Definitions for "Instrument landing system"
Keywords:  runway, ils, guidance, glide, aircraft
System for airplane landing in which the pilot is guided by radio beams.
A precise landing aid consisting of several components giving the pilot vertical and horizontal electronic guidance. Elements usually include: 1. an outer marker, a radio beam 4 to 6 miles from the touchdown point where the electronic signal begins; 2. an approach lighting system at the runway end; 3. a localizer radio beam which provides the horizontal guide; and 4. a glide slope which provides vertical guidance on the angle of descent for landing.
Although it sounds pretty generic, an ILS is a specific and accurate set of equipment used to provide a very accurate instrument approach. It provides both lateral (left/right) guidance through a localizer and vertical (up/down) guidance through a glideslope, all of which can be used completely blind outside the cockpit. Even fairly unsophisticated aircraft can use an ILS to get within 200' of most airports and this is the system that specially equipped and trained transport aircraft and pilots can use to land completely blind.