Plain English Meaning

The full set of equipment that makes an ILS approach work — the radio signals that keep the aircraft lined up with the runway and on the right descent path, the markers or distance equipment that tell the pilot how far out they are, and the lights that help them see the runway as they break out of the clouds.

Full Definition

The ground-based and airborne equipment that together make up an Instrument Landing System (ILS), providing precision lateral and vertical guidance to a runway. The three functional groups are: (1) guidance signals — the localizer for lateral (left/right) alignment with the and the for vertical (up/down) guidance; (2) or information — (outer, middle, and where installed, inner) and/or , indicating distance from the ; and (3) — lighting, and lights, and , which support the from instruments to at .