Editing Instrument landing system (section)

===Localizer back course===
Modern localizer antennas are highly [[directional antenna|directional]]. However, usage of older, less directional antennas allows a runway to have a non-precision approach called a ''localizer back course''. This lets aircraft land using the signal transmitted from the back of the localizer array. Highly directional antennas do not provide a sufficient signal to support a back course. In the United States, back course approaches are typically associated with Category I systems at smaller airports that do not have an ILS on both ends of the primary runway. Pilots flying a back course should disregard any glide slope indication.