Definition
An aircraft return displayed on an air traffic control radar screen produced solely by radio energy reflected off the aircraft's surface, without any signal generated by equipment on the aircraft itself.
Plain English
A blip on the controller's radar that comes only from radar waves bouncing off the aircraft's metal skin, not from any device on the aircraft sending a signal back.
Context Anchor
Seen in air traffic control radar discussions, especially when comparing radar returns from reflected signals with returns from an aircraft's transponder.
Derivation
Primary' comes from the Latin 'primus' meaning 'first.' It refers to the original form of radar, where the radar station does all the work — sending out a pulse and listening for the echo. 'Secondary' radar came later and relies on the aircraft's transponder to talk back.
Why Pilots Care
Aircraft without transponders or with inoperative transponders can still be detected and tracked by ATC using primary radar returns.
Analogy
It is like seeing a person with a flashlight because the light reflects off them. You know something is there, but the person has not called out their name or height.
Intuition Check
Do not read “target” as hostile or military here. In radar language, a target is simply an object the radar has detected.
Example Sentence 1
After the transponder failed, the controller could still track the aircraft as a primary radar target but could no longer see its altitude readout.
Example Sentence 2
With the transponder inoperative, the flight appeared only as a primary radar target on approach control's display.