instrument landing system
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instrument landing system[′in·strə·mənt ¦lan·diŋ ‚sis·təm]
A system of radio navigation which provides lateral and vertical guidance, as well as other navigational parameters required by a pilot in a low approach or a landing. Abbreviated ILS.
instrument landing system (ILS)
A radio aid to navigation intended to facilitate aircraft in landing. It provides lateral and vertical guidance to the optimum point of landing. The various components of an instrument landing system are the localizer, which guides the aircraft to the centerline of the runway; a glide-slope transmitter, which guides the aircraft along the required glide path; outer and inner markers, which indicate to the aircraft that it is passing overhead them; and the airport lighting system.