Which of the following describes vertical compass errors?

Vertical compass errors in aviation arise from the inherent nature of magnetic compasses, particularly when they are used in a vertical position, as is typical in helicopters during certain flight maneuvers. Each of the listed types of errors contributes to the overall inaccuracies that pilots might experience while relying on a magnetic compass.

Variation refers to the difference between true north and magnetic north, which can affect compass readings based on geographical location. Deviation, on the other hand, is caused by local magnetic fields within the aircraft, such as those created by electronics or metal structures, leading to inaccuracies in the compass reading that vary with different headings.

Magnetic dip refers to the tendency of a magnetic compass to tilt with the earth's magnetic field, which causes inaccuracies in the compass reading when the aircraft climbs or descends. Oscillation, while a term often associated with the effect of turbulence, also implies the abnormal behavior of the compass when the aircraft is in a turning maneuver, exacerbating errors.

Northern turning and acceleration errors describe specific behaviors of the compass based on the plane's orientation and speed. The compass tends to under-read during a turn toward the north and over-read while turning toward the south, while during acceleration, the compass erroneously shows a turn in the opposite direction.