When converting magnetic heading to true course, what do pilots need to do for easterly and westerly headings?

When converting from magnetic heading to true course, pilots must take into account the Earth's magnetic declination, which is the angle difference between magnetic north and true north. For easterly headings, the magnetic heading must be converted to true by adding the magnetic variation, because the magnetic north will be to the west of true north in these cases. Conversely, for westerly headings, the magnetic variation is subtracted. This adjustment is necessary to ensure navigation accuracy, as it aligns the pilot's course with the geographic reality represented by true north.

The choice to add for easterly headings and subtract for westerly headings reflects this fundamental principle of navigation. By using this method, pilots can accurately determine their true course, ensuring they maintain the correct track over the ground, especially when navigating using charts that display true north references.