A DoE-based scalable approach for the preliminary structural design of box-wing aircraft from regional to medium range categories

The present paper describes a Design-of-Experiment-based surrogate structural design approach conceived to deal with the sizing of the main structural components of unconventional lifting system, namely the box-wing. Such design method, based on the definition of metamodels for the evaluation of wing mass, stress and deflections, has been developed in order to comply with aircraft of different sizes, ranging from regional to short-medium range class. The aim is to develop a fast and reliable structural sizing model useful since the early stages of the aircraft design process. The model is specifically developed for an unconventional lifting system, the box-wing, for which no statistical or semi-empirical models and predictions are available to be used in conceptual design. The paper describes this approach by addressing all the main features of the developed structural sizing procedure. First, a set of variables, related to the wingbox structural components, is defined to parametrize the problem; by properly varying and combining these variables, a FEM-based Design-of-Experiment database is built. Then, the mathematical technique defining the surrogate model is described; specific scaling functions are defined to take the aircraft size variations into account. Finally, the accuracy of the proposed method is assessed by comparing the results of different box-wing structural solutions sized with both the DoE-based surrogate and the FEM analysis; the comparisons provided a good accuracy for the surrogate model, with a maximum error regarding the structural mass estimation below 4%.