## 4 Results and Analysis of the Flight Test
### Flight Test Process  
The working link of the airborne communication equipment is also shown in Figure 4, which is a bidirectional working mode. The communication link includes a mobile communication system, satellites, and satellite ground stations. The transmitting end is an airborne mobile communication antenna (equivalent diameter of 0.45 m) manufactured by China National Science and Technology Corporation and installed on the Camel 500 aircraft (Figure 5b). It can achieve a transmission rate of no less than 2 Mbps in the Ku band under propeller obstruction. The ground station uses a 4.5 m parabolic antenna for reception, located within the China Academy of Water Resources and Hydropower Sciences. The testing satellite is AsiaSat-5 communication satellite with a working frequency of 1419 MHz, for static and dynamic testing at a transmission bandwidth of 2048 Kbps. The test work includes communication link debugging, aircraft installation matching, and quasi-static/small-scale hanging flight testing. On 16 January 2022, an uplink and downlink test was conducted on the ground station at the office area of the Chinese Academy of Water Resources and Hydropower Sciences, with a test bandwidth of 2 Mbps. The results show that its function is good. On 17 January 2022, a transmission and reception performance test was conducted at the site of Chongqing Tuohang Technology Co., Ltd. The test bandwidth was confirmed to be 2 Mbps and the transmission and reception were normal through self-transmit and self-receive. The installation and matching process of the aircraft took about 15 days. The Camel 500 aircraft was used as the main body and loaded under the fuselage. The total loaded weight is less than 150 kg. The installation-matching effect of the aircraft is shown in Figure 5b, with the communication equipment located on the right side of the aircraft and the stabilization platform located on the lower side of the aircraft. The quasi-static hanging flight is conducted at the flight test site of Chongqing Tuohang Technology Co., Ltd. Through static hovering, slow turning, and small-scale flight, the imaging quality of the stabilization platform and the data transmission speed during the flight process are analyzed and the related parameters are adjusted in real time, providing technical preparation for subsequent typical field flight tests. Due to the lateral installation of the mobile communication system, when the flight direction is different, the space between the antenna and the satellite may be obstructed by metal propellers, resulting in a loss of some bandwidth. To test the impact of obstruction on communication bandwidth, the aircraft rotates 90\({}^{\circ}\) in the static process every 1 min to test the transmission effect. Small-scale flights are bounded by the airspace of the flight test site. During the flight, the aircraft tilts in both pitch and roll directions, with a tilt angle of no more than 10\({}^{\circ}\), which tests the ability of the stabilization platform to maintain vertical shooting of the ground during maneuvering. During the testing process, the airborne communication system located in Chongqing sent the ground data of the flight test site captured by the industrial camera loaded on the image stabilization platform to the processing center near the Beijing ground station via satellite. The processing center stored the received images and performed image stitching and other tasks. After completing flight tests at the test site and optimizing equipment performance, link connectivity, and bandwidth, a formal flight test was conducted on 18 January 2022 at a typical disaster site, Nappingba Island. The communication bandwidth of the flight equipment was configured to be 2 Mbps, and the two flight heights were 250 m and 450 m, respectively. The flight is conducted within the airspace of Nappingba Island, with a maneuvering speed of no more than 100 km/h.