Evaluating Longitudinal Stability-and-Control Characteristics in Hybrid Wing–Body Conceptual Design

At the conceptual phase, the tail volume ratio method is traditionally employed to initially size the empennage of tube-and-wing aircraft. Such a method is no longer applicable to certain hybrid wing–body (HWB) configurations, where the use of elevons and the absence of a horizontal stabilizer yield strong coupling between mass properties, aerodynamics, and stability-and-control (S&C) characteristics, which requires explicit assessment at the conceptual stage. Additionally, the lack of historical data for HWB calls for a physics-based approach to quantify the aircraft S&C characteristics. In this paper, an initial attempt to enforce the static margin constraint renders the entire HWB planform design space infeasible, indicating that it may overconstrain the HWB design space. To address the limitation, given that stability augmentation systems have been widely used in statically unstable military aircraft, this paper presents a novel approach to facilitate the assessment of S&C characteristics during conceptual design space exploration, where a physics-based S&C analysis module is integrated into a conceptual design environment. Trimmability, stability, controllability, and stabilizability constraints are identified and examined within the design space alongside the static stability constraint. A constrained optimization is performed to highlight the impact of accounting for S&C constraints on vehicle sizing.