instrument landing system (ILS)
A combination of three radio systems used in conditions of poor visibility to guide aircraft towards runways. A glide slope beam sent from the runway indicates the proper angle of descent, and the localizer beam indicates its direction. The outer marker beam, set about 8km (5 miles) from the runway, and the middle marker, at about 0.8km (0.5 miles), show distance.
Related categories INSTRUMENTATION
AERODYNAMICS AND AERONAUTICS
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