# Analysis of Drone Flight Stability for Building a Korean Urban Air Traffic (K-UAM) Delivery System
## 5 Drone Flight Data Analysis--Hovering  
Unlike fixed-wing aircraft, drones are aircraft that can take off and land vertically. Therefore, the task of testing vertical takeoff and landing is given for analyzing the stability of the drone's body. Hovering is a state in which a drone is launched into the air and remains in that position without moving. Among aircraft capable of vertical takeoff and landing, helicopters, multicopters (drones), and VTOLs can implement hovering. Aircraft that do not fall into this category (typically fixed-wing aircraft and autogyros) cannot hover because they stall and crash if they stop in midair. The hovering process consists of three steps:  
Step (1) Selection of flight location,  
Figure 10: Analyzing deviation data of the drone delivery route of Jinha—Myeongjin Bridge—Jinha course in Figure 7d. \begin{table}
\begin{tabular}{l c c} \hline \hline \multirow{2}{*}{**Course**} & **Distance Error** & **Altitude Error (\%)** \\ \hline (a) Office—Uliu Sports Complex—Office & 0 & 0.0068946 \\ (b) Office—Complex Welcome & 1.0691 & 0.10097 \\ Center—Office & (c) Office—Moonlight & 0 & 0.11727 \\ Campground—Office & (d) Office—Starlight & & \\ Campground—Office & 0 & 0.14045 \\ \hline (e) Jinha—Marine Sports Center—Jinha & 0 & 0.66181 \\ (f) Jinha—Ganjeolgot Sports Park—Jinha & 0 & 0 \\ (g) Jinha—Solgae Park—Jinha & 0 & 0 \\ (h) Jinha—Myeonggeon Bridge—Jinha & 0 & 0.11762 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Analysis of drone flight path course data errors in Ulju. Step (2) Ascent and descent of the aircraft in place,  
Step (3) Landing at desired location. In the study for this project, the hovering scenario was defined as in Table 4.  
Figure 11 shows the planned step-by-step hovering scenarios listed in Table 4 and the analysis of the drone body's hovering data. The drone's hovering data were conducted in Yeosu, and the stability analysis of the drone for hovering presented by the Korea. Transportation Safety Authority looks at two things: the left and right radius error and the altitude error when the drone takes off and lands. The hovering test of the drone body was specifically conducted in the areas of Gaedo and Jageum in Yeosu, as shown in Figure 12. The initial position before the drone took off was used as the origin, and the relative positions of the drone were calculated in real time and compared while the drone hovered according to the scenario. During the drone hovering performed in the Yeosu Gaedo in Figure 13a, the drone body shows a good example of safety in terms of shaking from side to side. The relative positions of the drones are relatively close to the origin, and the numerical error is also very small, with a difference of about 50 cm, as shown in Figure 13b. On the other hand, the drone hovering data collected in Yeosu, as shown in Figure 14, show a relatively bad example compared to the hovering performed in Gaedo. Figure 14a shows that the left and right movement of the drone becomes more severe \begin{table}
\begin{tabular}{c c} \hline \hline
**Step** & **Scenario** \\ \hline (1) & Takeoff and ascent 30 m \\ (2) & Maintain altitude at 30 m \\ (3) & Descending altitude 10 m \\ (4) & Maintain altitude at 10 m \\ (5) & Descending altitude 5 m \\ (6) & Maintain altitude at 5 m \\ (7) & Descent and landing \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Hovering Scenario. Figure 11: Planned hovering scenarios () in Table 4 and hovering tests of the drone (). during hovering compared to the initial position of the drone in Figure 12(a). The numerical error in Figure 12(b) also increases to 2 m compared to the maximum value of 50 cm in Figure 12(b).