If ESS TRU 1 and ESS TRU 2 fail, which interconnections enable TRU to power both the DC BATT BUS and DC ESS BUS?

• A. Automatic Closure Of The ESS TIE And The CROSS TIE
• B. Manual Closure
• C. ESS TIE Only
• D. CROSS TIE Only

Answer: (A)

Power is kept for essential systems by linking the DC bus(es) with automatic cross connections that allow any remaining source to feed both buses. When ESS TRU 1 and ESS TRU 2 are down, the two interconnections—ESS TIE and CROSS TIE—must close automatically so power can be shared between the DC BATT BUS and the DC ESS BUS. This dual closure creates a path for the single available source to supply both buses, preserving essential loads without requiring crew action. Closing only one tie or relying on manual action wouldn’t guarantee that both buses receive power.