Introducon: An unmanned aerial vehicle (UAV), commonly known as a drone, as an unmanned aircraft system (UAS), or by several other names, is an aircraft without a human pilot aboard. The flight of UAVs may operate with various degrees of autonomy: either under remote control by a human operator, or fully or intermittently autonomously, by onboard computers. [1] Compared to manned aircraft, UAVs are often preferred for missions that are too "dull, dirty or dangerous" [2] for humans. They originated mostly in military applications, although their use is expanding in commercial, scientific, recreational, agricultural, and other applications, [3] such as policing and surveillance, aerial photography, agriculture and drone racing. Civilian drones now vastly outnumber military drones, with estimates of over a million sold by 2015. This term emphasizes the importance of elements other than the aircraft. It includes elements such as ground control stations, data links and other support equipment. A UAV is defined as a "powered, aerial vehicle that does not carry a human operator, uses aerodynamic forces to provide vehicle lift, can fly autonomously or be piloted remotely, can be expendable or recoverable, and can carry a lethal or nonlethal payload". [7] ( Therefore, missiles are not considered UAVs because the vehicle itself is a weapon that is not reused, though it is also unmanned and in some cases remotely guided.) A radio-controlled aircraft becomes a drone with the addition of an autopilot artificial intelligence (AI), and ceases to be a drone when the AI is removed. [8] UAVs typically fall into one of six functional categories (although multi-role airframe platforms are becoming more prevalent):  Target and decoy – providing ground and aerial gunnery a target that simulates an enemy aircraft or missile  Reconnaissance – providing battlefield intelligence  Combat – providing attack capability for high-risk missions (see Unmanned combat air vehicle)  Logistics – delivering cargo  Research and development – improve UAV technologies  Civil and commercial UAVs – agriculture, aerial photography, data collection UAV components[edit] General physical structure of an UAV