How often are aeronautical charts updated for magnetic variation?

Aeronautical charts are updated for magnetic variation typically every 6 to 12 months, or as required. This frequency takes into account the gradual changes in the Earth's magnetic field, which can affect navigational accuracy. These updates ensure that pilots have the most current data when navigating, as even small variations can lead to significant course deviations over long distances.

The reason for the periodic updates is to maintain safety and reliability in aviation navigation. As tectonic shifts or other environmental changes occur, the magnetic declination (the angle difference between true north and magnetic north) can change. Therefore, it is essential for aeronautical charts to reflect these updates to aid pilots in making informed decisions mid-flight.