In the northern hemisphere, a magnetic compass will normally indicate a turn to the north if the aircraft accelerates while on which heading?

• A. An east or west heading
• B. A north heading
• C. A south heading
• D. A heading of 45 degrees

Answer: (A)

When a magnetic compass is accelerated in the northern hemisphere, it exhibits a predictable error known as acceleration error. The needle’s inertia causes it to lag slightly as the aircraft speeds up, and on east or west headings that lag shows up as the north-seeking end of the needle deflecting toward the north. So, during acceleration on an east or west heading, the compass will indicate a turn toward the north. If you were on a north or south heading, this specific northerly deflection from acceleration is not produced in the same way, so you wouldn’t see a turn to the north due to acceleration alone. This is the reason the correct answer points to an east or west heading.