left|100px The compass shows the aircraft's heading relative to magnetic north. Errors include Variation, or the difference between magnetic and true direction, and Deviation, caused by the electrical wiring in the aircraft, which requires a Compass Correction Card. Additionally, the compass is subject to Dip Errors. While reliable in steady level flight it can give confusing indications when turning, climbing, descending, or accelerating due to the inclination of the Earth's magnetic field. For this reason, the heading indicator is also used for aircraft operation, but periodically calibrated against the compass.
left|100px The compass shows the aircraft's heading relative to magnetic north Errors include Variation or the difference between magnetic and true direction and Deviation caused by the electrical wiring in the aircraft which requires a Compass Correction Card Additionally the compass is subject to Dip Errors While reliable in steady level flight it can give confusing indications when turning climbing descending or accelerating due to the inclination of the Earth's magnetic field For this reason the heading indicator is also used for aircraft operation but periodically calibrated against the compass