Editing Flight instruments (section)

===Heading indicator===
{{main|Heading indicator}}
;[[Image:Heading indicator.svg|left|100px]]
The heading indicator (also known as the directional gyro, or DG) displays the aircraft's heading  in [[Points of the compass|compass points]], and with respect to magnetic north when set with a compass. Bearing friction causes drift errors from [[precession]], which must be periodically corrected by calibrating the instrument to the magnetic compass.<ref name=faa/>{{rp|3-19 to 3-20}} In many advanced aircraft (including almost all jet aircraft), the heading indicator is replaced by a [[horizontal situation indicator]] (HSI) which provides the same heading information, but also assists with navigation.