Plain English Meaning

These are the built-in flaws of the magnetic compass. It does not always point to magnetic north accurately, especially when the aircraft is speeding up, slowing down, or turning. Pilots have to know about these flaws so they can interpret the compass correctly.

Full Definition

The collective term for the inherent inaccuracies that affect a magnetic compass in flight, caused by the physical design of the instrument and the way Earth's magnetic field interacts with it during acceleration, deceleration, and turns. The principal induced errors are variation, deviation, magnetic dip, acceleration/deceleration error, and northerly/southerly turning error.