Brazilian startup designs self-flying aerial vehicle for crop spraying

By Roseli Andrion  |  FAPESP Innovative R&D – A coffee grower in Minas Gerais, the state that produces more than half of Brazil’s coffee crop, commissioned an unmanned aerial vehicle (UAV) capable of vertical take-off and landing (VTOL) from researchers at Dallas Autonomus, a startup based in Jacareí, in the neighboring state of São Paulo.

According to Marcus Prianti, co-founder of the agritech startup, the grower’s main problems were having to spray his hillside coffee groves before sunrise in order to avoid the direct impact of solar radiation on moistened leaves, and not being able to use self-propelled spraying machinery because of the rugged terrain. “The steep hillsides also made using a tractor very difficult,” Prianti said.

Crop dusters (specialized fixed-wing aircraft, usually with turboprop or piston engines, designed to spray fertilizer and pesticide) are also unsuitable because of the complex topography. What about drones? “They do the job but have limited load capacity and battery life,” Prianti said. “With a load of 40 kg-50 kg, for example, drones can run out of battery before spraying is complete, so large or complex areas can’t be sprayed in a single flight.”

Based on this knowledge, Prianti and his business partner Paulo Pinheiro — a private airplane pilot and commercial helicopter pilot respectively — developed an autonomous helicopter for the customer. It is almost 6 m in length (more than a large pickup truck), equipped with a 5 m spray bar, and capable by design of carrying a payload of at least 100 kg for more than an hour.

The device is very robust, according to Prianti. “I’ll have to take it to the farm, so I need to make sure it won’t be fragile,” he said. “The farmer is used to robust and sturdy machinery. We want to offer him the equivalent of an aerial tractor.”

Professional aviation components

The electronics are all imported and certified by the Brazilian Air Force (FAB) for professional use in large UAVs. The device will be dual-fuel, meaning it can run on ethanol or gasoline, which will facilitate logistics and operation in remote or isolated areas. The grower is accustomed to combustion engines and will need simply to fill the tank with either fuel.

Its high-capacity lithium batteries and alternator are dedicated to powering the onboard electronics.

Opting for already certified professional systems should ensure fast-track approval by the National Civil Aviation Agency (ANAC) and National Telecommunications Agency (ANATEL). “We’re using mature communications and navigation technology in a vehicle we ourselves designed. That will guarantee reliability and flight safety,” Prianti said.

Dallas is partnering, for example, with the Aeronautical Technology Institute (ITA), whose headquarters are located in São José dos Campos, a neighboring city to Jacareí. The UAV is currently at an intermediate stage between proof of concept and minimum viable product (MVP). Test flights are expected to begin in July or August.

Parts may need to be replaced as a result of stress testing. “We don’t know how components will respond when the vehicle is stress tested or how many times the system will have to be disassembled, recalculated and reassembled. We plan to use the rest of the year to correct any flaws and make adjustments,” Prianti said.

Another aspect of the project is the development of custom spray products for the vehicle, which Dallas is doing in partnership with the farmer so as to obtain optimal results. “It often happens that farmers are accustomed to spraying a particular product but don’t get the right results when they use a drone because the liquid wasn’t designed for aerial spraying in those conditions, in terms of density, speed and airflow,” he explained.

Other opportunities

Payload capacity and range are both important in this segment. “It’s no use carrying 100 kg but flying for only 15 minutes if that’s not enough time to get the job done. It’s better to carry 50 kg and fly for 50 minutes, for example, while varying spray velocity. We’re aiming to have the best combination of payload capacity and range on the market,” Prianti said.

During their research, which is supported by FAPESP’s Innovative Research in Small Business Program (PIPE), the team detected other opportunities for use of the helicopter. “Forest spraying is one. An electric drone has a limited capability to reach a specific point in a forest, spray the area [with liquids or solids] and return to base, for example. Range is limited by the battery, especially for drones with a payload,” he said.

Downwash was also a factor in the choice of a helicopter, which flies less fast than an aircraft and causes less spray drift. “Droplets break up less at slower speeds. Fine particles are blown away by the wind. This way we reduce drift and waste,” he said.

Dallas says its UAV can also be used to spray sugarcane plantations, soybean fields and orange groves, among other crops. “It’s not always possible to fly crop dusters owing to limitations such as bad weather or lack of a landing strip, for example,” Prianti explained.

The UAV does not require a landing strip as it takes off and lands vertically. “You don’t need a lot of room for that, making its deployment relatively flexible,” Prianti said. “We’re developing as flexible a platform as possible. Drones can be used in forest restoration, for example, but not when very large areas are involved. Our helicopter will be able to reach restricted or inaccessible areas autonomously and with a high payload capacity to assure wider coverage.”

The platform will have multiple applications. “High payload capacity and range will enable users to transport tools, extinguish fires, transport vaccines to remote locations, and so on. We won’t be confined to the agricultural sector. Plus it’s a self-flying vehicle, with no pilot risk,” he said.

Properties above a certain size will benefit most from use of the vehicle. “Given its capacity, we’re interested in properties of 100 hectares or more. Electric drones can’t cover areas that big. Depending on the region and topography, crop dusters and other aircraft can’t either, leaving farmers without an efficient alternative for aerial spraying. Battery-powered drones are more efficient for smaller properties, however,” Prianti said.

The next stage of the project will involve the organization of an operating base. Dallas does not want to sell the vehicle but prefers to offer leasing arrangements out of bases near customers. “Demand is strong in southern Minas Gerais, for example, because it’s a coffee-growing center. We want to offer a service that meets the needs of agribusiness,” he said.