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 24 May 1989
59
AFM 91-19 / TM 5-629 / NAVFAC MO-314
mechanical incorporation is required. Disks or
upper air currents and creates a serious drift
power-driven rotary-tillers usually provide the
hazard.
best results. Subsurface blades have been used
d. Some distortion of the swath by the slip-
under special conditions, but are still experimen-
stream occurs with all aircraft. This is especially
tal.
true with single-engine aircraft, and the larger
the aircraft engine, the greater is the amount of
distortion. Nozzles that are evenly spaced on the
8-4. Aquatic Application Equipment. Aquatic
boom do not provide an even spray pattern with
herbicide applicators may be boat- or barge-
some aircraft. Instead, they result in an uneven
mounted blowers, sprayers, booms with injec-
and streaked swath. To compensate for these
tion systems, or granule spreaders having essen-
effects, additional nozzles (or nozzles with larger
tially the same features as ground equipment.
tips) should be placed at certain points along the
Liquid aquatic herbicides also can be applied
boom, as determined experimentally.
with a venturi pump/injector powered by prop-
e. The nozzles are usually designed and placed
wash. Slow-release granular herbicides can be
to control droplet size. Too many droplets below
applied by a Buffalo turbine or by dragging
100 micrometers in diameter increases the risk of
them in a porous bag behind a boat. Aerial
drift. High-velocity air passing over the face of a
applications are sometimes made for general
standard nozzle has more influence on droplet
control of aquatic weeds.
size than does orifice size or pressure. Droplet
size can be altered by changing the angle or
8-5. Aerial Spraying Equipment. Aerial ap-
position of the nozzle in relation to the air-
plication equipment has improved steadily
stream. For herbicide application, nozzles should
with the increased use of chemical sprays in
always be pointed away from the direction of
all areas of agriculture. The use of appro-
flight.
priate equipment, its proper adjustment,
f. Because aerial sprays are released from a
and skill in carrying out the spraying operation
greater height than ground sprays, drift hazards
are vital for satisfactory results. Because most
are an even greater problem. Also, the aircraft
aerial spraying will be done by specialists such
creates turbulence, propwash, and wingtip vor-
as the Air Force Aerial Spray Branch (356
tices, all of which increase the potential for drift
TAS/Aerial Spray, Rickenbacker ANGB OH
to nontarget areas. Aerial spraying should al-
43217-5008) or contractors, this description is
ways be carried out when the air is relatively
brief.
still. Drift retardant additives are used to mini-
a. The components of airborne sprayers are
mize the risk of drift under less than optimum
much the same as those of ground equipment,
spraying conditions.
and calibration methods are similar (see chapter
g. Precise flagging is necessary to guarantee
9). The application speeds of fixed wing aircraft,
proper swaths during field spraying. Flagmen
however, usually range from 90 to 200 mi/h, in
should always be equipped with an accurate
contrast to ground sprayer speeds of 3 to 5
measuring device for checking swath spacing.
mi/h.
Flagmen should move upwind of the spraying to
b. Spray pumps on aircraft are driven by a
minimize exposure to the spray.
V-belt drive from the main engine, a small
h. Ground-to-air communications enhance
direct-connected propeller, an electric motor, or
aerial application by allowing adjustments of
some other power source. Centrifugal pumps are
spraying altitude and swath spacing, reporting of
usually used because of the high delivery rates
nozzle malfunctions, etc.
required, and agitation is usually by hydraulic
bypass from the pump.
8-6. Fumigation Equipment:
c. Booms are generally shorter than the air-
a. Increased use of soil fumigants to control
craft's wingspan so as to reduce the effects of
weeds, plant-feeding nematodes, and soil-
the wingtip vortices. Although spray booms
inhabiting insects has resulted in numerous mod-
extending beyond the wingtips are used in apply-
ifications of fumigant injectors to meet special
ing some insecticides, they are not recommended
requirements. Fumigant injectors may be hand-
for the precision swaths required for herbicide
or power-operated and can be thought of as
treatments. Nozzles should not be extended
underground sprayers.
more than within 2 or 3 feet of the wingtips,
because upward movement of air at the wingtip
b. Fumigant injectors have a reservoir, a
vortices results in considerable loss of spray to
pump, and a metering device to control the
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