Where does the crew normally enter the Present Position information to update all three ADIRUs?

Where does the crew normally enter the Present Position information to update all three ADIRUs?

• A. Standby instrument panel
• B. MCDU
• C. Flight control panel
• D. ND

Answer: (B)

Entering the present position on the MCDU is how the three ADIRUs get their reference for alignment. When the aircraft’s current latitude and longitude are input via the MCDU (usually on the INIT/REF or POS page), that position is distributed to all three ADIRUs so they can compute a common reference frame and correctly align. The standby instrument panel, flight control panel, and ND are not used to input this position data; they are either displays or controls, not the data source for IRS alignment.

Entering the present position on the MCDU is how the three ADIRUs get their reference for alignment. When the aircraft’s current latitude and longitude are input via the MCDU (usually on the INIT/REF or POS page), that position is distributed to all three ADIRUs so they can compute a common reference frame and correctly align. The standby instrument panel, flight control panel, and ND are not used to input this position data; they are either displays or controls, not the data source for IRS alignment.