Topic: instrument-landing system

instrument-landing system (ILS), ground-based radio system designed to provide an airplane pilot with precise guidance for the final approach in landing. The pilot flies his aircraft along a course delineated by the intersection of two radio beams—the localizer beam for guidance in the horizontal plane and the glide-slope beam for guidance in the vertical plane. These beams activate an indicator in the aircraft that contains a horizontal needle sensitive to deviations from the glide slope and a vertical needle sensitive to deviations from the localizer path. By keeping both needles centered,... Read more