Instrument Landing System

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Instrument Landing System
Ils waterfall.png
Frequencies 108 MHz,335 MHz
Frequency Range 108 MHz - 335 MHz
Mode AM
Modulation
ACF
Bandwidth 15 kHz
Location Worldwide
Short Description Radio navigation system that allows aircraft to perform precision approaches in low visibility conditions.
I/Q Raw Recording
Audio Sample

Instrument Landing Systems are installed at the end of airport runways, and provide guidance to aircraft inbound to land. It is a dual-band system that uses the VHFVery High Frequency (30-300 MHz) airband for the localiser (horizontal axis), and the UHFUltra High Frequency (300-3000 MHz) airband for the glide path (vertical axis). The signal is amplitude modulated with 90 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz). and 150 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz). tones, which are directionally transmitted in such a way that the carriers overlap, forming the path for aircraft to follow. A CWContinuous Wave identifier is also transmitted, which allows pilots to check they have intercepted the correct ILS. Older ILS systems may still have marker beacons placed at fixed positions along the approach, but are being phased out in favour of Distance Measuring Equipment (DME).

Frequencies[edit]

The ILS frequency pairs are defined in ICAO Annex 10:

Localiser (MHzMegaHertz (MHz) 10^6 Hz) Glide Path (MHzMegaHertz (MHz) 10^6 Hz)
108.1 334.7
108.15 334.55
108.3 334.1
108.35 333.95
108.5 329.9
108.55 329.75
108.7 330.5
108.75 330.35
108.9 329.3
108.95 329.15
109.1 331.4
109.15 331.25
109.3 332
109.35 331.85
109.5 332.6
109.55 332.45
109.7 333.2
109.75 333.05
109.9 333.8
109.95 333.65
110.1 334.4
110.15 334.25
110.3 335
110.35 334.85
110.5 329.6
110.55 329.45
110.7 330.2
110.75 330.05
110.9 330.8
110.95 330.65
111.1 331.7
111.15 331.55
111.3 332.3
111.35 332.15
111.5 332.9
111.55 332.75
111.7 333.5
111.75 333.35
111.9 331.1
111.95 330.95

Video Examples[edit]

Additional Links[edit]