What is the Power OFF sequence for the electrical system?

• A. External power off, standby power switch off, EPS switch off, Bat 1 and 2 off
• B. Bat 1 off, Bat 2 off, EPS off, External power off
• C. STBY Bus off, EPS off, Bat 1 and Bat 2 off, External power off
• D. External power off, Bat 1 and Bat 2 off, EPS off

Answer: (A)

Shut down in a safe, controlled order to avoid backfeeding and to ensure essential systems aren’t cut off too early. Start by removing the external power source so ground power isn’t feeding the system while you’re de-energizing the internal sources. Next, switch off the standby power so the standby/essential bus isn’t kept alive unintentionally once the external source is gone. Then disable the emergency power system to stop its dedicated supply in a deliberate sequence rather than leaving it connected while the other sources are being turned off. Finally, power down the two batteries to complete the shutdown, ensuring no residual energy remains in the electrical system.