Definition
A device that transmits radio waves and measures the energy reflected back from objects in order to determine their position, distance, and movement. In aviation, radar is used by air traffic controllers to track aircraft, by pilots to detect weather and terrain, and by ground systems to provide surveillance and separation services.
Plain English
A system that sends out radio signals, listens for the echoes that bounce back off aircraft, weather, or terrain, and uses those echoes to figure out where things are and how they are moving.
Context Anchor
Pilots encounter radar in air traffic control services, weather avoidance, traffic displays, and reports such as “radar contact.”
Derivation
An acronym formed in the 1940s from Radio Detection and Ranging. 'Detection' means finding that something is there; 'ranging' means measuring how far away it is. Together they describe exactly what the system does.
Why Pilots Care
Radar supplies real-time position and weather data essential for avoiding collisions and hazardous conditions when visibility is limited.
Analogy
Radar is a little like using an echo in a dark canyon. You send out a sound, hear it come back, and use the time and direction of the echo to judge where the canyon wall is. Radar does that with radio energy instead of sound.
Intuition Check
Radar does not mean any aviation screen or map. It means the sensing system that detects objects or weather and helps determine where they are.
Example Sentence 1
Approach told us we were in radar contact ten miles south of the field and cleared us for vectors to the ILS.
Example Sentence 2
Air traffic control vectored the flight using radar returns when the aircraft entered the cloud layer.