Definition
An automatic protective device in an aircraft electrical system that interrupts current flow to a circuit when it detects an overload or short circuit, preventing damage to wiring and equipment. Unlike a fuse, a circuit breaker can be reset after it trips, restoring the circuit if the underlying fault has cleared.
Plain English
A small switch that pops out on its own when too much electricity is flowing through a wire, cutting the power before something burns up. Once the problem is fixed, you can push it back in to turn the circuit back on.
Context Anchor
Seen on the cockpit electrical panel and in emergency checklists, especially during electrical failures, smoke or fire events, or when a piece of electrical equipment stops working.
Derivation
From 'circuit' (a complete electrical loop) and 'breaker' (something that breaks or interrupts). The name describes exactly what it does — it breaks the circuit when current gets dangerous.
Why Pilots Care
Circuit breakers prevent electrical fires and protect critical systems; pilots must know which ones can be safely reset and which indicate a deeper problem requiring landing.
Analogy
Like the breakers in a house electrical panel — when too many appliances pull power on one circuit, the breaker trips and stops the flow. You reset it by flipping it back, but if it keeps tripping, something is wrong with the wiring or equipment.
Intuition Check
Do not assume a circuit breaker is just a normal on/off switch. In an airplane emergency, a popped circuit breaker may be evidence of an electrical fault, not just something to push back in.
Example Sentence 1
When the landing light stopped working, the pilot checked the circuit breaker panel and found that the breaker had popped out.
Example Sentence 2
During the emergency checklist the instructor had the student identify the circuit breakers tied to the avionics bus.