Under what condition should DME/ATD procedures and minima be used?

The correct condition for using DME/ATD procedures and minima is when direct pilot-controller communications are maintained. This is crucial because DME (Distance Measuring Equipment) and ATD (Area Traffic Data) rely heavily on continuous communication between the pilot and air traffic control to ensure safety and proper navigation.

In a situation where communications are direct and clear, controllers can provide timely instructions and updates regarding the aircraft's position, traffic advisories, and any changes to procedures. This interaction ensures that pilots can make informed decisions based on real-time information, which is essential for navigating through areas that may not have visual references or where other navigational aids may not be available or reliable.

Other conditions such as ideal weather, visual contact among aircraft, or being above a certain flight level do not specifically address the critical need for effective communication. While good weather and visual contact can enhance safety, they are not substitutes for the necessary communication protocol that underpins the safe execution of DME/ATD procedures. The reliance on direct communication is fundamental to the operational effectiveness of this air traffic management procedure.