Novel Surrogate-Assisted Structural Optimization Framework for Full-Aircraft Configurations

Designing lighter aircraft structures while satisfying strength, stability, and aeroelastic requirements remains a central challenge in preliminary aircraft design. Many early-stage aircraft structural optimization studies rely on beam, equivalent-plate, or semi-empirical structural representations, while many higher-fidelity studies focus on isolated components, particularly wings, rather than the simultaneous sizing of the wing, fuselage, and tail within a unified structural model. The present study addresses this gap by introducing a surrogate-assisted structural optimization framework for complete aircraft configurations. The framework is built around a fully parametric shell/beam-based finite element model of a representative long-range transport aircraft configuration with a high-aspect-ratio wing, coupled to aerodynamic loads computed using the subsonic source and doublet panel method. The proposed framework allows simultaneous sizing of the wing, fuselage, and tail under static strength, global buckling, and flutter constraints, while retaining a computational cost suitable for preliminary design studies. The optimization results are assessed through three independent surrogate-assisted optimization runs initialized from different sampling distributions and compared to a derivative-free optimization solver using the same computational budget. The independent runs identify feasible low-mass configurations with consistent convergence trends. The optimized design gives a full-aircraft modeled mass of 230.48 t, which remains below the reference maximum takeoff mass of 268 t and is consistent with the expected mass scale of representative long-range transport aircraft. Overall, the proposed framework provides a practical preliminary-design tool for exploring feasible full-aircraft structural layouts, identifying dominant load paths and active constraints, and generating candidate designs for subsequent higher-fidelity aeroelastic and certification-level refinement.