How often should a DG be re-adjusted?

• A. Every 5 minutes
• B. Every 10 minutes
• C. Every 15 mins
• D. Every 30 minutes

Answer: (C)

Directional gyro heading accuracy relies on periodic re-alignment with magnetic north. The DG uses a gyroscope that tends to drift over time due to friction and other mechanical effects, so its indication can slowly diverge from the actual magnetic heading. To keep navigation accurate, you realign the DG with the magnetic north at regular intervals. The standard practice is about every 15 minutes of flight, which strikes a good balance between keeping the instrument trustworthy and not overloading the cockpit with constant adjustments. If you notice a larger discrepancy, or you’ve had a significant yaw or turned through a large angle, re-align sooner. Waiting longer than 15 minutes can allow drift to accumulate enough to mislead you, while doing it far more often than necessary adds unnecessary workload.