If an aircraft crosses a magnetic meridian at 90 degrees, in which direction will a magnetic compass briefly indicate a turn when flying in the Northern Hemisphere?

Question: If an aircraft crosses a magnetic meridian at 90 degrees, in which direction will a magnetic compass briefly indicate a turn when flying in the Northern Hemisphere?

Answer options:

• Always to the North.
• Always to the South. ✅ Towards the nearest pole (Northerly turning error).
• There will be no error.

Correct answer: Towards the nearest pole (Northerly turning error).

Explanation: When turning from a northerly heading, the compass tends to lag, indicating a turn to the north (Northern Hemisphere). When turning from a southerly heading, the compass tends to lead, indicating a turn to the south. This is known as Northerly / Southerly turning error. At a 90-degree crossing, it will indicate a turn towards the pole it is turning to, i.e., Northerly or Southerly turning error.