The aerial crops spraying industry has been operating on some
limiting assumptions for many years.
The technology developed has favored the owner/pilot. Today's
aerial application aircraft try to maximize the Pilot's profitability. This raises the actual cost per acre sprayed.
If the aircraft were designed to maximize the profitability of
the Owner instead, the focus would be on a lower cost per acre. The primary
way this has been done is by ever-faster spray speeds. Unfortunately
higher spray speeds are a primary cause of unwanted spray drift.
Studies have shown that all things considered, spray speed makes
the biggest undesirable difference in droplet spectrum.
The other major problem in where technology is going is this simplistic
solution of increasing droplet size to reduce drift. Increasing
droplet size necessitates an increase in application rate. Although
increasing droplet size is generally effective, there are other
equally effective ways of controlling drift that do not require
increased application rate. Many of these other methods have the
added advantage of increased efficacy, which can reduce the amount
of chemical used.
CDA or Controlled Droplet Application technology has proven effective
at controlling drift. However CDA technology has problems with
high-speed application. Because of the overriding effect of wind
shear CDA techniques tend to lose their effectiveness at higher
speeds.
If the focus were not on pilot productivity, lower speed CDA techniques
would be more popular. We need to educate agricultural professionals
on the value of our solution. Although our focus is on cost per
acre, we are still able to offer competitive pay to pilots.
The efficacy -quality of results vs. amount used- of spray solutions
is increased by smaller droplet sizes. Drift is also increased
by smaller droplet size. The exact droplet size where drift occurs
is dependent upon conditions. Typically anything below 100 microns
would be considered unacceptable. And generally, anything over
250 microns would be considered acceptable. The range between
100 and 250 microns may drift depending upon conditions. It is
therefore a debated area. Normally we can maintain droplet control
and continue to increase efficacy down to 150 microns. This droplet
size of 150 microns is sometimes viewed as a problem. However,
remember our high-wing is designed to force the spray down and
spread it out. This makes the 150-micron droplet less susceptible
to drift.
It is important to note that successful CDA technology produces
an extremely narrow droplet spectrum. In a cloud made up of identical
sized droplets the droplets will fall or blow the same distance
as they travel to the ground. This allows us to compensate for
wind direction and still hit the target when larger planes would
be missing by dozens of feet. We have conducted tests to verify
our field results. We are producing fewer 100 Micron and smaller
droplets than a normal spray plane using typical drift reduction
techniques. The most important consideration is the amount of
active ingredient within the off target volume. Because we tend
to use more concentrated mixtures, an equal amount of drift cannot
be measured by spray volume alone. The exact answer varies from
mixture to mixture.
Our typical spray volume ranges from 1/4 of a gallon per acre
to 2 gallons per acre. Typical volumes on traditional spray planes
range from 1 gallon per acre to 10 gallons per acre. If the active
ingredient is needed at more than 2 gal. per acre, our plane is
often not economically competitive. Below 1 gal. per acre we
have a significant economic advantage.
It is important to note the most significant issue is the quality
of the results. Typical applications seek to increase profit
per acre for the farmer in a range of as little as $15 per acre
to over $150 per acre. A 20% better rate of control can double
everyone's profitability. The second most significant factor is
the cost of the active ingredient. This may range from $3 per
acre to over $45 per acre.
The biggest advantage we have over traditional aircraft is often
the better quality results we achieve with less active ingredient.
This advantage varies depending upon and the specific application.
So for the moment I'm going to speak of our results from a quantitative
view instead of a qualitative one. The most significant cost
in the operation of a spray plane is fuel. Our aircraft uses
only 4 to 7 gal. per hour of regular automotive fuel. The typical
spray plane uses between 20 and 45 gal. per hour of aviation gas
or jet fuel. Our aircraft can land on runways that are much closer
to the crop. Many times we can use a road or path beside the field,
or the access road to the field. This can minimize the commute
time even more so than the larger aircraft's high-speeds. Our
lower speed also allows us to turn quicker at the end of the field.
On small fields the ability to turn quickly between runs can
completely eliminate the larger aircraft's speed advantage. Also
our lower speed and CDA nozzles allows us to operate at lower
volumes per acre. This decreases the advantage the larger aircraft
has in tank capacity. We still typically require more labor cost
per acre sprayed. However the larger aircraft costs much more
to buy and maintain. This advantage of ours is exaggerated in
countries with cheap labor and tight capital, or on large farms
that want to operate their own planes.
The above information contains many generalizations. For your
specific applications call on our engineers to see how our aircraft
can help you.
Brian Turner
© Copyright VSTOL Aircraft 2000