SPRAY DRIFT FROM HIGH-VELOCITY AIRCRAFT

The downwind spray drift resulting from aerial application was investi gated using high-volume air samplers in a cotton field. A turbine-powe red, mono-plane was operated at 218, 241, and 265 km/h over a 700-m fl ight line oriented 23.6-degrees from a 610-m sampler line. Results usi ng cinnamyl alcohol tracer, quantified by gas chromatography, indicate d that concentrations collected from air sampler filters were not sign ificantly different (P = 0.05) for all velocity treatments at individu al stations up to a distance of 67 m from the flight line center. Drif t from the 218 km/h treatment was significantly (P = 0.05) greater tha n that from the 241 and 265 km/h treatments at individual stations fro m 79 to 201 m. Wind velocity ranged from 1.65 to 3.34 m/s. Spray dropl et volume median diameters were 247, 218, and 189 mum for the velociti es of 218, 241, and 265 km/h, respectively. Volume of spray in small d roplets less than 125 mum increased from 3.53 to 16.17% as velocity in creased. The strengths of wingtip aerodynamic vortex of the 241 and 26 5 km/h treatments, compared to that for 218 km/h, decreased by approxi mately 10 and 22%, respectively, thereby off setting the potential dri ft corresponding to a decrease in droplet size of 12 and 23%.