Which instrument primarily indicates the aircraft's heading?

The heading indicator is the primary instrument that indicates the aircraft's heading. It provides a continuous readout of the aircraft’s direction relative to magnetic north, which is essential for navigation and maintaining a desired course. The heading indicator operates by using a gyroscope, which maintains its orientation in space, allowing pilots to see their heading in degrees on a 360-degree circle.

Using the heading indicator, pilots can make informed decisions about navigation, course adjustments, and situational awareness during flight. This instrument is particularly crucial when flying in conditions where visual references are limited.

The other instruments listed serve different purposes: the turn coordinator indicates the rate of turn and whether the aircraft is in coordinated flight, the vertical speed indicator shows the rate of climb or descent, and the airspeed indicator informs the pilot of the aircraft's speed relative to the surrounding air. While all these instruments provide valuable information for piloting, the heading indicator specifically serves the function of indicating the aircraft's heading.