Definition
A precision approach and landing guidance system that uses microwave signals to provide aircraft with horizontal (azimuth) and vertical (elevation) guidance to a runway, along with distance information. MLS was developed as a successor to the ILS, offering wider coverage and curved approach capability, but has seen very limited operational deployment.
Plain English
A landing aid that uses microwave radio signals to guide an aircraft down to the runway, telling the pilot if they are lined up correctly and on the right descent path.
Context Anchor
Seen in flight plan equipment codes and instrument approach information when listing what navigation or landing systems the aircraft can use.
Derivation
Microwave refers to the high-frequency radio band the system uses (around 5 GHz). These shorter wavelengths allow more precise and flexible guidance signals than the older VHF/UHF signals used by ILS.
Why Pilots Care
On a flight plan, indicating MLS capability tells ATC the aircraft can fly an MLS approach if one is available. In practice, MLS approaches are rare, but the equipment code still appears in flight planning references.
Intuition Check
MLS is not the same as RNAV or GPS. It is a specific ground-based landing guidance system used by aircraft equipped to receive it.
Example Sentence 1
The aircraft's flight plan included an MLS equipment code, indicating it could fly a microwave landing system approach if needed.
Example Sentence 2
During the approach briefing the crew confirmed the receiver was tuned for the MLS signal.