Which type of maneuver is classified as abrupt and prohibited?

The classification of abrupt maneuvers as prohibited is specifically associated with cross-controlled (snap) maneuvers. These types of maneuvers involve rapidly changing the aircraft's control inputs in a way that can lead to a loss of control or stall conditions. Such abrupt actions can result in excessive loads on the aircraft's structure and could even lead to an unintended spin. The inherent risk in performing these sharp inputs is the potential for catastrophic failure in flight, hence why they are prohibited in training and operational scenarios.

In contrast, vertical, sideways, and curved maneuvers can be performed safely when conducted within the aircraft’s operational limits and typically do not introduce the same level of immediate danger as cross-controlled maneuvers. These other types of maneuvers can have specific applications in aerobatic flying within a safe framework, as long as they are executed with appropriate skill and awareness of the aircraft's dynamics and limits.