Definition
A maintenance troubleshooting procedure used on a reciprocating aircraft engine to identify a cylinder that is not producing power. The engine is run at a low power setting with the suspected magneto or ignition system selected, then shut down. A technician immediately measures the temperature of each cylinder, usually at the exhaust port or cylinder head. Any cylinder that is noticeably cooler than the others is not firing properly and is the source of the problem.
Plain English
A simple shop test where you run the engine, shut it down, then quickly feel or measure how hot each cylinder is. The cold one is the one that wasn't doing its share of the work.
Context Anchor
Used in aircraft maintenance troubleshooting after a piston engine runs rough, misses, or shows signs that one cylinder may not be working properly.
Derivation
Called a 'cold cylinder' test because the diagnostic clue is heat — or the lack of it. A working cylinder gets hot from combustion; a dead one stays relatively cold. The test simply finds the cold one.
Why Pilots Care
Identifies a failing cylinder before it leads to engine roughness, power loss, or complete failure in flight.
Grounding Statement
A cylinder that burns fuel makes heat quickly; a cylinder that does not fire stays noticeably cooler.
Intuition Check
This is not a test for cold weather or engine preheating. Here, cold means cooler than the other cylinders because that cylinder did not produce normal combustion heat.
Example Sentence 1
After a rough mag check, the mechanic ran a cold cylinder test and found that the number three cylinder was significantly cooler than the others.
Example Sentence 2
The cold cylinder test quickly showed the left magneto was not firing on the rear cylinders.