Which of the following statements correctly pairs AHRS initialization times?

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

Answer: (D)

AHRS initialization is about establishing a reliable attitude reference by calibrating sensor biases and aligning with gravity and magnetic fields. When the aircraft is on the ground, there’s no motion to help the algorithm distinguish biases or verify orientation, so the system spends more time gathering data to converge to a stable alignment—typically around a minute. In flight, the ongoing motion provides rich, changing data that lets the system resolve biases and align faster, so the initialization often finishes in tens of seconds. The pairing that uses about 70 seconds on the ground and roughly 10 to 35 seconds in flight matches this behavior and falls within common performance ranges. Other timings would imply unusually slow in-flight convergence or unnecessarily long ground alignment, which isn’t consistent with how AHRS typically behaves.