Definition
A precision approach and landing guidance system that uses microwave signals to provide pilots with azimuth, elevation, and distance information for an instrument approach to a runway. MLS was designed as a successor to ILS, offering wider coverage areas, multiple approach paths, and resistance to terrain-related signal interference, though widespread adoption was eclipsed by GPS-based approaches.
Plain English
A ground-based system that beams microwave signals out from the runway environment so an aircraft can determine exactly where it is on approach -- left or right of centerline, how high above the glide path, and how far from touchdown.
Context Anchor
Seen in instrument approach discussions, especially when describing runway guidance systems used in poor visibility or low ceilings.
Derivation
Microwave refers to a band of high-frequency radio waves (shorter wavelengths than those used by ILS). The shorter wavelengths allow the system to produce narrower, more precise guidance beams and avoid some of the signal-bending problems that affect ILS in hilly terrain or near buildings.
Why Pilots Care
It enables safe precision approaches at airports where terrain prevents standard ILS installation, increasing landing options and safety margins.
Intuition Check
Microwave does not mean kitchen-oven heat here. It means a type of radio signal used to carry landing guidance.
Example Sentence 1
The handbook lists the microwave landing system as a precision approach option, alongside ILS and GLS.
Example Sentence 2
During the low-visibility arrival, the crew switched to the MLS frequency for final guidance to the runway.