Definition
A common electrical conductor in an aircraft to which the power source is connected and from which individual circuits draw electrical current to power lights, avionics, instruments, and other electrical equipment.
Plain English
A central electrical bar inside the airplane where power comes in from the battery or alternator and is shared out to all the things that need electricity.
Context Anchor
Seen in aircraft electrical system descriptions, wiring diagrams, and abnormal or emergency procedures involving electrical power.
Derivation
The word 'bus' here is short for 'busbar,' from the Latin 'omnibus' meaning 'for all.' The name fits — a single conductor that serves all the circuits connected to it.
Why Pilots Care
A failure on the bus can disable several systems simultaneously, so pilots must recognize its role when diagnosing electrical problems in flight.
Analogy
A power distribution bus is like a power strip: one supply feeds it, and several separate items can receive power from it. The aircraft version is built into the electrical system and protected by switches, breakers, or fuses.
Intuition Check
Do not picture a transportation bus. In aircraft electrical systems, a bus is a shared electrical connection that carries power to several places.
Example Sentence 1
After the alternator failed, only the equipment connected to the essential power distribution bus remained available.
Example Sentence 2
A fault on the power distribution bus caused both the navigation lights and the communication radios to lose power at the same time.