Definition
An electromagnetic switch designed to handle high electrical current for short periods only, not continuous operation. It uses a coil to move an internal plunger that closes a heavy-duty contact, allowing a small control current to switch a much larger load current. Because the coil and contacts are not built to dissipate heat over long durations, an intermittent-duty solenoid will overheat and fail if energized for more than its rated time, typically a few seconds to a minute.
Plain English
A heavy-duty electrical switch that can carry large amounts of current, but only briefly. If you leave it switched on too long, it will overheat and burn out.
Context Anchor
Seen in aircraft electrical system maintenance, especially around starter circuits and other devices that are powered only for short actions.
Derivation
Intermittent comes from the Latin intermittere, meaning to leave off or pause. Duty refers to how hard and how long a component is expected to work. Together, intermittent-duty means the part is rated for stop-and-start use, not continuous use.
Why Pilots Care
Selecting the correct duty rating prevents overheating and failure in high-load electrical components during normal operations.
Analogy
It is like a doorbell button: it is designed to be pressed briefly. Holding it down for a long time can overheat parts that were only meant for short use.
Intuition Check
Do not read “intermittent-duty” as meaning the solenoid works unreliably or only sometimes. It means the solenoid is designed for brief powered use with rest time between uses.
Example Sentence 1
When the pilot pressed the starter button, the intermittent-duty solenoid clicked closed and sent battery current to the starter motor.
Example Sentence 2
Replacing an intermittent-duty solenoid with a continuous-duty unit avoids heat issues in the starter circuit.