Definition
A switch designed so that, as it moves between positions, the new contact is made before the previous contact is broken. This ensures the circuit is never momentarily open during switching, which is important when the connected device must not lose its signal source or reference even for an instant.
Plain English
A switch that briefly connects both the old and new positions at the same time as it changes over, so the circuit never goes dead during the switch.
Context Anchor
Seen in aircraft ignition systems, especially during engine shutdown, magneto checks, and troubleshooting an engine that may still fire when the cockpit ignition switch is OFF.
Derivation
Called a 'shorting' switch because, for a brief moment during the change, the two contacts are 'shorted' (connected) together. Also known as a 'make-before-break' switch, which describes the action directly.
Why Pilots Care
It provides a reliable way to disable the ignition and shut down the engine or prevent accidental starts during servicing.
Intuition Check
Do not assume shorting means an accidental electrical fault here. In a shorting switch, the short path is intentional and is used to shut the magneto off.
Example Sentence 1
The fuel quantity selector uses a shorting switch so the gauge never sees an open circuit when the pilot switches between tanks.
Example Sentence 2
During a preflight inspection the mechanic verified that the shorting switch properly disabled each magneto.