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In which frequency band does the Microwave Landing System (MLS) operate?
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The Microwave Landing System (MLS) was designed to replace ILS with an advanced precision approach system that would overcome the disadvantages of ILS and also provide greater flexibility to its users.
However, there are few MLS installations in use at present and they are likely to co-exist with ILS for a long time.
MLS is a precision approach and landing system that provides position information and various ground to air data.

The position information is provided in a wide coverage sector and is determined by an azimuth angle measurement, an elevation measurement and a range measurement.
A component of a Microwave Landing System (MLS) consisting of an Super High Frequency (SHF) transmitter radiating signals to provide vertical indications as an angular value to aircraft approaching the runway.

The Microwave Landing System (MLS) has the following features:

  • There are 200 channels available worldwide.

  • The azimuth coverage is at least ± 40° of the runway on-course line (QDM) and glideslopes from .9° to 20° can be selected. The usable range is 20-30 nm from the MLS site; 20nm in the UK.

  • There is no problem with back-course transmissions; a secondary system is provided to give overshoot and departure guidance ± 20° of runway direction up to 15° in elevation to a range of 10 nm and a height of 10,000 ft.

  • It operates in the SHF band, 5031 - 5090 MHZ. This enables it to be sited in hilly areas without having to level the site. Course deviation errors (bending) of the localiser and glidepath caused by aircraft, vehicles and buildings are no longer a problem because the MLS scanning beam can be interrupted and therefore avoids the reflections

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