The reference line used in a magnetic compass or heading indicator is called what?

• A. Lubber line
• B. Centerline
• C. Reference arc
• D. Heading line

Answer: (A)

The fixed reference line you use to read a heading on a magnetic compass or a heading indicator is the lubber line. This line stays in place on the instrument while the card or compass dial moves, providing the nose-point reference you align with the heading scale. On a magnetic compass, you read the heading where the lubber line crosses the scale; on a heading indicator, the gyro-driven card rotates while the lubber line remains fixed, so you read the current heading at that line. Other terms aren’t the standard name for this reference line—centerline describes the aircraft’s axis, while reference arc or heading line aren’t the conventional labels for this fixed reading reference.