What must be monitored in an INS?

• A. Fuel level
• B. Excessive drift
• C. Antenna alignment
• D. Crew workload

Answer: (B)

An Inertial Navigation System relies on integrating accelerometer and gyroscope data to track position, velocity, and attitude. Small biases and noise in these sensors cause errors to build up over time, so the reported navigation solution gradually drifts away from the true values. Monitoring for excessive drift helps you know when the INS is losing accuracy and needs reinitialization, alignment, or updating from an external reference (like GPS) to reset the error. The other options don’t reflect the INS’s internal error behavior: fuel level isn’t about navigation accuracy, antenna alignment isn’t a core INS concern, and crew workload doesn’t affect the inertial data.