Private Pilot Private Exam

What will the magnetic compass show if the aircraft is decelerated while on a west heading in the Northern Hemisphere?

1. No change in indication

2. A turn toward the north

3. A turn toward the east

4. A turn toward the south

The correct answer is: A turn toward the south

When an aircraft is on a west heading and experiences a deceleration, the magnetic compass will show a turn toward the north. This phenomenon occurs due to the principles of inertia and the design of the magnetic compass. As the aircraft slows down, the compass's magnetic needle tends to lag behind due to inertia. This results in a compass deviation that creates the illusion of a turn toward the north. The compass is influenced by the relative motion of the aircraft, and when the speed decreases, the compass will indicate a turn in the opposite direction of the aircraft’s heading before the deceleration started. In this case, since the aircraft was flying west and the pilot decelerates, the compass indication will momentarily shift to suggest a turn toward the north, rather than a turn toward the south or east. Understanding how the magnetic compass behaves under various conditions of flight is crucial for navigating accurately, especially when changing speed or heading.