Method for Improving the Natural Lateral-Directional Stability of Flying Wings

Poor lateral-directional flight quality is a critical technical problem in flying wing aircraft design. This paper proposes an approach to achieve lateral-directional dynamic stability of flying wing aircraft. This approach is different from general methods such as installing a wingtip vertical stabilizer or depending on a stability augmentation system. Through directly including the judgment of aircraft dynamic stability into the aerodynamic configuration design, sufficient lateral-directional stability can be guaranteed without relying on other systems. A lateral-directional dynamic stability satisfaction judgment function was built based on MIL-F-8785C. The lateral-directional dynamic stability was improved using only the adjustment of the spanwise dihedral layout. To validate the feasibility of this design method, this study selected a flying wing aircraft with a high aspect ratio as the object. Two optimized configurations with different aerodynamic shape but similar stability characters were finally obtained. Each configuration achieved flight quality which surpassed Level 2 requirements of MIL-F-8785C in the entire airspeed range.