Definition
A common conductor (typically a metal bar or strip) inside an aircraft's electrical system that distributes electrical power from the source (battery and alternator/generator) to multiple individual circuits and components. All loads connected to the same bus share the same voltage supply.
Plain English
A shared electrical 'rail' inside the airplane that power flows into from the battery and alternator, and then flows out of to feed all the things that need electricity — radios, lights, instruments, and so on.
Context Anchor
Seen in aircraft electrical system descriptions, cockpit switch panels, and emergency checklists for electrical problems.
Derivation
The word 'bus' here is short for the Latin 'omnibus,' meaning 'for all.' In electrical terms, a bus is a single conductor that serves all the connected circuits — power 'for all' of them. The same idea is why a passenger bus carries many people on one shared vehicle.
Why Pilots Care
Knowing which systems are tied to each bus allows a pilot to predict which instruments and lights will remain powered if one bus fails.
Analogy
An electrical bus is like a power strip in a house: one source feeds the strip, and several devices plug into it. If the strip loses power, everything plugged into it loses power too.
Intuition Check
Do not read bus as a vehicle here. In an aircraft electrical system, a bus is a shared point or path that distributes electrical power.
Example Sentence 1
When the pilot turned on the avionics master switch, power flowed from the main electrical bus to the avionics bus, bringing the radios and navigation equipment to life.
Example Sentence 2
The schematic showed the battery connected directly to the main electrical bus before power reached the avionics.