unmanned aerial vehicle

An unmanned aerial vehicle, or UAV — the everyday word is drone — is a flying machine that carries no human pilot on board. Instead it is flown either by a person on the ground holding a controller, or by an onboard computer following a stored plan, or by some blend of the two. Taking the pilot out of the aircraft is a bigger change than it sounds: the machine can be made small and cheap, it can fly into places too dirty, dull, or dangerous for a person, and no one is hurt if it crashes. That single shift is why drones have spread from a niche military tool into farms, film sets, delivery routes, and toy shops.

Drones come in two broad shapes, and the difference is essentially the difference between an airplane and a helicopter. Fixed-wing drones have stiff wings like a plane; as they fly forward, air flowing over the wings holds them up, so they glide along efficiently and can stay aloft a long time, but they must keep moving forward and usually need room to take off and land. Rotary-wing drones, the familiar little quadcopters with spinning propellers, hold themselves up by pushing air down with their blades; this lets them hover in one spot, rise straight up, and squeeze into tight places, at the cost of using more energy and rarely flying as far. Some craft mix both ideas to get hover plus range.

Drones are also described by how much they do on their own, a scale running from fully remote-controlled (a human steers every moment) up through following pre-set waypoints, to genuine autonomy where the drone senses obstacles, picks its own route, and reacts to wind and surprises without help. That autonomy, plus their bird's-eye view, is what makes them so widely useful: mapping fields, inspecting bridges and power lines, filming, searching for lost hikers, monitoring crops, and carrying small parcels.