Definition
In a Microwave Landing System (MLS), the approach azimuth is the lateral guidance signal that tells the aircraft its left-right position relative to the runway centerline during the final approach. It is transmitted from a ground station located beyond the stop end of the runway and provides horizontal course information across a wide angular sector, allowing curved or offset approach paths in addition to a straight-in approach.
Plain English
It's the side-to-side guidance an MLS gives you on approach. It tells the aircraft how far left or right of the runway centerline it is, so the pilot or autopilot can line up correctly with the runway.
Context Anchor
Seen in MLS instrument approach discussions, especially when describing the left-right guidance used to align with the runway.
Derivation
Azimuth comes from the Arabic 'as-sumut,' meaning 'the directions' or 'the ways.' In navigation it refers to a horizontal direction or angle measured around a reference point. So 'approach azimuth' simply means the horizontal direction information used during the approach.
Why Pilots Care
Provides precise lateral guidance for approaches in conditions where ILS is unavailable, supporting safer landings with wider coverage angles.
Analogy
Think of it as an electronic runway centerline extended out into the air. If the airplane is off to one side, the approach azimuth guidance helps bring it back toward the centerline.
Intuition Check
Approach azimuth is not descent guidance. It is left-right alignment guidance for the runway approach path.
Example Sentence 1
The crew intercepted the approach azimuth and tracked the MLS course inbound to the runway.
Example Sentence 2
When the approach azimuth needle showed a slight right deflection, the pilot made a small correction to realign with the centerline.