In what scenario would a pilot need to adjust for compass deviation?

A pilot needs to adjust for compass deviation specifically when there are known magnetic interferences in the cockpit. Compass deviation occurs due to local magnetic fields created by electrical equipment, ferrous materials, or even certain instrumentations within the aircraft that can affect the accuracy of the compass reading.

In situations where there are magnetic interferences, such as when using electronic devices or when certain components of the aircraft are energized, the compass may not provide a true indication of magnetic north. This would necessitate a correction to ensure that navigation remains accurate and safe.

Adjusting for compass deviation is critical to ensure that the pilot is aware of any discrepancies between the indicated heading and the actual heading due to these localized magnetic influences. This understanding helps in maintaining proper situational awareness and navigation integrity, particularly in instrument flying situations.