Examining aerial application swath pattern evaluations under in-wind and cross-wind conditions

Authors: Fritz, Bradley - Brad; GILL, MATT - University Of Illinois; BRETTHAUER, SCOTT - National Agricultural Aviation Association

Submitted to: Journal of ASTM International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/4/2019
Publication Date: 10/10/2019
Citation: Fritz, B.K., Gill, M., Bretthauer, S. 2019. Examining aerial application swath pattern evaluations under in-wind and cross-wind conditions. Journal of ASTM International. https://doi.org/10.1520/STP161920180123.
DOI: https://doi.org/10.1520/STP161920180123

Interpretive Summary: Evaluating and adjusting the position of spray nozzles on an aerial application spray boom is key to maximizing pattern uniformity and effective swath width. Though pattern testing is typically done flying into the wind, applications in the field are typically made under cross-wind conditions potentially shifting patterns. Field trials were conducted examining multiple application setups under in- and cross-wind conditions. The results showed that the finer spray treatments measured under in-wind conditions resulted in wider, more uniform effective swaths with cross-wind conditions heavily influencing the deposited spray pattern. Understanding these differences will ensure proper interpretation of field-collected spray pattern data and provide applicators with guidance on adjusting application methods to ensure on-target deposition of applied sprays.

Technical Abstract: Evaluating and adjusting the position of spray nozzles on an aerial application spray boom to account for the impact of propeller wash, airframe structures and application conditions is key to maximizing pattern uniformity and effective swath width while minimizing the potential for droplets being entrained in wing tip vortices. While pattern testing on agricultural aircraft is typically done with the pilot flying into the wind to maximize spray deposition onto sampling media, the reality is pilots typically make applications under cross-wind conditions which potentially shifts the pattern in the downwind direction, stacking up material on the upwind side and creating non-uniform droplet size deposits across the swath. Field trials were conducted examining two spray droplet size application setups with the boom extent of the furthest nozzles on the boom reducing from 84 to 57 percent under in- and cross-wind conditions. The results showed that the finer spray treatments measured under in-wind conditions resulted in wider, more uniform effective swaths with spray patterns measured under cross-wind conditions showing significant shifts in droplet size and pattern uniformity. Generally, spray pattern uniformity and effective swath widths were maintained until boom extent was reduced below 65 percent.