How is the magnetic compass affected by acceleration and deceleration?

The magnetic compass is influenced by acceleration and deceleration due to the way it relies on Earth's magnetic field to indicate direction. When an aircraft accelerates, the compass may lag behind the actual heading because the inertia of the compass card causes it to remain in its previous position temporarily. This can result in a heading that appears to be incorrect, often showing a turn away from the direction of acceleration.

Conversely, during deceleration, the compass can show a turn in the opposite direction, also due to the inertia of the compass card. The combination of these effects creates temporary errors in heading indications, which pilots need to be aware of to maintain accurate navigation.

Understanding this behavior is crucial for pilots, as it highlights the importance of compensating for these errors when making navigation decisions, especially during rapid changes in speed. The other choices do not accurately reflect the magnetic compass's behavior during acceleration and deceleration, as it is indeed affected by speed changes rather than remaining unaffected or functioning only correctly at constant speeds.