Microwave landing system

The microwave landing system ( MLS), Eng. Microwave Landing System, is a landing aid for aircraft, which transmits positioning signals in the range of 5 GHz. It was originally intended ( in the 80s ) as a successor system to the instrument landing system ILS, which operates in the VHF range. The International Civil Aviation Organization standardized the procedure in 1984. Succession decision was suspended in 1995 as GPS-based systems promised a cheaper alternative. Compared with the instrument landing system provides the MLS primarily the advantage that approach course and glideslope are freely selectable. Thus, segmented or curved approach paths are possible.

Operation

Depending on a tightly focused beam irradiates the approach area in horizontal and vertical plane. The MLS receiver in the aircraft detects when he is captured by the bottom station. Using the preamble, which are emitted, as well as other general information in all directions, the start time is known. The receiver is calculated from the time intervals between forward and backward running beam position to the runway or the glide path. About the azimuth antenna in addition data ( azimuth track, minimum angle of approach, in addition, for example, nature of the runway, wind shear or weather) transmitted. DME / P provides the removal ratio, in order to determine the position in space in conjunction with the two angles. The precision version of the distance measuring equipment (DME / P) is part of the MLS. But DME / P also satisfies the compatibility requirement of the standard DME. The higher precision of the DME / P resulted, inter alia, from an increased slope of the envelope of the query and response pulses. This is possible in DME / P systems, a precise determination of the pulse start time points.

MLS offers 200 transmission channels, ILS only 40

Signal characteristics

  • Time Reference Scanning Beam ( TRSB )
  • Frequency: 5030-5091 MHz
  • Removal ratio: DME / P
  • Backazimuth, that is, also for missed approach
  • Multipath curved and segmented approach
  • Air navigation
  • Airfield infrastructure
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