What can cause a flight director or autopilot to disconnect?

A flight director or autopilot can disconnect due to mode changes during transition, which refers to the system transitioning between different operational modes. For example, when a pilot manually inputs a change or alters the autopilot settings, such as switching from vertical navigation (VNAV) to approach mode, the system may disconnect if it does not interpret the input as a safe transition. This ensures that the aircraft responds appropriately to the pilot's commands and can maintain control during critical phases of flight.

When mode changes occur, there are safety protocols designed to maintain control and ensure that the autopilot or flight director does not inadvertently cause an unsafe situation. Therefore, if the autopilot detects that the requested mode cannot be achieved properly, it may disengage to allow the pilot to take full control. Understanding this behavior is crucial for pilots, particularly in managing the flight path and responding to any unexpected disconnections during flight operations.