What is the reason for swinging a compass, and how is it accomplished?

What is the reason for swinging a compass, and how is it accomplished?

• A. To align the compass with magnetic north during calibration
• B. To correct for dip errors in the Earth's magnetic field
• C. To compensate for deviations caused by magnetic fields in the aircraft by adjusting compensating magnets.
• D. To reduce vibration effects on the compass

Answer: (C)

Swinging a compass is about canceling the airplane’s own magnetic influence so the compass reliably points to magnetic north. The airframe, engine, and electrical systems generate stray magnetic fields that skew the needle away from the Earth's field. To fix this, pilots or mechanics adjust the internal compensating magnets (and any soft-iron elements) inside the compass. By placing the aircraft on the ground in a relatively quiet magnetic environment and comparing the compass reading with known, precise headings (north, south, east, and west), these adjustments are tweaked so the readings match the true headings. The result is a deviation card that shows how much the compass reading is off at each heading, which is then used in flight to apply the correct corrections. This isn’t about aligning the compass with magnetic north during a calibration, nor about correcting for the vertical dip of the Earth's field, nor about reducing vibration. It specifically targets the deviations caused by the aircraft’s own magnetic fields and fixes them with compensating magnets.

Swinging a compass is about canceling the airplane’s own magnetic influence so the compass reliably points to magnetic north. The airframe, engine, and electrical systems generate stray magnetic fields that skew the needle away from the Earth's field. To fix this, pilots or mechanics adjust the internal compensating magnets (and any soft-iron elements) inside the compass. By placing the aircraft on the ground in a relatively quiet magnetic environment and comparing the compass reading with known, precise headings (north, south, east, and west), these adjustments are tweaked so the readings match the true headings. The result is a deviation card that shows how much the compass reading is off at each heading, which is then used in flight to apply the correct corrections.

This isn’t about aligning the compass with magnetic north during a calibration, nor about correcting for the vertical dip of the Earth's field, nor about reducing vibration. It specifically targets the deviations caused by the aircraft’s own magnetic fields and fixes them with compensating magnets.