Definition
A line displayed on a navigation instrument or moving-map display that represents the desired course (track) the aircraft should be flying to reach a fix or follow a route. The aircraft symbol's position relative to the track bar shows whether the aircraft is left of, right of, or directly on the intended course.
Plain English
A line on the cockpit display that shows the path you're supposed to be flying. If your aircraft symbol is sitting on the line, you're on course. If it's off to one side, you've drifted and need to correct back.
Context Anchor
Seen during navigation instrument use and during NAVAID accuracy checks, when the pilot centers the indication and compares it with a known checkpoint or expected reading.
Derivation
‘Track’ here means the actual path over the ground the aircraft is flying. ‘Bar’ refers to the straight line drawn on the display to represent that path. Together: the line on the screen showing the path you want to fly.
Why Pilots Care
The track bar gives an immediate visual reference for staying on course. During NAVAID accuracy checks and instrument approaches, comparing the aircraft's position to the track bar is how the pilot confirms they're flying the correct path.
Intuition Check
Do not think of a track bar as a physical bar on the ground or a control in the cockpit. Here it means the moving bar or needle on the navigation display that shows left-right course error.
Example Sentence 1
The pilot noted the aircraft symbol had drifted slightly right of the track bar and made a small correction to get back on course.
Example Sentence 2
A two-dot deflection of the track bar prompted a heading correction to rejoin the inbound course.