What happens to the airplane's control when the sidestick is released during a turn?

When the sidestick is released during a turn, the airplane maintains its current turn rate. This is a fundamental characteristic of the fly-by-wire system used in the A320. The aircraft's control laws are designed to ensure that once a pilot commands a turn, releasing the sidestick does not abruptly change the aircraft's flight path or attitude.

Instead, the aircraft continues to execute the command given before the sidestick was released, effectively allowing it to maintain the same bank angle and turn rate until the aircraft reaches its next flight control threshold or the autopilot, if engaged, takes over. This design feature helps to provide smooth and predictable handling characteristics, enhancing stability and reducing pilot workload during maneuvers.

In contrast, maintaining a certain turn rate contributes to flight safety and efficiency, as abrupt changes in control could lead to undesirable aerodynamic effects. Thus, when considering the behavior of the aircraft in regard to pilot inputs, it becomes evident why maintaining the current turn rate is the correct response.