Definition
The ground-based equipment that makes up an Instrument Landing System (ILS), consisting of the localizer transmitter (lateral guidance to the runway centerline), the glide slope transmitter (vertical guidance along the proper descent angle), and the marker beacons or DME used to identify position along the approach. Together these transmitters produce the radio signals that the aircraft's ILS receiver interprets to fly a precision approach.
Plain English
The equipment on the ground that sends out the signals an aircraft uses to fly an ILS approach. It includes the transmitters that tell the airplane whether it is left or right of the runway centerline, whether it is above or below the correct descent path, and how far it is from the runway.
Context Anchor
Seen in instrument approach discussions when the handbook separates the equipment installed at the airport from the equipment carried in the aircraft.
Derivation
Component comes from a Latin root meaning “put together.” In this use, the word points to one part of a larger system. Ground simply identifies the part of the system located on the airport surface rather than in the aircraft.
Why Pilots Care
Knowing which parts of an approach system are ground-based helps pilots interpret NOTAMs, equipment outages, and approach minimum changes.
Intuition Check
Ground components does not mean every object on the airport surface. It means the specific installed equipment on the ground that supports the navigation or approach system.
Example Sentence 1
Before flying the ILS, the pilot checked NOTAMs to confirm that all ground components, including the glide slope, were in service.
Example Sentence 2
An outage of one ground component raised the decision height for the approach.