ILS Approach Procedures
Most navigation systems approved for en route and terminal operations under IFR, such as VOR, NDB, and GPS, may also be approved to conduct instrument approach procedures. The most common system in use in the United States is the ILS. An ILS (instrument landing system) operates as a ground-based instrument approach system that provides precision lateral and vertical guidance to an aircraft approaching and landing on a runway, using a combination of radio signals, during IMC conditions, such as low ceilings or reduced visibility due to fog, rain, or blowing snow.
The system consist of the following components:
- A localizer providing lateral (left/right) guidance along the extended centerline of the runway.
- A glideslope (GS) providing vertical (up/down) guidance toward the runway touchdown point, usually at a 3° slope.
- Marker beacons providing range information along the approach path.
- Approach lights assisting in the transition from instrument to visual flight.