Although the radial engine for an ag-plane in the United States was the mainstay before the advent of turbine powered ag-aircraft, the engine never gained much popularity in Brazil. During the early years of radial engine use in Brazil, obtaining support and a parts inventory was difficult. Today, even fewer of these radial engines are used, but where there is a radial engine ag-plane, it serves its owner very well.
In the Brazilian state of São Paulo, Produtiva Aeroagrícola Ltda operates not one, but two radial engine Air Tractor AT-401Bs. One has been converted to use alcohol at the approximate cost of $30,000 USD. As many Brazilian operators know from operating the alcohol Ipanema with its IO-540 Lycoming engine, this type of fuel in Brazil can be very economical compared to av-gas. This is also true for the powerful R-1340 engine manufactured by Pratt and Whitney over 50 years ago.
Treating mostly sugar cane, about 120,000 hectares (300,000 acres) a year, Produtiva Aeroagrícola has an impressive fleet of alcohol powered ag-aircraft; a Cessna C-188B Ag-Truck, an EMB-202A Ipanema and the Air Tractor AT-401B. The other AT-401B uses av-gas. It has not been converted to burn alcohol because Marino Neto, the owner of Produtiva Aeroagrícola, would like to sell it and replace it with a turbine powered ag-plane.
Why is the R-1340 better when powered by alcohol? Not only is it more economical, but the engine produces more power than its factory-rated 600 horsepower. Using alcohol, the engine consumes about 200 liters an hour (<50 gph), compared to the av-gas version that burns about 150 liters per hour (about 36 gph). The high cost of av-gas in Brazil offsets the smaller fuel burn.
There are other advantages to using alcohol as a fuel instead of av-gas in piston-powered aircraft engines. Alcohol burns cleaner with less carbon build up, which can be an issue with a radial engine. Also, the cylinder head temperatures (CHTs) are about 100°C cooler with alcohol. This is very critical because one of the weak points of an R-1340 is the cylinder heads are prone to cracking, sometimes even separating from the engine while in flight. By operating at a lower CHT, the life of the cylinder head is extended.
“I have logged over 400 hours just this last season in the 401 with its alcohol and fuel injection (the original engine was carbureted) conversion and have not experienced any problems with it,” explains Marino.
In Brazil, the driving factors for using alcohol over ag-gas is the economics and availability. In São Paulo state, alcohol is a readily available fuel, primarily because it is manufactured from sugarcane, which is a major crop in the region.
Alcohol (at this writing) costs approximately $2.50 reais per liter x 200 l/hr = $500 reais per hour (about $155 USD). However, av-gas costs about $6 reais per liter x 150 = $900 reais per hour (about $280 USD), a significant increase. When Marino considers that he flies the alcohol powered AT-401 around 250 hours a year, the savings of $400 reais per hour x 250 hours exceeds $100,000 reais (about $31,000 USD). This means the $30,000 USD conversion pays for itself every year!
Like other sugarcane operators in São Paulo state, Marino’s Produtiva Aeroagrícola’s season begins after the first rains in November with liquid fertilizer applications made at 50 liters per hectare (5 GPA). A liter of this fertilizer weighs about 1.2 kilograms (2.64 pounds). A typical load for the AT-401B is 1,200 liters (1,400 kilograms = 3080 pounds). The swath width for this application is 23 meters (about 75 feet).
After fertilizing is completed, insecticide treatments start as needed. These applications are applied at 30 liters per hectare (3 GPA) to control the “cigarrinha” insect (spittlebug). This insects creates a spit-like nest and damages the sugarcane plants.
From the middle of January until the middle of February, over a period of about four weeks, ethephon (brand name Ethrel) is applied as a growth regulator and an insecticide is added if needed. The ethephon controls, or slows, the rate of growth of the sugarcane plant, thus creating a higher sugar content. Sugarcane can be harvested as many as seven times in a five-year period. It is cut, then sprouts for another harvest in slightly under a year.
The insecticide applications continue until the middle of June, along with fungicide applications, even though irrigation is not used, as it is considered to be expensive.
Produtiva Aeroagrícola aircraft operate within a 120-kilometer radius (about 75 miles) of its main base at the Joaquin airport. It uses up to six satellite airstrips to be able to take off and land closer to fields being treated.
Marino formed Produtiva Aeroagrícola in 2011. He completed CAVAG (Brazilian FAA required ag-pilot training) at Santos Dumont in Cachoeira do Sul in 1991. He started his ag-flying career with Tangará Aeroagrícola in Orlândia. In 1998, he flew for Garcia Aviação Agrícola in Ribeirão Preto. In 2005, he flew for Precisão Aero Agrícola in Goiás before forming Produtiva Aeroagrícola.
Today, Produtiva Aeroagrícola employs four pilots for its four ag-planes, including Marino as the chief pilot and owner. The AT-401Bs use the Ag-Nav Platinum GPS, while the Ipanema has a Satloc Bantam and the Cessna uses a Satloc Litestar. All the aircraft are outfitted with STOL flood nozzles.
When treating sugarcane, it does not matter whether it is being grown for sugar or alcohol, the applications are the same. The price for the commodity determines whether sugar or alcohol is produced. When asked about the future of ag-aviation in São Paulo state, Marino says, “Our ag-aviation industry is growing despite Brazil’s political issues.”