What is the purpose of the MCDU in the A320's Flight Management System?

• A. To display flight crew reminders.
• B. To input and manage route, performance data, speeds, constraints, winds, and vertical profile; coordinates navigation and performance calculations.
• C. To monitor cabin temperature.
• D. To store and retrieve flight plan documents.

Answer: (B)

The MCDU is the cockpit’s primary interface to the Flight Management System. It is where you input and manage the flight plan and all related data the FMGS needs to compute navigation and performance. This includes the route (waypoints, airways), performance data (weight/fuel, cruise altitude), speeds and any constraints, winds and temperatures, and the vertical profile for climbs and descents. All of these inputs feed the Flight Management Computers, which generate the navigation guidance (LNAV) and vertical profile guidance (VNAV), along with the associated performance calculations such as speed schedules and fuel usage. The MCDU then displays these results back to you for validation and adjustment. It isn’t used to monitor cabin temperature or to store flight plan documents, which are handled by other systems.