A quadcopter, also called quadrocopter, or quadrotor is a type of helicopter or multicopter that has four rotors.
Although quadrotor helicopters and convertiplanes have long been flown experimentally, the configuration remained a curiosity until the arrival of the modern unmanned aerial vehicle or drone. The small size and low inertia of drones allows use of a particularly simple flight control system, which has greatly increased the practicality of the small quadrotor in this application.
An unmanned aerial vehicle (UAV) or unmanned aircraft system (UAS), commonly known as a drone, is an aircraft with no human pilot, crew, or passengers on board, but rather is controlled remotely or is autonomous. UAVs were originally developed through the twentieth century for military missions too "dull, dirty or dangerous" for humans, and by the twenty-first, they had become essential assets to most militaries. As control technologies improved and costs fell, their use expanded to many non-military applications. These include aerial photography, area coverage, precision agriculture, forest fire monitoring, river monitoring, environmental monitoring, weather observation, policing and surveillance, infrastructure inspections, smuggling, product deliveries, entertainment and drone racing.
Radio control (often abbreviated to RC) is the use of control signals transmitted by radio to remotely operate a device. Examples of simple radio control systems are garage door openers and keyless entry systems for vehicles, in which a small handheld radio transmitter unlocks or opens doors. Radio control is also used for control of model vehicles from a hand-held radio transmitter. Industrial, military, and scientific research organizations make use of radio-controlled vehicles as well. A rapidly growing application is control of unmanned aerial vehicles (UAVs or drones) for both civilian and military uses, although these have more sophisticated control systems than traditional applications.
A multirotor or multicopter is a rotorcraft with more than two lift-generating rotors. An advantage of multirotor aircraft is the simpler rotor mechanics required for flight control. Unlike single- and double-rotor helicopters which use complex variable pitch rotors whose pitch varies as the blade rotates for flight stability and control, multirotors often use fixed-pitch blades; control of vehicle motion is achieved by varying the relative speed of each rotor to change the thrust and torque produced by each.
Due to their ease of both construction and control, multirotor aircraft are frequently used in radio control aircraft and unmanned aerial vehicle (UAV) (drone) projects in which the names tricopter, quadcopter, hexacopter and octocopter are frequently used to refer to 3-, 4-, 6- and 8-rotor rotorcraft, respectively. There is also the X8 (also called octo-quad) configuration that is similar to the quadracopter design, except that it has eight rotors; the lower of which have a reversed rotation direction.
The DJI Phantom (Chinese: 精灵; pinyin: Jīng Líng) is a series of quadcopter unmanned aerial vehicles (UAVs) developed by Chinese technology company DJI.
Drone racing is a motorsport where participants operate radio-controlled aircraft (typically small quadcopter drones) equipped with onboard digital video cameras, with the operator looking at a compact flat panel display (typically mounted to the handheld controller) or, more often, wearing a head-mounted display (also called a "FPV goggle") showing live-streamed image feed from the aircraft. Similar to full-size air racing, the goal of the sport is to complete an obstacle course as quickly as possible. Drone racing began in 2011 in Germany with a number of amateur drone controllers getting together for semi-organized races in Karlsruhe.