The emergency power unit (EPU) provides emergency power for which systems?

• A. Only lighting systems.
• B. Electrical, engine, and hydraulic power for flight controls.
• C. Only air conditioning.
• D. Only communications.

Answer: (B)

The emergency power unit is focused on keeping the aircraft controllable when the main power sources are unavailable. It provides electrical power to essential systems and hydraulic power to the flight-control surfaces, so the cockpit instruments stay alive and the control surfaces can be moved even in an emergency. In many designs it can also support engine-start-related power, helping engines be brought online if needed. That combination—electrical, engine-related, and hydraulic power for flight controls—is why this option is the best fit. Limiting power to only lighting, only air conditioning, or only communications wouldn’t preserve control of the aircraft, since the flight-control surfaces and essential systems would still be unpowered.