Final answer:
In DG mode, heading should be checked against a known reference source approximately every 15 minutes, and any heading error corrected by recalibrating the DG using the magnetic compass or GPS. Regular checks are essential to compensate for gyroscopic drift.
Step-by-step explanation:
The question refers to the procedure for checking the heading in DG mode, which stands for Directional Gyro mode. It is essential to check the heading against a known reference source at regular intervals to ensure the accuracy of the navigation system. During long flights, pilots or navigators typically check the heading against a magnetic compass or GPS at least every 15 minutes. If any discrepancy is identified, it can be corrected by adjusting the DG to align with the known reference heading.
To remove any heading error, recalibrate the DG using the magnetic compass or GPS when the aircraft is in stable flight, free from turns, banks, or other maneuvers that could affect the magnetic compass reading. It is crucial to regularly check the heading to prevent a phenomenon known as gyroscopic drift, which can lead to inaccurate readings over time.