Which option correctly states the AHRS initialization duration?

• A. 60 seconds on the ground; 5-15 seconds in flight
• B. 90 seconds on the ground; 20-40 seconds in flight
• C. 70 seconds on the ground; 10-35 seconds in flight
• D. 45 seconds on the ground; 70 seconds in flight

Answer: (C)

AHRS initialization duration is about how long the Attitude and Heading Reference System needs to lock in its attitude and heading after power-up. On the ground, the system must perform a full calibration and bias estimation without the benefit of aircraft motion, so it typically takes longer—around 70 seconds. In flight, ongoing motion helps the estimator converge faster, so you’ll usually see a shorter initialization window, commonly about 10 to 35 seconds. The other time ranges don’t align with how these sensors stabilize: ground initializations that are too short or too long, or in-flight times that are outside the typical quick-convergence range, aren’t consistent with standard AHRS behavior.