Within the civil aviation cluster, the technological applications in agriculture represent a booming field consisting in acquisition of data through remote sensing and integration of sensor networks (crop status detection) or development of chemical and biological treatment applications. Drones in agriculture can be used for a variety of task, aimed to increase farm crop yields and accurately monitor fields, simultaneously decreasing time, labour and resources. While for some specific task a medium size drone can be chosen, on the other hand for other task like precision spraying of pesticide or fertilizer heavy lift drone are required. Prior to the approval of Yamaha R-MAX, an UAV helicopter which will be allowed to operate with a maximum payload of 98 kg, the Federal Aviation Administration (FAA) had only issued exemptions for much smaller drones weighing less than 55 pounds (24.98 kg). In Europe national legislations still lack of harmonization, and in Italy at the moment the local legislation restricts the possible choices to a maximum allowed take-off weight of 25kg without the necessity to submit a “permit to fly” documentation which is equivalent to the one required for a full scale commercial vehicle. Depending on the required task, one of the more important tasks of designing a multirotor Unmanned Aerial Vehicle (UAV) is the selection of a propulsion system that will provide desired performance in terms of payload and flight length or duration. Rigorous methods for selecting these drive components, that is, the motors, propellers, and batteries for electric UAVs are not readily available. A possible choice relies on using a Ready To Fly (RTF) UAV, but rapid changes in components and a fast evolution of the performance of engines and batteries allow possible updates of the existing UAV using aftermarket part to increase the flight envelope, a particularly interesting feature for heavy lift drone if a proper design method is adopted. Moreover, integration of technologies like LIDAR is easier to implement on UAV in which the design is not proprietary. In this work the technical requirements for agricultural tasks are investigated, and the state of the art of drone design method is presented, reporting an analysis of actual possibilities in terms of payload/flight envelope.