What is the required action for a controller before an aircraft enters the approach airspace during a transition?

The required action for a controller before an aircraft enters the approach airspace during a transition is to effect a point-out if needed. This action is crucial for maintaining situational awareness and ensuring the safety and efficiency of air traffic management.

A point-out involves a controller notifying another controller about the presence of an aircraft that is about to enter their airspace. It is essential when the aircraft's trajectory could potentially affect operations in the new controller's airspace. This notification allows for coordination between controllers, ensuring that any necessary measures are taken to accommodate the incoming aircraft, such as adjusting traffic flow or providing necessary separation from other aircraft.

This step enhances communication between the sectors involved and supports a seamless transition for the aircraft into the approach airspace. By prioritizing a point-out when appropriate, controllers are able to manage air traffic effectively and uphold safety standards in the skies.