Weight reduction of unmanned aircraft considering aerodynamic load uncertainties for reassessment of structural safety factors

• A probabilistic approach is proposed to evaluate uncertainties in the structural behavior of unmanned aircraft , enabling the reassessment of structural safety factors. • The study integrates Computational Fluid Dynamics (CFD) and Finite Element Method (FEM) analyses to model aerodynamic loads and structural responses under critical flight maneuvers. • The research demonstrates how to reduce the structural weight of unmanned aircraft while maintaining compliance with airworthiness certification standards, such as STANAG 4671. • A hybrid methodology combining deterministic and probabilistic methods is introduced, allowing section-specific adjustments to structural safety factors for optimized weight reduction. • The proposed method emphasizes post-design phase optimization, eliminating the need for new materials or design modifications, offering a practical and cost-efficient solution for existing aircraft models. This study introduces a novel method that applies a probabilistic approach to evaluate uncertainties and variabilities in the structural behavior of unmanned aircraft. With this method, the adjusted structural safety factor of the aircraft can be applied, allowing for the assessment and reinforcement of the structure while considering load uncertainties. Consequently, it reduces weight through reassessed structural safety factors while maintaining structural integrity. The load on the aircraft was derived from CFD and structural analysis simulations for the entire aircraft under critical flight maneuvers to consider physical uncertainties. Additionally, the loads obtained from each simulation were analyzed through reliability-based data analysis, and the probabilities of failure and failure rates in structural behavior were calculated. Also, the airworthiness certification regulation was considered concerning the failure rates of unmanned aircraft. Furthermore, this research proposes a new method to adjust unmanned aircraft's structural safety factors for weight reduction. The adjustment was performed on secondary structures, and then the integrity of the aircraft was examined using an integration of deterministic and probabilistic methods.