In flight the IR 1 FAULT light is flashing amber meaning ______.

In flight the IR 1 FAULT light is flashing amber meaning ______.

• A. the IR 1 may function for attitude and heading if selected to ATT
• B. the IR 1 is completely failed and unusable
• C. the IR 1 will automatically switch to the backup IR
• D. the IR 1 provides only power to the ADIRU

Answer: (A)

When an infrared inertial reference unit shows a fault light that’s flashing amber, it means the unit is degraded but not completely failed. The AHRS data from that IR can still be used, but with reduced redundancy. In this degraded state, attitude and heading information can continue to be provided if you select that IR as the attitude reference source (ATT). So, the system isn’t saying the IR is entirely unusable; it’s indicating limited functionality that you can rely on only if you specifically choose IR1 for ATT. This is why the option describing IR1 function for attitude and heading when selected to ATT is the best fit. The other statements aren’t correct in this context: a complete failure would typically imply no usable data from that unit, and the light doesn’t automatically mean the backup IR will take over without pilot selection. It also isn’t simply about providing power to the ADIRU—IR1 still feeds attitude/heading data, not just power.

When an infrared inertial reference unit shows a fault light that’s flashing amber, it means the unit is degraded but not completely failed. The AHRS data from that IR can still be used, but with reduced redundancy. In this degraded state, attitude and heading information can continue to be provided if you select that IR as the attitude reference source (ATT). So, the system isn’t saying the IR is entirely unusable; it’s indicating limited functionality that you can rely on only if you specifically choose IR1 for ATT.

This is why the option describing IR1 function for attitude and heading when selected to ATT is the best fit. The other statements aren’t correct in this context: a complete failure would typically imply no usable data from that unit, and the light doesn’t automatically mean the backup IR will take over without pilot selection. It also isn’t simply about providing power to the ADIRU—IR1 still feeds attitude/heading data, not just power.