Droplet drift characteristics of aerial spraying of AS350B3e helicopter

Abstract: The use of aircraft for aerial spraying is an important aspect of precision agriculture (PA). In China, many scholars are engaged in research on aerial spraying technology with agricultural unmanned aerial vehicle (UAV), but few of them concentrate in the field of agricultural manned helicopter. Up to now the related studies about manned agricultural helicopter in China are mainly focused on pesticides efficacy analysis. It usually lacks practical assessment of actual application parameters, especially the regular patterns of droplet drift after spraying. In order to determine the regular patterns of droplet drift of the AS350B3e helicopter with the AG-NAV Guía system, spray tests were conducted with different operating parameters, and the precision operating parameters (time, velocity, height, trajectory) were obtained by the light airborne BeiDou real-time kinematic (RTK) differential system. There are many factors that affect the characteristics of helicopter spraying drople0t drift, including the effective composition and type of liquid prepared, droplet size, aircraft operating parameters, weather conditions, terrain, the operator's sense of responsibility and skill level. In this paper, the deposition distribution and drift law of droplets in the sampling lines were evaluated for 6 single-pass applications in 4 different ranges of flight velocities, and the effects of adding aerial adjuvant on droplet drift distance and amount were compared. The analysis results showed that the position of the effective spraying area was affected by natural wind velocity and wind direction, and would shift to the downwind direction area from the helicopter route with different degrees. When the helicopter was operated at 70, 90, 100, and 120 km/h, the effective swath width increased slowly and then decreased sharply with the increase of flight velocity. It was found that flight velocity of 100 km/h was the peak inflection point of effective spray width variation. Among the 6 single-pass application tests, when the wind velocity was 1.1-2.3 m/s, the minimum width of the target spray area was in the range of 27.61-48.94 m in the horizontal downwind direction of the spray area, and the measured downwind drift distance was close to or less than the downwind effective swath width. It was also found that droplets with droplet size below 200 μm were more likely to drift, which accounted for more than 70% of the total number of droplets in the drift area. Therefore, when the helicopter was in operation, it should reserve a buffer zone (safety zone) of 50 m at least and the aviation nozzle should be selected reasonably to avoid the hazards of droplet drift. Adjuvant was also a key factor affecting drift. It indicated that the use of aerial adjuvant had a significant effect on the percentage of droplet drift in the total amount of spray, and the addition of aerial adjuvant could reduce the droplet drift by 33.94% under the same operating conditions. The results of this study can provide technical basis for the improvement of the performance of the helicopter spraying system, which is of great significance to the reasonable spraying of pesticides, the reduction of the drift and the improvement of the utilization rate of pesticides.