What is the function of autothrust on the A321?

• A. It levels off the airplane automatically
• B. It controls vertical navigation
• C. It automatically maintains target speed by adjusting engine thrust under autopilot/flight management guidance
• D. It locks speed during approach

Answer: (C)

Autothrust on the A321 is the speed-control system. Its job is to automatically maintain the target airspeed by adjusting engine thrust in response to the speed error signaled by the flight guidance system (autopilot/flight management guidance). When a speed target is set, autothrust increases or decreases thrust to keep you on that target through climb, cruise, and approach. It works with the autopilot’s guidance but handles thrust, not the vertical path, so it isn’t about leveling off or guiding vertical navigation. It also doesn’t “lock” a speed in a fixed state; it continuously adapts to wind, weight, and configuration to hold the target speed.