C.M. Riley


Executive Summary

The combined effects of aircraft type and atomizer on the deposit of a simulated insecticide spray were examined in a total of six trials. Spray applications were made along a single flight line with the Grumman Avenger equipped with Teejet 11010 hydraulic nozzles and the M18 Dromader equipped with either the Sergonair high speed rotary atomizer or the Micronair AU 4000. Spray deposition was assessed on foliage simulators deployed within the forest canopy up to a distance of 400 m downwind of the spray line. Spray deposit for the Grumman Avenger/TeeJet 11010 system was evaluated and compared with the M18 Dromader/Sergonair system in four trials. The Grumman Avenger/Teejet 11010 and M18 Dromader/Micronair AU 4000 system were evaluated and compared in two trials.

In each application the deposited droplet spectrum was characterized by greater numbers of larger droplets from the hydraulic nozzle system and greater numbers of smaller droplets from the rotary atomizers. For a given mass of spray deposit the Sergonair system produced an average deposit density almost five times greater than the Teejet system and approximately two and a half times greater than the Micronair system.

Spray deposit densities (i.e. droplets per needle) when standardized to an emission rate of 1 ml of spray emitted per metre flown were consistently (approximately two to three fold) higher with both rotary atomizer systems. In all trials the profiles of mass deposit, when standardized to 1 g of material emitted per metre flown, were similar in shape for the two application systems used. Profiles typically showed a peak deposit in the first 100 m downwind of the spray line with deposit tending to level out beyond 200 m. In three out of four comparisons the calculated total mass of material deposited from the Grumman Avenger/Teejet 11010 system was greater than that from the M18 Sergonair system. In the first of the Grumman Avenger/Teejet 11010: M18 Dromader/Micronair AU 4000 comparisons the latter system produced a greater total mass deposit however, in the second application this trend was reversed. Differences in mass deposit corresponded to relatively few large droplets generally representing less than 5% of the total number of deposited droplets.