Definition
A method of identifying ferrous metals and distinguishing between different types of steel by holding a sample lightly against a grinding wheel and observing the pattern, color, length, and bursting characteristics of the sparks produced. Each ferrous alloy produces a distinctive spark pattern that allows trained personnel to identify the material.
Plain English
Touching a piece of metal to a grinding wheel and looking at the sparks it throws off. Different steels and irons make different spark patterns, so a mechanic can tell what kind of metal it is by the way the sparks look.
Context Anchor
Seen in aircraft maintenance and repair work when a mechanic needs to identify an unknown steel part or piece of material.
Derivation
Spark comes from an old English word meaning a small glowing particle. The name is literal: the glowing particles thrown off the metal are what the mechanic studies during the test.
Why Pilots Care
A failed spark test indicates an ignition problem that can cause rough running, power loss, or failure to start, directly affecting flight safety.
Intuition Check
Do not assume this means a test of a spark plug or ignition spark. In this maintenance context, the sparks come from grinding metal, and the sparks are used to help identify the metal.
Example Sentence 1
Before fabricating the replacement bracket, the mechanic ran a spark test on the stock to confirm it was the correct grade of steel.
Example Sentence 2
If the spark test shows no jump across the gap, the plug or lead must be replaced before flight.