# Design, Manufacturing, and Flight Testing of an Experimental Flying Wing UAV
## 7 Discussion  
This paper reports the design, manufacturing, and testing of an experimental flying wing UAV. The major achievements of this study include the aerodynamic performance design based on the matching plot, weight estimation approach, and conventional aircraft design procedures. By using the matching plot, the appropriate wing loading and power loading that can satisfy all performance requirements are determined clearly. By using the weight estimation approach, the aircraft's empty structure mass is parameterized as a function of the wing reference area. By using the parameterization results, the maximum take-off weight is formulated and estimated successfully. Design parameters such as the zero-lift drag coefficient and induced-drag factor are temporarily given empirical values from the first calculation and recalculated in the aerodynamic performance design procedure. The feedback of the  
Figure 17: Airspeed in the second round of the second flight test (time = 32–35 s). Figure 18: **Attitude** in the second round of the second flight test (time = 32–36 s). zero-lift drag coefficient and induced-drag factor is terminated when the feedback values become similar to the initial ones. Strength analysis is not considered in this study. It will be included in our future work. Based on the design results, an experimental flying wing UAV is then built. This is the TKU UAV laboratory's first attempt to perform the whole main structural assembly of the composite materials of an aircraft. After successfully assembling the main and secondary modules, necessary inspections and flight plans were completed, and the first flight test was performed on 29 May 2018. The actual total weight exceeds the original design weight of 6.5 kg. This large error can be attributed to the ratio of the empty weight to wing reference area. The empirical value of this ratio was not sufficiently accurate in the weight estimation approach. This was mainly because this is our first attempt to manufacture the main structural assembly of an aircraft using composite materials. The empirical value should improve after gaining more manufacturing experience. For a payload of 2.5 kg, the maximum takeoff weight is 11.12 kg and wing load is 101.85 Nt/m\({}^{2}\). The performance of our flying wing UAV is as follows. 1. The maximum lift coefficient is still assumed to be 1.2, and the stall speed at sea level is 11.77 m/s. 2. At cruising altitude (100 m), the cruising speed is 23.06 m/s and cruising power is 113 W. The maximum speed at cruising altitude is 25.36 m/s and maximum power demand is 192 W.
3. The absolute ceiling is still 500 m.
4. At cruising altitude (100 m), the turning factor (load factor) is 1.21, and the turning radius is 25.13 m at flight speed of 12.94 m/s. Figure 19 shows the matching plot for the actual experimental flying wing UAV. The second flight test only recorded flight trajectory, airspeed, ground speed, and attitude angle, and limited analysis of the data was conducted after the flight experiment. Figure 19: Matching plot for actual experimental flying wing UAV. **Supplementary Materials:** The flight data record was uploaded to the PX4 flight review at [[https://review.px4.io/upload](https://review.px4.io/upload)]([https://review.px4.io/upload](https://review.px4.io/upload)), and it can be found at [[https://review.pyx4.io/plot_app?log=d78a4212-fd7b-4345-a92d-0887](https://review.pyx4.io/plot_app?log=d78a4212-fd7b-4345-a92d-0887) ec4 ac78a]([https://review.pyx4.io/plot_app?log=d78a4212-fd7b-4345-a92d-0887](https://review.pyx4.io/plot_app?log=d78a4212-fd7b-4345-a92d-0887) ec4 ac78a).