Definition
The rotating compass-card face on a VOR or HSI Course Deviation Indicator, marked in 360 degrees, used to select and display the desired course to or from a navigation station.
Plain English
The round dial on a navigation instrument that shows compass directions in degrees, which the pilot turns to pick the course they want to fly.
Context Anchor
Seen when using a course deviation indicator during radio navigation, especially when selecting a course to or from a ground station.
Derivation
Azimuth comes from the Arabic 'as-sumut,' meaning 'the directions' or 'the ways.' In navigation it refers to a horizontal direction measured in degrees around a circle. The dial, then, is simply the circular face that displays those directional bearings.
Why Pilots Care
It lets the pilot read the selected course or radial directly and confirm the aircraft is tracking the intended path.
Intuition Check
Do not read the azimuth dial as the airplane’s actual heading by itself. It is the selected navigation direction or course scale, not a guarantee of where the nose is pointed.
Example Sentence 1
The pilot turned the azimuth dial to 270 to select the westbound course from the VOR.
Example Sentence 2
With the azimuth dial showing 090, the CDI needle centered as the aircraft flew due east on the radial.