Definition
In an aircraft electrical system, a bus is a common conductor — typically a metal bar or heavy wire — to which multiple electrical sources and loads are connected. Power from generators, alternators, or batteries feeds into the bus, and the bus distributes that power outward to the various circuits and components that draw from it.
Plain English
A bus is the central connection point in the electrical system. Power comes in from sources like the battery or alternator, and goes out from the bus to the things that need electricity — radios, lights, instruments, and so on.
Context Anchor
Seen in aircraft electrical system diagrams, maintenance manuals, and cockpit discussions of which equipment is powered by which electrical source.
Derivation
Short for 'busbar,' which itself comes from 'omnibus bar' — Latin 'omnibus' meaning 'for all.' The bar serves all the circuits connected to it, just like an omnibus (the original meaning of 'bus') was a vehicle for everyone.
Why Pilots Care
When something goes wrong electrically, knowing which bus a component is on tells you what else might be affected. Many aircraft have multiple buses (main bus, avionics bus, essential bus) so that a fault on one bus doesn't take down everything. Understanding the bus structure is key to handling electrical failures correctly.
Analogy
A bus is like a power strip: one power source feeds the strip, and several devices plug into it. If the strip loses power, everything plugged into it loses power too.
Intuition Check
Bus does not mean a passenger vehicle here. In aircraft electrical systems, a bus is a shared electrical supply point for multiple pieces of equipment.
Example Sentence 1
After the alternator failed, the pilot shed non-essential loads to keep the battery from draining the essential bus.
Example Sentence 2
The technician inspected the battery bus connections for corrosion during the inspection.