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SPECIAL REPORT
TR 76-113-01
DEVELOPMENT OF A FIELD MANUAL FOR THE
CHARACTERIZATION OF SPRAY FROM
SMALL AIRCRAFT
Prepared by
R. K. Dumbauld and J. E. Rafferty
Prepared for
Forest Service
U.S. Department of Agriculture
Equipment Development Center 2
Missoula, Montana 59801
and
Methods Application Group
Davis, California
Final Report Under Contract No. 26-3694
December 1976
H. E. CRAMER COMPANY, INC.
University of Utah Research Park
P. O. Box 8049
Salt Lake City, Utah 84108
LIBRARY COPY
ROCKY MT. FOREST & RANGE
EXPERIMENT STATION
NO. 7734 2809
FIELD MANUAL FOR CHARACTERIZING
SPRAY FROM SMALL AIRCRAFT
Prepared by
R. K. Dumbauld and J. E. Rafferty
Prepared for
U. S. Department of Agriculture
U. S. Forest Service
Missoula Equipment Development Center
Missoula, Montana
Contract No. 26-3694
December 1976
H. E. CRAMER COMPANY, INC.
University of Utah Research Park
P. O. Box 8049
Salt Lake City, Utah 84108
TR 76-113-02
Section
TABLE OF CONTENTS
Title
ACKNOWLEDGEMENTS
INTRODUCTION
EQUIPMENT REQUIRED FOR FIELD CHARACTERI-
ZATION OF SPRAY FROM SMALL AIRCRAFT.
2.1 Grid Layout and Sampling Equipment
2.2 Equipment for Field Analysis of Spray Deposit
Cards
2.3 Equipment for Field Laboratory Analysis
DESIGNING THE SAMPLING GRID: OPERATIONAL
CONSIDERATIONS
8.1 Design of the Sampling Grid
3.2 Operational Considerations
FIELD CHARACTERIZATION OF THE SPRAY DIS-
SEMINATION SYSTEM
‘hel Plastic Templates for Sizing and Counting
Drops
4.2 Swath Width and Drop Density
4.3 Field Estimation of Volume Median Diameter
FIELD LABORATORY CHARACTERIZATION OF THE
AIRCRAFT SPRAY DISSEMINATION SYSTEM
5.1 Drop Density Distribution in the Swath
5.2 Determination of the Swath Drop-Size Dis-
tribution, Mass Median, Average Mass and
Number Mean Diameters
5.3 Estimation of Spray System Deposition,
Deposition Efficiency (Mass Recovery)
and Swath Width Based on Mass Deposition
REFERENCES
Page
68
ACKNOWLEDGEMENTS
The procedures described in this manual are principally based on expe rience
gained during the conduct of spray characterization trials at Townsend, Montana in
the late spring of 1976 and from an analysis of the data obtained during these trials.
Many people participated in the development of the procedures outlined in the manual.
In particular, the authors gratefully acknowledge the very valuable assistance of
William McIntyre (Dugway Proving Ground, Dugway, Utah) and Robert Ekblad (U. S.
Forest Service, MEDC, Fort Missoula, Montana) in all phases of the work. We are
also indebted to John Barry and Lynne Whitcombe, U. S.:Forest Service, FI&DM
Applications Group, Davis, California for their assistance in data analysis during the
Townsend trials. The very helpful assistance of our colleagues W. R. Santee and
A. L. Hancock during the post-trial data analysis is also gratefully acknowledged.
SECTION 1
INTRODUCTION
The purpose of this manual is to describe field procedures for the rapid
characterization of the spray deposit from small aircraft spray systems prior to
forest spray operations. The techniques described in this manual are intended to
assist spray project entomologists in establishing the applicability of specific spray
system characteristics to particular application problems and to assist aircraft
engineers in implementing and testing the effects of field changes in aircraft spray
systems intended to improve application characteristics. Techniques are described
for:
2 Establishing the design of a sampling grid and test plan for
determining spray characteristics
e Estimating the volume median, number median and average
mass diameters of the spray deposit
° Estimation of the minimum effective swath width produced
by the spray equipment and the mass per unit area deposited
within the swath width
e Estimation of the spray system deposit efficiency within the
swath
Section 2 defines the field equipment required to accomplish the spray char- |
acterization. The development of a test plan and design of a sampling grid are dis-
cussed in Section 3. The description of field procedures for spray characterization
is contained in two sections. Section 4 describes procedures for the preliminary
estimation of volume median diameter and swath width immediately after an aircraft
spray flight so that immediate decisions can be made regarding aircraft flight altitude,
nozzle type, nozzle configuration and other factors affecting spray deposit. Tech-
niques for use in the field laboratory to confirm these preliminary estimates of
volume median diameter and swath width and to obtain quantitative estimates of
the number median diameter, average mass diameter and associated mass recovery
are described in Section 5.
SECTION 2
EQUIPMENT REQUIRED FOR FIELD CHARACTERIZA-
TION OF SPRAY FROM SMALL AIRCRAFT
The successful conduct of spray characterization field trials requires a
relatively large amount of equipment. Because field trials are usually conducted
in remote areas, most of this equipment must be acquired in advance of the trials.
The necessary equipment for establishing the sampling grid, conducting the trials,
and analyzing the data is listed and briefly described in this section. In some cases,
equipment is identified by manufacturer or catalog number. These designations do
not constitute an endorsement of the equipment, but are given to assist in identifying
the type of equipment or material necessary for accomplishing the objectives of the
project.
2.1 GRID LAYOUT AND SAMPLING EQUIPMENT
Table 2-1 lists equipment required to lay out the sampling grid and to sample
the spray drops and meteorological parameters. A brief description of the intended
use of the equipment is also provided in the table. More detailed descriptions of the
use of the equipment are given in Section 3 below.
The sampler cards most often used in sampling spray drops containing oil- ©
red or organic tracer dyes are 17 by 11 centimeter cards, Kromekote Cover 65
pound paper, glossy coated both sides, manufactured by the Champion Paper and
Fiber Company, Hamilton, Ohio. A plastic card holder, manufactured by the Gen-
eral Binding Company for Missoula Equipment Development Center (MEDC, USFS),
has proven very effective in field characterization trials. The card holder is designed
so that several sampling cards can be placed in the holder at one time and the top card
removed after a trial to expose a clean card for the next trial. The lips of the card
holder are such that the effective sampling area of the exposed card is about 14 by 9
centimeters. Further information concerning other types of sampling cards and the
card holders can be obtained from MEDC.
4
TABLE 2-1
SAMPLING AND GRID LAYOUT EQUIPMENT
Sampler Cards
Card Holders
Collection Boxes
Marking Pens
Manilla Rope and Ties,
Tape Measure
Wooden and/or Metal
Stakes, Sledge
Smoke Grenades
Low-Level (2-meter) Wind
Direction and Speed Sensor,
Recording Equipment
Pilot Balloons and
Helium (Optional)
Tethersonde (Optional)
Collection of spray drops
Protection of cards (from smudging, etc. )
and ease of handling
Contain cards and holders for disposition
and collection in the field
Marking individual sampler cards with
sampler location and trial number
Layout of sampling lines
Identification of sampling locations and
lines
Smoke plumes aid pilot in locating spray
grid and director in estimating wind
velocity relative to sampling layout
Continuous chart record of wind speed
and direction
Vertical profiles of wind direction and
speed
Vertical profiles of temperature, wind
direction, wind speed and relative
humidity
TABLE 2-1 (Continued)
Transit or Theodolite
Protective Clothing and/or
Large Plastic Bags
Communications
Equipment
Orienting sampling lines and meteor-
ological equipment; theodolite can also
be used to track pilot balloons
Protection of field workers and equip-
ment in aircraft spray path
Communications between field crew and
between field crew manager and project
director
Boxes for transporting the cards to and from the field laboratory and along
the sampling lines are necessary. These boxes are conveniently constructed from
plywood. Suggested inside dimensions are 13 centimeters wide, 20 centimeters
deep and 36 centimeters long. A wide canvas shoulder strap attached to the ends
of the box facilitates carrying the cards and card holders along the sampling lines.
A small section can be added to the box for transporting marking pens, which may
be required to alter the numbers identifying the sampling positions.
Manilla ropes, tape measure, stakes and sledge hammers are necessary
for laying out the sampler lines. Bright tape, such as surveyor's tape, is tacked to
the 3/8 inch manilla rope using hog rings or other suitable fasteners at 10-foot inter-
vals. One-hundred foot lengths of manilla rope are conveniently handled in the field.
Quarter-inch stock metal rods cut 2,5 feet in length are used to mark card positions
along the sampling lines.
Smoke grenades, such as the U. S. Army Grenade, Hand M-18, with yel-
low or white smoke are essential in conducting field characterization trials. The
smoke plumes serve to indicate the wind speed, wind direction and atmospheric
diffusion conditions,
A battery operated low-level (2-meter) wind direction and speed sensor
with associated strip-chart recording equipment is necessary for documenting mete-
orological conditions during the characterization trials and in establishing preferred
wind directions at a given site prior to the trials. Recording strip-chart speeds of
3 inches per hour should be specified and changeable gears to permit chart speeds
of 12 inches per hour. The Electronic Weather Station (EWS) manufactured by
Climatronics Corporation, Hauppauge, New York, and equipped for measuring
and recording wind speed and direction is typical of instruments meeting the above
requirements. Pilot (10-gram) balloons are used to obtain vertical profiles of
wind speed and direction. Continuous measurements of wind speed and direction
and temperature in the vertical to heights above the planned aircraft altitude are also
TABLE 2-3
EQUIPMENT FOR FIELD LABORATORY ANALYSIS OF
SPRAY DEPOSIT CARDS
Cork Bulletin Board
Large Bulletin Board
Push Pins
Card Illumination Lamp
Counting and Sizing Card
Templates
Measuring Magnifier,
Data Sheets
Pencils, Pencil Sharpeners,
Grease Pencils, Cleaning
Tissue, Stapler, Note Pads,
Envelopes, Rubber Bands,
Paper Clips
Graph Paper (10 x 10 to the
Centimeter and Probability
x 2 Log Cycle)
Programmable Electronic
Calculator (Optional)
Work base for sizing and counting drops
Tacking card to bulletin board
High-intensity illumination of counting
area
Identification of card area for counting
and sizing drops
Counting and sizing drops
Data recording, data organization
Graphic data display
Mathematical calculations
LT
ie See ae
(wd) Y3L3WVIO dOYd
34
99.5
98 99
20 30 40 50 60 70 80 90 95
10
CUMULATIVE NUMBER DISTRIBUTION (percent)
Cumulative number distribution for Trial &
FIGURE 3-7.
7
(wo) Y3ZL3WVIG dOUuG
35
93.9
98 99
90 95
CUMULATIVE NUMBER DISTRIBUTION (percent)
20 30 40 50 60 70 80
10
Cumulative number distribution for Trial 7.
FIGURE 3-8.
i i aaa
es
(wi) yY313WVIO dOYNG
36
r
i '
H '
H $
i f = if
et ' '
‘ i
t
99.99
99.9
38 99
90 95
CUMULATIVE NUMBER DISTRIBUTION (percent)
20 30 40 50 60 70 80
10
Cumulative number distribution for Trial 9.
FIGURE 3-9.
33.92
39:9
oo 3
90° 35
20 30 40 50 60 70 80
0)
(wi) Y3L3SWVIG dOYG
37
CUMULATIVE NUMBER DISTRIBUTION (percent)
Cumulative number distribution for Trial 11.
FIGURE 3-10.
99.99
33:9
98 .99
90 95
20 30 40 50 60 70 80
1)
(wd) y313WwvIa dOYNG
38
CUMULATIVE NUMBER DISTRIBUTION (percent)
Cumulative number distribution for Trial 18.
FIGURE 3-11.
p = density of the spray material
qd, i = drop diameter representing the lower limit of the ti size
. category
h
d = drop diameter representing the upper limit of the it size
: category
The results obtained by applying Equation (3-3) to the drop counts and drop-size data
for the five trials are shown in Table 3-4. The mass distributions for Trials 6, 7,
9, 11 and 18 have been plotted on log-probability scales in Figures 3-12 through 3-16.
The mass median diameter is the drop diameter that divides the spray dis-
tribution within the swath into two equal parts by mass. The value of the mass median
diameter for each trial can be determined from Figures 3-12 through 3-16 by noting
the drop diameter corresponding to the 50-percent point of the cumulative distribu-
tion and is marked by the symbol + in the figures. Since density is linear with drop
size, the mass median diameter and volume median diameter (VMD) are equivalent.
The number median diameters (NMD) and volume median diameters (VMD) obtained
for the five trials are summarized in Table 3-5.
a MASS RECOVERY ESTIMATES
The mass recovered within the swath for each of the five trials was also
estimated from the estimates of spray deposit density for each of the sampling cards
P ‘ : t
in the swath. The mass per unit area (Mj) deposited on the j e card was estimated from
the relationship
39
OF
TABLE 3-4
CUMULATIVE MASS DISTRIBUTIONS FOR
TRIALS 6, 7, 9, 11 AND 12
Drop-Size Category (1)
~
~
i)
Upper Limit
Drop Diameter
(um)
171,1 212.3 251.08 289.7
83,77 128.3 171.1
47.71
27.64 47.71 \
jm 3.134 10.37 22,42
27.64 47.71 67.90
Cumulative
Percent
by Mass
67.33 89. 09 97.45 98.60
Upper Limit
Drop Diameter
(um)
289.7
a
N
~
a
251.8
79.58 98.09
Upper Limit
Drop Diameter
(um)
Cumulative
Percent
by Mass
88, 20 108.6 170.5 254. 7 297.5
37.34 54.72 717.92 90. 73 93. 61
Upper Limit
Drop Diameter
(um)
129.1 170.5 191.4
o
id
to
a
Cumulative
Percent
by Mass
72.65
98, 05
55.77
Upper Limit
Drop Diameter
(um)
Cumulative
Percent
by Mass
149.8 170.5 - | 191.4 212.4 233.5 254.7
70. 94 83.70 97.93
np
Bt
a
~
a
Fed
©
r—)
@
@
nN
uo
(wit)
Y3SLSWVIG dOud
41
99
98
20 30 40 50 60 70 80 90 935
10
CUMULATIVE MASS (percent)
Cumulative mass distribution for Trial 6.
FIGURE 3-12.
ee ee ee eas Jette loss
es he ae !
wwf
ra RARE (ly ie a
102
(wo) YysL3aWVIG
dOud
42
20 30 40 50 60 70 80 s0.lUSSllCSSCSD
CUMULATIVE MASS (percent)
10
Cumulative mass distribution for Trial 7.
FIGURE 3-13.
98 99
90 95
20 30 40 50 60 70 80
Eee eee
i0
(wh) Y3ZLSWVIC dOYG
43
CUMULATIVE MASS (percent) ~
14, Cumulative mass distribution for Trial 9.
FIGURE 3
(wn) Yy3L3WVIO
44
36. 3
90 35
20 30 40 50 60 70 80
CUMULATIVE MASS (percent) ©
O
Cumulative mass distribution for Trial 11.
-15.
FIGURE 3
i ppeed they oe
ma 1 Fi ‘ wee af t ry wh ‘
te tptote wheebe Bead fa 8 .
36 99
90 95
20 30 40 50 60 70 80
CUMULATIVE MASS (percent)
To)
cat Eipree nes vee eaten! et Soe ae pi It a a wal Sites ay Ae - Sis ie —
A Hert ee eae bell bedi pee | 5 pe Oe 1 Pert: ee lag t a Ww
eaten e ARE 15; eae 7 ea 6 iis 7 ne Oo
tif benfet bh op B weer ares (0 SE | ile
{ ' 1 ' ‘ ; ‘
(wh) Yy3sL3WVIG dOoXa
45
Cumulative mass distribution for Trial 18.
FIGURE 3-16.
TABLE 3-5
NUMBER MEDIAN AND VOLUME MEDIAN
DIAMETERS IN MICROMETERS
- Trial Number
Number
Median
Diameter
(um)
Volume
Median
Diameter
(4m)
46
|r
I
M. —4 aaa =
j A, 2 “a Ga)
J i=
where the terms appearing in Equation (3-6) have been defined in Section 2 above.
The distribution of mass deposition along the sampling lines for Trials 6, 7, 9, 11
and 18 obtained from Equation (3-6) is shown in Figures 3-17 through 3-21, The
total mass recovery per unit length of flight path is estimated from the expression
MR = § s Mj (3-7)
where
S = separation distance between cards on the sampling line
Values of the mass recovered in the swath of the five trials calculated by using
Equation (3-7) are given in Table 3-6. Table 3-6 also presents estimates of the
deposition efficiency within the swath. This was calculated by dividing the mass
recovery by the amount of material released by the aircraft per unit length of the
flight path and multiplying the result by 100 to obtain units of percent.
47
x. ~ — ene Sa ae en eS ee - eee oe ——m
u i
i : i t
; : i
-4 H ‘a _
: 1
_ Se eee tae pe + SS Se ee nt ee een nee =} _ —
a ee pee ee en ee er ee _———— $$ $$
55 60 65 — 70
CARD NUMBER
50
wW
t+
Mass deposited along the sampling line for Trial 6.
FIGURE 3-17.
48
DEPOSITION (mg m~2)
103
102
FIGURE 3-18.
CARD NUMBER
Mass deposited along the sampling line for Trial 7.
49
w 6W) NOILISOd3G
CARD NUMBER
FIGURE 3-19. Mass deposited along the sampling line for Trial 9.
10?
(z-u Bw) NOILISOd3G
25 3| 37
CARD NUMBER
19
I3
Mass deposited along the sampling line for Trial 11.
FIGURE 3-20.
51
CARD NUMBER
Mass deposited along the sampling line for Trial 18.
FIGURE 3-21.
52
Mass
Recovery
(g m7})
Material
Disseminated
(g m7})
Deposition
Efficiency
(Percent)
TABLE 3-6
MASS RECOVERY, MATERIAL DISSEMINATED
AND DEPOSITION EFFICIENCY
Trial Number
53
SECTION 4
DEVELOPMENT OF A
FIELD MANUAL
As noted in Section 1, the major purposes of this study are to establish
procedures to achieve reproducible estimates of the deposits on card samplers
and to establish methods and procedures for the rapid characterization of aircraft
spray. Section 4.1 below describes the procedures followed in developing the recom-
mendations contained in the field manual for designing the sampling grid and for set-
ting meteorological limits. The procedures used in developing the recommendations
contained in the field manual for analyzing deposit data to obtain spray characteriza-
tion information are described in Section 4, 2.
4.1 DESIGNING THE SAMPLING GRID AND OPERATIONAL CONSIDERATIONS
The decision to recommend inwind aircraft flight patterns rather than cross-
wind flight patterns for characterizing aircraft spray was reached early in the study.
It was evident from the beginning that only a limited number of cards could be ana-
lyzed to obtain a rapid quantitative estimate of volume and number median diameters
and the mass deposited in an effective swath width. A brief consideration of sampling
requirements for crosswind flights relative to those for inwind flights shows that
inwind flights are better suited for spray characterization trials. In the absence of
atmospheric and aircraft turbulence, a drop with settling velocity V released ata
height H above the ground will impact at the distance x downwind from the point
of release equal to
{= == (4-1)
54
where U is the mean wind speed in the layer between the ground and height H. For
a release height of 50 feet (15.24 meters), a wind speed of 5 miles per hour (2. 24
meters per second), a 20-micrometer drop with a settling velocity of 0.0394 feet
per second (.012 meters per second) will impact at a distance of about 1.8 miles
(2838 meters) from the point of release. A 200-micrometer drop with a settling
velocity of 2.3 feet per second (0.7 meters per second) released under the same
conditions will impact at about 160 feet from the release point. The presence of
atmospheric and aircraft-induced turbulence or downdrafts will cause some of the
20- and 200-micrometer drops contained in a spray cloud to impact at distances
closer to the point of release. Nevertheless, sampling lines must extend for rela-
tively long downwind distances to ensure that the full drop spectrum is sampled if
the material is released from an aircraft traveling crosswind. With tawind flights,
the 20- and 200-micrometer drops travel the same distances, but when the aircraft
crosses the sampling line and continues upwind from sulficient distances, drops of
all sizes are transported by the wind to the sampling line. The sampling line for
inwind releases need only be long enough to contain the effective minimum swath
width so that mass per unit area, mass recovery and minimum swath width can be
specified. As shown below, the crosswind extent of the sampling lines required for
these purposes is relatively small.
The requisite lengths of the aircraft release line upwind of the sampling
line and the sampling line itself can be estimated using dispersion-deposition model-
ing techniques. Ground-level deposition downwind from an instantaneous elevated
point source can be expressed by the following relationship (Cramer, et al., 1972)
55
where
oD)
"
source strength
H = release height
o' = standard deviation of the wind azimuth angle in radians
= standard deviation of the wind elevation angle in radians
x = downwind distance from the source
V = settling velocity of a drop
el
|
mean wind speed
y = lateral distance from the cloud centerline
The cloud growth in the lateral and vertical is assumed rectilinear with distance
from the source. The deposition at a point due to that portion of an inwind line
source extending a distance (RL) upwind of the point can be obtained by integrating
Equation (4-2) from x=0 to x=RL. Thus,
RL
Dep' = i Dep dx (4-3)
0
Under the assumption that aN = oF, , the above expression becomes
2 2
a Q'H /2n HV Vv H
Dep!) 2 SS ae NOD I eee -1 (4-4)
on (H7 + “) : 2 o/2 gq'? a H?+
y 20,01 (H ty ) E "
(Equation (4-4) continued on
following page. )
56
(Equation (4-4) continued. )
1/2
= (eas) 7 HV
oT (RL) e.g
= oa (H ty’)
E
2 2
Vv
fom gee agg = ee)
20. UW NE ty
; g
+y i
em | He (Ge w |
2c! BL) a(n + )
where the source strength Q' is expressed as the amount of material released per
unit line length. Equation (4-4) can be used to estimate the length of the release
line (RL) required to ensure that deposition at the point remains nearly constant
as the length (RL) is increased. For example, Figure 4-1 shows deposition at a
point for release lines upwind of the point of various lengths using the following
inputs in Equation (4-4)
Q' = 1 gram per meter
oF = 0.04363 radians (2.5 degrees)
u = 4 meters per second
H = 30 meters
y = 0 meters
V = 0.028, 0.08, 0.23, 0.48 meters per second
where the settling velocities V are for spherical drops of unit density corresponding
to approximate diameters of 30, 50, 90 and 150 micrometers.
57
DEPOSITION (g m~2)
4 6 8 10> 2
LENGTH OF RELEASE LINE (meters)
FIGURE 4-1. Ground-level deposition as a function of the upwind length of the
release line.
58
Inspection of Figure 4-1 shows that, for a 30-micromcter drop (V=0, 028
meters per second), the deposition at the point does not increase appreciably
after the release line length is about 100H (3000 meters) or longer. On the other
hand, deposition does not increase for a 150-micrometer drop (V=.48 meters per
second) after the inwind release line length is about 400 meters or more upwind
of the point. Similar curves were plotted for other release heights and for meteor-
ological input parameters expected during characterization trials. Based on an
analysis of these data and the experience gained during the Townsend trials, the
following general guidelines were developed for use in the field manual:
@ If most of the spray cloud mass is contained in drops with
diameters 50 micrometers or less and wind speeds u
are 4 meters per second or less, the length of the release
line RL upwind of the sampling grid should be about
100 times the aircraft altitude H (RL =100H).
e If most of the spray cloud mass is contained in drops
with diameters between 50 and 100 micrometers and
u is equal to or less than 4 meters per second, RL
should be about 70 H.
® If most of the spray cloud mass is contained in drops with
diameters greater than 100 micrometers and wu is equal
to or less than 4 meters per second, RL should be
equal to 35H.
It should be mentioned that the above estimates of the length of the release line are
conservative in the sense that shorter line lengths upwind of the sampling grids
might be satisfactory. Aircraft-induced turbulence and wake effects and the fact
that the aircraft-generated spray cloud has an initial vertical dimension of at least
several meters all act to decrease the required length of the upwind release line.
59
Equation (4-4) can also be used to estimate the length L of the crosswind
sampling line required to contain the swath. Figure 4-2 is a plot of the crosswind
deposition profile at the sampling line for an inwind release line length of 3000
meters (100H), a settling velocity of 0.028 meters per second, an aircraft altitude
of 30 meters, source strength of 1 gram per meter, and values of oF equal to
2.5 and 5 degrees. The abcissa is labeled in units of nH, where y in Equation
(4-4) has been set to nH. Inspection of Figure 4-2 shows that deposition at a cross-
wind distance of + 3H (£90 meters) is nearly a factor of 10 less than at the center
of the swath. Thus, a crosswind sampling line length equal to 6H would ensure that
about 90 percent by mass of deposition from a spray cloud comprised of 30-micro-
meter drops would be contained within the sampling line. The deposition for drops
of large diameter decreases more rapidly in the lateral or crosswind direction. For
this reason, more than 90 percent by mass of deposition from clouds comprised of
drops 30 micrometers and greater would be contained within a swath width of 6H. A
crosswind line length L equal to 10H is recommended for use in the field manual to
allow for some error in the aircraft crossing the sampling grid at the center of the
sampling line.
From 10 to 20 samplers should be in the swath to adequately define the
crosswind deposition profile. If, for example, we require that 15 samplers be
within the crosswind sampling length 6H, then the requisite sampler spacing S is
- = 0.4H (4-5)
Since the recommended length of the sampling line L is 10H, a total of 25 samplers
should be used on each sampling line. The trials at Townsend indicated that a sam-
pler spacing of 0,4H is more than adequate; a value of S=0.4H is therefore recom-
mended in the field manual. Thus, for an aircraft release height of 30 meters, the
60
a
Se
Re
2
2.
= ..
n
=
Be
WW
Bun.
-4H -3H ah =F O H 2H 3H 4H
CROSSWIND WIDTH (meters)
FIGURE 4-2. Crosswind deposition for an upwind release line length of 100H, H=
30 meters and V=0. 028 meters per second. The dashed line is for
oO, = 2.5 degrees and the solid line is for o,=5 degrees.
61
recommended sampling line length is 300 meters with a sampler spacing of 12
meters along the line.
Inspection of Figure 2-1 shows that the sampling lines on the Townsend
trials were approximately in the shape of an equilateral triangle. While it was not
recognized at the time, a grid design in the shape of an equilateral triangle is
ideally suited for spray characterization trials, since this design can accommo-
date large variations in wind directions without introducing large errors in the
analysis of sampler card data. Figure 4-3 is a diagram of the sampling design
recommended in the field manual. Inspection of Figure 4-3 shows that this design
tends to limit the angle between the aircraft flight path (flown into the wind) and a
sampling line to 90 + 30 degrees. An example of the flexibility of the grid design
for use with various wind directions is shown in Figure 4-4. If north is assumed
toward the top of Figure 4-4, sampling line A in Figure 4-4 can be used for all
winds from 150 through 210 degrees and from 330 through 30 degrees. Sampling
line B in Figure 4-4 can be used for all winds from 30 through 90 degrees and
from 210 through 270 degrees; similarly, sampling line C in igure 4-4 can be
used for all winds from 90 through 150 degrees and from 270 degrees through 330
degrees. The choice of the proper flight path for any given trial depends on the
mein wind direction measurements made just prior to conduct of the trial.
High wind speeds and high levels of ambient atmospheric turbulence are
not conditions recommended for conducting spray characterization trials for several
reasons. First, high winds and turbulence levels require the inwind release line be
extended to much longer upwind distances from the sampling lines and also require
longer sampling lines. Second, the consequent enhanced downwind spray drift
results in decreased deposition in the swath and possibly may cause the spotting of
cars and other objects outside the sampling grid area. For these reasons, the
recommendation is made in the field manual to conduct spray characterization
trials when mean wind speeds are less than 4 meters per second (9 miles per hour)
62
A le —»1S=0.4H
FIGURE 4-3, Simple equilateral triangle sampling grid for characterizing aircraft
spray. The length of the sides L are 10 times the aircraft flight
altitude H and the sampler spacing S is 0. 4H.
63
a0 300
270° 90° =. 270° 90°
we “00
C
se 300
A
Oo wo
FIGURE 4-4. Illustration of the use of the sampling lines of the grid design shown
in Figure 4-3 with winds from various directions.
64
2
and when ambient turbulence levels are moderate or low. Section 3.2.3 of the field
manual is reproduced in Appendix A and contains a description of a visual method,
using smoke from smoke grenades, for judging ambient turbulence levels. Section
3.2.3 of Appendix A also contains procedures for determining the sampling line for
use in the trial from wind direction measurements.
4.2 ANALYSIS OF SAMPLING CARD DATA
The second major purpose of this study was to establish methods and pro-
cedures and to recommend equipment to enable two or three persons to obtain
quantitative estimates of spray deposit density, volume median diameter, number
median diameter, mass deposition and the minimum effective swath width from the
sampling data within 5 hours after flight time. The basis of the recommendations
for accomplishing these objectives made in the field manual is discussed in the
following paragraphs.
Spray Deposit Density
The density of drops deposited on the sampling cards can only be quantita-
tively estimated by counting the stains, using a suitable magnifying instrument and
template to mark the area to be counted. As noted in Section 3.1, difficulty was
encountered in obtaining similar and unbiased estimates of spray deposit density
using two analysts during the post-trial analysis. Although no definite conclusion
cou'd be drawn from the brief study performed, it appeared that the difficulties
occurred because different areas of the cards were counted by the analysts and
because different estimates of the number of drops with stains less than 50 micro-
meters in diameter were obtained. For this reason, the Bausch and Lomb No.
81-34-35 measuring magnifier is recommended for use only when drops having
stain diameters less than 50 micrometers are not of major interest. Also, the
65
template for use in the counting procedure was redesigned so that the same area
would be counted by the analysts. Since the estimation of spray deposit density by
counting stains is usually mastered with only limited experience and proceeds
rather rapidly, the field manual contains the recommendation that spray deposit
density be estimated by counting a minimum of 200 stains on each of the sampling
cards within the swath.
Volume Median Diameter
Two methods were used for obtaining 'quick-look" estimates of the VMD
while in the field immediately following a trial: the direct-estimation method sug-
gested by Mr. McIntyre and the D-max method suggested by Maksymiuk (1964). The
results obtained from these two procedures are discussed in Section 2.5 and sum-
marized in Table 2-2. In general, the D-max method yielded larger-diameter esti-
mates than the direct-estimation procedure. Table 4-1 shows a comparison of VMD
estimates obtained in the field using these two procedures with similar estimates
made during the post-trial analysis from the cumulative mass distributions. Table
4-1 indicates that, except for Trials 6 and 7, the D-max method employed during
the post-trial analysis yields VMD estimates slightly larger than VMD's obtained
from the cumulative mass distribution curves for the trials. On the other hand, the
direct-estimation method tends to yield estimates of VMD that are lower than VMD's
from the cumulative mass distributions, except for Trial 6. Because the D-max
method is considerably easier for untrained personnel to apply, it is recommended
in the field manual for estimating VMD's in the field for a "quick-look" analysis
immediately after a trial has been conducted.
Prior to the field trials at Townsend, it was hoped that simple transforma-
tion formulas, based on the assumption that the drop diameters were log-normally
distributed, could be used to obtain average mass and number median diameters
from estimates of the volume median diameter made using either the direct-estima-
66
TABLE 4-1
ESTIMATES OF VOLUME MEDIAN DIAMETERS (um) FROM
THE FIELD AND POST-TRIAL ANALYSES
Trial Field D-max Method Cumulative
Number Direct-
Mass
Estimation Post-Trial Distribution
236
206
155
149
67
tion or D-max techniques. The results of the post-trial analysis indicated, how-
ever, that such relationships were very sensitive to the geometric standard devia-
tions of the drop distributions and that the geometric standard deviations could not
be estimated for different spray materials with sufficient accuracy without measur-
ing the mass or number distribution. For this reason, we believe drop-size dis-
tributions of the spray deposit are required. Measurement of the mass distribu-
tion should also yield more quantitative estimates of the VMD for a given trial.
Because of the limitation on time and personnel for analyzing the card data,
the decision was made to investigate means of reducing the number of cards analyzed
and the consequent effect on estimates of VMD. Experience in analyzing the card
data during the post-trial period indicated that two relatively inexperienced analysts
could count and size drops as well as calculate the mass distribution, using 3 to 5
_ eards in the swath, within 5 hours after flight time. Table 4-2 shows VMD's esti-
mated from the mass distribution obtained by analyzing 3, 5 and all the cards in the
swath, The total number of cards in the swath is also shown in the table. The 3
cards used in the analysis were selected from the center and the two ends of the
swath. When 5 cards were used, 2 additional cards located midway between the
center card and the ends of the swath were analyzed. As Table 4-2 shows, VMD's
estimated by obtaining the mass distributions from 5 cards were very similar to
those obtained using all the cards, the maximum error of 5. 8 percent occurring in
Trial 11.
Number Median Diameter
Number median diameters estimated from the number distribution from
all cards in the swath and from 5 cards in the swath are given in Table 4-3. The
data presented in Table 4-3 show that number median diameters obtained from an
analysis of 5 cards in the swath are very similar to those obtained by analyzing all
cards in the swath.
68
TABLE 4-2
VOLUME MEDIAN DIAMETERS ESTIMATED FROM
THE MASS DISTRIBUTION FROM 3, 5
AND ALL CARDS IN THE SWATH
Trial Total Number Volume Median Diameters (um)
Number of Cards
in Swath All Cards 3 Cards
210
69
TABLE 4-3
NUMBER MEDIAN DIAMETERS ESTIMATED FROM THE
NUMBER DISTRIBUTION FROM 5 CARDS AND
ALL CARDS IN THE SWATH
Trial Number Median Diameter (lm)
70
Average Mass Diameter
Estimates of the average mass diameter (AMD) are used in the recommended
field procedure for estimation of mass recovery in the swath. Table 4-4 gives values
of the average mass diameters estimated from the mass distribution obtained by
analyzing 3, 5 and all cards within the swath.
Mass Recovery Estimates
Because in many cases all sampling cards within the swath cannot be ana-
lyzed for mass deposition, the following procedure is recommended in the field
manual for estimating mass recovery in the swath. The mass in milligrams assoc-
iated with the average mass diameter drop, estimated from the analysis of the mass
distribution on 5 cards within the swath, is calculated from the expression
m = 5,236x10~° p (AMD)° (4-5)
where the units of AMD are micrometers and the density of the spray material p
is in grams per cubic centimeter. The AMD for the swath is assumed representa-
tive of the AMD for each card in the swath. The mass per unit area deposited on
th
the j card in the swath (Mj) is then estimated from the expression
~
M, (mgcm ) = mN (4-6)
where
N. = spray deposit density for the ia card in the swath
71
TABLE 44
AVERAGE MASS DIAMETERS ESTIMATED FROM THE
MASS DISTRIBUTION FROM 3, 5 AND
ALL CARDS IN THE SWATH
Average Mass Diameter (4m)
Trial
nner All Cards
72
The estimated mass recovered in the swath MR in units of grams per meter is
thus
-1
MR(gm) = 108 )) (4-7)
where S is the sampler separation distance in meters.
Mass recoveries using the above procedure based on the analysis of data
from 5 cards are compared with mass recoveries estimated from the mass depos-
ited on all cards within the swath in Table 4-5, The largest estimation error occurs
for Trial 7 where the 5-card analysis procedure overestimates the mass recovery
estimate from all cards in the swath by 27 percent.
It should be noted that the mass recovery estimates in Table 4-5 are based
on the analysis of sampling cards designated as being within the swath, where the
swath width was specified, except for Trial 7, as the distance between sampling
cards on the sampling line showing spray deposit densities greater than 20 drops
per square centimeter. For Trial 7, the flight altitude was 50 feet higher than
during the other trials and resulted in a lower spray deposit density over a greater
distance along the sampling line. The swath width for Trial 7 was specified as the
distance between sampling cards on the sampling line showing spray deposit den-
sities greater than about 12 drops per square centimeter. Thus, even though spray
deposit density within the swath for Trial 7 was less, for example, than for Trial 6,
the mass recovery for Trial 7 is greater than for Trial 6 because the swath is about
four times as wide.
The higher percentage error made in estimating mass recovery from the
5-card analysis procedure for Trial 7 may be a combined result of the lower spray
73
TABLE 4-5
MASS RECOVERIES ESTIMATED FROM THE MASS DISTRIBUTION
FROM 5 AND ALL CARDS IN THE SWATH
Mass Recovery (g m7)
74
deposit density and the fact that a lower percentage of cards in the swath (5 of 31
total cards) were analyzed than in the case of other trials.
Summary
Rapid estimates of the minimum swath width and spray deposit density
within the swath can be made in the field immediately after the aircraft flight by
counting stains on one sampling card on each end of the sampling line. Rapid esti-
mation of the volume median diameters using the D-max method is recommended
for use in the field.
Results of the post-trial analysis of data from 5 of the Townsend trials
indicates that quantitative estimates of the volume median, number median and
average mass diameters can be developed within a 5-hour period after flight time
from cumulative mass and number distributions based on the analysis of 5 cards
within the swath. Errors in estimating these parameters from an analysis of 5
rather than all cards in the swath were less than 10 percent. Thus, procedures
for estimating the volume median, number median and average mass diameters
from the analysis of 5 sampling cards are recommended in the field manual.
As might be expected from the cubic relationship between drop diameter
and mass recovery and the other approximations used in the 5-card analysis pro-
cedure, percentage errors in estimating mass recovery using this procedure are
greater than experienced in estimating the other spray characteristics. However,
because the analysis of trial data must be completed on a timely basis, the 5-card
analysis procedure is recommended for use in the field manual in estimating mass
recovery.
75
RETERENCES
Cramer, H. E., etal., 1972: Development of dosage models and concepts, Final
Report under Contract DAAD09-67-C-0020(R) with the U. S. Army. Des-
ert Test Center Report DITC-TR-72-609, Ft. Douglas, Utah.
Maksymiuk, Bohdan, 1964: A rapid method for estimating the atomization of oil-
base aerial sprays. Journal of Economic Entomology, Volume 57, No. 1,
p- 16.
76
Section
TABLE OF CONTENTS
Title
INTRODUCTION
1.1 Background
1.2 Study Objectives
1.3 Report Contents
DESCRIPTION OF THE TOWNSEND SPRAY CHAR-
ACTERIZATION TRIALS
2.1 Design of the Sampling Grid for the Townsend
Trials
2 Stain Factors
3 Field Analysis Procedures
-4 Meteorological Data
5 Field Laboratory Analysis Procedures
POST-TRIAL ANALYSIS
3.1 Determination of Spray Deposit Densities on
Sampling Cards and Swath Width
3.2 Determination of Drop-Size Distribution by
Number and Mass Number Median and Volume
Median Diameters
3.3 Mass Recovery Estimates
DEVELOPMENT OF A FIELD MANUAL
4.1 Designing the Sampling Grid and Operational
Considerations
4.2 Analysis of Sampling Card Data
REFERENCES
P age
co Cc
20
22
31
39
54
54
65
76
Appendix
TABLE OF CONTENTS (Continued)
Title
FIELD MANUAL FOR CHARACTERIZING SPRAY
FROM SMALL AIRCRAFT
WIND MEASUREMENTS
FIELD LABORATORY ESTIMATES OF SPRAY
DEPOSIT DENSITIES
ii
Page
C-1
SECTION 1
INTRODUCTION
} ee BACKGROUND
The U. S. Forest Service utilizes contractor-supplied and -operated air-
craft for the aerial application of pesticides during most forest spray projects. The
effective utilization of aircraft spray systems requires, among other things, that
basic parameters affecting spray deposit patterns such as flow rate, drop-size dis-
tribution and aircraft altitude be accurately adjusted for each spray operation. There
are a number of important logistical constraints affecting the field measurements of
spray pattern characteristics. For example, because of cost factors, the spray air-
craft is normally scheduled to be available at the site of the spray project only a few
days prior to the commencement of spray operations. Thus, the time available for
quantifying spray characteristics and making any required adjustments is very short.
In recognition of the need to develop quantitative field procedures for the
rapid characterization of spray patterns, the Methods Application Group (MAG) and
the Missoula Equipment Development Center (MEDC), Forest Service, USDA, init-
iated a field program in conjunction with the Northern Region 1976 Pilot Project to
develop and evaluate spray characterization procedures. A contractor, the H. E.
Cramer Company, Inc. assisted MEDC in the development and evaluation of these
during the Northern Region 1976 Pilot Project.
1.2 STUDY OBJECTIVES
The specific objectives of the work performed for MEDC by the H. E.
Cramer Company were to:
(1)
(2)
(3)
The factors to
terizing small
Establish procedures to achieve reproducible deposits on
deposit card samplers and to estimate the number of spray
drops per square centimeter, volume median diameter,
number median diameter, mass per unit area and mini-
mum effective swath width from deposit card sampler
data.
Establish methods and procedures and recommend the
equipment required to enable two or three persons to
complete the characterization of aircraft spray within
5 hours following a field trial.
Evaluate the methods, procedures and equipment used in
the Northern Region 1976 Pilot Project at Townsend,
Montana.
be considered in the development of a field methodology for charac-
aircraft spray included the following:
Advantages of inwind flight patterns versus crosswind
flight patterns
Meteorological limitations imposed on the conduct of
field trials
Optimum flight altitude of the aircraft
Minimization of grid sampler requirements
Optimum arrangement of card samplers
® The times or points at which the aircraft spray system
should be turned on and turned off during a characteriza-
tion flight
1.3 REPORT CONTENTS
This technical report describes the spray characterization trials conducted
during the Northern Region 1976 Pilot Project at Townsend, Montana; the post-trial
analysis of the sampler card and meteorological data obtained during the Townsend
trials; and, the background for the development of the field manual for character-
izing spray from small aircraft. Section 2 below describes the characterization
trials at Townsend, including the design of the sampling grid as well as the ''quick-
look" field analysis and field laboratory analysis of the sampler card data. The pro-
cedures used in the post-trial data analysis and the results of this analysis are »
described in Section 3. Section 4 presents the detailed background of the develop-
ment of the field manual for characterizing spray aircraft. There are three appen-
dices to the report. The "Field Manual for Characterizing Spray from Small Air-
craft" developed as a result of this study is reproduced in Appendix A. Appendix
B contains summary tables of wind direction and wind speed measured during the
characterization trials. Estimates of the spray deposit density made during the
laboratory analysis of all sampler cards in the spray swath at Townsend are con-
tained in Appendix C.
SECTION 2
DESCRIPTION OF THE TOWNSEND
SPRAY CHARACTERIZATION
TRIALS
The Townsend spray characterization trials were conducted from 27 through
30 June, 1976, in an area north of Townsend adjacent to the Silos Recreation Area,
using a Bell 205 helicopter equipped for aerial spray applications. As shown in
Table 2-1, there were a total of 19 trials. An Orthene mix was used in 8 trials
while a Dylox mix was used in the remaining 11 trials. The Orthene was prepared
for spraying by using 1.33 pounds of Orthene, 0.01 pounds of Rhodamine B dye and |
0. 885 gallons of water to make one gallon of spray. One-half gallon of Dylox liquid,
0.48 gallon of Hi Sol 4-5-T solvent and 0.02 gallon of Automate Red B dye were used
to make one gallon of the Dylox spray mix. As noted in Table 2-1, the aircraft
flight altitude was 50 feet above the ground in all trials except Trial 7, where the
flight altitude was 100 feet. Eight Beecomist spray heads were used in the first 11
trials and in Trial 14. Four heads were placed on the booms on each side of the hel-
icopter at distances of 8, 14, 20 and 24 feet from the centerline of the helicopter.
Four Beecomist spray heads were used in Trials 12 and 13, two on each side of the
helicopter at distances of 8, 14, 20 and 24 feet from the centerline of the aircraft.
The Beecomist spray heads were calibrated at the site to deliver a total of 36.4 gal-
lons per minute of Orthene and 18.2 gallons per minute of Dylox, regardless of the
number of heads used. A total of 31 Spraying Systems Flat Fan Spray Tip Nozzles
No. 8006 were used on Trial 15; the nozzles were equally spaced with 16 nozzles on
the right spray boom and 15 on the left spray boom. Nineteen Spraying Systems Flat
Fan Spray Tip Nozzles No. 8010 were used on the remaining trials with 10 nozzles
equally spaced on the right boom and 9 on the left boom. The flat fan nozzles were
not field calibrated for flow rate, but were set to deliver a total flow rate of 18,2
gallons per minute of Dylox, according to factory specifications, for each of the
trials.
TABLE 2-1
BASIC SPRAY DATA FOR THE TOWNSEND
CHARACTERIZATION TRIALS
Total
Spray Spray Flow
Material Nozzles Rate
(gal min™
Aircraft
Height
(ft) 1)
Orthene 8 Beecomist
Orthene 8 Beecomist
Orthene 8 Beecomist
Orthene 8 Beecomist
Orthene 8 Beecomist
Orthene 8 Beecomist
Orthene 8 Beecomist
Orthene 8 Beecomist
uo ao vr on Fr WO NY FE
Dylox 8 Beecomist
ry
Oo
Dylox 8 Beecomist
—
H
Dylox 8 Beecomist
iw)
Dylox 4 Beecomist
-
co
Dylox 4 Beecomist
4
4
4
4
4
4
4
4
.2
2
As
ae
2
2
i
is
Dylox 8 Beecomist
31 Flat Fan
1 a No. 8006
19 Flat Fan
ac No. 8010
19 Flat Fan
a No. 8010
19 Flat Fan
No. 8010
19 Flat Fan
No. 8010
Dylox
Dylox
*Approximate time of trial (actual time not recorded but known to be within the hour
following Trial No. 7).
Because the spray lines were not purged of water for Trial 1, the sampler
cards for Trial 1 were not analyzed. Also, it was noted that the flat fan nozzles
used on Trial 16 were oriented at various angles to the horizontal. In the subse-
quent trials, the nozzle attitudes were changed so that the 6 tips on the outboard
section of the right boom and 5 tips on the outboard section of the left boom were
directed straight down (90 degrees to the horizontal), The remaining 4 tips on the
inboard section of the left and right booms were oriented forward and down at an
angle of 45 degrees from the horizontal.
All trials were conducted with the helicopter flying into the wind except
for Trial 8, where the flight path was crosswind. The helicopter flew at an air
speed of 90 miles per hour on all trials.
2.1 DESIGN OF THE SAMPLING GRID FOR THE TOWNSEND TRIALS
Figure 2-1 shows a map of the sampling grid which was located north of
Townsend in a large field between Montana Highway 12 and the Silos Recreation Area
just east of the shore of Canyon Ferry Lake. It should be noted that sampling line C
was moved to the position shown in Figure 2-1 prior to Trial 5. For the first four
trials, sampling line C was oriented north-south with its northern extremity at the
middle of sampling line B. The final grid configuration shown in Figure 2-1 was
designed to take advantage of the wind directions expected to occur over the site
during the characterization trials in which the helicopter released material while
flying into the wind. Sampling line A was nominally oriented east-west for use when
the wind directions were either up- or down-valley parallel to the shoreline of Can-
yon Ferry Lake. Sampling line B was oriented southwest-northeast for use when the
winds were downslope through a pass located northwest of the site. Sampling Line C
was moved to the location shown in Figure 2-1 after it became evident that advantage
should be taken of the weak downslope flow from the mountains west of the site and
weak upslope flow from Canyon Ferry Lake.
Bench Mark R/W
HIGHWAY 12
_______. JL OLD ABANDONED HIGHWAY
ee eH HH % eee
*" RENCE
*
S x
————— *
*
359° 0° Si|*
511.4 500.3' o |x
Si le
\ N
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“a! 5 —— *
N -
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212 Fr, | Dar
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| = 2
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\ | |*
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Qi l*
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Qi lx
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gw WHITLEY ke @ CLIMATRONICS | ee
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54° : oe:
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CONTEL 3 — as Control Point along
___TETHERSONDE @ 438 eae” Se a Ak Seen, See
Sh WE ATR TR WRT ET METI RRR ER TTR RERE RR %
re) 500 FEET l ; FENCE NV RSS
1700 — AIRSTRIP —
7s’
FIGURE 2-1. Schematic diagram of the sampling grid for the Townsend spray characterization trials. Dimen-
sions are in feet.
2.2 STAIN FACTORS
The following equations for converting the diameters of stains observed on
Kromekote cards, used in the Townsend Trials, to diameters of the drops impacting
on the cards were obtained in a laboratory analysis conducted by the Department of
Agricultural Engineering, University of California, Davis Campus, under contract to
MAG:
Orthene Spray
y = =8,9%10 x" # 0.47% + 37,6 (2-1)
Dylox Spray
-6 2 :
y = 5.73x10 x + 0.199x + 7.68 (2-2)
where
y = drop diameter in micrometers
x = stain diameter in micrometers
A separate study conducted by John Barry and Lynne Whitcombe of MAG showed that
no significant increase in stain diameters occurred beyond 5 minutes of elapsed time
after drop impact on the sampler cards.
2.3 FIELD ANALYSIS PROCEDURES
A "quick-look" field analysis to estimate volume median drop diameter and
swath width for each trial was initiated in the field 5 to 10 minutes after drops from
the spray cloud were no longer impacting on the Kromekote cards. A "direct-esti-
mation" method was used to estimate the characteristic volume median diameter
od
(VMD) for each trial. The D-max procedure developed by Maksymiuk (1964),
although suitable for use as a "quick-look"' method and applied after some trials
in the field, was used more frequently in the field laboratory analysis and is
described in Section 2.4 below.
The direct-estimation procedure was suggested for use in estimating VMD's
for the Townsend Trials and was used with success by Mr. William McIntyre, Dug-
way Proving Ground, Dugway, Utah. Mr. McIntyre has developed the talent of
observing a drop-stained card and visually selecting the stain representing the VMD
for agiven card. As might be expected from the cubic relationship between the
diameter and volume of a sphere, the drop stain representing the VMD is slightly
larger than the average size of stains appearing on the card. Prior to and during
the Townsend Trials, Mr. McIntyre trained two personnel from the H. E. Cramer
Company in applying his visual estimation technique. It appears that about one week
of working with an experienced instructor and drop-stained cards is required to
become proficient in estimating the VMD using this technique. The major drawback
of the method is that training is required before confidence can be placed in the VMD
estimates. The major advantage is that, once the technique is mastered, VMD esti-
mates are rapidly obtained.
In the Townsend Trials, the VMD was estimated in the field using the direct-
estimation technique and a sampler card from the swath on the sampling line most
nearly perpendicular to the aircraft flight path. The card was selected by walking
along the card line and visually observing the density of stains on each card and
selecting one card from the line judged to be of the density in the center of the swath.
Usually, the card selected was near the center of the swath. The direct-estimation
technique was then used to choose the stain on the selected card which represented
the VMD. The diameter of the stain was measured to the nearest 50 micrometers
using a Bausch and Lomb measuring magnifier (Catalog No. 80-34-35) with 100-
micrometer divisions. The appropriate stain-drop relationship described in Sec-
tion 2.2 was applied and the VMD field estimate entered on a form similar to the
example 'Rapid Inspection Data Sheet" shown in Figure 2-2. The swath width was
also visually estimated in a similar manner by selecting the first cards from either
end of the swath where the stain density became uniform. The VMD for these cards
was estimated using the procedure outlined above. The average mass diameter (AMD)
was estimated using the following expression, which assumes that the drop-size dis-
tribution is log-normally distributed:
2
In (AMD) = In(VMD) - 1.5 1n o, (2-3)
where
a = geometric standard deviation of the drop-size distribution
An assessment of sampling card data from previous trials conducted by the Forest
Service using Bell 205 helicopters showed that a value for 2 of 1.5 was best suited
for use in the Townsend Trials. It should be noted that the relationship between AMD
and VMD is sensitive to the value of a For this reason and because the distribu-
tion is often not strictly log-normal, this procedure is not recommended for use in
the field manual given in Appendix A. The mass of the AMD drop in milligrams m
(Drop Mass in Figure 2-2) was obtained from the relationship
Th = 7p (AMD) _ x 10°” (2-4)
where
p = density of the spray material in grams per cubic centimeter
10
ET
Test 2 Air Speed 90 mph Spray Material Orthene
Date/Time 27 June 76/0715 MDT Flow Rate 36.4 gal min - Material Density 1.044
Aircraft 205 Flight Level 50 feet Row Number B
=—=S=°3:33=eeN— SSS
Card Number for VMD 61
Estimated VMD: Stain 450 um Actual 232 um
SWATH WIDTH
Left Card Number Right Card Number
VMD: Stain 250um Actual 150um VMD: Stain _600um Actual _290um
Average Mass Drop Diameter 117 um Average Mass Drop Diameter 226 um
Drop Mass 8s 1X "ie mg Drop Mass 6.3 x 107° mg
Number of Drops 240 Number of Drops 65
Density 131 mg m~" Density 255 mg oy
FIGURE 2-2, Rapid Inspection Data Sheet used in the field at Townsend trials to estimate VMD and swath width.
As indicated in Figure 2-1, each line was greater than 1000 feet in length.
A dispersion-modeling experiment prior to the start of the trials indicated that a
sampler spacing of 10 feet would be more than adequate to ensure that at least 10 to
20 cards would be included within the expected swath width. For this reason, sam-
pler card positions were marked at 10-foot intervals along all three sampling lines.
For the first four trials, the sampling cards were mounted in plastic holders on
metal stakes about 1.5 feet above the ground. This procedure was used because it
is often more convenient to elevate the cards above surrounding grass clumps and
other obstructions and because a previous experiment conducted by MEDC with a
different spray material had indicated that there was no significant difference between
characterization parameters measured on elevated cards and cards placed on the
ground. After the first five trials, it became evident that the narrow elongated drop
stains were due to the wind transport of the drops causing them to impact on the
elevated cards at an oblique angle. In Trial 5, stains on cards placed on the ground
in cleared areas close to a few elevated samplers on the stakes were nearly circular,
probably because wind speeds close to the ground are light and the trajectory of the
drops was more nearly perpendicular to the ground. The sampling cards in their
plastic holders were placed on the ground in cleared areas next to the metal stakes
on all succeeding trials. The sampling positions were numbered sequentially on
each sampling line starting at the east end of line A, the northeast end of line B,
and the north end of line C.
Climatronics Corporation and Beckman-Whitley sensors were used at the
positions shown in Figure 2-1 to measure wind direction and wind speed at 2 meters
above the ground. Measurements of wind direction, wind speed, temperature and
relative humidity were made to altitudes of 100 feet using a balloon-borne sensor
(tethersonde) and associated recording equipment, manufactured by Contel Corpora-
tion, at the position shown at the east end of sampling line B. A hot-film anemometer
held aloft by a pilot balloon was used at a position near the east end of sampling line
A to measure winds at an altitude of 50 feet,
12
The density p of the Orthene spray material was 1. 044 g em and the density of
-3
the Dylox material was 1.067 g¢cm .
The spray deposit density on the cards representing the edges of the swath
was estimated by counting stains with a hand-held magnifying glass and a clear plas-
tic template similar to the template shown in Figure 2-3. In the Townsend Trials,
the stains were first counted in the small (1 square centimeter) square in the upper
left corner of the template. If the number of stains counted in this square exceeded
50, no further counting was done on the card. If less than 50 stains were counted,
additional squares were counted until the total of stains counted exceeded 50. The
mass density of the drops on the card was then estimated from the expression
m x Number of Stains Counted
Mars Deneny = a = Number of Squares Counted
(2-5)
and the result entered on the Rapid Inspection Data Sheet. The entries on the data
sheet were then reviewed with the project director.
Table 2-1 contains the volume median diameters and swath widths esti-
mated in the field during the Townsend Trials.
2.4 METEOROLOGICAL DATA
The H. E. Cramer Company was supplied with the strip charts containing
the wind directions and wind speeds measured by the Beckman and Whitley sensors
and Climatronics sensors at a height of 2 meters. The mean wind directions and wind
speeds measured at the two instrument locations (see Figure 2-1) did not differ sig-
nificantly. The recorders used with the Beckman and Whitley sensors were operated
at a higher chart speed, thus permitting 30-second average wind directions and
speeds to be abstracted from the charts. Appendix B contains tables of the 30-
13
CARD EDGE
es
vac
a oe
—
|
'
Pau
EACH SQUARE = | CM?
FIGURE 2-3. Template for counting of drops on sampler cards in the field.
14
This report is published as part of a Forest Service program to improve aerial
application of insecticides, specifically by using insecticides and delivery sys-
tems tailored to the forest environment. The program is being conducted
jointly by the Equipment Development Center, Missoula, Mont., and Methods
Application Group, Davis, Calif., under the sponsorship of the Forest Insect
and Disease Management Staff. Information or questions regarding this work
should be directed to:
WO-FIDM
Methods Application Group
2810 Chiles Rd.
Davis, Calif. 95616
A report on Equipment Development and Test Project 7069, Characterization
of Small Spray Aircraft funded by the Forest Insect and Disease Management
Staff.
TABLE 2-1
VOLUME MEDIAN DIAMETERS (VMD) AND
SWATH WIDTHS ESTIMATED IN
THE FIELD DURING THE
Sampling Line
Used
TOWNSEND TRIALS
Trial VMD Swath Width
Number (micrometers) (feet)
232 200
232
=> WOW DO wee a> 4. > & @ Fo. w.Q &
15
second average wind data obtained from these records for approximately a 5-minute
period beginning 5 seconds before the helicopter passed over the sampling line.
2.5 FIELD LABORATORY ANALYSIS PROCEDURES
The forest Service arranged for space in the Townsend grade school for
use as a field laboratory in carrying out a more detailed analysis of the sampling
cards than was possible in the field. The sampling cards were returned to the
school after each morning and evening set of trials. Two procedures were used in
the field laboratory to estimate the VMD characteristic of each trial. These were
variations of the direct-estimation procedure described in Section 2-3 above and
D-max method described by Maksymiuk (1964).
The direct-estimation method was used to estimate the VMD on each card
within the swath. The VMD characteristic of the trial was then obtained by calcu-
lating a mass weighted VMD from the expression
VMD = ———————_- (2-6)
where
VMD, = VMD estimated for the jh card in the sampling line
t
M; = mass density from Equation (2-5) for the j A card in
the sampling line
N = total number of cards analyzed
16
A value of 1.5 for o, was again used in Equation (2-3) to estimate the AMD from
5
the BMD estimated for each of the cards,
-The D-max method was applied in the following stepwise procedure:
(1) The largest stains on each card in the swath width were
measured to the nearest 50 micrometers using the Bausch
and Lomb measuring magnifier.
(2) The stain diameters were converted to drop diameters
using the appropriate relationship for Orthene or Dylox
given in Section 2.2.
(3) The five largest measured drop diameters were arranged
in ascending order. If two or more drops were of the
same size, they were counted as separate drops and
listed sequentially in the list of the five largest drops.
(4) Beginning with the smallest drops in the list, the differ-
ence in diameter between sequentially listed drops was
noted. If no difference between sequential diameters in
the list was greater than 32 micrometers, the largest
drop was used in Step 5 below. Ifa difference greater
than 32 micrometers, the diameter of the drop just
below the point where the difference in diameters
exceeded 32 micrometers was used in Step 5 below.
(5) The drop diameter selected in Step 4 above was divided
by a factor of 2.2 to obtain the estimate of VMD charac-
teristic of the trial.
a
This D-max procedure was applied in the field laboratory by John Barry
and Lynne Whitcombe of MAG for 11 of the 16 trials analyzed. To check the easc
of application of the method and the reproducibility of the estimates using different
analysts, the D-max method was reapplied at the H. E. Cramer Company in Salt
Lake City after the trials were completed. The results obtained in the field, using
both the direct-estimation procedure and the D-max methods, and in the post-trial
analysis using the D-max method are given in Table 2-2, Comparison of the VMD
estimates obtained by the direct-estimation procedure and the D-max method shows
that, in every case, the D-max method applied in the field yielded larger values of
VMD. The field and post-trial D-max estimates of VMD show good agreement.
Sampling card data for Trials 6, 7, 9, 11 and 18 were analyzed in greater detail .
during the post-trial analysis described in Section 3 below, including estimation of
VMD from a cumulative drop-size distribution for all cards in the swath.
The density of drops per square centimeter for each card in the swath was
also estimated in the field laboratory for the trials listed in Table 2-2, using the
counting procedure outlined in Section 2.3, a template similar to that shown in
Figure 2-3 and the Bausch and Lomb magnifier rather than the large magnifying
glass used in the field. The spray deposit densities obtained in this analysis are
given in tabular form in Appendix C.
18
TABLE 2-2
LABORATORY ESTIMATES OF VMD BY THE DIRECT-ESTIMATION
AND D-MAX METHODS
Trial Direct Estimate D-Max Estimate of VMD (um)
Number of VMD
19
SECTION 3
POST-TRIAL ANALYSIS
The only valid means of confirming the estimates of the number of spray
drops per square centimeter, volume median diameter, and the mass deposited on
the sampling cards made during the Townsend trials was to perform a more com-
plete analysis after the trials, including the development of volume and number
cumulative distributions for selected trials. The additional analyses were also
required to reach decisions regarding the types of procedures that could be recom-
mended for use in the field to obtain the best rapid estimates of spray characteri-
zation parameters.
To ensure that reproducible results could be obtained, the decision was
made to perform the post-trial analysis in duplicate. Arrangements were made
by MEDC with Dugway Proving Ground to have Mr. McIntyre count and size stains
for selected trials, Mr. William Santee of the H. E. Cramer Company was assigned
the task of counting and sizing stains for the same trials. Because of the limited
time and funds available for the post-trial analyses, data from only 5 trials could
be analyzed in the requisite detail. Two trials where the Orthene mix was sprayed
and 3 where the Dylox mix was sprayed were selected for analysis. Trials 6 and 7
were chosen for the Orthene mix because these trials were the only 2 trials where
the aircraft flew into the wind and the drops were sampled using cards placed on
the ground. Trials 9 and 11 were chosen because the standard configuration of 8
Beecomist spray heads was used and the aircraft flight path into the wind was nearly
perpendicular to the sampling line. Trial 18 was chosen because a standard config-
uration of 19 Flat Fan No. 8010 spray heads was used on the helicopter spray boom,
A plastic template similar to that shown in Figure 3-1 was used in both
the counting and sizing of drop stains. One of the three template sizes of 4, 8 or
20
FIGURE 3-1.
Template used for counting drops.
21
16 square centimeters wis chosen, depending on visual inspection of the density of
stains on a sampling car|, for use in the counting and sizing of stains to ensure that
a minimum of 200 stains were considered. Each stain diameter was measured and
counted using the Bausch and Lomb measuring magnifier and assigned to one of 8-
to-12 stain diameter categories. The upper limits of the stain diameter categories
used in the analyses of the five trials are shown in Table 3-1. The drop diameters
corresponding to the category limits shown in Table 3-1 were calculated from the
stain-factor relationships given in Section 2. 2.
3.1 DETERMINATION OF SPRAY DEPOSIT DENSITIES ON SAMPLING CARDS
AND SWATH WIDTH
After the stains on the sampling cards from the sampling line used in the
trial were counted and sized, the density of stains on each card was calculated from
the expression
1
N =—
j A, 4
I
(3-1)
ASL
i ar
1, J
where
N. = spray deposit density for the - card in the line (drops
-2
em =)
A, = area of the template counted for the - card (cm?)
I = total number of stain size categories counted for the
jth card
n= number of drops counted in the Fo drop size category on
J the jth card
22
TABLE 3-1
UPPER LIMITS IN MICROMETERS OF STAIN AND
DROP-SIZE CATEGORIES USED IN THE
POST-TRIAL ANALYSIS
Drop-Size Category
: Upper
sa [i eee
Drop | 83.77} 128.3 | 171.1 | 212.3 | 251.8) 289.7) 325.9) 360.5) 393.4
Drop
= nfm fv» [om fo
€Z
= r[on fw [ow [om
The results obtained by using Equation (3-1) to calculate spray deposit densities
for the five selected trials are shown in Figures 3-2 through 3-6 for both observers.
Inspection of the figures shows that one analyst consistently estimated higher den-
sities than the other (counted more drops). We are unable to account with certainty
for this consistent bias. It should, however, be noted that Mr. McIntyre and Mr.
Santee did not necessarily count stains in the same location on the sampling card.
Each analyst counted stains in the area he felt was representative of the observed
density on each card. A possible explanation of the bias is that the analysts differed
in their selection of the area of the card that was representative of the observed den-
sity, one analyst always selecting an area with a higher density than the other. To
examine this possibility, the two analysts were asked to examine some cards and
estimate spray deposit density after the analysis of the trials had been completed.
The exact area to be counted was marked and both analysts counted the same area.
The estimates of deposit densities by the two analysts were considerably closer,
but some bias was still present. Areas on additional cards were marked and the
analysts were asked to count only stains that were larger than 50 micrometers, since
the measuring magnifier was marked in 100-micrometer intervals. The result of
this experiment showed no bias between the two analysts. Sufficient time and funds
were not available to undertake the recounting of all the cards to further examine the
bias problem. However, in the field manual, the templates have been designed so
that the same area is counted on all cards and the recommendation is made that
stains less than 50 micrometers not be counted when the Bausch and Lomb measuring
magnifier is used. If drops producing stains less than 50 micrometers are important
in the estimate of drop density or mass deposition, a more accurate measurement
device should be used.
The profiles of crosswind spray deposit density shown in Figures 3-2 through
3-6 can be used to estimate the minimum swath width based on spray deposit density.
Estimates of the minimum swath width for five trials are shown in Table 3-2. Swath
widths for all trials except Trial 7 were estimated as the distance between cards on
24
(z-w9 sdoip) ALISNSG LISOd30 AVYdS
CARD NUMBER
The dashed and solid lines repre-
sent results obtained by two different analysts.
FIGURE 3-2. Spray deposit density for Trial 6.
25
110
105
0O|
95
85
80
75
(z-W2 sdoap) ALISNSO LISOd3Q AVHdS
26
CARD NUMBER
The dashed and solid lines represent results obtained by two
FIGURE 3-3. Spray deposit density for Trial 7.
different analysts.
(z-W9 sdoip) ALISNSQ LISOdSQ AVudS
CARD NUMBER
The dashed and solid lines repre-
sent results obtained by two different analysts.
FIGURE 3-4. Spray deposit density for Trial 9.
27
|
ete lem
!
(zo sdoup) ALISNSQ LISOd3q0 AVYdS
'
He
1
28
CARD NUMBER
The dashed and solid lines represent results obtained by
FIGURE 3-5. Spray deposit density for Trial 11.
two different analysts.
CARD NUMBER
The dashed and solid lines repre-
sent results obtained by two different analysts.
FIGURE 3-6. Spray deposit density for Trial 18.
29
APPENDIX A
FIELD MANUAL FOR CHARACTERIZING
SPRAY FROM SMALL AIRCRAFT
This appendix contains a complete copy of the field manual developed
under the contract.
plotting mass recovery, drop contamination density and cumulative mass distribu-
tion. Keuffel and Esser Company Numbers 461510 and 46840 should satisfy most
requirements. Finally, a desk-top programmable calculator is recommended for
simple and rapid analysis of the numerical data developed from the card counting
and sizing as described in Section 5.2. The 9820A Calculator manufactured by
Hewlett-Packard, Loveland, Colorado, is ideally suited for this purpose, since it
allows alpha-numeric printout and identification of input parameters. Also, when
used in conjunction with the 9862A Calculator Plotter, an automated plotting capa-
bility is provided. The use of a preprogrammed calculator greatly reduces the
chances of human errors affecting the results and significantly reduces the time
required to complete the analysis.
12
SECTION 3
DESIGNING THE SAMPLING GRID; OPERATIONAL CONSIDERATIONS
Trials for determining the characteristics of small aircraft spray systems
are est conducted with the aircraft flying at a low altitude and headed into the wind.
The inwind flight trajectory ensures that the entire drop-size spectrum of the spray
cloud can be sampled with a minimum number of samplers and also provides esti-
mates of the minimum swath width that can be expected under operational conditions
during the forest spray project. In this section, the design of a sampling network
for measuring spray characteristics and suggestions for conducting the trials are
described.
Oe kL DESIGN OF THE SAMPLING GRID
3.1.1 Choosing The Site
Large cleared and relatively level areas are ideally required for determining
spray characteristics. Buildings, trees, power lines, and other obstructions inter-
fere with the placement of sampling lines, with the wind-flow field, and with the air-
craft flight pattern. Since the card samplers are placed on the ground, high grass or
bushes can intercept the drops before they reach the cards. For this reason, mowing
or other means of removing large plant forms in the immediate vicinity of the sampling
lines may be required. Irregularities in the ground surface can also act to confound
the results of the trials and should be avoided where possible. The aircraft pilot must
maintain level flight for some distance downwind of the sampling line as the aircraft
approaches the sampling line and for even greater distances upwind of the sampling
lines. The requisite length of the flight line depends, as will be discussed later, on
the height of the aircraft. Aircraft heights of 50 to 100 feet require characterization
sites exceeding one square mile in area. Sites where the public can easily gain access
13
should be avoided, since some of the dyed spray material could easily be deposited
on people or cars within the spray area.
BoL.2 Grid Geometry
As noted above, an inwind flight trajectory ensures that the entire drop-
size spectrum of the spray cloud can be sampled with a minimum number of sam-
plers. The grid should be designed such that sampling lines are crosswind. Expe-
rienced meteorologists and test personnel know that specifying a mean wind-direction
for a short-period averaging time well in advance of a trial is extremely difficult
under the best of circumstances. Therefore, the sampling grid must be designed to
accommodate variations in the mean wind direction to prevent the introduction of
serious errors in the data analysis. For this reason, the equilateral triangle design
shown in Figure 3-1 is recommended. Inspection of Figure 3-1 shows that this
design tends to limit the angle between the aircraft flight path (flown into the wind)
and a sampling line to 90 + 30 degrees. Figure 3-2 shows the combinations of sam-
pling lines and mean wind directions which would apply if north is assumed to be at
the top of Figure 3-1. According to Figure 3-2, sampling line A can be used for all
wind directions from 150 through 210 degrees and from 330 through 30 degrees. Sam-
pling line B can be used for all winds from 30 through 90 degrees and from 210 through
270 degrees. Similarly, sampling line C can be used for all winds from 90 through
150 degrees and from 270 through 330 degrees. The choice of the proper flight path
for any given trial is made, as explained in Section 3.2.3 below, from mean wind
direction measurements made just prior to conduct of the trial.
Knowledge of the most frequent wind directions at the site chosen for the
trials would assist in orienting the triangular design to further ensure that sampling
lines are oriented crosswind. Spray projects are normally conducted during the
early morning and late evening hours during periods of fair weather. The light wind
conditions usually present during these hours are generally favorable for maximum
14
A e—e1S=0.4H
FIGURE 3-1. Simple equilateral triangle sampling grid for characterizing aircraft
spray. The length of the sides L are 10 times the aircraft flight
altitude Ht and the sampler spacing S is 0. 4II.
oo
270° 90° 270°
8
Now
zz
</00
FIGURE 3-2. Illustration of the use of the sampling lines A, B and C of the basic
grid design shown in Figure 3-1 with winds from various directions.
16
canopy penetration and minimum off-site drift of the spray material. Strong winds
and high levels of atmospheric turbulence generally diminish spray deposition in the
immediate target area and increase the possibility of downwind drift. The above
considerations also apply to the determination of aircraft spray characteristics.
Thus, one of the sampling lines should be oriented to be crosswind relative to the
wind directions expected during the early morning or late evening hours. A trained »
micrometeorologist can often determine expected mean wind directions for these
periods from a knowledge of the topographical features in the area.
Length of the Triangular Sides
Each side of the triangular grid array must be long enough to contain the
swath width or contamination density of interest. While rather complicated diffusion-
deposition formulas can be used to determine the length L as a function of droplet
settling velocity, height of the aircraft and meteorological conditions--experience has
shown that the simple expression
L = 10H (3-1)
where
ge
|
length of side
H = aircraft height
normally guarantees the swath width will be contained. Thus, if the aircraft flies at
a height of 15 meters (50 feet), the length of each side of the triangular array should
be 150 meters (500 feet).
Sampler Spacing
The sampler spacing along each side of the array must be sufficiently dense
that statistically stable estimates of the volume median diameter and other spray
17
characteristics can be obtained. Again, modeling and ficld experience show that
the expression
p= se = 0ae (3-2)
where
S = maximum sampler separation distance
provides an adequate sampling array density. Thus, for an aircraft flight altitude
of 15 meters (50 feet), the maximum distance between card samplers on the sam-
pling line should be 6 meters (~20 feet).
3.1.2 Aircraft Height and Spray Line Length
For the purpose of characterizing aircraft spray, it is generally desirable
that the aircraft fly as low as possible to minimize sampling grid requirements while
satisfying flight safety requirements. Consideration must also be given to the oper-
ational requirements of the spray project for which the characterization is performed.
If the project is to be conducted over rough terrain the aircraft may not be able to
operate safely at altitudes lower than 30 meters (100 feet) above the canopy. In this
case, the characterization trials should be conducted with an aircraft altitude of 30
meters above the ground. A 15-meter (50-foot) minimum altitude often meets both
requirements of safety and grid design. The flight altitude may have to be increased,
however, if the density of the stains from drops deposited on the sampling cards is
so great that spray characteristics cannot be determined. Since the stain spread
factor of drops depends on the type of material released by the aircraft, the type of
sampling card and other spray characteristics that may not be known prior to the
trials, it is difficult to recommend a specific aircraft altitude. A simple one-trial
18
experiment at an aircraft altitude of 15 meters can be concede prior to final spec-
ification of the grid design to determine if the cards will be covered so heavily that
stains cannot be counted and sized. On the other hand, a value for the length L of
300 meters can be used in the grid design for a 30-meter aircraft altitude with a
sampler separation distance S of 6 meters appropriate for an aircraft altitude of
15 meters. If the first trials indicate that a 15-meter altitude results in spray den-
sitites that cannot be conveniently counted, the flight altitude can be increased to 30
meters and every other sampling position removed from each side of the triangular
grid. Since spray density is nearly inversely proportional to aircraft altitude, an
increase in aircraft altitude by a factor of two will reduce deposition density by half.
The length of the inwind release line required to ensure that the crosswind
mass recovery sampled on the grid is not affected also depends on the aircraft alti-
tude as well as spray characteristics and meteorological conditions. Calculations
show that if much of the spray cloud mass is comprised of drops with diameters of
50 micrometers or less and wind speeds are less than or equal to 4 meters per sec-
ond, the length of the release line RL upwind of the sampling grid should be about
one-hundred times the aircraft altitude, or
RL = 100H {D < 50um} (3-3)
If most of the mass of the spray cloud is comprised of drops between 50 and 100
micrometers in diameter and wind speeds are less than 4 meters per second, the
length of the release line upwind of the sampling grid should be about seventy times
the aircraft altitude, or
RL = 70H {50 <D < 100um} (3-4)
19
Finally, if most of the spray cloud mass is comprised of drops greater than 100
micrometers in diameter, the length of the release line upwind of the sampling
grid need only be about thirty-five times the aircraft altitude, or
i
RL = 35H {100um < D} (3-5)
In every case, the release line must begin at least 50 to 100 meters downwind of the
sampling grid. Longer distances may be required to stabilize the aircraft altitude
and the flow rate in the spray dissemination system.
3.1.3 Summary of Grid Design Requirements
The sampling grid recommended for use in characterizing spray from small
aircraft is shaped in the form of an equilateral triangle.
. The length of each side of the triangle L is
Lite LOH
where H is the planned aircraft flight altitude.
The maximum separation distance S between sampling cards placed along
each side of the triangle is
S' = 0.4H
The release line should extend upwind from the sampling line a distance
RL given by
20
100H; D<50um
RL = 4 70H; 50<D<100um
35H; 100um<D
where RL depends on the size of drops expected to be generated by the spray air-
craft.
For example, assume the planned aircraft flight altitude for the spray char-
acterization is 15 meters (50 feet) above the ground and most of the mass is expected
to be contained in drops with diameters between 50 and 100 micrometers. The
length of each side of the triangular grid should be
L = 10H = 10 (15) = 150 meters (~500 feet)
The distance between sampling card positions along each side of the triangle should
not be more than
S = 0.4H = 0.4 (15) = 6 meters (20 feet)
The inwind release line should extend upwind from the sampling line a distance
RL = 70H = 170(15) = 1050 meters (3500 feet)
21
3.2 OPERATIONAL CONSIDERATIONS
Seed Dressing The Grid
After the length of the triangular sides of the sampling grid and the sampler
grid spacing have been determined, the transit or theodolite and the manilla rope
are used to lay out the sampling lines. The manilla rope is stretched taut at right
angles to the most probable wind direction expected during the early morning hours
using the theodolite to ensure that the line segment is straight and correctly oriented.
Quarter-inch stock metal rods are then driven or forced into the ground at the pre-
determined sampling intervals marked by the surveyor's tape tacked to the rope.
The rope is then moved and the above procedures repeated until the sampling line
length is long enough to form one side of the triangular grid array. The transit is
then used to measure the 60-degree angles and lay out the next two sides of the array.
Wood stakes, 5 to 6 feet high and marked with bright tape, should be placed at the
end of each leg of the triangle and at the center position of each leg. It may be nec-
essary to clear a small area around each metal rod so that plants or other material
do not intercept drops that would otherwise impact on the card.
Cards for three or more trials can be premarked and placed in cardholders
prior to each day's operation. At a minimum, the marks placed on each card should
identify the trial (or flight) number, sampling line number, and sampler location on
the line. For example, the identification 13-A-50 might indicate Trial 13, Sampling
line A and the 50th-card position on sampling line A. The cards in their cardholders
can be packed in ascending numerical order in the wooden boxes described in Section -
2.1 for transportation to the field site such that one or two boxes, depending on the
length of the sampling line, are sufficient to dress one side of the triangular array.
The cardholders should be placed at the side of each stake so that the stake does not
intercept drops which would otherwise strike the card, The cardholder must be
placed flat on the ground and care must be taken that loose soil or dust is not kicked
onto the card in placing the card or in picking up the samplers after the trials.
22
Because of the triangular grid array, not all cards on all sides of the array
will be exposed during a single trial or aircraft pass over the grid. ‘To avoid con-
fusion in sample card designation, it is best to pick up all premarked cards on all
sides of the array after each trial. Those cards obviously not exposed during the
trial can be remarked later for use in trials at a later time. If cards on one side
of the array are not exposed and left for the next trial, care must be taken to change
their trial identification as they are picked up in subsequent trials and after they have
been exposed to spray deposits.
3.2.2 Location and Operation of Meteorological Equipment —
The low-level (2-meter) wind-direction and speed sensors and associated
recording equipment are best located near the center of the triangular grid, well
away from any of the sampling lines. Vehicles or other obstructions to wind flow
should never be placed near the sensors when data are being recorded. Manufac-
turer's instructions must be carefully followed during the assembly and placement
of the equipment to prevent damage. Special care must be taken in fitting the wind
vane and speed assemblies into their sockets so that heavy thrust is not placed on
the bearings of the drive. The bearing must always be checked for damage by
checking for completely free rotation of the vanes.
In using the transit or theodolite to orient the wind vane, it must be rem-
embered that wind direction is always recorded as the direction from which the wind
is blowing. The orientation point should be in the direction of the most frequently-
occurring wind. Select a nearby prominent landmark that can be seen in dim light
and is not likely to be obscured by clouds or fog. If no landmark is convenient,
drive a stake for use in sighting the vane. Align the transit or theodolite with the
vane and orientation point and note the direction. Rotate the head of the wind vane,
after loosening the alignment screw to permit free movement, until the recorder
pen is making a trace at the center of the chart when the vane is pointing toward
23
the orientation point. Tighten the alignment screw and recheck the orientation.
Repeat the process until the recorder pen is centered while the vane is pointed
toward the orientation point. Note the direction of the orientation point on the
chart. This procedure will have to be repeated if, during the trials or just prior
to a trial, the wind direction is such that the recorder pen is moving back and
forth from one edge of the chart to the other.
If possible, the wind equipment should be operated continuously during the
period of the characterization trials and for several days prior to the trials. The
continuous record is useful in determining wind-flow patterns to be expected during
the early morning and evening hours when the trials are to be conducted. A chart
speed of 3 inches per hour is adequate for continuous recording of the wind direction
and speed, but the chart speed should be increased to a minimum of 12 inches per
hour before the spray run of the aircraft and continued for a 10- to 15-minute period
after the aircraft has completed the spray run. Since chart drives do not always
operate accurately, the correct time should be entered opposite time "hacks" or
marks on the chart at frequent intervals. The trial number, time and date of each
trial must be indicated in the margins of the chart. Any significant weather phenom-
ena or changes in instrumentation (reorientation) should also be noted directly on the
charts.
The operation of a tethersonde and release of pilot balloons for measuring
vertical wind and temperature structure during the conduct of characterization trials
are optional. An experienced meteorologist can make use of these observations in
predicting the times for onset of favorable winds. If the trials are being conducted
for research purposes, the vertical meteorological data are essential for document-
ing trial conditions. It is beyond the scope of this manual to explain the use of this
information in the conduct and detailed analysis of spray trials. If at all possible,
the measurements should be made and included in the documentary support of the
trials. The tethersonde base station location and point where pilot balloons are
released should be located as near as possible to the sampling grid array without
24
causing interference with aircraft operations. Manufacturer's instructions for oper-
ating the tethersonde must be carefully followed, especially those for calibration of
the equipment. Instructions for making pilot balloon measurements and reducing
the observations to obtain wind directions and speeds are contained in the publication
"Winds Aloft Observations Manual, Handbook No. 5" published by the National Oceanic
and Atmospheric Administration (NOAA) and available from the U. S. Government
Printing Office. It should be noted that accessory equipment for operation and anal-
ysis of the tethersonde and pilot balloon data are not included in the equipment lists
given in Section 2.
3.2.3 Conducting the Trial
Spray characterization trials are best conducted under reasonably steady-
state meteorological conditions. Large changes in wind direction can result in
shifts in the spray cloud pattern which serve to confound the determination of the
effective swath width and deposition efficiency. The best spray deposition patterns
are usually obtained during the early-morning and late-evening hours when the wind
speeds are low and the thermal stratification is neutral. However, meteorological
conditions during these hours are typically unsteady. The procedures described
below are suggested as the most effective means of ensuring that conditions are suf-
ficiently steady for the conduct of spray characterization trials.
Operate the 2-meter wind recording equipment at a chart speed of 12 inches
per hour for at least 1 hour prior to the trials. For the two most recent 10-minute
periods, lightly draw two straight lines, each 2 inches long (equivalent to 10 minutes
of chart record) through the recorded wind direction data to obtain estimates of the |
mean wind direction during each of the 10-minute periods. If the two 10-minute mean
wind directions do not differ by more than 15 degrees, the wind direction is suffic-
iently steady for conducting a trial. Draw similar lines through the two most recent
10-minute periods of wind speed. If both of the 10-minute average wind speeds fall
within the limits of 1.5 to 4 meters per second (3.5 to 9 miles per hour), wind speed
25
conditions are favorable for conducting a trial. Release a smoke seein and observe
the vertical spread or diffusion of the smoke. In the very early morning or very
late in the evening when wind speeds are light, the smoke may not spread vertically
with distance to the height of the planned aircraft altitude. If the smoke "hugs"' the
ground with little vertical spreading as shown in Figure 3-3(a) indicating a very
stable thermal stratification of the atmosphere, delay the trials. In the late morn-
ing or in the afternoon, the smoke may lift quickly from the ground as shown in
Figure 3-3(b), may form loops alternately lifting from and intersecting with the
ground, or diffuse too rapidly. Under these conditions, the atmosphere is too
unstable and spray characterization trials should be delayed. If the smoke plume
grows regularly in the vertical with increasing downwind distance as shown in Fig-
ure 3-3(c) and reaches the aircraft altitude at a reasonable distance from the source
(a distance equal to about 10H), diffusion conditions are suitable for characterization
trials. If the wind direction and speed criteria outlined above are also satisfied, the
trials should be conducted.
Two persons are required to be present on the sampling grid during the
trial, one to monitor the 2-meter wind equipment and the other to release a smoke
grenade and communicate with the aircraft pilot. When the grid is cleared, the
aircraft is airborne, and the meteorological conditions are satisfactory, a second
smoke grenade should be released at the center stake of the triangular side of the
sampling array facing the wind to serve as a guide to the aircraft pilot. The pilot
maintains the correct altitude, aligns his aircraft with the smoke plume and flies
upwind towards the source of the smoke. The spray dissemination equipment should
be turned on at a distance downwind from the smoke source that allows the flow rate -
to become stabilized. Dissemination is then continued past the sampling grid for a
distance corresponding to the precalculated length of the release line RL discussed
in Section 3.1.2 above. The person monitoring the wind equipment should mark each
chart to indicate the points on the chart corresponding to the time the aircraft passes
over the sampling line, and the time. Other information, such as the trial number,
26
AIRCRAFT ALTITUDE
AIRCRAFT ALTITUDE—
“4
—— AIRCRAFT ALT TUDE $$
FIGURE 3-3. Schematic diagram showing smoke plume diffusion under (a) condi-
tions too stable for characterization trials, (b) conditions too unstable
for characterization trials and (c) favorable conditions for spray char-
acterization trials.
27
time duration of the trial, sky cover, observations of the spray-cloud behavior and
other observations pertinent to the conduct of the trial should also be noted.
After the spray cloud has settled and the droplets have dried on the cards,
preparations for the field characterization of the spray trial, discussed in Section
5 below, can be made.
3.2.4 Trial Log
An example form for recording pertinent information regarding the spray
system and meteorological data for each trial is shown in Figure 3-4, Many of the
items can be completed in the field prior to and just after the trial has been con-
ducted. The analysis of the pilot balloon and tethersonde data to obtain vertical
profiles of wind and temperature data may take several hours or days to complete
and can be entered later. Nozzle spacing on aircraft booms is often nonuniform and
nozzles may or may not be located beneath the aircraft body. Note that space has
been provided in Section III of the Trial Log for use in sketching the nozzle spacing
and configuration used in the trial.
28
FIGURE 3-4
TRIAL LOG
Trial Number Time/Date Time Zone
Row Row Azimuth oO Card Separation m
Number of Cards
SPRAY SYSTEM DATA
. Aircraft
Spray Nozzle Nozzle Orientation
a
Airspeed (mph) Flow Rate gallons min™
Flight Altitude (ft orm) Aircraft Heading 0
Spray Material Material Density g em73
Stain Factor Formula
Stain Factor Constants
METEOROLOGICAL DATA
Cloud Cover % Temperature °C
2-m Wind Direction © 2-m Wind Speed m sec!
%
Relative Humidity
(Optional Measurements Using Pilot Ballons and/or Tethersonde)
Wind Profile Temperature Profile
Height (m)| Direction (°)| Speed (m sec“) Height (m)| Temperature (°C)
29
FIGURE 3-4 (Continued)
Il. NOZZLE CONFIGURATION
Aircraft Centerline
IV. REMARKS
30
SECTION 4
FIELD CHARACTERIZATION OF THE SPRAY DISSEMINATION SYSTEM
The procedures described below for determining swath width, drop density
within the swath and volume-median diameter are designed to provide in-the-field
characterization of the aircraft spray. For example, these 'quick-look" procedures
are intended to provide aircraft spray engineers with the information required to
make immediate decisions regarding necessary changes in nozzle types, nozzle
configurations, flow rate and to make other mechanical adjustments in the dissemi-
nation system to improve spray characteristics. These procedures are also in-
tended for use in determining any changes required in the aircraft flight altitude,
separation distance of the card samplers and other features of the test plan to achieve
better results. Final characterization of the aircraft spray system requires a more
complete data analysis which is described in Section 5.
4.1 PLASTIC TEMPLATES FOR SIZING AND COUNTING DROPS
The analysis procedures described here and in Section 5 require the use of
clear plastic templates to overlay the exposed sample cards. Sample templates are
attached to this manual. Since continued use of the templates will eventually result
in their becoming scratched and unusable, it is necessary to provide replacements.
This can best be accomplished by having a draftsman draw the templates on tracing
paper at three times the size shown in the figures using a No. 0000 Leroy pen. This
original drawing is then photographed, reduced 33.3 percent and then reproduced on
clear 4 mil mylar film. The negative produced in this process can be used over and
over to make new templates as required.
4.2 SWATH WIDTH AND DROP DENSITY
The spray project entomologist is interested in obtaining the widest swath
width in which droplet density exceeds a specified amount known or thought to produce
31
the requisite pesticide effectiveness. A "quick-look"' estimate of the minimum swath
width and drop density within the swath width can be obtained by following the simple
procedures described below.
After the visible spray cloud has settled or dispersed, proceed on foot from
one end of the exposed card line until spray deposition on the sampling cards becomes
visible to the naked eye. Visually inspect the next few cards and note the position of
the first card on which the drop density appears to be uniform. After inspecting this
card to be certain that the stains have dried, estimate the spray drop density on this
card using the following step-wise procedure:
(1) Remove the card from its holder.
(2) Place the template shown in Figure 4-1 over the card and fasten
the card and template to the clipboard.
(3) Use the large hand-held magnifying glass to count the number of
stains in the small (1 square centimeter) square in the upper left-
hand corner. Note the number of stains on scratch paper.
(4) Continue to the next square moving down the extreme left column
of squares on the template. Count the stains in the square and add
the number to the number of stains determined for the first square
(step 3). If the total number of stains exceeds 100, no more squares
need be counted. If the total number of stains is 100 or less, con-
tinue to count the stains in squares until the total number of stains
exceeds 100 for all squares counted.
(5) Enter the card number, total number of squares counted (area in
square centimeters) and total number of stains in the columns
provided in the field information sheet shown in Figure 4-2.
(6) Divide the number of stains by the area and enter the drop density
in the last column of Figure 4-2.
32
CARD EDGE
EACH SQUARE = | CM?
FIGURE 4-1. Template for counting of drops on sampler cards in the field.
33
FIGURE 4-2
FIELD ESTIMATE OF SWATH WIDTH AND DROPLET DENSITIES
Date
Trial Number
Row/Line Number
Density
(drops cm
~2)
Card Number for Left Edge of Swath
Right Edge of Swath
Estimated Swath Width
34
(7) Replace the card in its cardholder and return the cardholder
to its original position for later pickup.
If the drop density on this first card is less than the density required to produce the
requisite pesticide effectiveness, use the density just measured as a guide and walk
along the card line towards cards showing greater densities and attempt visually to
select a card showing the requisite density. For example, if the first card shows a
density of 10 drops per square centimeter and the required density is 20 drops per
square centimeter, proceed along the card line and select a card showing twice the
density of the card just measured. Follow the same procedure for counting the stains
to obtain drop density. If the measured drop density on the selected card is greater
than or approximately equal to the required density, the edge of the swath can be
obtained by linear interpolation. As soon as this edge of the swath is defined, walk
to the other end of the card line and use the same procedures to define the other edge
of the swath.
After defining the swath width, use the procedures for counting stains out-
lined above to estimate the drop density of the card near the swath center visually
indicating the greatest density. Estimate the drop density on at least two other cards.
If the drop density distribution along the card line is uniform or Gaussian (bell-shaped),
select a card half-way between the swath end and swath center on either side of the
card showing the greatest density. If the distribution is slightly asymmetrical, which
can occur when the aircraft does not fly directly into the mean wind, select the addi-
tional cards for analysis from the side of the distribution with the longest "tail." When
the distribution appears highly assymmetrical, an additional trial must be conducted to
estimate the minimum swath width. After the drop-density estimates have been com-
pleted, enter the position numbers of the cards marking the swath edges at the bottom
of the form shown in Figure 4-2; subtract the position numbers and multiply by the sam-
pler separation distance to obtain the estimated swath width. Enter the swath width on
the form.
35
The analysis of drop density on 5 cards is usually more than sufficient to
define the swath width for field use and provide the necessary information to allow
aircraft engineers to make necessary adjustments in spray equipment and assist
the project entomologist in making a preliminary estimate of the spray system per-
formance, In many cases, measurement of the drop density at the swath edges may
provide sufficient information in the field. More complete information will be avail-
able after the field laboratory analysis is completed (see Section 5),
It should be noted that the drop density analysis and the volume median diam-
eter analysis described in Section 4.3 below are best accomplished using two people,
one to count the drops and the other to record the information.
4.3 FIELD ESTIMATION OF VOLUME MEDIAN DIAMETER
The procedures outlined in this section for the field estimation of the volume
median diameter (VMD) are based on the approach suggested by B. Maksymiuk (1964),
Although Maksymiuk tested his approach using propeller-driven slow and medium
speed aircraft and oil-based sprays, recent experience in applying the method with
helicopter equipment and oil- and water-based sprays indicates the method is also
adequate for the field estimation of VMD's for this type of equipment and sprays.
In the following discussion, it has been assumed that the ''stain factor" has
been measured prior to the trials. The stain factor is the relationship between the
drop size before impaction on the sampling card and the size of the stain produced by
the drop on the card. A typical relationship is given by the expression
DD = atb (SD) tc (SD) (4-1)
where
DD = drop diameter
SD = stain diameter
36
and a, b, and c are constants determined in the laboratory. In the above expression
there is no specific provision for the spread of the stain as a function of time after
the drop impacts. For some oil-based sprays and some types of sampling cards,
the stain can continue to spread for hours after drop impact. When long periods of
time are required for stabilization of stain diameters, the analysis of VMD (and per-
haps drop density estimation) must either be delayed until stabilization occurs or the
time after drop impact be included in the stain factor expression. Also, in the case
of long stabilization times, cards may either have to be left on the sampling grid for
longer times or special care taken to protect the cards during collection from the
grid to prevent smudging.
The D-max method for estimating VMD is based on inspection of sampling
cards for large diameter stains. In theory, use of the method requires selecting and
measuring the largest stain on every card along the sampling line before selecting
the five largest drops. In practice, the larger diameter stains usually occur near
the center of the swath on the cards which also exhibit the highest drop densities, thus
simplifying the estimation procedure. The following procedure is recommended.
(1) Select the sampling card near the center of the swath exhibit-
ing the highest drop density.
(2) Visually inspect the card and select the largest stain appearing
on the card.
(3) | Measure the stain diameter to the nearest 50 micrometers
using the measuring magnifier graduated in 100 micrometer
intervals.
(4) If there are several stains nearly as large as the largest
stain on the card, measure their diameters.
37
(5) Enter the card number and stain diameter(s) on the form
shown in Figure 4-3.
(6) Proceed to the next card to the left (right) and repeat the
measurement procedure.
(7) Continue measuring the largest stains on cards to the left
(right) of the swath center until it becomes obvious that
additional cards could not yield one of the five largest drops.
(8) Repeat the measurement process on the right (left) side of
the swath center.
(9) Using the stain factor, compute the drop diameter for the
largest stains on each card, and enter the results on the
form shown in Figure 4-3. A battery-operated pocket cal-
culator is recommended for use in making this calculation.
(10) Select the five largest drop diameters from the tabulated
values and enter their card numbers and diameters in the
spaces provided on the right-hand side of the form; enter
the largest diameter at the top and the smallest diameter
at the bottom. If two or more drops are of the same size,
they should still be counted as separate drops and listed
sequentially in the "Five Largest Drops" table.
(11) The largest drop appearing in the "Five Largest Drops"
table is used in the next step to estimate the VMD for the
trial, providing that the difference in diameter between
any two successively ordered drops does not exceed 32
38
FIGURE 4-3
FIELD CHARACTERIZATION OF VOLUME MEDIAN DIAMETER (VMD)
Trial Number Spray Material
Time/Date Flow Rate
Row/Line Number Miscellaneous
Aircraft 7
Aircraft Altitude
Aircraft Speed Set ee Stain Factor a
: Stain Factor Relationship: Constants b
DD = at+b(SD) + c (SD) :
DD = Drop Diameter
we sD
Stain Diameter
Largest Stains and Drops
Card Number | Stain Diameter | Drop Diameter
_
_
ee
°
—
39
Five Largest Drops
Card Number Drop Diameter
DD/2.2 (80-120 mph)
VMD =
DD/2.5 (> 120 mph)
micrometers. Ifa difference in diameter greater than 32
micrometers occurs between any of the drops, the drop just
below the 32-micrometer gap is used in the next step.
(12) |The VMD for the trial is estimated by dividing the drop
selected in Step (11) by a factor of either 2.2 or 2.5,
depending on the speed of the aircraft as noted in the
form. Enter the VMD in the space provided.
As mentioned above, two formulas are shown on the form in Figure 4-3 for calculat-
ing VMD. If the aircraft speed during the trial was between 80 and 120 miles per
hour, the largest drop diameter DD is divided by the conversion factor 2.2. If
the speed was greater than 120 miles per hour, DD is divided by 2.5. These con-
version factors (2.2 and 2.5) are somewhat arbitrary. Maksymiuk (1964) established
that the factors were dependent on aircraft speed. However, inthe trials used to
develop the technique, the aircraft flew at 80 miles per hour and at 170 miles per
hour, resulting in the definition of the two factors shown in the table. Since a more
definitive estimate of VMD will be obtained in the field laboratory analysis described
in Section 5 below, it may be possible to obtain refined estimates of the conversion
factors for use in subsequent trials. As an example of the application of the D-max
technique, assume that the aircraft speed was 90 miles per hour and the five largest
drops diameters measured on the cards in ascending order were 263, 286, 286, 321
and 335 micrometers. The VMD for the trial is calculated as follows:
VMD = =— = 130 micrometers
After completion of the procedure for estimating VMD, the field crew can
collect the cards and prepare the sampling grid for the next trial.
40
SECTION 5
FIELD LABORATORY CHARACTERIZATION OF THE AIRCRAFT
SPRAY DISSEMINATION SYSTEM
Field laboratory procedures for determining the swath width from drop
density counts, evaluating the drop-size distribution within the swath width to obtain
the volume median, average mass and number median diameters, and the mass re-
covery and deposition efficiency within the swath are described below.
eel DROP DENSITY DISTRIBUTION IN THE SWATH
The field laboratory procedures for estimating the drop density on sampling
cards are similar to those described in Section 4.2 above. In the laboratory, however,
drop densities are estimated for all cards within the swath and more drops are counted
on each card to improve accuracy. In addition to defining the drop density distri-
bution in more detail, the distribution is used (see Section 5.3) to calculate mass
recovery within the swath.
The first step is to select the sampling cards to be analyzed. Using the re-
sults obtained from preliminary counts made in the field (see Figure 4-2), select the
card on each edge of the swath that shows a drop density below the density producing
the requisite pesticide effectiveness. If this cannot be done from the preliminary
data entered on the form shown in Figure 4-2, it may be necessary to count some
cards near the swath edge to redefine the swath width before proceeding to determine
the drop densities on all cards within the swath.
For counting and sizing drops in the field laboratory, the template illustrated
in Figure 5-1 and the measuring magnifier are used to count the drops. The 4,8, and
16 square-centimeter areas are arranged on the template so that the top of the area to
be counted is at the center of the card when the line at the top of the template labeled
41
oP
3903 dYuVvo
3903 GHyv9d
FIGURE 5-1.
Template for counting and sizing drops on sampler cards in the field laboratory,
3903 GYuvo
NW) >
with the corresponding area is aligned with the top of the sampling card. ‘In the
counting procedure, the whole area (4, 8 or 16 square centimeters) will be counted.
Select an area which will result in at least 200 drops being counted. With a little
experience, one can usually readily select the proper area to be counted by visual
inspection of the card. After this selection has been made, the area to be counted
should be examined for obvious anomalies that might affect the accuracy of the count.
These anomalies include smeared drops, foreign matter on the card or shadows
(absence of drops) where deposition has been prevented by a leaf or some other
object. If anomalies occur, move the template to an unaffected portion of the card,
Once an anomaly-free area has been found, anchor the template and card to the
cork board with push pins. The results of the drop density count are recorded on
the Drop Density and Mass Deposition Data Sheet shown in Figure 5-2. Record the
trial number, row/line number and card number, and area being used for counting
on this data sheet,
When the measuring magnifier suggested for use in Section 2 is employed,
stains less than 50 micrometers (um) in diameter should not be counted. If drops
with stains less than 50 um are important in determining mass recovery (i.e., more
than 5 percent of the mass distribution is comprised of drops with stain diameters
less than 50 wm in diameter), a more precise instrument is required to count and
measure the stains. As a general rule, drops with diameters a factor of three less
than the volume median diameter (VMD) estimated in the field do not greatly contrib-
ute to mass recovery. Thus, if the relationship between stain and drop diameter
is given by an expression similar to Equation (4-1), the critical stain diameter can
be calculated from
(5-1)
43
FIGURE 5-2
DROP DENSITY AND MASS DEPOSITION DATA
Trial Number Average Mass Diameter (um)
Row Number Mass (mg)
; = eee 3 -2
Conversion Factor: loz. acre = 1.427x10 mgem
Area (cm?) Density _ %
Mass Recovery (mg m7)
Deposition Efficiency (percent)
44
where
CD = critical stain diameter
VMD = volume median diameter estimated in the field for a given
trial
a,b = constants from stain factor determination given in Equa-
tion (4-1)
If the value obtained for CD is less than 50 um, then a more precise instrument
than the Bausch and Lomb measuring magnifier is required to count and size stains.
The template areas in Figure 5-1 are divided into five columns to assist in
counting the drops. Each column is counted using the measuring magnifier and the
total number of drops for each column is noted on scratch paper. Stains that inter-
sect the outer perimeter of the template area should be included in the count only if
more than one-half of the area covered by a stain is inside the perimeter line. Stains
that intersect the lines dividing the area into columns must be counted in only one
column, usually by assigning them to the column at the left of the line no matter how
much of the stain is contained in a column. After all five columns are counted, the
results are summed and entered in the "Stain Count" column in Figure 5-2. Calcu-
late the drop density by dividing the stain count by the template area used and enter
the result in the 'Drop Density" column provided in the Figure. Count all cards
included in the swath width. The columns labeled "Deposition" in Figure 5-2 will
be completed after calculating the average mass diameter in Section 5.2 below.
5.2 DETERMINATION OF THE SWATH DROP-SIZE DISTRIBUTION, MASS
MEDIAN, AVERAGE MASS AND NUMBER MEAN DIAMETERS
The mass median, average mass and number median diameters are deter-
mined from the drop-size distribution for the swath. Experience has shown that the
45
drop spectrum analysis of 5 cards within the swath width is normally sufficient to
estimate these parameters within 15 percent of the values that would have been
obtained if all cards within the swath had been analyzed. The error is frequently
less than 5 percent. The 5 cards for analysis are selected by using 1 card from
each end of the swath, 1 card near the swath center and 1 card on each side of the
center card located approximately half the distance between the end and center cards.
Before the drops are counted and sized, the drop-size categories must be
specified.
Selection of Drop-Size Categories
Normally, 8 to 10 drop-size categories are sufficient to adequately define
the drop spectrum. The upper and lower limits of the stain size intervals must be
determined before the stains are counted and sized. The following step-wise pro-
cedure for selecting the limits of the stain size intervals is suggested:
(1) Draw the line defining the relationship between stain and drop
diameter on linear graph paper as shown in Figure 5-3, using
Equation 4-1; in Figure 5-3, a=7.68, b=.199 and c=5,73 x
107°, The curve should extend from the smallest-diameter
stain to the largest-diameter stain counted in the "quick-look"
field analysis.
(2) Mark the position on the curve of the stain VMD estimated in
the "quick-look" field analysis by the D-max method. For
example, the point marked + in Figure 5-3 corresponds to
a VMD stain diameter of 600 um or a drop diameter of 130
um.
46
| ates — aes —— = + ee mgs ie <7 ef
Oo (e) Oo Oo oO Oo
(@} Oo oO ©) oO © 8
© t q e) © © t
(wn) Y3ZL3WVIC NIVLS
} ? *
100 140 180 220 260 300 340
DROP DIAMETER (ym)
60
The + symbol is
-max field analysis.
FIGURE 5-3. Stain factor relationship for example trial data.
D
-look"
quick
"
the stain VMD obtained from the
47
(3)
(4)
It should be noted that the basic graph shown in Figure 5-3 can be generated
before the trials.
(4-1) to convert the stain upper limits to drop-size upper limits.
Having determined the drop-size categories, the drops on the cards can now
Divide the line in Figure 5-3 into about five class inter-
vals below the point marked + using standard intervals
of 50 um, 100 um or multiples of 50 um. The measur-
ing magnifier is not accurate if the class intervals are
less than 50 um. For the example shown in Figure 5-3,
the upper limits of the stain class intervals become 100,
200, 300, 400, 500 and 600 um as shown by the abort
horizontal lines. The lower limit of the smallest class
interval should correspond to the smallest drop counted
in the spray deposit density count.
Divide the line in Figure 5-3 above the point marked +
into five intervals using standard stain intervals of 50 um
or 100 um or other multiples of 50 um. In the example
shown in Figure 5-3, this procedure results in stain cat-
egory upper limits of 800, 1000, 1200, 1400 and 1600 um.
If the VMD estimated by the D-max method is less than
100 micrometers, it may be necessary to divide the
straight line above the point marked + into more than
five intervals to obtain a representative mass distribution.
shown in Figure 5-4 and use the stain factor equation relationship given by Equation
size upper limits on the Drop Spectra Data sheet.
be counted and sized. The template shown in Figure 5-1 is also used in making the
48
Enter the stain class intervals on the Drop Spectra Data sheet
Enter the drop-
67
FIGURE 5-4
DROP SPECTRA DATA
Material 3
Test 9 Row/Line Cc Spray Material DYLOX Density _1. 067 (g cm )
Analyst: John Doe Stain Factors: a= _ 7.68 » b=_0.199 , c=5.73x10-6
~ NUMBER
OF DROPS
oe
CARD NO. rae
DROP DENSITY
(drops em™?)
par: ee
TEMPLATE
NUMBER
OF DROPS
DROP a
| Ne | cm
NUMBER
OF DROPS
DROP DENSITY
(drops em~2)
CARD NO,
46
TEMPLATE
AREA
8 cm
10.380 6. 750
on 11.38 7.500
CARD NO,
= =
TEMPLATE
AREA
NUMBER
OF DROPS
CARD NO, 44
aS ae
7.375 7. 562 hs
TEMPLATE
AREA
DROP DENSITY
-2 13.12
eet 4 cm“)
os
CARD NO. NUMBER
pari oo OF DROPS
TEMPLATE
DROP DENSITY
(drops em~2)
NUMBER
OF DROPS
CARD NO.
TEMPLATE
AREA
cm
Mean Drop Diameter
(um)
Mean Drop Mass
(mg)
Sum of Drop Densities
by Size Category
Average Drop Densitics
x 10-6
44, 88
by Size Catagory
23.19 ls
ical
drops cm
Cumulative Drop Densitics | 4.638 13.61
3.152 | 2.86
x10-5 | x10-4
Cumulative Percent of
Drop Densities
Average Deposition hy
Size Category (mg env)
Cumulative Mass 3.177
(mg) x107~4
Cumulative Percent
of Mass
FIGURE 5-4 (Continued)
Size Category
0.375
|
i
BREE
ESR
234.2 277.1
1.113 | 2.703
x107*|x 1074
= .
5.421
x 1074
9.486 | 1.924
x10-4] x1073
a aie
2.350 0.4375 0, 1250 0.025
8.5
7.362 3.712 | 3.637
86. 80 98.17
32,60 32.6L | 32.64
99.91
1.486
x 10-5
1.736
x 10-3
8.971
x10-4
4.518
x1074
1, 207
x 10-2
96.05 96, 21 100
drop spectra counts. Again, a minimum of 200 stains should be counted and sized
using a procedure similar to the procedure described in Section 5.1 for obtaining
drop densities, except that the measuring magnifier is used to size stains and clas~
sify them according to size intervals. After the card and template have been secured
to the cork board with push pins, the magnifier is used to measure the drops in each
column. Counting and sizing is best accomplished using two people, one to size drops
and another to record each drop in terms of a size-category number on scratch paper.
After the stains in each column are counted and sized, sum the number of stains in
each category. When the counting and sizing of drops in all five columns of the
selected area have been completed, the subtotals are added and the total number of
stains in each size category entered on the form shown in Figure 5-4 er-each card
analyzed. The example calculations in Figure 5-4 for Card Number 43 show that 41
stains were counted in a 16 square-centimeter area of the template that were less }
than 100 um in diameter, 118 stains were less than 200 um and equal to or greater
than 100 um, etc. Inthe example, a total of 545 stains were counted on Card Number
43 in the 16 square-centimeter area of the template. The 8 square-centimeter area
of the template could have been used and more than 200 stains counted. Note that the
8 square-centimeter area was used in analyzing the remaining four cards. The drop
density for each size category is obtained by dividing the number of drops in the cate-
gory by the template area used in the analysis. These drop densities are entered on
the Drop Spectra Data sheet.
After all five cards have been analyzed, determination of the drop-size dis-
tribution parameters can proceed. For convenience in explaining the calculations,
the rows used in these calculations on the Drop Spectra Data sheet have been iden-
tified by the letters A through I.
Row A - Mean Drop Diameter
The volume mean drop diameter in each size category is calculated from
the expression
51
2 2 3
d,+d."d,+dd,+d
= a 2 2 Loe (5-2
4 ins
where
qd, = drop lower limit for the size category
d, = drop upper limit for the size category
For example, the entry in the first column of Row A is calculated as
1/3
a= jena” a 17.6)" Zhe LITAG (27. 6)" a 7.9)
4
23.0um
Repeat the calculation for each size category and enter the result in the appropriate
column of Row A.
Row B - Mean Drop Mass
The mean drop mass in milligrams for each size category is calculated from
the relationship
m = feo) na x 10°?
(5-3)
= 5,236 x10, @°
where
p * density of spray material in grams per cubic centimeter
52
For the example shown in Figure 5-4, where the density of the spray material is
1.067 grams per cubic centimeter, the entry in the first column of Row B is
3
i
5,236 x 107° (1. 067) (23. 0)°
6.797 x 10° milligrams
Repeat the calculation for each size category and enter the result in the appropriate
column of Row B.
Row C - Sum of Drop Densities by Size Category
The sum of drop densities by size category is obtained by summing the
drop density in each size category over all the cards analyzed in the swath. In
the example shown in Figure 5-4, the result for the first column in Row Cis
2.562 + 5.500 + 8.625 + 5.500 + 1.000 23. 187
23.19
where 2,562 is the drop density from Card 43, size category 1, 5.5 is the drop
density from Card 46, size category 1, etc.
Repeat the summation procedure for each size category and enter the results
in the appropriate column of Row C.
Row D - Average Drop Densities by Size Category
The average drop density in each size category is obtained by dividing the
sum of drop densities in Row C by the number of cards included in the analysis
(5 in this case). For the example shown in Figure 5-4, we thus obtain
53
which should be entered in the first column of Row Dfor size category 1.
Repeat the calculation for each size category and enter the result in the
appropriate column of Row D.
Row E - Cumulative Drop Densities
The cumulative drop densities shown in Row E of Figure 5-4 were calculated
from the average densities recorded in Row D. The cumulative density recorded in
each size category column of Row E is the cumulative sum up to and including the
average drop density recorded for that size category in Row D. For the example
shown in Figure 5-4 in Row E for category size 3, the cumulative drop density is
4.638 + 8,976 + 7.362 = 20.976 = 20.98
Continue the summation procedure across Row D until the cumulative density for each
size category has been calculated and recorded in the appropriate column of Row E.
Also, enter the cumulative sum for the largest category (32.64 in Figure 5-4) in the
total columns of Row E.
Row F - Cumulative Percent of Drop Densities
The cumulative percent of drop densities is calculated for each size category
by dividing the cumulative drop density for each category in Row E by the cumulative
drop density in the Total Column of Row E and multiplying by 100. For the example
in Figure 5-4, the cumulative percent in the first column of Row F for size category 1
is
54
32.64. ° 100 = 14.21 percent
Calculate the cumulative percent of drop densities for every size category and record
the result in the appropriate column of Row F.
Row G - Average Deposition by Size Category
The average mass deposition by size category is calculated by multiplying
the mean drop mass in a given size category in Row B by the corresponding ave rage
drop density in Row D. Thus the average deposition for category 1 in Row G of
Figure 5-4 was obtained from
=6 -5
(6.797 x 10 ) (4.638) = 3,152 x 10 milligrams per square
centimeter
Complete the calculation for each size category and enter the results in the appro-
priate column of Row G.
Row H - Cumulative Mass
The cumulative mass for each size category shown in Row H of Figure 5-4
is calculated from the average deposition values recorded in Row G. The cumulative
mass recorded in each size category column of Row H is the cumulative sum up to
and including the average deposition recorded for that size category in Row G. For
the example shown in Figure 5-4 in Row H for size category 3, the cumulative mass
is
4 3
=5 - - -
3.125 x 10° + 2,862 x 10 + 8.194 x 10 + 1.137 x 10
55
Continue the summation procedure across Row G until the cumulative mass for each
size category has been calculated and recorded in the appropriate column of Row H.
Also enter the cumulative sum for the largest category (1.207 x ic in Figure 5-1)
in the Total column for Row H.
Row I - Cumulative Percent of Mass
: The cumulative percent of mass is calculated for each size category by
dividing the cumulative mass for each category in Row H by the cumulative mass
in the Total column of Row H and multiplying by 100. For the example shown in
Figure 5-4, the cumulative percent in the first column of Row I for size category
1 is
3.152 x 10°
=9 x 100 = 0,26 percent
1.207 x 10
Calculate the cumulative percent of mass for each size category and record the result
in the appropriate column of Row I.
Mass and Volume Median Diameter
The mass median diameter is the drop diameter that divides the spray de-
position distribution into two equal parts by mass. Thus, 50 percent of the mass
deposited in the swath is due to deposition from drops with diameters greater than
the mass median diameter and 50 percent is due to deposition from drops with
diameters less than the mass median diameter. The mass median diameter is ob-
tained from a graph of the cumulative percent of mass from Row I of Figure 5-4
plotted as a function of the drop upper limit for the size category on logarithmic
probability paper.
56
Figure 5-5 shows the example distribution from Row I of Figure 5-4 plotted
on 2-cycle log probability paper. The first point at the lower left of Figure 5-5 cor-
responds to a cumulative percent of mass of 0.26 percent from Row I and size cate-
gory 1, where the drop upper limit is 27.6 um. After all the points are plotted for
cumulative percentages less than about 95 percent, connect the points on the graph.
The mass median diameter is the diameter where the mass distribution curve inter-
sects the 50-percent line on the plot. As shown in Figure 5-5, the mass median
diameter for the example is about 125 um. Since the mass and volume median diam-
eters are equivalent (density is linear with drop size), the volume median diameter
is also 125 um.
Average Mass Diameter
The average mass diameter (AMD) is calculated from the expression
= 1/3
AMD = 10° £D_
Tp Ny
3 D 1/3
AMD = 1.2407 x 10 = (5-4)
PND
where
D = Total cumulative mass deposited on all cards from the Total
column of Row H in Figure 5-4
Ny = Total cumulative drop density of all cards from the Total
column of Row E in Figure 5-4
57
8g
400
300
200
DROPLET DIAMETER (pm)
“S
Oo
20} - =
10
0.2 05
FIGURE 5-5.
c
}
i
Se Se ae eee
5 10 20 30 40 50 60 70 80 90 95 98 99
CUMULATIVE MASS (percent )
Cumulative mass distribution for the example trial. The symbol + marks the
median of the cumulative mass distribution.
Thus, for the example distribution in Figure 5-4
1.207 x 10°" 1/3
7 3
AMD 1.2407 x 10 | aa es
= 87um
Number Median Diameter
The number median diameter (NMD) is the drop diameter which divides
the spray deposition distribution into two equal parts by number of drops counted.
Thus, 50 percent of the total number of drops deposited in the swath have diameters
greater than the number median diameter and 50 percent have diameters less than the
number median diameter. The number median diameter is obtained from a graph of
the cumulative percent of drop densities from Row F of Figure 5-4 as a function of
the drop upper limit for the size category on logarithmic probability paper.
Figure 5-6 shows the example distribution from Row F of Figure 5-4
plotted on 2-cycle probability paper. The first point at the lower left of Figure 5-6
corresponds to a cumulative percent of drop densities of 14.21 percent from Row F
and size category 1 where the drop upper limit is 27.6 wm. After all the points are
plotted for cumulative percents less than about 95 percent, connect the points on the
graph. The number median diameter is defined at the point where the number distrib-
ution curve intersects the 50-percent line on the plot. As shown by the + symbol in
Figure 5-6, the number median diameter for the example is about 54 um.
The preceeding calculations were performed using an electronic calculator
with scientific notation, a memory and the capability of raising numbers to fractional
powers. In Section 2, it was recommended that a desk-top programmable calculator
59
98 99
90. 95
70 80
20 30 40 50 60
ie)
OOO) ©- ©
oor o wo
40
30
20
2
=
400
300
200
(wt) yYsI3WVIO 137d0Na
CUMULATIVE NUMBER (percent)
The + sym-
Cumulative number distribution for the example trial.
bol denotes the number median diameter.
FIGURE 5-6.
60
be available for use by the field-project crew. If such a calculator we . available,
most or all of the calculations performed in this section could be completely auto-
mated so that an operator need only enter the material density, upper drop limits,
card number, number of drops counted in each size category and the area counted.
Automated calculation capabilities greatly reduce both the time required to complete
the analysis and the chances that errors will be made in the analysis.
Der e ESTIMATION OF SPRAY SYSTEM DEPOSITION, DEPOSITION EFFICIENCY
(MASS RECOVERY) AND SWATH WIDTH BASED ON MASS DEPOSITION
The mean mass diameter calculated in Section 5.2 above, the drop density
distribution in the swath from Figure 5-2, and the aircraft dissemination information
can be used to estimate spray system deposition, mass recovery within the swath and
deposition efficiency. Figure 5-7 is a copy of Figure 5-2 in Section 5.1, the Drop
Density and Mass Deposition Data sheet, with data entered from the same trial used
as an example in Section 5.2 for calculating swath parameters. The card numbers,
template areas counted, number of stains counted and drop densities were entered in
the form according to the procedures outlined in Section 5.1.
The deposition occurring on each card is obtained under the assumption
that the mass distribution calculated in Section 5.2 is representative of the distribu-
tion on each card in the swath. Thus, the mean mass of all drops on the card is
assumed to be
a ~1 :
m = 5.236 x 10 0) (AMD)? (5-5)
where AMD is the average mass diameter calculated from Equation (5-4).
For the example trial,
61
FIGURE 5-7
DROP DENSITY AND MASS DEPOSITION DATA
Trial Number _ 9 Average Mass Diameter 87.15 (um)
eee =4
Row Number C Mass 3.698 X 10 “(mg)
: -1 _ 3 | =2
Conversion Factor: 10z. acre = 1.427x10 mgcm
D siti
Template rop Deposition
: >) Density “ae
Area (cm") (drops cm 2) (mg em7”)
4.44 1.641x10°° 2.342
8.13 3.005x10— 4,288
9.81 3.629x10 5.178
19.00 7.026xX10— 10. 026
34.06 1.260x10 17. 975
$7.13 1.373x1072 19.591
37.00 1. 368x10_ 19,525
30.38 1.123x10- 16. 029
39.00 1.442x10° 20.580
40.38 1.49310 5 21. 306
$2.13 1, 188x105 16. 952
33.38 1.234x10 17. 612
35.13 1.299x10° 18.535
39.63 1.465 x10_ 20. 910
36.13 1.38610 19. 063
39.75 1.470 X10 20. 976
35.88 1. 327x10° 18. 931
32.25 1.193x10 17.018
25.63 9.476x10_ 13.522
11.50 4.253x10 6. 068
ot ot
Qa
a
fo oon)
8
8
8
8
8
8
8
8
8
8
8
8
8
6
: 306. 427
1
3 as
Mass Recovery 5. 6684 10 (mgm ~)
Deposition Efficiency 18. 66 (percent)
62
-10 3
m = 5.236 x 10. (1.067) (87.15)
-4
= 3.698 x 26 mg
This value is entered in the space provided for mass at the top of the form shown in
Figure 5-7. The deposition on each card is then calculated by multiplying the mean
mass m by the drop density for each card. For Card Number 42
4
—
7.026 x 107° mg cm
19.00 x 3.698x10
Using the conversion factor to obtain ounces per acre, we obtain
3
it
7.026 x 107° mg _ x 1.427 x10 10. 03 ounces
2 acre
cm
The multiplication is completed for each card in the swath and the results entered
on the data sheet.
The total mass recovery along the sampling line is calculated by summing
the deposition from all cards in the swath and multiplying by the separation distance
between cards. In this example, the card spacing was 10 feet (304. 8 centimeters).
The sum of the deposition is shown in the row labeled Total on the data sheet. There-
fore, the total mass recovery along the sampling line is
.21474 mg x 304.8cm = 65.453 mg
2 cm
cm
63
or 6,5453 x 10° mg m”? - The sampling line in this example case was not at right
angles to the mean wind direction during the trial or to the flight path of the aircraft
into the wind. Figure 5-8 is a schematic diagram showing that the wind direction
was at an angle of 33 degrees with a line perpendicular to sampling line C. There-
fore, the deposition integrated across the sampling line is greater than the mass
recovered across the swath as represented by the dashed line at right angles to the
wind direction in Figure 5-8. The corrected mass recovery is
6.5453 x 10°mg x cos (33°) = 5.6684 x 10°mg
m m
The deposition efficiency in the swath can be calculuted using the mass
recovery in the swath and the aircraft dissemination information. In the example
trial, the aircraft was releasing 36.3 gallons of spray material per minute at an
airspeed of 90 miles per hour. Converting these data into milligrams released
per unit length of flight path, we obtain
18,15 gat hours - mile 60 min » 3785. gem” Oe 10° mi
min 90 miles 1609. 3m hour gal
= 3.037 x 10 age mn
The deposition efficiency is then calculated to be
3
car x 100 = 18.66percent
é x
When the deposition producing pesticide effectiveness is known, the minimum
effective swath width where deposition exceeds the effective deposition is easily de-
64
FIGURE 5-8. Schematic diagram showing wind direction with respect to sampling
line C for the example trial.
65
termined from the information on the Drop Density and Mass Deposition Data sheet
shown in Figure 5-7. A plot of the deposition shown in the table versus card number
is given in Figure 5-9. For example, suppose the effective pesticide deposition is
60 ounces per acre. Since the samplers were separated by 10 feet in this trial, the
effective swath width is
168 feet x cos (33°) = 145.5 feet
after correction for the angle of wind direction with respect to the sampling line.
66
L9
DEPOSITION (ounces/acre)
220
200
180
I60
140
120
100
80
60
40
20
38
40 42 44 46 48 5O 52 54 56
CARD NUMBER
FIGURE 5-9. Deposition in ounces per acre across the sampling line for the example trial,
58
REFERENCES
Morris, A. L., D. B. Call and R. B. McBeth, 1975: A small tethered balloon
sounding system. Bulletin American Meteorological Society, Volume 56,
Number 9, p. 964.
Maksymiuk, Bohdan, 1964: A rapid method for estimating the atomization of vil-
base aerial sprays. Journal of Economic Entomology, Volume 57, No. 1,
p. 16.
68
APPENDIX B
WIND MEASUREMENTS
Table B-1 contains a summary of 30-second average wind directions and
wind speeds for the spray characterization trials conducted near Townsend, Montana.
The measurements were made at a height of 2 meters using Beckman and Whitley
sensors and Esterline-Angus recorders. Data from Trials 1, 4 and 8 were not
analyzed. Only 5-minute average wind directions and speeds are given for Trials 2
and 3 because the recorders were operating at a low speed for these trials and more
detailed estimates could not be made.
TABLE B-1
WIND MEASUREMENTS FOR THE TOWNSEND TRIALS
Wind Direction Wind Speed
(degrees) (mph)
aqmjooaanad oe
Us
8.
1.
ls
es
7.
se
7
6.
6.
TABLE B-1 (Continued)
Wind Direction Wind Speed
(degrees) (mph)
(Continued)
4
5.
4,
4.
5.
5.
5.
4.
5.
5.
ogogagaaoua ano ul
°
aonFrF UI nanon
ef er en. ert Mer (ve era ie
eo oOo @ © .o © aS © cn
TABLE B-1 (Continued)
Wind Direction Wind Speed
(degrees) (mph)
SccoonNnconuamo
annruanoacon
2
3
3.
2.
2.
2.
3.
2.
2.
2.
.
oooococoouce
NNNNNNN YD LD
. a ae ee ° s
BH
TABLE E-1 (Continued)
Wind Direction Wind Speed
(degrees) (mph)
Sa IN Sn Go O.9
2.
5.
4.
4
3.
2.
3.
2.
2.
2.
oudaqa ono o qo uo
PrP Po a a & CO ©
ieee ita Sane, . e .
aoouunruarnana wa ©
TABLE B-1 (Continued)
Wind Direction Wind Speed
(degrees) (mph)
ww NM DY w& & & w Ww w
oon ooo au >
.5
0
0
3)
0
Aa)
0
-0
0
-0
ouowmoonowoowoao I
Sie oF 6 ay weer. “e .
ooo ooo uc oOo Ul
APPENDIX C
FIELD LABORATORY ESTIMATES OF
SPRAY DEPOSIT DENSITIES
This appendix contains a tabulation of spray deposit densities estimated
for each card in the swath during 16 of the spray characterization trials conducted
near Townsend, Montana. These estimates were made in the field laboratory at
Townsend using procedures described in Section 2 of the main body of the report.
No density estimates are presented for Trials 1, 4 and 8. The deposition data for
Trial 1 were invalid because the helicopter spray system was not purged of water.
Trial 4 was the last trial in a series of morning trials in which the elevated position
of the cards relative to the ground caused the stains to be elongated making the anal-
ysis of spray characteristics other than spray deposit density difficult. Because the
relatively high wind speed during Trial 4 increased the elongation of stains on the
cards, the data were not analyzed. In Trial 8, the spray helicopter flew crosswind
and the sampling grid was not adequate for estimating spray deposit densities in the
swath,
TABLE C-1
SPRAY DEPOSIT DENSITIES FOR THE TOWNSEND
SPRAY CHARACTERIZATION TRIALS
Card Drop Drop Card Drop
Number Density _ Density -2 Number Density _
(Drops cm (Drops cm_) (Drops cm .
BP OU. 3) CO ge
BPrPeEPPPrPPAN PPAR RP WAT DOHF OO
Trial 5
6
4.
3
4.
4
3
4.
4
4
3
3
3.
3
oO
. e e
—
ONIP OR RAOUL PAO
. . . ce «@
wndornrowoanrtreo
TABLE C-1 (Continued)
Drop Drop
Density Density
(Drops cm~2) (Drops cm72)
Drop
Density
(Drops cm72)
Card
Number
Nn et eo a ee ee ae ote
wmuUnmwon oo wp
Dae]
a
FOOrRrrFOrRFKR RFA RP DEF WWOONR@DARKRRDWOR
.3
io
4
al
.3
«6
.3
Ale
23
a
4
ap
9
9
ru |
5
9
.6
AAS)
«6
Aas:
4
.3
«8
ee a el ey er is lek os Me en Oe. et ers OOS. el Le iets viet etl an te
WBF ONWEHFARWAARARANUNUN MO PN HP KE KH OH
eet) las et Aue cot cee te
OrnrF © Oe Oo
TABLE C-1 (Continued)
Drop
Density
(Drops cm™2)
Drop
Density
(Drops cm72)
Drop
Density
(Drops cm~2)
Card
Number
Card
Number
wWwwwn >
oor nr ©
bo bo
ao
18
15
17
15
13
10
16
11
10
ao
st
Se
ORWOROTHEHEwDAARHOHWWHOANDAHONHD
Trial 12
Ce Os AO Oy NO RCO Ue On ne ae wae cer ee ea ete
NNO DNWAUMOWAONNDTWHWHWRrROAAKFAWHOrRAN DD
ore oe ee
Trial 11
WORE DPR RPOZORANWW RO W
oowoaoaorrk wow
FO ONnNNnNnWHLDOD
ee ie ee ee sc .s
a
C+
TABLE C-1 (Continued)
Drop
Density
(Drops em~2)
Drop
Density
(Drops cm72)
Drop
Density
(Drops em72)
Card
Number
Card
Number
a
os
ee
bo
NDF ENNNNNNNHPHHE HE
CMMORADONGHHwDAONA
OR DODRFONKHF WAH DAWWAWAOONDHDHOHPNONCOS
iJ)
=
0.
9.
9.
4.
8.
9.
0.
0.
5
6
4
4
7
8
1
6
3
8
4
8
7
ay
4
8
il oe
:
pew po x
Lia 13 Trial 14
TABLE C-1 (Continued)
Drop
Density
(Drops em?)
Drop
Density |
(Drops cm~*)
Drop
Density
(Drops em72)
Card
Number
Card
Number
Card
Number
63
64
Trial 18
a
PND
NHR eH
HE cor
dD bv
e pO
ADPmOAWBWHAWHREHDWOCOWSO
1)
co
Trial 16
SP PD WC DO
oOo © WY C
WP WP Ww
OoOnnvNra
2) So. eee ee SC eee ier ew 6 Mee a Se) le ten 2 Seb us
FWmMUNUNRDWAOROH@AHAWUAWWARWNO
on yp
oo
ew
Ce
Go ©
<2
8
Re
.6
3
4
5
4
.3
me
0
.3
-9 25
3 29
4
4
5
6
.0
6
5
al
5
8
:3
6
9
8
Suck) Cis We. So es ee Se Cle Ss. ate, le
OrRNFP UO DWMArFRFWRUDONF DOCK
TABLE C-1 (Continued)
Drop Drop Drop
Density Density Density
(Drops cm~2) (Drops cm~2) (Drops em=2)
oe ee
ANF OaANoOrnnarorg
io
Cro
:
2
4
2.
8.
4
5