Description

Safety nets help prevent imminent or actual hazardous situations from developing into major incidents or even accidents. Safety nets, for airborne phases of flight and for preventing collision between aircraft and collision with terrain or obstacles, are either ground-based or airborne:

• Ground-based safety nets are an integral part of the ATM system. Using primarily ATS surveillance data, they provide warning times of up to two minutes. Upon receiving an alert, air traffic controllers are expected to immediately assess the situation and take appropriate action.
• Airborne safety nets provide alerts and resolution advisories directly to the pilots. Warning times are generally shorter, up to 40 seconds. Pilots are expected to immediately take appropriate avoiding action.

Ground-based Safety Nets

The following safety nets are typically in operation in ATM automation systems: