If the Captain's PFD, ND, and upper ECAM screen show a diagonal line, what should be done?

When the Captain's Primary Flight Display (PFD), Navigation Display (ND), and upper Engine Condition and Monitoring (ECAM) screen show a diagonal line, it indicates a failure of the displays, typically related to power loss or a bus fault affecting the Captain's side systems. In this situation, transferring the display configurations is necessary to restore critical flight information.

By placing the EIS (Electronic Instrument System) Display Management Computer (DMC) selector to the Captain 3 position, you are effectively instructing the system to route the backup displays to the Captain’s side. This allows for the necessary information to be displayed correctly, ensuring that the captain retains access to vital flight data and can continue flying the aircraft safely.

Other options, though they may seem plausible, do not address the immediate need for the correct display configuration. The ECAM/ND XFR selector to CAPT position relates to transferring the ECAM and ND displays but does not directly resolve the underlying issue with the DMC. The same applies to placing the DMC selector to the F/O 3 position, which would shift focus to the First Officer's side rather than remedying the issue directly at the Captain's display. Additionally, pressing the PFD/ND XFR button