2.2.3. Wing Design

For the wing, the maximum lift coefficient *CL*,*max* was calculated using Raymer [18] sizing methods. For the wing area S, the wingspan b and the taper ratio *λ*, the initial values were defined before the execution of the sizing iterations. In the following design process, S was obtained through the iterating mass estimation, while b and *λ* were chosen values. With the lift coefficients of the selected airfoils at different positions from the reference aircraft, the maximum lift coefficient was obtained. In contrast to current generation aircraft, the wing is not used to store fuel and is, therefore, not subjected to passive stress relief.

The advantage of the WTP, in this case, is the mass of the motor, gearbox, DC/AC converter and propeller acting as a load reducing bending moment with a long lever arm. This can result in an increase of the local wing bending moment along the wingspan. The additional stress is compensated for by applying a factor to the wing mass since the maximum absolute bending moment occurs at MTOM. This factor is calculated as the ratio between the wing bending moment for an aircraft wing in a theoretical "standard" configuration (inboard engine and fuel in wing; usual estimations applicable) and the selected configuration (WTP and dry wing). The additional wing root bending moment can be reduced by increasing the wingspan and, therefore, increasing the lever arm of the WTP mass. This further improves the aircraft performance by reducing the weight.
