HIGH VOLUME AERIAL SPRAYING
22,400 gallons per hour is a lot of spray; however, this volume was successfully accomplished in July, 1999 on a production model Air Tractor 802. Working in conjunction with Transland, Inc. and AeroFlow Systems, Air Tractor equipped the AT-802 with specially designed equipment to disperse 18 gpa at 160 mph with a 65-foot swath.

Responding to the growing need for high volume spray applications, Air Tractor, Inc. equipped and tested the dispersal system required for 20 gallon per acre. High volume applications are often favored by growers of certain vegetable crops for better spray coverage and for some forestry applications. Agricultural aviation can now offer customers this high volume option.

To achieve the high volume Transland, Inc. developed a 4-inch inlet pump which discharges into a 3-inch spray valve and boom system. As the spray moves at 12 mph through the dispersal system, the liquid is divided at the strainer and sent to each 3-inch spray boom.

However, one area that is often overlooked is the flow rate through the check valve. Air Tractor decided on using the AFS standard check valve, both because of its high capacity as well as its ability to eliminate leaks and dripping associated with the normal diaphragm check valve. The AFS check valve has a flow rate capable of 5. 3 gallons/minute at 25 psi. vs. 2.5 gpm for the Tee-Jet 4166 and 2.1 gpm for the CP check valve.

The AT-802 was equipped with 84 AFS check valves. Interestingly, the same flow rates could also be obtained by using only 64 check valves, but with larger spray tips. Nozzles used with the AFS check valves were Spraying Systems 2560 degree flat fan capable of flowing 4.6 gal./min. at 26 psi.

How well did the spray system work?

Sam Cooke, Test Pilot - Air Tractor, Inc., "The actual rate was calculated at 374 gallons a minute which translates to a 65-foot swath and just under 18 gpa. The AFS check valves worked fine. One thing I really like about the check valves and nozzle is that they are not near as heavy as the brass ones and so maneuvering would be better with this many nozzles and check valves. They are streamlined and not so much is hanging in the breeze. The drift control also looks good."

Gary Coker, Research and Development - Air Tractor, Inc., "My experience with the AFS check valves is that they are light, easy to install, easy to operate, and they don't create much drag. The test flight was at 160 mph and if it was slowed down to 140 the volume would be over 20 gpa. I havenít seen the check valves leak at all."

The AT-802 with the high volume dispersal system will be on exhibit at the 1999 NAAA Convention in Reno.