In what way do magnetic fields generated by electrical equipment and steel parts in the airplane affect the magnetic compass?

In what way do magnetic fields generated by electrical equipment and steel parts in the airplane affect the magnetic compass?

• A. Deviation
• B. Magnetic interference
• C. Attenuation
• D. Distortion

Answer: (A)

Magnetic fields produced by electrical equipment and steel parts inside the airplane create a local magnetic field that combines with Earth’s field. The compass needle aligns with the resultant field, so the reading is offset from magnetic north. This offset is called deviation. It varies with heading and is corrected with a compass deviation card or by calibration. Other terms aren’t as precise here: the onboard field specifically causing the offset is deviation, not attenuation (we’re not weakening the field) or distortion (the term doesn’t describe the systematic offset you calibrate). External magnetic interference could refer to outside sources, but the question targets the aircraft’s own field, hence deviation is the correct concept.

Magnetic fields produced by electrical equipment and steel parts inside the airplane create a local magnetic field that combines with Earth’s field. The compass needle aligns with the resultant field, so the reading is offset from magnetic north. This offset is called deviation. It varies with heading and is corrected with a compass deviation card or by calibration.

Other terms aren’t as precise here: the onboard field specifically causing the offset is deviation, not attenuation (we’re not weakening the field) or distortion (the term doesn’t describe the systematic offset you calibrate). External magnetic interference could refer to outside sources, but the question targets the aircraft’s own field, hence deviation is the correct concept.