dip error

northerly turning error

northerly turning errorclick for a larger image
Aircraft is turning right when on a northerly heading. The compass in this case lags and shows 330° when the aircraft is in fact on 000°. When the aircraft is initiating turn on a southerly heading, the compass leads in that it shows 150° when the aircraft is still at 170°. There is no such error when aircraft is turning through easterly or westerly heading. The compass needle catches up once the aircraft is level or when aircraft is passing through easterly and westerly headings.
An error in an aircraft magnetic compass. In the Northern Hemisphere, the compass lags behind the turn when turning left or right through a northerly heading and races ahead when turning through a southerly heading. The error results because the float on which the compass magnets are mounted is unbalanced to compensate for the vertical component of the earth's magnetic field. Also called dip error.