Definition
A cockpit instrument that displays the temperature of one or more engine cylinder heads, allowing the pilot to monitor whether the engine is operating within its approved temperature range.
Plain English
A gauge that shows how hot the top part of the engine cylinder is getting, so the pilot can tell if the engine is running too hot.
Context Anchor
Seen in engine cooling discussions and in the cockpit engine instruments of many piston-engine airplanes, especially air-cooled engines.
Derivation
The cylinder head is the closed top end of an engine cylinder, where combustion is hottest. A sensor mounted there feeds the gauge, so the name simply describes what is being measured and where.
Why Pilots Care
Excessive cylinder head temperature can lead to detonation, loss of lubrication, and rapid engine damage or failure.
Intuition Check
Do not treat this as the same as oil temperature. The cylinder-head temperature gauge shows heat at the cylinder heads, not the temperature of the engine oil.
Example Sentence 1
During the climb, the pilot noticed the cylinder-head temperature gauge approaching the top of the green arc and lowered the nose slightly to improve cooling airflow.
Example Sentence 2
Before takeoff the pilot noted a normal reading on the cylinder-head temperature gauge after engine run-up.