Development of a Wing Mass Estimation Method for a High-Aspect-Ratio Box-Wing Regional Aircraft

Computationally efficient and sufficiently accurate mass estimation methods are required for the design exploration of aircraft with nonconventional configurations at the conceptual design stage. This paper investigates a box-wing regional aircraft developed within the LuFo project DOXWING, characterized by high-aspect-ratio wings and small stagger, for which traditional semi-empirical equations are insufficient to accurately estimate the wing mass due to the high aspect ratio and closed-wing configuration. To successfully perform the sizing of the box-wing configuration while accounting for aeroelastic effects, an aero-structural analysis framework was used and refined by taking all six sectional force and moment resultants into account in the sizing methodology, and using a more comprehensive definition of load cases based on the top-level aircraft requirements to ensure a wider coverage of the flight envelope. Following the framework’s validation through a comparison of its analysis results with corresponding reference values for both conventional and unconventional aircraft configurations, a parametric study was carried out for the DOXWING aircraft, which is comparable in size to the ATR72-class aircraft, by varying the wingspan, wing area, and wing loading. A better understanding of how these design parameters affect the wing mass and aerodynamic performance will enable more meaningful analyses in the subsequent conceptual aircraft design processes. Finally, a weight-estimation-relationship (WER) equation for wing-mass estimation is derived from the results of the parametric study, while a surrogate model is introduced to further enhance the prediction accuracy in regions where the nonlinear interactions between design variables cannot be fully represented by the WER equation. The proposed framework achieves a mean absolute percentage error (MAPE) of 2.71% against reference wing masses from the literature, while the derived WER equation approximates sizing results for the DOXWING aircraft with 0.98% MAPE, supporting rapid conceptual design studies and showing that wing mass increases progressively with aspect ratio at fixed wing area and wing loading within the investigated design space.