When should aircraft be informed that radar service has been terminated at towered airports?

At towered airports, it is essential to inform aircraft when radar service has been terminated, particularly when radar coverage is lacking within half a mile of the runway's end. This notification is critical to ensure pilots understand that they will no longer receive the benefits of radar traffic advisories and flight monitoring. This situation can occur due to various factors, such as the limitations of the radar system or environmental conditions that affect radar operation.

Understanding when to provide this information helps pilots adjust their situational awareness and rely on visual references and alternative navigation methods. This proactive communication is vital for maintaining safety, especially in busy traffic environments where pilots need to be vigilant in monitoring their surroundings without radar support.

The other options do not accurately represent when radar service termination information should be relayed. For example, terminating service during bad weather or at takeoff may not provide the necessary and timely context for pilots to prepare appropriately. Additionally, informing pilots upon reaching a specific altitude doesn't align with the necessity for situational awareness near the runway, which is crucial right before and during landing and takeoff phases.