The backup flight instrument attitude indicator gyro inputs come from which source?

• A. Its own internal three-axis gyro stabilization system
• B. The integrated avionics system inertial reference unit (IRU)
• C. Both its own reference system source and the integrated avionics system
• D. The GPS

Answer: (A)

The standby attitude indicator relies on its own internal three-axis gyro stabilization system. This gives the instrument an independent attitude reference (pitch, roll, and yaw) that remains available even if the primary flight avionics fail. While the integrated avionics IRU can provide attitude data to the main instruments, the backup indicator is designed to be self-contained so a common failure doesn’t leave you without attitude information. GPS isn’t used to feed the standby attitude indicator; it might assist some systems for attitude in other contexts, but the standby display gets its gyro input from its own internal gyro.