By: Dick Turner - Chief Designer
The information that follows is based on studies by different
universities and over 15 years of experiences with our spray planes.
We have no lawsuits from spray drift accidents and a lot of satisfied
customers. Now let me tell you how we take care of a crop, and
do as little damage to the environment as possible.
The big push in normal spray aircraft is bigger turbine engines,
larger hopper or chemical tanks to put out more chemical per acre
per flight. Why so? Let’s say you have insecticide that calls
for 1 liter per hectare. The big airplane is going to mix the
liter of chemical with 20 liters of water so he can spread the
21 liters of liquid over the 1000 square meters of crop, right?
Wrong. The big plane flies at 120 to 140 mph. As it enters the
field the pilot turns on the nozzles. At that speed up to half
evaporates and may end up as far as 8 to 10 miles away from the
field or wander around waiting for some rain to put it in the
water supply. What of the other 10 or so liters that fell to the
crop? Well, about half it ran off onto the ground. So of the liter
that left the plane 50% is all over the county side, of the1/2
liter that got to crop, 1/2 of it ran onto the ground. So the
250 cc that stayed on the plants does the job. The big plane wasted
750ccs, put about 500cc who knows where, and 250cc are headed
for the ground water.
The 500cc is all over the place because the big planes use hydraulic
nozzles, the nozzles operating normally make all different sizes
of droplets. The size of a drop is measured in microns. There
are 3-micron drops up to 1,200-micron drops from hydraulic nozzles.
Here is what that means, in a three mile per hour wind from a
height of 10 feet a drop 3 microns in diameter will drift 8 miles.
10 microns will drift 1 mile. 15 microns will drift 2000 feet.
100 microns will drift 50 feet, and 500 microns will drift 5 feet
and this is in a 3-mph wind. This data is from a study at the
University of California at Davis. The 500cc that landed on the
crop we estimate that 50% ran off. Why, because leaves shed water,
try it; pour water on a leaf and with the normal shaking of the
plant from the aircraft passing above it. It shakes about 50%
off (please note all aircraft have a little down wash off the
wings) this is where we arrive at 250cc of chemical left, remember
this is over an area of 1000 square meters. This is why chemicals
have to be so strong, we waste 50 to 75%.
Now a new game plan for your future and mine. We use CDA nozzles.
That is Controlled Droplet Application. Our present nozzle is
the Micron X1 patented and made in England, their main web page
is located at http://www.micron.co.uk/ This is a description the nozzle. The Micron X-1 is a spinning
disc rotary atomizer designed to allow the Controlled Droplet
Application (CDA) of insecticides and fungicides on airblast sprayers
(we adapted it to our light weight aircraft). The Micron X-1 offers
huge savings compared with hydraulic nozzles. By efficiently producing
only the spray droplet sizes appropriate for insecticide and fungicide
application the Micron X- 1 cuts spray volumes, costs and minimizes
the risk of environmental contamination. See this web page for
further data on the CDA nozzle http://www.micron.co.uk/technologies.html.
The unique thing about a CDA nozzle is that nearly all the droplets
are the same size.
A study done by the University of Texas A&M found equal size droplets
drift equal distances and fall at the same rate. This means if
we produce an 18-meter wide swath from 3 meter high that’s how
wide it stays as it falls to the ground. Remember the 120 to 140mph
speed of the big spray plane. Our plane sprays at 50mph. This
lowers the evaporation substantially. The reason we do this is
a study done by NASA in the sixties. It stated that the ideal
spray speed for aerial spraying for best droplet placement and
drift control is 44 mph. At that time, no aircraft could come
close. A helicopter would have came the closest, but at 44 mph
they still have a donut shaped down wash that destroys the even
pattern of the spray. This goes away when the helicopter reaches
about 80 mph. Close, but no cigar.
Our aircraft flies safely at 40 mph, but at 50 mph and a with
an 18 meter wide swath this produces 2-2.5 hectares or about 5
acres per minute production. Evaporation is lower because of the
speed, it is also lower because we don’t use just water. We use
water mixed with oil. Special mineral oil, or in some crops we
use vegetable oil. In sugar cane we mix with molasses, oil and
water. Molasses is a by-product of refining sugar and is very
inexpensive. This all mixes, because we add a small amount of
a chemical that breaks the surface tension of the liquids. Note.
Now that we are using oil or molasses with our mixture, it will
not evaporate quickly.And these additives also tend to encapsulate
the chemical in a drop so that the water and active ingredients
don’t evaporate. If you pour oil or molasses on your hand or a
leaf, it sticks. It doesn’t run off onto the ground.
So now we have an aircraft spraying at 50 mph. It is spraying
a chemical mixture that doesn’t evaporate. The aircraft is equipped
with nozzles so that we can control the drift. To this we add
a wing with a special design that blows the spray down into the
crop. So now with insecticides we can lower the dose by 50 to
75%. Putting the majority of it into the crop. No longer is a
liter necessary for a hectare. 1/2 to 1/4 liter per hectare is
the norm. The farmer likes this as well. With many chemicals costing
$50 to $100 per liter. Some people might say fine. I could do
the same mixtures in a big plane. No, that won’t work. Number
one: 120 to 140 mph is too fast. They don’t have the precise control
we have at the lower speed. We carry thirty to fifty gallons of
mix; they carry 400 to 600 gallons. This amount of our mixture
is too expensive. We spray 10 to 20 hectares per flight. They
normally spray 10 to 20 hectares per flight also.
Next, our system includes training. Many companies spray all day.
Wrong!! We teach the people to be ready to spray at first light.
Then we only spray till the wind goes over 12 mph or until the
thermals start lifting the spray. Then we stop till the evening.
Rest in the afternoon or do maintenance on the aircraft then we
spray till dark. This is the way it should be done with all aircraft,
but the normal AG planes think that with the extra water they
can give the crop a bath. The heat just makes the drift and evaporation
worse.
For the year two thousand we are going to add an injector spray
system. This means the chemicals are injected into the boom lines
just before the nozzles. It will also give us closed system chemical
handling increasing saftey for the loaders. The tank will have
a dump valve on the bottom. If you have problems and you are forced
to pull the emergency dump you are only dumping the water, oil
or molasses mix. These will not damage the environment or people
on the ground.
We have not found any chemical that we cannot mix with oil or
molasses and make it stick to the crop and not evaporate. I hope
I’ve explained the system to you in an understandable way. If
you have any questions please ask.
One other item, in Venezuela we are spraying with some organic
compounds. We spray a fungus that attacks the pest insect and
then kills it. A few days later the fungus dies, biodegrades,
and leaves us with a healthy crop and no chemical residue. We
hope this type of product becomes more common. And we are anxious
for our aircraft to take advantage of more such products in the
future.
Thanks,
Dick Turner
Copyright March 2000