Definition
The signal projected from a localizer antenna in the direction opposite to the published front course. When usable, the back course provides lateral guidance to a runway from the reciprocal direction, but course indications are reversed compared to a normal localizer approach unless the avionics have a back course mode.
Plain English
A localizer antenna sends a navigation signal off both ends. The main side is used for the published approach. The opposite side is the back course, and it can sometimes be used to line up with the runway from the other direction.
Context Anchor
Seen on instrument charts, approach procedures, and intersection descriptions where a localizer back course helps define a fix or route.
Derivation
‘Back’ here simply means the opposite end of the localizer signal — the side away from the published front course. The term is descriptive rather than technical: the front course goes one way, the back course goes the other.
Why Pilots Care
The localizer needle senses are reversed on the back course, so pilots must fly opposite the indicated deflection to stay on centerline.
Intuition Check
Back course does not mean any course flown back toward an airport. In instrument flying, it means the opposite-side signal from a localizer.
Example Sentence 1
After missing the approach, the pilot was cleared for the back course to the opposite runway.
Example Sentence 2
Approach control cleared the aircraft for the back course to the reciprocal runway.