What happens to the vertical mode if a new altitude is selected on the FCU when ALT* is displayed?

When a new altitude is selected on the Flight Control Unit (FCU) while the ALT* mode is displayed, the system behavior defaults to engaging the current vertical speed (V/S). This allows for a smooth transition towards the newly selected altitude without abruptly changing the aircraft’s vertical flight path.

Selecting a new altitude while in the ALT* mode indicates that the aircraft is still managing altitude but is ready to respond to a new target. By engaging the current V/S, the aircraft retains its current rate of climb or descent, effectively allowing the pilot to manage the altitude change fluidly, rather than making more abrupt changes that can lead to passenger discomfort or operational inefficiencies.

This approach is critical for maintaining stability and control during flight, as it minimizes sudden adjustments to the aircraft’s performance.