AIR DEFLECTOR EFFECTS ON AERIAL SPRAYS

Air deflectors (Chimavir Air Services, Ltd., Israel) were installed on an agricultural aircraft and tests were run to investigate: (1) the a lteration in downwind residue results (drift) due to release height, ( 2) the influence on droplet sizes conducted with a laser drop size ana lyzer in a wind tunnel, and (3) the changes in airflow near the spray boom as observed from wind tunnel tests. A turbine-powered monoplane w ith air defectors was evaluated for spray drift losses and deposit cha racteristics in a cotton field. Air-burden residue from application he ights of 3.0, 4.6, and 6.1 m were investigated using high-volume air s amplers along a 610-m sampler line oriented at 23.6-degrees from a 700 -m flightline. Spray deposit was measured (concurrent with the downwin d airborne drift sampling) from collection of residue on Mylar plastic sheets spaced at 61-m intervals from the first air sampler to beyond the flightline. Gas chromatographic analysis was used to measure the c oncentration of cinnamyl alcohol tracer. Results from air samplers ind icated that the 3.0-m release height had significantly (P = 0.05) less airborne drift (2.19 ppm) than the 4.6 m height (9.52 ppm) and 6.1 m height (11.37 ppm). No differences (P = 0.05) in fallout deposit level s were detected, although the 4.6 m height tended to have a higher lev el of deposit (6.06 ppm) than the 3.0 m height (4.29 ppm) and the 6.1 m height (4.62 ppm). Spray droplet sizes produced in a wind tunnel wit h and without a deflector were examined for a custom-sized RF 25-degre es fan nozzle (3.06 L/min at 276 kPa, Delavan-Delta, Inc., Lexington, Tenn.) and a D6-46 disk and core nozzle (Spraying Systems Co., Wheaton , Ill.). Both nozzles were oriented 45-degrees down and back with airs tream velocities of 60 and 75 m/s. Water-soluble formulations were exa mined and included (1) cinnamyl alcohol, (2) bifenthrin, and (3) water . Overall mean droplet sizes (Malvern) with the deflector were 235 mum , whereas without the deflector they were 182 mum. The downwash of air around the deflector was quantified in terms of mean, steady-state ai r velocity and direction. Measurement points were selected on a two-di mensional grid that ran longitudinally with the axis of the wind tunne l. Air was deflected to an angle of 50-degrees from horizontal. A 54 m ls airflow was decelerated to 40 mls behind the deflector.