Which instrument uses magnetic north as the reference to determine heading?

• A. Mach meter
• B. Magnus effect
• C. Magnetic compass
• D. Mandatory altitude

Answer: (C)

Direct heading information comes from a device that aligns with Earth’s magnetic field, pointing toward magnetic north. That makes the magnetic compass the instrument used to determine the aircraft’s heading relative to magnetic north. The other items don’t provide heading information: a Mach meter shows airspeed (Mach number) rather than direction; the Magnus effect is a physical aerodynamic phenomenon, not an instrument; and a term like mandatory altitude isn’t an instrument at all. In practice, pilots also learn about magnetic variation and deviation to translate magnetic heading to true course and account for local magnetic influences, but the magnetic compass is the one that uses magnetic north as its reference for determining heading.