What does it indicate when the magnetic compass shows a turn in the opposite direction after turning left to a heading of 180°?

When a magnetic compass shows a turn in the opposite direction after turning left to a heading of 180°, it reflects a common characteristic of magnetic compasses known as magnetic dip or compass deviation. This phenomenon can occur during turns, especially when making a 180-degree turn.

As the aircraft or vessel executes the turn, the compass can momentarily lag behind and indicate a turn in the opposite direction, which is particularly noticeable when nearing the cardinal points. This behavior is a result of the way the magnetized needle responds to both the magnetic forces of the Earth and the accelerative forces acting on the craft during turns.

This response is typical for magnetic compasses and not necessarily indicative of any equipment failure or navigational error. Recognizing this normal behavior helps pilots and navigators to better interpret compass readings during maneuvers, avoiding confusion and ensuring a more accurate understanding of the vessel's heading.