## 5 Results
### First Level
In comparing aerodynamic coefficients for both take-off and landing configurations, with or without the morphing droop nose device, it has been observed that the use of a morphing leading-edge is necessary to respect the performance level required for the landing conditions, in terms of the maximum lift coefficient. The use of the morphing leading-edge increases the stall angle by approximately \(\Delta\alpha(C_{L,max})=+5 deg\) for the landing condition. The performance improvement, in terms of the lift coefficient, is \(\Delta C_{L,max}=+15\%\), while the drag coefficient variation \(\Delta C_{D}\) is negligible. In take-off conditions, the use of the morphing leading-edge increases significantly the stall margin \(\Delta\alpha(C_{L,max})=+2.5 deg\), and it leads to an increment of \(\Delta C_{L,max}=+10\%\) and a constant decrease of \(\Delta C_{D}=-5\%\) on the complete \(C_{L}\) range. Figure 8: Non-dimensional shape functions of undeformed (**a**) and morphing (**b**) wing geometries: colors indicate the values of the function \(\mathbf{S}(\psi,\eta)\) in the non-dimensional square domain. Figure 9: Vertical leading-edge position parameter (**a**), and corresponding morphing Class/Shape function Transformation (CST) shape and skin curvature variation (**b**). The optimal three-dimensional shapes, selected after the aerodynamic assessment, are used as target shapes for the definition of the objective functions coupled with the estimation of the set of critical load cases for the second level of optimization. Moreover, they permit the definition of the optimal actuation points along the skin [23]. The mapping between the target and undeformed shapes allows the definition of the optimal actuation points which represent the best arc-length positions along the skin where the compliant structure can be connected, for the purpose of introducing the shape changes in the most efficient way. This approach also enabled a preliminary study of the morphing skin structural configuration, before the internal structure is defined, using the same points to introduce the enforced displacements that correspond to the shape changes defined by the target shapes. This step has allowed us to define the most suitable lamination sequence to be assigned to the skin material, which will be introduced in the third level of optimization. The set of critical load cases, used by the second level of optimization, are shown in Figure 11 in terms of the pressure distribution acting on the wing. The first load case refers to the wing shape without a morphing leading edge, with an angle of attack of \(\alpha=18\) deg and a dynamic pressure of \(q_{D}=2561\) Pa, which correspond to the landing conditions at sea level. The second load case refers to the maximum droop nose deflection shape, with an angle of attack of \(\alpha=0\) deg and a dynamic pressure of \(q_{D}=5000\) Pa, which correspond to the Placard speed \(V_{F}\) at sea level. Figure 11: Pressure coefficient \(C_{p}\) that correspond to undeformed shapes and placard speed conditions (**a**) and to morphing shapes and landing conditions (**b**). Figure 10: CAD surfaces of the Reference Aircraft (RA) wing with an optimal morphing droop nose.