What is required in order to conduct ASR final approaches with only secondary radar?

In order to conduct ASR (Airport Surveillance Radar) final approaches using only secondary radar, the presence of an emergency condition is crucial. When an emergency exists, it allows the pilot to operate under specific guidance that may not otherwise be available. The pilot's concurrence is also essential, as it emphasizes the need for mutual agreement between the air traffic control (ATC) personnel and the pilot regarding the situation's urgency and the decision to proceed with such an approach.

Secondary radar relies on transponder signals from the aircraft, which may not always be available or reliable. Under typical circumstances, ATC may require primary radar to ensure safe landings, but in an emergency, the primary requirement shifts to the immediate needs of the pilot and aircraft safety. Therefore, the existence of an emergency and the pilot's agreement justify the use of secondary radar alone for conducting the ASR final approach.

The remaining options do not align with the requirements for conducting safe approaches in emergency situations. For instance, claiming radar service is unavailable or that primary radar must be in use lacks the necessary context to justify the reliance solely on secondary radar. In addition, visual contact with the aircraft does not inherently negate the need for emergency conditions or pilot agreement when utilizing secondary radar exclusively for an ASR