There is no acceleration/deceleration error on which heading?

When navigating, especially in relation to magnetic compasses, the effects of acceleration and deceleration can cause the compass to display erroneous readings, particularly when the aircraft is heading north or south. This phenomenon occurs due to the alignment of the magnetic field and the inclination of the compass.

In a north or south heading, if the aircraft accelerates, the compass will lag behind, and if it decelerates, the compass will lead ahead. This is due to the physics of magnetic fields and how they interact with the compass magnet.

However, when flying on an east or west heading, the effects of acceleration or deceleration do not create these misleading compass readings. This is because the magnetic forces acting on the compass needle are aligned in such a way that they remain stable during changes in speed. Therefore, when a pilot is flying on an east or west heading, there is no error incurred from acceleration or deceleration, allowing for more accurate navigation without the need to account for compass variations caused by speed changes.