Definition
On a turn coordinator or turn-and-slip indicator, the small arrow-shaped pointer or symbol used as the reference mark that the miniature aircraft (or needle) aligns with to show a standard-rate turn. When the wing of the symbolic aircraft, or the needle, points to the arrowhead, the aircraft is turning at three degrees per second.
Plain English
It's the little arrow mark on the turn instrument. Line the moving part up with that mark and you know you're turning at the standard rate.
Context Anchor
Seen on instrument displays that show turn rate, especially during instrument flying when the pilot is checking the rate of a turn.
Derivation
Arrowhead comes from the head, or pointed end, of an arrow. The aviation use keeps that idea: the mark is shaped like a small point and directs your eye to a specific indication on the display.
Why Pilots Care
Enables rapid visual confirmation of turn rate so the pilot can maintain standard-rate turns and coordinated flight without looking away from the panel.
Intuition Check
Arrowhead does not mean an actual arrow or weapon part here. It means a small pointed display mark used as a reference on the instrument.
Example Sentence 1
He banked gently until the wing of the miniature aircraft lined up with the arrowhead, holding a standard-rate turn onto the new heading.
Example Sentence 2
When the arrowhead remained on the center mark, the airplane maintained a constant heading.