# Design of a Hand-Launched Solar-Powered Unmanned Aerial Vehicle (UAV) System for Plateau
## 5 Field Experiment
### Flight Parameters of HighAltitude Experiment  
The flight parameters of takeoff and cruise at high altitude are shown in Figure 17. Figure 17a shows the climbing process of the UAV: The UAV took off from an altitude of 4600 m, climbed to 4700 m, and turned to level flight. In order to ensure the safety of taking off at high altitude, the vehicle-mounted takeoff was adopted, and the instantaneous airspeed of departure was 16 m/s. Figure 17b presents a part of parameters from the stable cruise phase. The absolute cruising altitude of the UAV was 4700 m, the altitude was about 100 m, cruise airspeed was about 10.5 m/s, and the flight trajectory was a circular route around the mission area. In this field experiment, the UAV's mission flight path mainly included a quadrilateral flight path and a circular flight path. The quadrilateral flight path was suitable for takeoff and landing and searching targets in a wide range. The circular flight path was used for tracking and monitoring designated areas or targets. Figure 18 shows the circular flight path and the quadrilateral flight path in the flight test, respectively. From the circular flight path (Figure 18a), it can be seen that the aileron-free UAV tracked the path well under the condition of no wind, and the flight trajectory had almost no overshoot. Figure 18b shows the situation of the UAV tracking a quadrilateral flight path with 7 m/s positive wind. The UAV tracked the path well on the upwind side. However, on the downwind side, the flight path had overshoot. In general, the aileron-free UAV achieved the required path tracking for the mission, although maybe the tracking was less accurate than aileron UAV in windy conditions. In order to increase the proportion of solar cells laid and reduce the structural weight of the wings brought by the control surface, the UAV eliminated ailerons as roll control and used a rudder to control both roll axis and yaw axis. Figure 12 shows the free response simulation of rudder deflection when the UAV flew at different altitudes. In the flight test, the control characteristics of the UAV were verified. Figure 16: The high-altitude field experiment of UAV in Qiangtang, Tibet: (**a**) Vehicle-mounted takeoff, (**b**) cruise phase for mission, (**c**) hard landing in extreme environment. Figure 17: Flight result of field experiment: (**a**) Climb phase, (**b**) cruise phase. Figure 19 shows the data of the roll angle and rudder deflection when the UAV changed from a circular flight path to a straight-line flight path, which means the UAV turned left from the clockwise circular route and entered a straight-line flight path. As seen in the figure, the roll angle command appeared at 15 s with a command value of 30 degrees, and the rudder deflected after 0.3 s and a deflection value of 28 degrees after 1.5 s. The roll angle response time was slightly slower, about 5 s, because the roll angle of the aileron-free UAV was not directly caused by the rudder deflection but by the sideslip, which was an indirect process for the rudder. In general, the response characteristics of the roll angle were consistent with the simulation results. According to different mission objectives, the UAV can carry different weight and power consumption of the payloads. Weight and power consumption and other parameters will affect the weight coefficient of batteries. Heavier and higher power consumption of payload usually means worse flight endurance. In the field test, the UAV completed its flight test with two different payloads: Payload 1 was a small fixed-focus camera weighing only 50 g and a low-power transmission with power of 600 mW and payload 2 was an optical-infrared composite optronics pod weighting 450 g and a remote digital graph transmission with an effective distance of 15 km and a power of 15 W. In the case of constant total weight, different payloads not only mean different additional power consumption, but also affect the carrying capacity of batteries, which is closely related to flight endurance.