Abstract:Aiming to elucidate the effects of 3WQF120-12 single-rotor unmanned aerial vehicle (UAV) on the effect of droplet, deposition distribution, ground loss droplets, drift, and applicability when spraying areca palm. The impact of different working heights of UAV on the spraying effect of areca palm canopy was mainly studied. In this experiment, the red stain aqueous solution with a mass fraction of 0.5% was selected and instead of pesticides. The droplets were collected on coated paper and analyzed by an image processing software (DepositScan). The results showed that when the operation height was 12.09m, 11.46m and 10.40m, respectively, the operation height had no significant influence on the droplets deposition amount of the sampling points in each layer of the areca palm. Meanwhile, the deposition level in the upper canopy could reach 53.27%, that of the lower canopy and fruit layer can reach 59.19% and 27.91% of the upper canopy. The results of the droplets deposition at the ground loss sampling points showed that the droplets deposition of the three column sampling points on the ground was significantly affected by different operation heights. When the operation height was 10.40m, the droplets loss on the ground was the least, and the average deposition level was about 19.9%. The data of the drift area showed that the three working heights had no significant influence on the droplets deposition of the sampling points in the drift line. When the working height was 12.09m, the drift line sample location measured the largest amount of drift and the working height of 10.40m had the smallest. At the same time, it was found that the downwind distance corresponding to 90% drift accumulation could reach as far as 36.35m. Therefore, sufficient safety distance must be left for practical operation. The areca aerial spraying was very different from that of conventional crops, mainly in working speed and height. The speed of areca aerial spraying was about 1.5m/s, which was much lower than usual speed (3~5m/s), and the working height can usually be more than 10m. The wake vortices were mainly influenced by working height, as the working height increased, the amount of droplets deposition was decreased, especially in the upper layer of the areas’ canopy. Due to the operation speed was slow, the acting time of the rotor wind field was relatively long. The combined action of downwash airflow and crosswind in the rotor wind field can significantly improve the penetration of droplets. In this experiment, there were three different working heights, and the droplet volume median diameter (VMD) of droplets in each layer was changed significantly with the working heights. With the increase of crosswind and working height, the droplet volume median diameter (VMD) of droplets in each layer was decreased, and the mean deposition and percent area coverage rate in the fruit layer could increase by up to 53.75% and 62.20%, respectively. In actual operations, appropriate operation parameters can be selected according to the growing period and the occurrence part of diseases and pests.