Propeller Wash Effects on Spray Drift
2005
Thomson, S.J. | Womac, A.R. | Mulrooney, J. | Deck, S.
For aerial spray application, there is some question if off-target drift (both near and far) is influenced by which boom is spraying and the direction of propeller wash rotation. This information may be useful when switching off one boom close to a field boundary. The effect of alternate boom switching and propeller wash direction on aerial spray drift from a turbine-powered aircraft was investigated. Both high volume and alpha cellulose spray sampling sheets were placed at three sample lines to collect drift fallout 104, 134, 195, and 317 meters downwind, perpendicular to the flight path. An aqueous mixture of malathion was applied from the aircraft through fifty D6-46 hollow cone tips. Five total replications were conducted over two days. Each replication had four treatment combinations of boom switch (left or right, on or off) and airplane direction. Propeller wash effects were surmised from boom selection and aircraft direction. Data from a preliminary study served as a basis for refinement of analysis procedures. The present analysis introduced weather variables besides wind and adjusted downwind distances to account for wind direction. Results showed that neither active boom nor boom location (upwind or downwind) was statistically significant for either sampling method at the 0.05 level. There was significant influence of horizontal sampler location for the Hi-Vol samplers (p=0.0347), and solar radiation was significant at the 0.01 level for both.
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