Automatic pilot

An autopilot is a device used to guide an aircraft without direct assistance from the pilot. ... At the same time, the aircraft follows the flight plan route. If an autothrottle is not installed, the pilot must make all power adjustments appropriate to the autopilot mode and phase of flight.A position-based autopilot controls the aircraft so that it always follows desired position profile. The autopilot system moves the control surfaces so that the aircraft's motion reduces the error between the desired aircraft attitude and recorded actual aircraft attitude.vehicle without constant human intervention.

The earliest automatic pilots could do no more than maintain an aircraft in straight and level flight by controlling pitch, yaw, and roll movements; and they are still used most often to relieve the pilot during routine cruising. Modern automatic pilots can, however, execute complex maneuvers or flight plans, bring aircraft into approach and landing paths, or make possible the control of inherently unstable aircraft (such as some supersonic aircraft) and of those capable of vertical takeoff and landing. Automatic pilots are also used to steer surface ships, submarines, torpedoes, missiles, rockets, and spacecraft.