Dennis R Gardisser, WRK of Arkansas LLC
It is essential that pesticide applications be made uniformly across the treated area. There has been a lot of discussion recently about the need, or lack of need, for nozzles to be placed in the center section on aircraft. This issue will not be resolved here, but hopefully it will increase awareness of the potential need. The need seems to be more prevalent with the application volumes or 5 GPA or greater. The “rule of thumb” that seems to work well is to have one half as much flow in the center section as the outboard sections – biased toward the torque side of the section.
Sampling results at Operation SAFE clinics doesn’t always show a need for center nozzles. Flights directly into the wind may allow the center section to fill in.
A recent analysis of an AT-802 at a fly in at Park Rapids, Minnesota emphasizes the need for center nozzles. This aircraft had no center nozzles. Three pattern collections are shown on the top of the output page and the average in the center. The center of the pattern exhibits a reduction of deposit in that area. The existence of this void was obvious on each of the three passes. The identification of the specific aircraft has been changed.
Recent tort litigations have centered on alleged pattern non-uniformity. Field streaking is never a good thing. Operators should carefully place nozzles to achieve optimum distribution all across the boom. Operation SAFE pattern documentation is an excellent place to start – to be followed by careful follow up of actual applications.