ABSTRACT
The microwave landing system (MLS) was adopted in 1978 as the long-term instrument landing system's (ILS) replacement. MLS is based on the principle of time referenced scanning beams and provides precision navigation guidance for approach and landing. The system provides three-dimensional approach guidance, i.e. azimuth, elevation and range; it also provides multiple approach angles for both azimuth and elevation guidance. This chapter reviews MLS principles and discusses its advantages over the ILS. An integral part of the MLS is a distance measuring equipment (DME) system to provide range; this can either be a conventional DME system or a dedicated system operating in the 962 MHz to 1105 MHz frequency range. DME frequencies are automatically tuned with the azimuth and elevation beams to provide range information. Typical MLS airborne equipment is illustrated by the CMA-2000 system. This system is installed on a number of military aircraft in the USA including the C-130 and Air Force One.
