Definition
A switch that opens or closes its electrical contacts when a rotating shaft reaches a specific rotational speed. It is commonly used in turbine engine starting systems to drop out the starter and ignition circuits once the engine has accelerated to a self-sustaining speed.
Plain English
An electrical switch that automatically turns a circuit on or off when something spinning reaches a set speed. It senses how fast a shaft is turning and changes state at the chosen RPM.
Context Anchor
Seen in aircraft electrical system, engine starting system, landing gear, and warning system descriptions.
Why Pilots Care
Prevents the starter from remaining engaged at high RPM and causing mechanical damage.
Intuition Check
Do not assume “speed-sensitive” always means aircraft airspeed. In this term, the switch may respond to the speed of any monitored moving part, such as an engine, starter, or wheel.
Example Sentence 1
As the turbine accelerated through the cutoff RPM, the speed-sensitive switch dropped the starter offline.
Example Sentence 2
During the magneto check the mechanic verified that the speed-sensitive switch functioned correctly at idle.