What is the role of the magnetic compass during IFR flight?

• A. To provide magnetic direction when GPS is unavailable.
• B. To indicate heading based on gyro.
• C. To measure rate of turn.
• D. To provide magnetic direction when the heading indicator is unreliable, and to account for turning and acceleration errors that affect compass readings.

Answer: (D)

The magnetic compass provides a direct magnetic reference that you can rely on when other sources are not trustworthy, making it essential in IFR when the gyro-based heading indicator is unreliable or unavailable. Gyro instruments can drift or become inaccurate during turns and accelerations, so the compass serves as a real magnetic heading to confirm or recover your direction. However, its readings are affected by turning and acceleration errors (ANDS), especially during maneuvers or speed changes, so you interpret the compass with those known error patterns in mind and cross-check with other navigation sources when possible.