Editing Flight instruments (section)

===Magnetic compass===
{{main|Compass}}
;[[Image:Aero Magnetic Compass.jpg|left|100px]]
The compass shows the aircraft's heading relative to magnetic north. Errors include [[Compass variation|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 [[Aircraft compass turns|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.<ref name=faa/>{{rp|3-9 to 3-13, 3-19}}