Which flight mode is NOT a direct function of the autothrust system?

The autothrust system on the A320 operates in several flight modes that are designed to optimize engine thrust based on the aircraft's flight conditions and pilot inputs. The modes most commonly associated with the autothrust system include Speed, Fixed, and Managed Thrust, each serving a specific purpose in maintaining the desired performance and efficiency during different phases of flight.

Open Loop, as a term in aviation, refers to a flight mode where parameters such as thrust are not automatically adjusted based on the aircraft's current state or conditions. In contrast, the other modes—Speed (which maintains a selected speed), Fixed (which sets thrust to a fixed level), and Managed Thrust (which allows the system to control thrust in conjunction with the flight management system)—are all integral to the autothrust's functionality.

Thus, the choice of Open Loop is accurate because it signifies operation without the direct intervention or adjustments of the autothrust system, making it a distinct mode that does not align with the automatic thrust management features offered by the autothrust system. This understanding is crucial for recognizing how these systems interact with flight management and ensuring pilots effectively monitor and respond to changes in flight status.