*3.3. Results of the Total Aircraft Iteration*

The results of the vertical tail, as seen in Table 3, show that the on-wing wiring option is not suitable for both configurations, as it would lead to large VTPs, which significantly increase the overall weight and drag of the aircraft. The aircraft with on-wing wiring are therefore neglected in the following calculations that account for the aircraft changes and only the cross-wiring options are studied further. Additionally, MICADO could not reach convergence for aircraft with volume coefficients above 0.1425 since this leads to an aircraft that is not physically feasible, as can be seen in Figure 6.

For the PT2025 configuration, the aircraft VTP optimization was unable to reach a converged result, as the increase in mass, required thrust and change in CG, due to the larger VTP, led to a further increase in the necessary tail area. After one iteration, the updated VTP area was 20.26 m2, already outside MICADO's calculated design space. Therefore, no results for this configuration can be shown.

For the PT2025opt configuration, the aircraft level calculation could be conducted, with the results displayed in Figure 8. In contrast to the method described in Section 3.2, the position of the horizontal tail was allowed to change, since the whole aircraft design and horizontal stability were taken into account. The resulting surface area and volume coefficient, as well as the change in OME and mission fuel are given in Table 4.

**Figure 8.** Original (blue) and resized (amber) vertical tail for the PT2025opt aircraft with cross wiring (Configuration 4).

Compared to the considerations of the isolated vertical tail, the resulting fin surface area is decreased. The larger distance between the aerodynamic centres of the wing and the vertical tail, as well as the changes in the whole aircraft explain the difference between the relative change of the fins surface area and the volume coefficient. The mass savings for the vertical tail of 79.6 kg offset the extra mass of the cables of 67.7 kg, resulting from the cross-wiring configuration. The cascading effects described in Section 3.1 also explain why the decrease in the OME is 182.0 kg, 102.4 kg more than the mass savings for the vertical tail. The additional drag reduction due to the smaller vertical tail leads to a combined fuel saving of 4.7% for the design mission of 510 NM.

**Table 4.** Comparison of VTP, OME and mission fuel of the original and optimized PT2025opt aircraft with cross wiring (Configuration 4), taking into account the iteration of the whole aircraft.

