Compass Deviation

Compass deviation occurs when nearby ferromagnetic materials (such as iron or steel) or electrical circuits within an aircraft generate a magnetic field that interferes with the compass. This interference causes the compass needle to point in a direction that differs from Magnetic North.

Effects of Different Materials

• Ferromagnetic materials (e.g., iron, steel) and electrical currents can create localized magnetic fields, leading to compass errors.
• Non-ferromagnetic materials (e.g., brass, aluminum) do not produce magnetic fields and, therefore, have no effect on the compass.

Understanding Compass Deviation

• The deviation angle is the difference between Magnetic North and the direction indicated by the compass needle.
• Deviation is measured in degrees East or West relative to Magnetic North and is referred to as the angle between Magnetic North and Compass North.
• Each aircraft has a deviation card or compass correction table, which lists the deviation for different headings to help pilots correct for compass errors.

Regular compass calibration ensures accuracy in navigation, minimizing the effects of deviation caused by onboard magnetic influences.