This study proposes a system of systems (SoS) architecture of aircraft health management (AHM) to evaluate the cost-effectiveness of its introduction into aircraft maintenance of civil aviation. First, the SoS architecture is described to capture the interrelationship of the strategic capabilities required among the relevant stakeholders including manufacturer, airlines, and the regulatory authority by using the Unified Architecture Framework (UAF). Parameters to measure strategic capabilities and operational activities are identified, and those relationships are defined using parametric causal correlation using system dynamics approach. Then, the AHM performance, effect, and associated implementation costs are formulated and two patterns of AHM introduction are evaluated using the open operational data of Delta Air Lines. The results show that multiple AHM functions increase operational reliability, airline benefits and reduce the required number of mechanics.

Lightweight stiffened shells, such as lattice, sandwich, and skin-stringer structures, are widely employed in rocket design owing to their high buckling strength. Although weight minimization under buckling constraints has been extensively studied for each structural type, selecting the most efficient configuration among them remains a key design issue. This study performs a comparative optimization of various stiffened shell types to identify the lightest configuration satisfying the prescribed buckling requirement and to elucidate their structural characteristics. The buckling load, used as a constraint, is evaluated through the finite element method (FEM) to ensure both accuracy and computational efficiency. To further reduce the analysis cost, a surrogate model is constructed to approximate the buckling load based on sampled design variables and FEM results. The model is iteratively refined using the Expected Feasibility (EF) function as an infill criterion to enhance prediction accuracy. The discrepancy between the FEM-calculated and surrogate-predicted buckling loads at the optimal solution was kept below 1%, confirming the reliability of the proposed approach. Among the examined structures, the sandwich configuration exhibited the lowest structural weight.

This study proposes an efficient structural analysis approach for lattice structures composed of various types of unit cells by applying reduction techniques at the unit-cell level. Three analytical models---the full model, the statically reduced model, and the dynamically reduced model---were compared to evaluate computational efficiency and analytical accuracy. Through static deformation and natural frequency analyses, the statically reduced model was found to maintain accuracy equivalent to that of the full model while significantly improving computational efficiency. Furthermore, a multi-objective optimization using the NSGA-II algorithm was conducted to maximize specific bending stiffness and minimize specific torsional stiffness, and the applicability of the reduction techniques to the optimization was investigated. The results showed that the statically reduced model reproduced the optimization trends of the full model and achieved a substantial improvement in computational efficiency. These results indicates that the proposed method provides an efficient analytical approach that contributes to lattice structure design and optimization.