Definition
A cockpit-mounted electrical switch that connects or disconnects the aircraft battery from the airplane's electrical system. When closed (ON), it allows battery power to flow to the bus, energizing the avionics, lights, starter circuit, and other electrical loads. When open (OFF), it isolates the battery from the system.
Plain English
The switch in the cockpit that turns the aircraft battery on or off. With it on, the battery can power things in the airplane. With it off, the battery is disconnected and nothing electrical runs from it.
Context Anchor
Seen during engine start and shutdown procedures, often as part of the aircraft’s master switch or electrical power controls.
Why Pilots Care
It supplies battery power needed to start the engine, run lights, radios, and instruments until the alternator or generator takes over.
Intuition Check
Do not assume the battery switch starts the engine by itself. It only makes battery power available; the engine still needs the normal starting action.
Example Sentence 1
Before starting the engine, the pilot turned the battery switch ON to energize the starter and avionics.
Example Sentence 2
After landing, the pilot turned the battery switch off to prevent draining the battery overnight.