## 4 Results and Discussion
### Estimation Accuracy--Side Gusts
Figure 38: Comparison of the gust value with the estimation results—descent crossing a gust area; entire descent part of simulation (complementary filter, (**A**) T\({}_{\rm cv}\) = 0.5 s, (**B**) T\({}_{\rm cv}\) = 0.8 s, (**C**) T\({}_{\rm cv}\) = 1.0 s, (**D**) T\({}_{\rm cv}\) = 1.5 s). A detailed examination of the arrows marked with numerical values for the selected increasing gust in Figure 39 allows for a computational comparison. With a time constant of 0.5 s, the peak gust value in the full estimation is 1.01 m/s lower than the reference, while the low-frequency estimation shows a larger deviation of 1.83 m/s. The delay in the full estimation is 0.79 s, which is a deterioration over the 0.35-s delay observed in the low-frequency estimation. Increasing the time constant to 0.8 s allowed for an almost perfect match (0.11 m/s difference between the reference measurement) of the peak gust value considered while the full estimation delay increased to 0.93 s. Computational evaluation confirmed that increasing the time constant to 1.0 and 1.5 s resulted in an underestimation of the maximum gust values and increase in the delay to 1.1 s for \(\mathrm{T_{cv}}=1.5\). Examining the numerical labels on the arrows in Figure 40 enables a precise comparison of the minimum values for the selected weakening gust scenario. With a time constant of 0.5 s, the minimum value differs by 0.68 m/s in the full estimation and by 1 m/s in the low-frequency estimation. The delay with respect to the reference measurement is only 0.03 s for the full estimation, and the low-frequency estimation is ahead of the baseline measurement by 0.35 s. When comparing the changes in the full estimated values for this selected case, the closest value of underestimation was achieved for a time constant of 1.0 s (0.2 m/s difference), with a relative small delay at the level of 0.33 s. A time constant of 1.5 s already overestimates the minimum value by 0.12 m/s, also increasing the estimation delay to 0.43 s.  
For the considered cases, the best results were obtained for a time constant of 0.8 s for a gust with increasing velocity and for a time constant of 1.0 s for a gust with decreasing velocity. However, every increase in time constant in this algorithm for the level flight phase is associated with an increase in the delay of complete estimation, which is presented in detail in Table 3.  
Afterward, the estimation results for the simulation conducted in level flight were presented. Three data ranges were selected for graphical analysis: the entire simulation (0-180 s), a series of selected gusts (50-85 s), and a single gust (60-74 s). The CF results reflect the impact of variations in the time constant \(\mathrm{T_{s}}\) on the estimation result. For analysis, the same time constants were selected for comparison. Figure 40: Comparison of the gust value with the estimation results—descent crossing a gust area; single selected gust (complementary filter, (**A**) \(\mathrm{T_{cv}}=0.5\) s, (**B**) \(\mathrm{T_{cv}}=0.8\) s, (**C**) \(\mathrm{T_{cv}}=1.0\) s, (**D**) \(\mathrm{T_{cv}}=1.5\) s). The evaluation based on charts presented in Figures 41-43 leads to the conclusion that the best representation of the estimation results compared to the reference measurement was obtained for the time constant of 1.0 s. By examining the arrows annotated with numerical values for the selected rising gust speed in Figure 42, a computational comparison can be made. When using a time constant of 0.5 s, the differences between peak gust values are 2.54 m/s for complete estimation and 3.65 m/s for the low-frequency estimation with reference wind measurements. The full estimation shows a relatively small delay of 0.38 s compared to the reference, but no delay is observed in the low-frequency estimation. Raising the time constant to 0.8 s reduces the peak value of the overall estimation; however, the maximum value still surpasses the reference by 1.20 m/s.