angle of attack with little effect on lift and drag characteristics. When combined with the tail elevator, nose down moment increment of 6? angle of attack can be obtained with the angles of attack smaller than 32? and favorable effect on lift-drag performance is produced. The longitudinal control ability at high angles of attack is improved. The design developed in this paper can provide a reference for control surface design for blended wing body tailless configuration.

Key words: tailless configuration, lower surface spoiler, tail elevator, high angles of attack, longitudinal control