Definition
A controller automation tool used in the terminal radar environment that monitors the spacing between successive aircraft on final approach to the same runway and provides visual and aural alerts to the controller when the distance between a trailing aircraft and the aircraft ahead is, or is predicted to become, less than the required separation minimum.
Plain English
A computer aid that helps approach controllers keep landing aircraft properly spaced. It watches the gap between one aircraft and the one in front of it on final approach, and warns the controller if they are getting too close or are about to.
Context Anchor
Seen in discussions of terminal air traffic control automation, especially around busy airport arrival and departure operations.
Derivation
‘Terminal’ here refers to the terminal radar area around an airport, not the passenger terminal building. ‘Proximity’ comes from Latin proximus, meaning ‘nearest,’ so the tool is literally an automated alert about how near one aircraft is getting to another.
Why Pilots Care
The alerts allow controllers to issue timely instructions that prevent controlled flight into terrain or obstacle strikes.
Intuition Check
Do not read “terminal” as the airport building here. In ATPA, “terminal” means the air traffic control area around an airport; ATPA is a controller alert, not a cockpit alert.
Example Sentence 1
Approach told the trailing aircraft to reduce speed to 160 knots after an ATPA alert showed the spacing was tightening on final.
Example Sentence 2
During low-visibility approaches, ATPA provides an extra layer of protection against terrain conflicts near the airport.