Assessments were made of the physical properties of spray deposits from upwind and crosswind, single and multiple flight applications of oil-carrier spray applied by a small aircraft equipped for commercial weed spraying. Volume deposits were determined colorimetrically on petri dish collections of the dyed spray. Droplet assessment data were obtained from photographic enlargement of printflex sampling cards.Three peaks of spray deposit were found, resulting from the propeller blast and the wing-tip vortices. A greater percentage of spray was recovered at ground level, and more variation in volume deposit and droplet size occurred across the effective spray swath, in the upwind flight than in the crosswind flight application. Information obtained from these tests will be used in the construction of a spray booth, designed to apply simulated aerial sprays on a practical small-plot basis, for determining the causes of injury to grain crops resulting from aerial application of herbicide-oil mixtures.
Low-order modeling of wing tip vortices using an augmented vortex lattice method