Influence of Helicopter's Downwash upon the Dispersion of Sprayed Chemicals

Abstract

Aerial application of pesticide is widely used on paddies and forests in Japan. In order to avoid accidental dispersion of chemicals in neighbouring places, the flight speed and altitude of a helicopter must be suitable for a specified droplet size of chemicals and given wind conditions. The wake pattern of downwash was observed by tracing suspended balloons in the air and was filmed by a cinecamera for various flight conditions. The velocity profiles of downwash were determined by analyzing the trajectries of the balloons. Then by superposing the sedimentation velocity of droplets and wind velocity, dispersion pattern of droplets were figured. These results were also recognized by the experiment of aerial application on the rice growing fields. © 1994, Pesticide Science Society of Japan. All rights reserved.