Which action triggers BUSS activation across both PFDs?

Which action triggers BUSS activation across both PFDs?

• A. Pressing the PFD refresh button
• B. Powering on the aircraft
• C. Selecting the BKUP SPD/ALT pushbutton on its associated side
• D. Pulling the emergency bus link

Answer: (C)

Activating the backup power path for the displays is what makes both PFDs run from a common backup source. On the A320, the PFDs normally get power from their own buses, but when you press the BKUP SPD/ALT pushbutton on the side, the system switches the displays to the backup feed and ties both sides to that shared source. This reversion keeps essential speed and altitude information visible on both screens even if the normal power buses are unavailable, giving the pilots a consistent, readable pair of PFDs. The other actions don’t perform this cross-connection to the backup power: pressing the PFD refresh button only updates what’s shown on the screens, powering on the aircraft simply starts systems without forcing a BUSS reversion, and pulling the emergency bus link is a different procedure not used to activate the BUSS for both PFDs in normal fault conditions.

Activating the backup power path for the displays is what makes both PFDs run from a common backup source. On the A320, the PFDs normally get power from their own buses, but when you press the BKUP SPD/ALT pushbutton on the side, the system switches the displays to the backup feed and ties both sides to that shared source. This reversion keeps essential speed and altitude information visible on both screens even if the normal power buses are unavailable, giving the pilots a consistent, readable pair of PFDs.

The other actions don’t perform this cross-connection to the backup power: pressing the PFD refresh button only updates what’s shown on the screens, powering on the aircraft simply starts systems without forcing a BUSS reversion, and pulling the emergency bus link is a different procedure not used to activate the BUSS for both PFDs in normal fault conditions.