automatic terminal information service. See ATIS.
automatic volume control (radio receiver circuit). A circuit in a radio receiver that keeps the volume relatively constant as the input signal strength varies.
automation (manufacturing process). A process in which various manufacturing steps are programmed so they can be performed automatically, without requiring any input from a human operator.
automaton. A robot that can be programmed to automatically follow a predetermined set of instructions.
autopilot. See automatic pilot.
auto rich (reciprocating engine fuel air mixture). A fuel-air mixture whose ratio is kept constant in the rich range by an automatic mixture control in the carburetor or fuel injection system.
autorotation (aircraft flight condition). The rotation of an aircraft about any of its three axes caused by an aerodynamic force. An aircraft in a spin rotates because of an autorotative force.
autorotation (helicopter operation). Descent of a helicopter without engine power applied to its rotor. An aerodynamic force causes the rotors to spin.
If the engine in a helicopter fails, the freewheeling unit between the engine and the rotor allows the rotor to free-wheel, or turn without engine power, and an aerodynamic force, called an autorotative force, turns the rotor.
A landing made in a helicopter without the use of engine power is called an autorotative landing.