How is the engagement of the autopilot confirmed?

The engagement of the autopilot is confirmed through the Flight Mode Annunciator (FMA). The FMA provides pilots with critical information about the current flight mode active in the autopilot system, displaying various statuses such as whether the autopilot is engaged or disengaged. It visually indicates which flight parameters are being controlled by the autopilot, including lateral and vertical modes, ensuring pilots have real-time awareness of the aircraft's automated flight systems.

The other systems mentioned, such as the Flight Management Guidance Computer (FMGC), Multi-function Control and Display Unit (MCDU), and Navigation Display (ND), serve different purposes. The FMGC is involved in flight planning and performance computation, the MCDU is primarily used for inputting flight data and accessing performance information, and the ND provides navigation information to the pilot but does not directly confirm autopilot engagement. Hence, the FMA is the specific element that validates autopilot engagement.