Definition
A radar return from an aircraft that has no operating transponder, but which the ATC computer system has identified across successive radar sweeps and is actively following as a moving target on the controller's display.
Plain English
An aircraft the radar can see only by bouncing signals off its skin, with no transponder reply, but the system has locked onto it and is keeping track of where it goes.
Context Anchor
Seen in ATC radar display symbology, such as ARTS III or DBRITE displays, when a controller is looking at radar targets.
Derivation
"Primary" here refers to a primary radar return -- the raw echo of the radar pulse bouncing off the aircraft itself -- as opposed to a secondary return, which is a signal sent back by a transponder. "Tracked" means the computer has correlated the target across sweeps and is following its movement.
Why Pilots Care
Allows controllers to provide traffic advisories and maintain separation for aircraft that have no transponder or whose transponder is inoperative.
Grounding Statement
Picture radar sending out a pulse, receiving a bounce back from an aircraft, and the display system following that same bounce as it moves.
Intuition Check
Do not read primary as meaning most important. In this radar context, primary means the target is shown from reflected radar energy rather than from a transponder reply.
Example Sentence 1
With the transponder inoperative, the flight appeared on the controller's scope as a tracked primary target with no altitude information.
Example Sentence 2
On the DBRITE display the non-transponder aircraft appeared only as a tracked primary target moving toward the final approach course.