## 4 Results and Discussion  
Thirty-five analyses were carried out as part of the study. Table 3 displays the UAV positions that were involved in the thirty-five analyses conducted for the study. All analyses were performed longitudinally at a distance of \(\Delta\)x = 13 m.  
The trailing UAV's lift coefficients (\(C_{L}\)) that are results of the aerodynamic effect are plotted against the lateral distances between the UAVs in Figure 13. In this figure, different vertical distances are shown with different curves. It is evident that \(\Delta\)y = 0 m always has the maximum \(C_{L}\) value for whatever the lateral distance position is. In other words, regardless of the lateral distance, when the leading UAV and the trailing UAV fly at the same altitude, the trailing UAV has the maximum lift coefficient. The \(\Delta\)y = 0.133\(b\) and \(\Delta\)y = \(-\)0.133\(b\) curves represent the positions where the trailing UAV flies one vehicle height higher and lower than the leading UAV (0.133\(b\) = 1.6 m, where \(b\) is the wingspan). These two curves present the same values, except for the points \(\Delta\)z = 12 m and \(\Delta\)z = 13.5 m. Similarly, the \(\Delta\)y = 0.266\(b\) and \(\Delta\)y = \(-\)0.266\(b\) curves at the positions where the trailing UAV flies two vehicle heights higher and lower than the leading UAV have very close values. However, these curves have lower \(C_{L}\) values than the \(\Delta\)y = 0.133\(b\) and \(\Delta\)y = \(-\)0.133\(b\) curves. In the same altitude plane (\(\Delta\)y = 0 m) with maximum \(C_{L}\) value, it was determined that the \(C_{L}\) value decreased by similar amounts when diverging up or down. So, the \(C_{L}\) values of the trailing UAV show a symmetrical value change when the same altitude plane is considered as the plane of symmetry, which is consistent with the schematic diagram in Figure 6. In close-formation flight, where the lateral distance between the two UAVs is 1.5 times the wingspan (\(\Delta\)z = 18 m), the \(C_{L}\) values are slightly different for different vertical distances. For these positions in the context of \(C_{L}\), it can be said that the aerodynamic effect between the two UAVs is significantly reduced. The drag coefficients of the trailing UAV for different lateral distances are shown in Figure 14. The \(C_{D}\) values for different vertical distances are presented by different curves, with the lateral distance values being variable. At \(\Delta\)z = 15 m and \(\Delta\)z = 18 m, the change in vertical distance becomes insignificant; i.e., the \(C_{D}\) values are approximately the same. For other lateral distance values, the \(\Delta\)z = 0 m curve has the lowest \(C_{D}\) values. Conversely, \(\Delta\)z = 0.266\(b\) and \(\Delta\)z = \(-\)0.266\(b\) curves have the highest \(C_{D}\) values. These two curves contain approximately the same values. Similarly, the \(\Delta\)z = 0.133\(b\) and \(\Delta\)z = \(-\)0.133\(b\) curves have approximately the same results for the same lateral distances. As in the \(C_{L}\) plot, \(C_{D}\) values around the same altitude plane (\(\Delta\)z = 0 m) show a symmetrical distribution in the upward and downward direction for different vertical distances. The optimum position, where the trailing UAC can achieve the greatest aerodynamic improvement, is identified as the position of the maximum lift-to-drag ratio of the trailing UAV during close-formation flight. The maximum aerodynamic performance curve is generated when two UAVs fly at the same altitude in comparison to other vertical distances, as shown in Figure 15. A symmetrical representation with respect to the axis at the same altitude is formed by the values at various vertical distances. In other words, the outcomes of the analyses with \(\Delta\)y = 0.133\(b\) and \(\Delta\)y = \(-\)0.133\(b\) concur. The results of the analyses with \(\Delta\)y = 0.266\(b\) and \(\Delta\)y = \(-\)0.266\(b\) likewise coincide. The investigation using horizontal