What are common compass errors and how can a pilot mitigate them during flight?

• A. Variation, deviation, and turning errors; mitigate by cross-checking with other navigation sources and using standard headings.
• B. Temperature errors; mitigate by re-calibrating compass in flight.
• C. Magnetic anomalies; mitigate by ignoring the compass.
• D. Only variation errors; mitigate by using GPS.

Answer: (A)

Compass readings can be affected by three common errors: variation, deviation, and turning errors. Variation is the difference between true north and magnetic north, and it changes with location and over time. Because charts often show true headings, you must apply the charted variation to use the correct magnetic heading, and you should cross-check your course with other navigation sources (GPS, VOR, pilotage) while flying using the magnetic headings shown on the plan.

Deviation comes from the airplane itself—electrical systems and metal inside the aircraft distort the local magnetic field around the compass. The typical remedy is a compass swing before flight to map out the deviation for each heading, then carry and use a deviation correction card in flight to apply those corrections as you fly.

Turning errors arise when you start or stop a turn; the pendulous magnet inside the compass lags, and accelerations or decelerations can skew the indicated heading. Mitigate by anticipating the heading you want, using standard-rate turns when possible, and continuing to cross-check the compass against other instruments or navigational sources during and after the turn. By understanding these errors and actively corroborating with other sources, you maintain accurate heading throughout the flight.