What does a compass require to function properly in an aircraft?

A compass in an aircraft relies on the Earth's magnetic field to indicate direction, and for it to function accurately, it must account for magnetic deviation. This deviation occurs due to local magnetic fields created by electronic equipment, metal components, and other structures within the aircraft. Adjusting for magnetic deviation is critical to ensure that the compass provides a true indication of heading. This adjustment is typically made during the installation of the compass and should be checked regularly to ensure continued accuracy due to any changes that may affect local magnetic fields.

While high altitude calibration, regular cleaning of the glass, and connection to the electrical system may be relevant to certain instruments or components in an aircraft, they do not directly address the fundamental requirement for a compass to provide accurate headings. These factors do not change the compass's reliance on the magnetic field and its associated deviation corrections.