ILS – Instrumental Landing System is a radio navigation system that supports aircraft landing operations in limited visibility and low cloud ceiling conditions. Depending of the system category, it offers precise automatic guidance from the range boundary to the designated point on the glide slope (the maximum height for manual landing procedure by pilot) or the touch-down point on the runway. The system controls both the angle of approach and azimuth with additional 3 radio beacons (markers) for aircraft position calculation on the landing slope.
The markers are named: external, medium and internal. There is not always a need for all 3 markers, although at least one – the external marker, which is the furthest away from the runway must always be installed.
The ILS consists of 3 modules:
- Localizer (LLZ)
- Glide Path controller (GP)
- Markers (MRK) to define the distance to the runway threshold.
Today the ILS set is frequently enhanced with a DME radio beacon to provide distance measurement. The DME antenna is installed on the approach transmitter mast.
There are three ILS categories which influence also the category of an airport. The ILS commissioned at the Katowice/Pyrzowice airport is the THALES 420 which, when specific conditions are met (including in particular the lighting system, barrier elimination, signage), can operate at the highest category level. The current Katowice/Pyrzowice ILS has been classified as Category I, i.e. helps aircraft land with the decision height of 60 m and the runway visual range (RVR) not less than 550 m. The range (coverage) of the ILS is 30 NM.
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