What is the purpose of Essential vs Non-Essential power buses?

• A. To improve cabin comfort
• B. To enable automatic fault isolation
• C. To ensure critical systems stay powered during faults while non-essential loads may be shed
• D. To allow manual selection of power sources

Answer: (C)

The main idea is to keep critical systems powered while giving up non‑essential loads when electrical faults or abnormal conditions occur. By organizing power into essential and non-essential buses, the system can automatically isolate faults and shed non-essential loads, so the buses supplying flight controls, avionics, essential flight deck instruments, and other safety‑critical equipment remain energized. This preserves the ability to fly and navigate safely even if part of the electrical system is damaged or overloaded, while non‑critical cabin systems can be powered down to conserve energy. Manual source selection isn’t the primary purpose; the goal is reliable operation of the systems that matter most during faults by prioritizing essential power.