Anagricultural aircraft is anaircraft that has been built or converted foragricultural use – usuallyaerial application ofpesticides (crop dusting) orfertilizer (aerial topdressing); in these roles, they are referred to as "crop dusters" or "top dressers". Agricultural aircraft are also used forhydroseeding.
The most common agricultural aircraft arefixed-wing – such as theAir Tractor,Cessna Ag-wagon,Gippsland GA200,Grumman Ag Cat,PZL-106 KRUK,M-18 Dromader,PAC Fletcher,Piper PA-36 Pawnee Brave,Embraer EMB 202 Ipanema, andRockwell Thrush Commander – buthelicopters are also used.
Generally, agricultural aircraft have piston or turboprop engines. The only known exception is thePolishPZL M-15 Belphegor which has a jet engine.
Crop dusting with insecticides began in the 1920s in the United States. The first widely used agricultural aircraft were converted war-surplus biplanes, such as theDe Havilland Tiger Moth andStearman. After more effectiveinsecticides andfungicides were developed in the 1940s, andaerial topdressing was developed by government research inNew Zealand, purpose-built agricultural fixed-wing aircraft became common.
In the US and Europe, agricultural aircraft are typically small, simple, and rugged. Most have spraying systems attached to the trailing edges of their wings, and pumps are usually driven by wind turbines. In places where farms are larger, such asNew Zealand,Australia, the formerWarsaw Pact nations, and parts of the developing world, larger and more powerful aircraft have been used, including turboprop powered aircraft such as thePAC Cresco, twin engined types such as theLockheed Lodestar and theWSK-Mielec M-15 Belphegor – aturbofan-poweredbiplane. All tend to be of simple, ruggedSTOL design. Sometimes aram air turbine is used as an auxiliary power source for the pumping machinery instead of taking power directly from the engine (because this can be installed without any modifications of the airplane's mechanical systems). In places where dedicated use as an agricultural aircraft is uneconomic, utility types such as theAntonov An-2 biplane andDe Havilland Canada DHC-2 Beaver have been used.
In the case ofhelicopters, tanks are placed on or outside the body of the aircraft, while a spray rig, extending outward to the sides, is attached well below the main rotor blades. Hydroseeding is often done by helicopters using tanks and drop systems much like those used foraerial firefighting.
To reduce drift of the sprayed materials, agricultural pilots attempt to fly just above the crops being treated. Fields are often surrounded by obstacles such as trees, telephone lines, and farm buildings. Purpose-built agricultural airplanes have strengthened cockpits to protect the pilot if an accident occurs.
Aerial spraying has been controversial since the 1960s, due to environmental concerns aboutpesticide drift (raised for example byRachel Carson's bookSilent Spring). It is now often subject to restrictions, for example spraying pesticide is generally banned in Sweden, although exceptions can be made such as for an area plagued by mosquitoes during summer. The aerial spread of fertilizer has also raised concerns, for example in New Zealand fertilizer entering streams has been found to disproportionately promote growth of species that are more able to exploit the nutrients, in a process known aseutrophication, which has led to restrictions on topdressing near waterways.
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