What is the purpose of swinging an aircraft magnetic compass?

Swinging an aircraft magnetic compass is primarily done to update the compass correction card. This process involves adjusting the compass to account for the magnetic variation caused by the aircraft's magnetic field and other influences, such as electrical equipment or nearby magnetic objects. By swinging the compass, the pilot can determine the compass's deviations at specific headings and then create a correction card that allows for accurate readings during flight.

This procedure is crucial for ensuring that pilots can rely on the compass for navigation, as accurate heading information is vital for safe and effective operation. The compass correction card provides the necessary adjustments to compensate for any discrepancies noted during the swinging process, leading to enhanced navigational accuracy.