What is the function of the avionics bus, and how is it typically protected?

• A. The avionics bus powers cockpit avionics and is often protected by circuit breakers and may be on a separate battery or power source to ensure stable power
• B. It powers exterior lights only
• C. It is unprotected and connected directly to the main battery
• D. It only powers the autopilot computer

Answer: (A)

The avionics bus is the power feed for cockpit avionics—things like radios, navigation equipment, flight instruments, and the autopilot. It’s kept separate from other electrical loads so sensitive avionics get clean, stable power and aren’t dragged down by non-avionics systems.

Protection is built in to prevent faults from cascading. Circuit breakers (and fuses) cut power if there’s a short or overload on that bus, safeguarding the avionics and the rest of the electrical system. In many aircraft, this bus also has a dedicated power source or standby feed, so the avionics can stay powered even if the main power source or engine-driven generators droop or fail. This combination of circuit protection and, often, a separate or backup power source keeps critical cockpit systems available and stable when power conditions change.