A novel yaw control method for flying-wing aircraft in low speed regime

The innovative control effectors (ICEs) such as split drag rudder (SDR) or spoiler slot deflector (SSD) have been proved useful for the directional control of flying-wing aircraft. As opposed to the traditional rudder, the yaw control moment produced by a SDR is non-linear with respect to its deflection. The control reversal phenomenon arises at higher angle-of-attack in the low speed regime, causing unwanted directional oscillations. Such a behavior may lead to flight accident while landing or take-off. The aerodynamic efficiency of the SDR is investigated for a miniature flying-wing aircraft (XQ-6B) using computational fluid dynamics (CFD) approach. The classical unilateral SDR operating mode and the biased-differential SDR operating mode are presented and discussed. A novel control strategy based on the angle-of-attack feedback for the biased-differential deflection is proposed and verified in nonlinear numerical simulation. The results show that the non-linearity and control reversal problems present in the behavior of SDR can be alleviated with this scheme. Finally, the results obtained by testing the proposed technique in real low speed flight are presented in order to validate the improvements in the yaw control capability of SDR.