Definition
A control on the Horizontal Situation Indicator (HSI) used to position the heading bug around the compass card to a desired magnetic heading. The selected heading is displayed by the bug and is the reference used by the autopilot or flight director when operating in heading mode.
Plain English
A small knob on the HSI that lets the pilot set a chosen heading. Turning it moves a marker (the heading bug) around the compass dial to the heading the pilot wants to fly or have the autopilot fly.
Context Anchor
Seen on an HSI during instrument flying, especially when setting or changing a desired heading.
Why Pilots Care
It provides a precise, repeatable way to command a heading reference that the autopilot can track or that the pilot can follow visually on the HSI.
Intuition Check
Do not assume turning the heading select knob turns the airplane by itself. It sets the desired heading marker; the airplane follows it only if the pilot flies that heading or the automation is using it.
Example Sentence 1
After ATC issued a vector, the pilot turned the heading select knob to 270 and engaged heading mode on the autopilot.
Example Sentence 2
After receiving the new clearance, she used the heading select knob to set 090 before engaging heading mode on the autopilot.