Which instrument is primarily used to measure pitch attitude?

The attitude indicator is the primary instrument used to measure pitch attitude in an aircraft. It provides pilots with a visual representation of the aircraft's orientation relative to the horizon. The instrument consists of a gyroscopic representation of the horizon and a symbolic airplane that pivots up and down as the aircraft climbs or descends.

When the aircraft's nose points up towards the sky, the airplane symbol moves above the horizon bar, indicating a climb; conversely, when the nose points down, the airplane symbol dips below the horizon bar, indicating a descent. This real-time feedback is critical for maintaining proper aircraft control during flight, particularly in conditions where visual references outside the cockpit may be limited.

In contrast, the altimeter measures altitude, the heading indicator shows aircraft direction, and the vertical speed indicator provides a rate of climb or descent. While these instruments are essential for flight operations, they do not provide the specific information regarding pitch attitude that the attitude indicator does.