###### Abstract  
To investigate the spray atomization characteristics of aerial nozzles adapted to manned agricultural helicopters under medium-low airflow velocity (0 to 27.8 m/s) conditions, the droplet size test was carried out in both wind tunnel and field tests. In the wind tunnel test, the laser diffraction device (LDD) was used to test the spray droplet size of CP02, CP03, and CP04 aerial nozzles. A Bell206L4 helicopter was used in the field test. The results in the wind tunnel test showed that due to the nozzles had been used for a long time and the cause of wear, the spray stability of individual nozzles was affected during the test. The limitation of droplet size measurement by using LDD was also found. The field test results showed that the main distribution range of the droplet size measured in the field test was consistent with the results of the wind tunnel test, but the droplet size value was significantly higher and the uniformity of droplet size distribution was poorer than the wind tunnel test value due to the influence of the actual environment. However, the results of field test and wind tunnel test can still be used as a reference for each other. mannned helicopter; aerial nozzle; wind tunnel; filed test; droplet size distribution; agricultural application +
Footnote †: journal: Appliedparameters, and airflow disturbance, drift easily occurs, and droplets will be off from the targets. If not properly controlled, it is easy to harm non-target crops and even cause immeasurable losses [3]. Nozzale is the most critical component in aviation application equipment, and it will directly affect control effect of the application. Droplet size is an indicator of atomization performance, which is also a reference for nozzle design and selection [4; 5]. Related studies have shown that if the droplet size is too large or too small, it will cause problems such as waste loss or drift and phytotoxicity. Only when the droplet size is in the optimal range, the target crop can capture the droplets and the best control effect can be achieved [6; 7]. Therefore, to ensure good aviation spraying effect, it is necessary to carry out detailed measurements to characterize the droplet size distribution of nozzle spray [8]. Wind tunnel test and field test are the most commonly used methods for studying the droplet size distribution. Compared with the field test, the wind tunnel test can accurately simulate the aircraft flight condition by controlling the airflow velocity, less interference from external factors, and repeatability, so it is highly accepted in basic theoretical research related to droplet size [9; 10; 11; 12; 13]. However, limited by wind tunnel space size and measurement methods, a wind tunnel test can only study the droplet size distribution near the nozzle, but cannot reflect the droplet size distribution after the droplet is finally in contact with the target. In addition, the secondary rupture may occur in the sedimentation process, which is also impossible to simulate in the wind tunnel test [14]. Therefore, wind tunnel test results are not equivalent to field test results and can only be used as a reference for field test results and a basis for regularity prediction. An optimal research method should combine wind tunnel tests with field tests to obtain the accurate droplet size distribution. Some scholars have carried out a combination of wind tunnel and field tests on the droplet size distribution. [PERSON] et al. [15; 16] evaluated the penetration uniformity and drift potential of droplets with different droplet sizes on crop canopy through field experiments, then further quantified the droplet size distribution characteristics and drift potential of each nozzle through wind tunnel test until the appropriate nozzle type was finally selected. [PERSON] et al. [17] compared the droplet size distribution and spray width of air induction nozzles and conventional flat fan nozzles in wind tunnel and greenhouse. [PERSON] et al.