A magnetic compass swings and dips during turns, which makes it hard to read in rough air. The heading indicator solves that problem with a gyroscope, showing the aircraft's direction of flight without magnetic errors.

The gyro drifts over time because of friction and Earth's rotation. Pilots realign it with the magnetic compass periodically, usually every fifteen minutes or so during cruise. Without that correction, the heading slowly becomes wrong.

Common names and types

• Directional gyro in light aircraft
• Horizontal situation indicator in advanced cockpits
• Electronic heading displays on glass panels
• Slaved gyros that correct automatically

Before GPS, this instrument was the primary reference for en route navigation. It still matters as a backup when satellite signals are unavailable or jammed.