## 1 Introduction  
The essential prerequisites for advanced fighter aircraft are excellent aerodynamic performance, strong maneuverability, and favorable stealth performance. Currently, low-aspect-ratio tailless configurations are the focused research on future fighters, such as the Boeing F/A-XX program. This configuration employs a detached vortex pattern to generate the high lift required for take-off, landing, and high angle of attack maneuvering at low speed, and uses the attached flow pattern for efficient high-speed cruise [1]. The low-aspect-ratio wing retards the deterioration of longitudinal stability, increases the critical Mach number, and improves the drag divergence characteristics. Furthermore, the tailless configuration reduces the structural weight and improves the aerodynamic and stealth performance of the aircraft, and is of great significance in the design of fighter aircraft. So, low-aspect-ratio tailless configurations are potential for future fighter. However, owing to the absence of a traditional tail, longitudinal control of a low-aspect-ratio tailless configuration is a major issue. To deal with the issue, some technologies are applied in advanced fighters, such as all moving canard wings and thrust vectors, but there is little literature about the aerodynamic design of a low-aspect-ratio tailless configuration with consideration of longitudinal trimming. Besides, civil aircraft with tailless configurations also suffer the same issue [2]. During cruise, all control surfaces should be faired to avoid trim drag [3]. Therefore, for practical purposes, the aircraft should be trimmed at cruise. The early flying wing configuration utilized a swept wing and downloaded wingtip to attach static stability, wherein the wingtip acted as a horizontal tail [4]. However, this approach made the outer wing highly loaded, leading to local lift loss at the wing tip as it was prone to stall. In addition, the induced drag increased owing to the worsening spanwise lift distribution [5]. In recent years, there has been significant development in aerodynamic design and multidisciplinary optimization, and several new approaches have been proposed. Boeing developed the WingMOD to achieve the trim requirements of a blended-wing-body (BWB) configuration at cruise by designing a new transonic airfoil for the centerbody and adjusting the twist distribution [6], the centerbody leading-edge carving was incorporated into the airframe design, making the configuration trimmed and statically stable without the need to download another part of the aircraft. In addition, the outer wing was optimized to improve aerodynamic efficiency without the constraint of the pitching moment, which enabled effective trimming with proper airframe design [7]. Subsequently, the design idea that the cruise point, maximum lift-to-drag ratio point, and pitch trim point should lie along the same flight attitude, was firstly put forward for BWB aerodynamic design [8]. Based on this idea, numerous practical aircraft were designed by optimizing the planform and airfoil design [2; 8; 9]. Although there has been significant research on the aerodynamic design of a tailless configuration with trim constraints, most studies focus on the tailless configuration with high-aspect ratio. Consequently, research on the aerodynamic design of a low-aspect-ratio tailless configuration with trim constraints is lacking. For a low-aspect-ratio tailless configuration, the constraints should include not only the requirement for aerodynamics and structure, such as lift-to-drag ratio, pitching trim, and loading, but also the requirement for Radar stealth, which is mainly decided by the planform shape of the configuration [10]. This study focuses on the aerodynamic design of a low-aspect-ratio tailless configuration based on the principle [8] for tailless configuration that the zero-pitching moment, cruising design lift coefficient, and maximum lift-to-drag ratio are coincident. The study of this paper is organized as follows: Section 2 verifies the numerical method.