Which designation is typically used to indicate a necessary action on radar systems?

The designation that indicates a necessary action on radar systems is commonly understood to be "Drop." In radar operations, when an operator is instructed to "drop" a target, it signifies that they should disregard or eliminate that specific target from the tracking or display. This could occur if the target is no longer relevant or if it poses a lower priority in the context of the operation being conducted.

In various tactical scenarios, managing the array of targets displayed on radar is crucial for situational awareness and effective decision-making. Thus, the command to "drop" is vital, as it helps streamline the focus on the most pertinent threats or contacts, thereby enhancing operational efficiency. While other terms like "Push," "Lift," and "Hold" may refer to different actions or statuses, "Drop" specifically denotes the elimination or disregard of a target in radar systems, making it the correct choice for conveying necessary action.