by Bill Lavender

ST. GEORGE, NSW AUSTRALIA — It’s mid-morning and the air temperature and humidity are building. You have a Roundup application due a few miles from the strip. You aren’t really sure about the wind, but pretty confident it is coming from a drift-safe direction. You have long runs with obstacles at both ends of the field. You know it is imperative to produce the exact right size droplet consistently throughout the application to avoid drift and offer the best efficiency for the application. With the long runs, after diving your aircraft into the field, you realize your airspeed is going to fluctuate, especially as your load becomes lighter. The GPS, with its flow controller, should handle that for you, but what about the droplet size? Will the GPS’s compensation change your droplets’ size to smaller as the flow controller opens up the spray valve, increasing the boom pressure to accommodate the faster airspeed? What size droplets will you be producing? What about the temperature and humidity changes, as well as the airspeed, how will these factors affect droplet size? Although the runs are long and the field is big, with a relatively low volume application you are sure there will be a change in the temperature, humidity and airspeed by the time you complete spraying this field.

This is the type of scenario that every ag-pilot has faced numerous times during a season. Up until recently, the application’s droplet size was only a guess. Maybe the aircraft’s spray system was set-up for the correct droplet size based on the beginning parameters of the application, but by the end of the job, the pilot doesn’t really know the various sizes of droplets that were produced throughout the application, increasing the potential drift and possibly a downgrade in efficiency.

JARBA of Australia, with its Smart Drop Technology, resolves this problem. JARBA has developed a streamline boom that is capable of changing the nozzle angle from straight back at 0° to 110° downward while in flight, automatically. By programming a set of parameters into the JARBA through its Farmscan Airlink flow control unit, the boom will rotate in flight as the aircraft’s airspeed changes. Also, the pilot has the flexibility to adjust the amount of change to compensate for temperature and humidity.

Droplet size is not an exact science when produced by an aircraft. There are many variables that come into play that can change the droplet size, e.g. boom pressure, airspeed, temperature, humidity, type nozzle, nozzle position, etc. However, a benchmark can be set that produces a specific size droplet. From this data, the pilot, using JARBA, can interpolate a best guess of the droplet size created by a change in a variable.

Using data from Queensland University’s trials in its wind tunnel at specific application criteria, JARBA can duplicate a droplet size. By dialing in the desired Vmd, orifice size, boom pressure, flat fan nozzle size and airspeed, a medium droplet size becomes known. From that point, the JARBA boom takes over, adjusting pressure and nozzle angle relative to the wind to produce the desired droplet size for the conditions at hand.

For the JARBA boom to work properly, the pilot must have a good idea of the size droplet needed for the changing parameters of the job. For instance, if he knows the temperature and humidity rises, he knows he should make the droplet larger. The same holds true for approaching sensitive areas.

The pilot can have dramatic effects on droplet sizes. Because of this, he must understand that when he tells the Airlink to change from a 200 Vmd droplet to 400 Vmd he has increased the number of droplets by eight times. If he goes even further from 200 Vmd to 600 Vmd the effect is 27 times the number of drops at three times the size. If you don’t believe even the smallest variation in droplet size is important, consider the following: An increase in droplet size from 200 Vmd to 250 Vmd is a 25% increase in droplet size and a 100% increase in the number of droplets.

THE JARBA Boom Smart Technology has other features to help the pilot control his application. Along with the ability of the boom to rotate, it has pneumatically controlled shut off points 2/3 the length of the boom and at the T-Boom. With the shut-off points, the pilot can set up the aircraft while in flight to work adjacent to a drift-sensitive area.
JARBA also offers a nozzle for the boom system, although other brand nozzles can be used as well. However, the JARBA brand nozzle has been specifically designed with the JARBA boom in mind.

The JARBA Twin Tips nozzle has a built-in 20° angle to it reducing drag. The flat fan design has a 40° deflector with any size orifice available. Typically, a JARBA boom is set up with alternating JARBA Twin Tip nozzles, one with a #6 and #15 orifice and one with a #10 and #20 orifice. With this set up, most aircraft can be calibrated to disperse between 1/2 gallon per acre and four gallons per acre. The choices are endless, by simply modifying the orifice sizes.
JARBA is a division of Jones Air, owned and operated by Scott and Peter Jones. Daryl Jones, the father of Scott and Peter, formed Jones Air from an existing business in 1975. Today, Daryl is retired and flying his Walter-powered turbine Lancair to different locales throughout Australia.

Jones Air uses Smart Drop Technology on all of their 10 ag-aircraft; three TPE331-11 Dromaders, three TPE331-10 510-gallon Thrush, two AT-802 Air Tractors, one Ag Truck and one AT-301 Air Tractor. The company operates from three satellite strips based in St. George and locations within 10 miles to the southeast and southwest. Cotton is the primary crop that is sprayed by Jones Air, from November through March, with defoliation in March and April.
Jones Air was the first ag-aviation Australian company, and possibly the first in the world to be ISO 14001 certified. Peter Jones explains that this certification shows due diligence in an effort to be environmentally safe and conscientious. He often questions the time and effort required to maintain the ISO, but accepts it as insurance against future problems.

JARBA has a demo CD that explains with pictures how the system works. You can contact them for a copy of the CD by emailing Peter Jones, peter@jonesair.com.au, with any further questions about this remarkable new technology that can help the ag-operator perform the best possible application job.