Which instrument indicates the rate of turn in degrees per second?

The turn-and-slip indicator is specifically designed to show the rate of turn in degrees per second. It typically features a needle or ball that moves in conjunction with the aircraft's orientation relative to the turn. This instrument allows pilots to gauge how quickly the aircraft is turning, which is critical for maintaining controlled flight and achieving desired flight paths, especially during coordinated turns.

The artificial horizon, while essential for indicating the aircraft's orientation relative to the horizon, does not provide specific turn rate information. The heading indicator shows the aircraft’s current heading but does not indicate the rate of turn. The vertical speed indicator measures the rate of climb or descent in feet per minute, unrelated to the turn rate. Thus, the turn-and-slip indicator is the only instrument among the options listed specifically designed to inform pilots of the aircraft’s rate of turn in degrees per second.