How often must a compass be swung for calibration purposes?

A compass must be swung for calibration purposes annually to ensure its accuracy in indicating the direction. This calibration process helps account for variations that may arise from changes in the aircraft's magnetic environment, which can be influenced by factors such as electronic equipment, changes in the aircraft structure, or even modifications to the aircraft's interior.

Regular annual calibration helps maintain reliable navigation and safety, as a malfunctioning or inaccurately calibrated compass can lead to navigational errors that could compromise flight safety. While there are other maintenance checks required at different intervals, such as during an annual inspection or based on flight hours, the specific requirement for compass calibration is set at once a year to ensure optimal operational reliability.