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Magnetic Compass Acceleration & Turning Errors

FAA Ref: FAA-S-ACS-6C Area VI Task A (Pilotage and Dead Reckoning)

Scenario & Physics Summary

ANDS (Accelerate North, Decelerated South) and UNOS (Undershoot North, Overshoot South) magnetic dip errors explained.

Interactive 3D Visual Plates & Scenario Media

Magnetic Compass Acceleration & Turning Errors Plate 1

Plate 1: Magnetic Compass Acceleration & Turning Errors

Magnetic Compass Acceleration & Turning Errors Plate 2

Plate 2: Magnetic Compass Acceleration & Turning Errors

Magnetic Compass Acceleration & Turning Errors Plate 3

Plate 3: Magnetic Compass Acceleration & Turning Errors

Magnetic Compass Acceleration & Turning Errors Plate 4

Plate 4: Magnetic Compass Acceleration & Turning Errors

Aerodynamic & Operational Physics

Earth magnetic flux lines dip downward near the poles. The magnetic compass card center of gravity is offset to counter dip.
Acceleration Error (East/West headings): Acceleration causes CG inertia to lag, rotating card toward North (ANDS). Deceleration rotates card toward South.
Turning Error (Turning North/South): Turning FROM North causes lag (Undershoot North). Turning FROM South causes lead (Overshoot South).

FAA Exam Gotcha Alert

FAA Exam Trap: Acceleration error occurs ONLY on East and West headings. Turning error is maximum when turning through North or South.

Frequently Asked Questions & Exam Explanations

What does the ANDS mnemonic stand for?

Accelerate North, Decelerate South on East or West magnetic headings in the Northern Hemisphere (reversed in Southern Hemisphere for dip direction).

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