Compass Deviation

Compass deviation is the error induced in a direct-reading magnetic compass caused by local magnetic fields within the aircraft, such as those from avionics, wiring, and metal engine components. Deviation differs from magnetic variation in that it is unique to each individual aircraft and varies depending on the heading being flown. Pilots use a compass correction card mounted near the instrument to adjust their magnetic heading to a compass heading.

Key Points

• •Error caused by local magnetic fields within the aircraft, such as avionics and metal components.
• •Unique to each individual aircraft — unlike magnetic variation, which is location-based.
• •Varies in magnitude depending on the specific heading the aircraft is flying.
• •Corrected using a compass correction card mounted near the compass.

Related Terms