An autopilot is a device, usually associated with aircraft, that helps to guide planes with little or no input from a human. Although the term is typically used for planes, it may also refer to the autopilot on ships and spacecraft. In some cases the term autopilot may describe a futuristic description of any sort of vehicle that fully navigates itself, including ground transport like cars.
It is in long-distance plane flight that the autopilot becomes almost a necessity, as it quickly becomes fairly unfeasible for a pilot to be paying constant attention to the sky for the long periods of time needed to fly. Although possible, and although this was and is done in many cases, it can lead to pilot fatigue, which in turn can lead to mistakes being made that can have dire consequences to the flight. An autopilot allows the pilot to transfer many of the mundane tasks of long-distance flight to an automated system, allowing them to keep only a distracted focus for long periods of time, and ward off serious fatigue.
The original autopilot appeared in 1914, and was shown to the world by Lawrence Sperry, who undertook a flight in which he removed his hands from the controls for an extended period of time. The autopilot included a system connecting gyroscopic indicators to the rudders and elevators of the aircraft. This allowed the plant to flight both straight and level without any input from the pilot, with the gyroscopes correcting for any variations that might occur.
Modern autopilots have three main levels they can be set to, with each subsequent level taking more control over the flight of the plane. Autopilots are generally mandated for any commercial air vehicle that seats more than twenty people, as these are generally the craft that undertake long journeys, and therefore need the fallback of an autopilot. Smaller airliners and personal aircraft only occasionally have an autopilot system, since generally they are flying for only a few hours at a time, and the pilot can be expected to be remaining in constant control of the aircraft.
The first level of autopilot on a modern plane only handles the roll axis of the plane, and so is known as a single-axis autopilot. This helps keep the wings level, so that the flight doesn’t roll from side to side. This type of autopilot is sometimes referred to as a wing leveler. The second level of autopilot handles both the roll axis and the pitch access of the plane, and is known as a two-axis autopilot. A two-axis autopilot may be very sophisticated, using radio navigation to help correct the flight fairly drastically.
The third axis of an autopilot, the yaw axis, is only necessary on larger aircraft, helping to automate the heading itself of the plane. Most large commercial aircraft have a three-axis autopilot, and in fact almost every step of the process, from takeoff to landing, can be automated. Especially in airports with severe weather conditions, like fog, a Category IIIb, or autoland, landing may be regularly utilized, as the machines can compensate for a lack in visibility. Category IIIc further automates the taxi, and although not currently used, is looking at being implemented in some airports, for a truly automated flight experience.