Autothrottle

An autothrottle, also called autothrust and abbreviated A/T or A/THR, is an automatic system that manages an aircraft's engine power so that the pilots can specify a desired airspeed or thrust setting rather than moving the throttle levers by hand. Working alongside the autopilot's flight director system to carry out a full flight plan, it can hold a target indicated airspeed in speed mode or hold a fixed power setting appropriate to a phase of flight, such as takeoff, climb or descent, in thrust mode, adjusting the aircraft's pitch instead to control speed; it also protects against unsafe conditions such as speed decaying toward a stall, and it reduces crew workload while metering fuel more precisely than manual control, which both saves fuel and extends engine life. On most airliners it remains available from takeoff through landing and disengages automatically a couple of seconds after touchdown, though pilots retain the ability to override it manually at any time.