Before entering the airfield, what must drivers do regarding their radio equipment?

Before entering the airfield, drivers must conduct an operational test of their radio equipment to ensure it is functioning correctly. This step is critical for maintaining effective communication with air traffic control and other personnel on the airfield. Proper radio operation is essential for safety, as clear communication can help prevent accidents and ensure that drivers are informed about the current airfield conditions, instructions, and any potential hazards.

Conducting an operational test allows drivers to confirm that the equipment is not only powered on but also transmitting and receiving properly. This ensures that in an event of an emergency or a need for coordination while driving on the airfield, the driver will be able to communicate as necessary.

The other options, such as adjusting volume, changing frequency, or clearing past messages, are not comprehensive requirements for ensuring that the radio equipment is operational. While they might contribute to the overall functionality of the radio, they do not specifically confirm that the system is working and ready for use. Thus, conducting an operational test is the key action that ensures safety and proper communication as part of airfield driving protocols.