Commercial Pilot License (CPL) Practice Exam

The selection of C, Altitude Error, is accurate because it is not a recognized error type associated with magnetic compasses. Magnetic compasses are influenced by several specific errors, including Northerly Turning Error, Deviation, and Variation.

Northerly Turning Error occurs due to the magnetic field alignment when the aircraft is turning towards or away from the magnetic north. Deviation refers to errors caused by magnetic interference from electrical equipment or metal structures within the aircraft itself. Variation is the difference between true north and magnetic north, which varies based on geographic location.

Altitude Error, on the other hand, pertains to altimeters and their inaccuracies due to changes in atmospheric pressure with altitude and does not relate to the functionality or errors of magnetic compasses. Thus, it appropriately represents a concept distinct from the commonly recognized compass errors.