Definition
A flight director or autopilot mode in which the aircraft automatically follows the localizer signal of an Instrument Landing System (ILS), keeping the aircraft aligned with the runway centerline during an instrument approach.
Plain English
The flight director (or autopilot) locks onto the runway alignment signal and steers the aircraft to stay on the extended runway centerline as it flies the approach.
Context Anchor
Seen when using a flight director system during an instrument approach that includes a localizer.
Derivation
Localizer comes from 'localize' — to identify a precise location or line. The localizer beam defines the line you must stay on; tracking means following that line continuously. Together: following the line that locates the runway centerline.
Why Pilots Care
Precise localizer tracking prevents lateral deviations that could lead to an unstable approach or missed landing.
Intuition Check
Do not read “tracking” here as simply watching or recording something. In this context, it means actively following the localizer signal to stay lined up left and right.
Example Sentence 1
Once established inbound, the crew engaged localizer tracking and the flight director held the aircraft centered on the approach course.
Example Sentence 2
During the approach briefing the instructor emphasized smooth localizer tracking to avoid overshooting the centerline.