Agricultural Aviation Technology

Dennis R. Gardisser, PhD, P.E.WRK of Arkansas

Robert E. Wolf, PhDKansas State University

Application Altitude

• High

• Low

• Window

10ft – 14 ft

Drift potential vs. Height

Example

Aircraft Boom Design

• Location relative to the wing

• Nozzle setup & orientation on the boom

• Microfoil booms

• Positive action shutoff

• Boom suck back

Boom length/location

Distance below trailing edge of wing

Wing

Boom

Perpendicular

Must be >= 10 inches

Spray outlet

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

Important Droplet Statistics:

Operational Area

RS = (Vd.9 – Vd.1)/VMD

Relative Span

RS = (Vd.9 – Vd.1)/VMD

ASABE DSC and Volume Median Diameter (DV0.5) From PMS* Laser Spectrometer

• Very Fine (VF) < 182µm• Fine (F) 183-280µm• Medium (M) 281-429µm• Coarse (C) 430-531µm• Very Coarse (VC) 532-655µm• Extremely Coarse (XC) >656µm

*USDA ARS College Station, TX

Droplet Spectra Classification (DSC)

Droplet SizeRange

Droplet Spectrum Generation

• Pressure effects– Low pressure– High pressure

• Aerodynamic effects• Nozzle type effects

– Flat fan– Deflector– Sheet– Disc & Core– Straight stream– Electrostatic– Rotary

Cutting Droplet Size in

Half

Results in ?? Times the Number of Droplets

==2 more droplets fill in the sphere

500Microns

500Microns 250

Microns

Air Temp 85F

Canopy top 105F or more!

Canopy Floor 75F

Hot air goes which direction?

Size

• 290/250 = 1.16

• 290 micron droplet is 16% larger than 250

• This may not appear to be a big change, but???

Droplet Data• 250 v. 290 micron droplet

• Change in size?

• Change in Volume or Weight?

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!

0.125 orifice,300 deflector

0

100

200

300

400

500

600

700

100 110 120 130 140 150 160

MPH

DV

0.5

0

2

4

6

8

10

12

14

16

V<

10

0µ

m

20psi 40psi 60psi 20psi 40psi 60psi

Pressure Effects

0.125 orifice,50 deflector

0

100

200

300

400

500

600

700

100 110 120 130 140 150 160

MPH

DV

0.5

0

2

4

6

8

10

12

14

16

V<1

00µm

20psi 40psi 60psi 20psi 40psi 60psi

Pressure Effects

300 deflector, 40psi

0

100

200

300

400

500

600

100 110 120 130 140 150 160

mph

DV

0.5

0

2

4

6

8

10

12

14

16

V<

10

0µ

m

0.061 0.078 0.125 0.171 0.061 0.078 0.125 0.171

Orifice Size Effects

Use of models

• USDA

• AgDrift

• Australia

USDA Aerial Nozzle Atomization Models

Model Input Screen

Weather

• Wind Speed

• Wind Direction

• Relative Humidity

• Evaporation Potential

• Inversions

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.

Strong Inversion

Cloud of 5-25 u oil droplets generated under unstable conditions

105 foot temperature monitoring tower

8’ 41°F

16’ 41°F

32’ 40°F

64’ 40°F

105’ 38°F

8’ 33°F16’ 36°F32’ 37°F64’ 38°F

105’ 38°F

.5 mph wind

2.5 mph wind

Shallow surface inversionSTABLE conditions up to 64’ NEUTRAL conditions at 105’

Cloud is dispersing

Courtesy – George Ramsay, Dupont

Record Keeping

• Frequency

• Where to take measurements

• Usefulness of weather offsite (ie. Local airports)

• Utilization of smoke or other visual references

Flight Pattern

• Upwind

• Downwind

• Speed (Slow v. Fast)

• Helicopter v. Fixed wing

Surfactants

• Expected effects

• Potential to make the situation worse

• Clean out concerns

Desired Effect from Additives

Actual Effect from Additives

Air Temp 85F

Canopy top 105F or more!

Canopy Floor 75F

Hot air goes which direction?

Questions??