On which principle does the heading indicator operate?

The heading indicator operates on the principle of rigidity in space, which is a fundamental characteristic of gyroscopes. When a gyroscope is spinning, it maintains its orientation regardless of the position of the surface it is mounted on, provided that the gyro is not disturbed. This means that as the aircraft turns or tilts, the heading indicator remains stable and continues to indicate the direction the aircraft is facing due to the gyro’s resistance to changes in its axis of rotation.

This principle allows pilots to have a reliable reference for their heading, which is especially important during navigation and in conditions where visual references are limited. Proper use of the heading indicator involves periodically checking and adjusting it against the magnetic compass to ensure accurate readings, as the gyro can precess over time and drift from true headings.

Other options encompass different principles that do not apply to the function of the heading indicator. Gravity would pertain more to altimeters and vertical speed indicators, while air pressure relates to pitot-static instruments. Magnetic forces are involved in the functioning of a magnetic compass, not in the gyroscopic mechanism of the heading indicator.