Aerial application of pesticides has the potential to reduce the amount of pesticides required as chemicals are applied where needed. A prototype Unmanned Aerial Sprayer with a payload of 20 kg; a spraying rate of 6 liters per minute; a spraying swathe of 3 meters, coverage rate of 2 to 4 meters per second and 10 minutes of flight time was built using state of the art technologies. The project is a joint development by University of Agricultural Sciences, Dharwad, KLE Technological University, Hubballi and SkyKrafts Aerospace Pvt. Ltd. The technology for the prototype was divided into electronic, software and mechanical components. Hexacopter configuration with six propellers was chosen, as it provides a good compromise between the stability of an Octocopter and longer flight times of a Quadcopter.

The airframe of the sprayer was designed from ground up using modern industrial design methodologies. Carbon fiber was a natural choice for the structural frame along with aerospace grade 6061 aluminum. The design was simulated in several iterations and test models were created using Hylam sheets. Electronics and software were derived from px4 and pixhawk, both of which are stable open source flight controller projects. This allowed us to rapidly prototype the sprayer at the same time giving us the freedom to reprogram the flight controller for spraying applications. The weight of the sprayer is 50 kg including a payload of 20 kg. The sprayer can generate a total thrust of 104 kg, providing a Thrust to Weight Ratio (TWR) of a little over two. The energy sub-system calculated for multiple current and voltage ratings of Lithium Polymer (LiPo) batteries and suitable off the shelf battery modules were used. The system is modular; functional components such as motors, propellers, autopilot, spraying system or batteries can be replaced with a different one with little effect on the other components or the sprayer itself. The spraying system consists of a DC powered pump with a six downward facing nozzle on two spray booms, three on each side; each nozzle can be adjusted to control the spraying rate.