SYMPOSIA PAPER Published: 25 November 2019
STP161920180123

Examining Aerial Application Swath Pattern Evaluations under In-Wind and Cross-Wind Conditions

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Proper boom positioning of nozzles to account for propeller wash, airframe structure, 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 that pilots typically make applications under cross-wind conditions that potentially shift the pattern in the downwind direction, stacking up material on the upwind side and creating nonuniform 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 ranging from 84 to 57% of aircraft wingspan under in- and cross-wind conditions. As boom extend reduces, less spray material is entrained in wing tip vortices, though at some point further reduction results in poor spray patterns and significant reductions in effective swath width. The object of this work was to examine the methodologies currently used to evaluate spray patterns from aerial systems, particularly focusing on how deposition rate and droplet size patterns shift under different wind direction scenarios. The results showed that the finer spray treatments measured under in-wind conditions resulted in wider, more uniformly effective swaths, while spray patterns measured under cross-wind conditions showed shifts in droplet size class across the pattern and overall pattern uniformity. Generally, spray pattern uniformity and effective swath widths were maintained for all flow conditions until boom extent was reduced below 65%.

Author Information

Fritz, Bradley, K.
USDA ARS Aerial Application Technology Research Unit, College Station, TX, US
Gill, Matthew, P.
University of Illinois, Urbana, IL, US
Bretthauer, Scott
National Agricultural Aviation Association, Alexandria, VA, US
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Details
Developed by Committee: E35
Pages: 24–38
DOI: 10.1520/STP161920180123
ISBN-EB: 978-0-8031-7685-0
ISBN-13: 978-0-8031-7684-3