Which cause of magnetic compass inaccuracies can be compensated for during maintenance?

The cause of magnetic compass inaccuracies that can be compensated for during maintenance is deviation. Deviation refers to the errors in a magnetic compass that result from magnetic fields produced by electrical equipment or magnetic materials located within the aircraft itself. These errors can vary depending on the aircraft's orientation and the equipment being used at any given time.

During maintenance, technicians can adjust the compass or make magnetic corrections to minimize the impact of deviation. This is often accomplished by utilizing compensating magnets or by calibrating the compass against a known reference to ensure it provides accurate readings.

In contrast, variation refers to the difference between true north and magnetic north and is inherent to geographical locations; it cannot be adjusted during maintenance. Magnetic interference is often situational and can be transient, thus not amenable to systematic compensation. Magnetic dip affects compass performance based on latitude and the angle of the Earth's magnetic field, which cannot be corrected through maintenance procedures. Therefore, deviation is the only factor that can be effectively compensated for during maintenance routines.