When an aircraft is on a magnetic heading of 180° and begins a left turn towards the east, how will the compass react?

When an aircraft is on a magnetic heading of 180° and begins a left turn towards the east, the compass will indeed indicate a turn in the proper direction but lag throughout the turn.

This happens due to the properties of the magnetic compass, which responds to changes in heading based on the magnetic field of the Earth. During a left turn, the compass will initially show a heading that is slower to change than the actual heading of the aircraft. This lag occurs because the liquid inside the compass takes time to settle and indicate the new direction after the aircraft has physically changed its heading.

In practical terms, while the aircraft is turning left towards the east (which is a heading of 90°), the compass will struggle to keep up with this change, resulting in a reading that does not accurately reflect the aircraft's true heading until the turn is completed and the compass catches up. This characteristic of the magnetic compass is essential for pilots to understand to ensure they interpret the readings correctly during maneuvers.