What action is taken when the FCC fails during flight?

When the Flight Control Computer (FCC) fails during flight, the appropriate action taken is that the autopilot disconnects. This is crucial for ensuring the safety of the aircraft and its crew. When the FCC, which is responsible for managing the autopilot and other flight control systems, encounters a failure, it typically cannot maintain control over the aircraft’s autopilot functions.

Disengaging the autopilot in response to FCC failure allows the pilots to take full control of the aircraft manually. It is critical for the pilots to be aware of the aircraft’s status, and manual control enables them to respond to the situation and make necessary adjustments to maintain safe flight operations.

In contrast, the other options provided do not directly reflect the expected action taken during an FCC failure. For instance, while the aircraft may indeed revert to manual mode when control systems fail, this is a consequence of the autopilot disconnecting rather than a separate action that occurs independently. Similarly, vertical speed mode engaging or the PFD displaying emergency settings are not standard responses to an FCC failure and would not take precedence over the need for the pilots to regain manual control through disengaging the autopilot.