When is radar service terminated for a visual approach?

The correct answer indicates that radar service is terminated automatically upon clearance to contact the tower. This is a standard procedure in air traffic control operations. When an aircraft is cleared for a visual approach, the pilot is instructed to switch to the tower frequency for further instructions. At this point, the radar service is no longer necessary because the aircraft is now under the jurisdiction of the tower, which manages arrivals and departures in closer proximity to the runway.

This procedure streamlines communication and ensures that the tower can give the pilot the most relevant instructions as the aircraft approaches to land. The transfer of control from radar to the tower is a critical aspect of maintaining safe operations in busy airspace, as it delineates responsibilities between different air traffic entities.

The other options relate to scenarios that do not accurately reflect the protocol for terminating radar service during a visual approach. For instance, switching frequencies, reaching the runway threshold, or confirming visual contact do not inherently signify the end of radar service, as the transition to tower frequency is the specific action that mandates this termination.