1. Agricultural Aviation Technology
Dennis R. Gardisser, PhD, P.E.
WRK of Arkansas
Robert E. Wolf, PhD
Kansas State University

2. Application Altitude
High
Low
Window

3. Drift potential vs. Height
Example
10ft – 14 ft

4. Aircraft Boom Design Location relative to the wing
Nozzle setup & orientation on the boom
Microfoil booms
Positive action shutoff
Boom suck back

5. Boom length/location

7. Distance below trailing edge of wing
Boom
Perpendicular
Must be >= 10 inches
Spray outlet

8. ASABE Standard S572
Explanation of Dv.1, Dv.5 or VMD, Dv.9, & RS (Relative Span)
Meaning of key words (Fine, Medium, etc.)
Need to limit amount of small droplets or fines
Practicality of regulation requiring 600 VMD droplet spectrum

9. Important Droplet Statistics:
RS = (Vd.9 – Vd.1)/VMD
VMD
(50%)
Operational Area
VD0.9
(90%)
VD0.1
(10%)

10. Relative Span
RS = (Vd.9 – Vd.1)/VMD

11. ASABE DSC and Volume Median Diameter (DV0. 5) From PMS
ASABE DSC and Volume Median Diameter (DV0.5) From PMS* Laser Spectrometer
Droplet Spectra
Classification (DSC)
Droplet Size
Range
Very Fine (VF) < 182µm
Fine (F) µm
Medium (M) µm
Coarse (C) µm
Very Coarse (VC) µm
Extremely Coarse (XC) >656µm
These size categories are developed from an ASAE standard reference nozzle set with a laser instrument. Spray nozzles and their operational parameters must then be characterized by the same laser instrument. The DSC categories from VF to XC are from the ASAE standard, the size ranges were obtained with the USDA ARS PMS system at College Station, Texas. Other instruments may give slightly different droplet size ranges with the respective DSC, but it is expected that a different laser system would give the same DSC for the same spray spectrum when the reference nozzles have been used to develop the droplet size ranges for each DSC with that different laser system and that system is in turn used to classify the DSC of the given spray spectrum. The standard requires that the same system be used for classifying nozzles that is used for establishing the size categories with the ASAE standard reference nozzle set.
*USDA ARS College Station, TX

12. Droplet Spectrum Generation
Pressure effects
Low pressure
High pressure
Aerodynamic effects
Nozzle type effects
Flat fan
Deflector
Sheet
Disc & Core
Straight stream
Electrostatic
Rotary

13. Cutting Droplet Size in Half
Results in ?? Times the Number of Droplets
Cutting Droplet Size in Half =
500
Microns
250
Microns
2 more droplets fill in the sphere

14. Air Temp 85F Canopy top 105F or more! Canopy Floor 75F
Hot air goes which direction?
Canopy top 105F or more!
Canopy Floor 75F

15. Size 290/250 = 1.16 290 micron droplet is 16% larger than 250
This may not appear to be a big change, but???

16. Droplet Data 250 v. 290 micron droplet Change in size?
Change in Volume or Weight?

17. Volume or Weight Remember that this is a cube root relationship.
If it was twice as big we would multiply
2 * 2 * 2 = 8 times heavier
For 290/250 = 1.16
1.16 * 1.16 * 1.16 = 1.56
Implies that a 290 micron droplet is 56% heavier than a 250!

18. 0.125 orifice,300 deflector Pressure Effects
Highest pressure has largest droplet at every speed – magenta line (upper left to lower right)
Lowest pressure has most fines at speeds greater than 120 mph (lower left to upper right) – red line

19. 0.125 orifice,50 deflector Pressure Effects
Highest pressure – largest droplet – Magenta line
Lowest pressure – most fines – red line

20. 300 deflector, 40psi Orifice Size Effects
This graph represents what happens when a big orifice is specified. Sky blue line (upper left to lower right) is the .171 orifice – has the smallest droplet spectrum at any speed. Also not that at speeds greater than 140 mph the larger orfiice has the most fines (graph lower left to upper right) – dark blue line.

21. Use of models
USDA
AgDrift
Australia

22. The following three slides are added as a reminder of the tools available to aerial applicators to help configure the spray system to achieve the desired droplet spectra specifications. Again, these models have been the subject of previous programs so try to avoid spending much time in detail of each. Reinforce the value these models can be to the industry.
This is the CP03 USDA model – technical version. Vd.1 and Vd.9 are added as well as the graphs at the bottom to show how the droplet spectrum fits into the model. There is much more information on the technical version if one takes the time to understand the data.
The same information can be derived from the same model on the CP Products home page.

23. USDA Aerial Nozzle Atomization Models
Example view. This page is not interactive, however remind the audience that the 4 yellow boxes (in the 4 red circles) can be adjusted to affect the resulting droplet spectra characteristics. With this model, operators will need to be familiar with CP-03 orifices (.062, .078, .125 and .172) available and the deflector choices (30°, 55° and 90°),. Straight stream deflectors would be 0°, 5° and 30°.
Items in the larger circle will change as inputs are adjusted. Briefly review all the terms as it relates to drift probability – VMD, RS, %<100, %<200, and DSC (droplet spectra classification).

24. This screen is not interactive
This screen is not interactive. This is the AgDrift computer model input screen which has several libraries of model input parameters that operators can select to describe their particular operation. There are 72 different aircraft that are contained in the Aircraft library. Several different spray nozzles or droplet size distributions can be selected. The USDA atomization models are incorporated in AgDRIFT and there are several other input variables including height of flight, and weather conditions so spray drift can be more accurately predicted.
Model Input Screen

25. Weather Wind Speed Wind Direction Relative Humidity
Evaporation Potential
Inversions

26. Recognizing Inversions:
Under clear to partly cloudy skies and light winds, a surface inversion can form as the sun sets.
Under these conditions, a surface inversion will continue into the morning until the sun begins to heat the ground.

27. Strong Inversion

28. Courtesy – George Ramsay, Dupont

30. Record Keeping Frequency Where to take measurements
Usefulness of weather offsite (ie. Local airports)
Utilization of smoke or other visual references

31. Flight Pattern Upwind Downwind Speed (Slow v. Fast)
Helicopter v. Fixed wing

32. Surfactants Expected effects Potential to make the situation worse
Clean out concerns

33. Desired Effect from Additives
VMD
(50%)
VD0.9
(90%)
VD0.1
(10%)

34. Actual Effect from Additives
VMD
(50%)
VD0.9
(90%)
VD0.1
(10%)

35. Air Temp 85F Canopy top 105F or more! Canopy Floor 75F
Hot air goes which direction?
Canopy top 105F or more!
Canopy Floor 75F

36. Questions??