GB/T 38924.9-2020 is part of a series of standards for environmental test methods for civil light and small unmanned aerial vehicle (UAV) systems (take-off weight ranging from 0.25 kg to 150 kg), specifically designed to evaluate the waterproof performance of UAV systems (including aircraft and ground stations). This standard specifies a complete waterproof testing process, including test conditions, specific testing procedures, result evaluation criteria, and reporting requirements. Its purpose is to examine whether UAVs can withstand the impact of rainwater sprayed or dripping onto their surfaces. The "test equipment and instruments" mentioned in the standard typically include rain (waterproof) testing equipment used to simulate different rainfall conditions, such as comprehensive rain test chambers capable of conducting IPX5 (water jet) and IPX6 (powerful water jet) level tests. Such equipment mainly consists of a water supply system, nozzle devices, and flow control and measurement systems, and serves as key testing apparatus for verifying the safety and reliability of UAVs in rainy environments.