If the aircraft is powered only by emergency buses supplied from the ship batteries, how long will the electrical system run?

• A. 60 minutes
• B. 30 minutes
• C. 120 minutes
• D. 90 minutes

Answer: (A)

When you run the aircraft on emergency power, the duration is governed by how much energy is stored in the ship’s batteries and how much load the emergency buses must support. With the system limited to the emergency buses powered only by those batteries, you’re relying on a fixed energy reserve allocated to essential systems. For this airplane, that reserve is sized to keep the essential systems alive for 60 minutes, giving time to maintain critical flight instruments, navigation, communication, and control functions long enough to land safely. Shorter durations would not provide a guaranteed window to reach a suitable landing, while longer durations would require larger batteries or additional power sources that aren’t installed. Hence, the electrical system will run for about 60 minutes.