Which statement describing the A320's electrical power sources in normal flight and typical backups is correct?

• A. External power can supply primary AC power in flight; engine generators serve as backups; standby battery provides emergency power to essential systems if needed.
• B. Two engine generators provide primary AC power; APU generator serves as backup; external power can be used on the ground; standby battery provides emergency power to essential systems if needed.
• C. Two engine generators provide primary DC power; APU provides AC; external power is used only on the ground; standby battery not used.
• D. Primary AC power is provided by the APU generator with engine generators as backups; external power is never used.

Answer: (B)

In normal flight, the two engine-driven generators supply the primary AC power to the aircraft’s electrical buses. The APU generator acts as a backup source of AC power, available if needed to support essential systems or when an engine generator is unavailable. External power is used on the ground when the aircraft is connected to a power source at the gate or in a stand, not during flight. The standby battery provides emergency DC power to essential systems if all AC sources are lost, keeping critical equipment functioning for a limited time.

The other statements mix up which sources provide primary power (DC vs AC), whether external power is used in flight, or the role of the standby battery, so they don’t reflect how the A320’s electrical system is normally arranged.