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Magnetic Compass Acceleration & Turning Errors
CASA Ref: CASR Part 61 MOS Schedule 3 CNAV 1.2 · FAA Ref: FAA-S-ACS-6C Area I Task H (Flight Instruments)
Scenario & Physics Summary
ANDS (Accelerate North, Decelerated South) and UNOS (Undershoot North, Overshoot South) magnetic dip errors explained.
Interactive 3D Visual Plates & Scenario Media
Plate 1: Magnetic Compass Acceleration & Turning Errors
Plate 2: Magnetic Compass Acceleration & Turning Errors
Plate 3: Magnetic Compass Acceleration & Turning Errors
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).
CASA & FAA Exam Gotcha Alert
CASA / 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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