Magnetic compass

A magnetic compass is a direction instrument that aligns with the Earth’s magnetic field and shows heading relative to magnetic north. It is used as a basic reference in flight, especially as a simple independent backup to gyroscopic or electronic heading indications. Its indications can be affected by turning, acceleration, deceleration, magnetic variation, deviation, and weak horizontal magnetic force near the magnetic poles. A pilot uses the compass with a compass card or correction data and interprets its reading with the known compass errors in mind.