Indication of an existing or pending situation that requires particular attention or action.

Note.– The term “situation” in the context of Short Term Conflict Alert (STCA) is to be understood as related to the proximity of a pair of aircraft as well as their relative positions and speed.

Converging of aircraft in space and time which constitutes a predicted violation of a given set of separation minima.

Alert which does not correspond to a situation requiring particular attention or action (e.g. caused by split tracks and radar reflections).

A ground-based safety net is functionality within the ATM system that is assigned by the ANSP with the sole purpose of monitoring the environment of operations in order to provide timely alerts of an increased risk to flight safety which may include resolution advice.

Principles which apply to aeronautical design, certification, training, operations and maintenance and which seek safe interface between the human and other system components by proper consideration to human performance.

Human capabilities and limitations which have an impact on the safety and efficiency of aeronautical operations.

Alert which is correctly generated according to the rule set but is considered operationally inappropriate.

Spacing between aircraft, levels or tracks.

A ground-based safety net intended to assist the controller in preventing collision between aircraft by generating, in a timely manner, an alert of a potential or actual infringement of separation minima.

The amount of time between the first indication of an alert to the controller and the predicted violation of a given set of separation minima.

Note.– The achieved warning time depends on the geometry of the situation.

Note.- The maximum warning time may be constrained in order to keep the number of nuisance alerts below an acceptable threshold.