FAA Ground School Practice Test

If an aircraft is on a north heading and accelerates, how does the magnetic compass react in the northern hemisphere?

1. Indicates a turn toward the east

2. Indicates a turn toward the west

3. Indicates correctly

4. Indicates an increase in altitude

The correct answer is: Indicates correctly

When an aircraft is on a north heading and experiences acceleration in the northern hemisphere, the magnetic compass behaves in a specific way due to the Earth's magnetic field and the principles of inertia. In this scenario, when the aircraft accelerates, the compass tends to lag behind the aircraft's actual heading due to inertia. This lag creates a temporary indication that the aircraft is turning towards the east. However, because the correct answer indicates that the compass "indicates correctly," it highlights a fundamental aspect of compass operation: under steady, straight acceleration without any turns, the magnetic compass aligns with the aircraft's movement. It's important to realize that the compass will initially show a false indication of eastward turn because of the acceleration but will stabilize to accurately reflect the north heading once the acceleration is consistent and the aircraft levels out. This scenario demonstrates the potential confusion pilots might face with compass interpretation during transitions in flight dynamics. Thus, while it's true that upon acceleration the compass indicates a turn, the underlying principle here is about understanding that under ideal conditions, the compass should ultimately indicate the true heading without error.