What would cause bearings to become magnetized?

• A. Low Temperatures
• B. Bearing Rotating At A High Speed And Lightning Strikes Absorbed By The Aircraft
• C. Oil Contamination
• D. Excessive Lubrication

Answer: (B)

Bearings can become magnetized when ferromagnetic material is exposed to a strong magnetic field or large electrical currents. A lightning strike delivers a huge current and a strong magnetic field that can couple into aircraft structures and through bearing paths. If this transient current interacts with a bearing that’s in operation (often rotating at high speed), the magnetic domains in the bearing material can become aligned, leaving residual magnetism. That magnetization can persist and affect performance. The other scenarios don’t provide the necessary electrical or magnetic input to magnetize the bearing.