Definition
An electrical switch whose contacts move from one position to the other rapidly and decisively, regardless of how slowly the operating lever or button is moved. A spring-loaded internal mechanism stores energy as the actuator is pressed, then releases it suddenly once a threshold is reached, snapping the contacts open or closed in a single quick motion.
Plain English
A switch built so the contacts always flick over quickly, even if you press the button slowly. The internal spring forces a clean, fast change between on and off.
Context Anchor
Seen in aircraft electrical systems, especially where a small movement must give a definite signal, such as a gear-position, door-position, or control-position switch.
Derivation
Called 'snap-action' because the contacts literally snap from one position to the other. The term describes the behavior, not a brand or category — the spring stores energy and then releases it in a snap.
Why Pilots Care
Delivers dependable electrical operation in critical aircraft systems and reduces the risk of arcing or intermittent connections that could affect safety.
Analogy
It works like a click-type light switch at home: your finger moves it partway, then the switch snaps the rest of the way to a definite on or off position.
Intuition Check
“Snap-action” does not mean the switch is broken or that something has snapped off. It means the switch is designed to move quickly and positively once it reaches its operating point.
Example Sentence 1
The landing gear position indicator uses a snap-action switch so the gear-down light comes on cleanly the moment the gear reaches the locked position.
Example Sentence 2
During preflight checks the pilot verified that the master electrical switch operated with the crisp feel of a snap-action design.