Definition
The temperature of the burned gases leaving an engine's combustion chamber, measured by a probe (thermocouple) placed in the exhaust stream. In piston aircraft engines it is used to monitor combustion and adjust the fuel/air mixture; in turbine engines it is a primary indication of engine operating condition and a limit not to be exceeded.
Plain English
How hot the gas is as it leaves the engine after the fuel has burned. Pilots watch this temperature to know whether the engine is burning fuel correctly and to make sure it isn't running too hot.
Context Anchor
Seen on engine instruments, during engine run-up, cruise power setting, fuel-air mixture adjustment, and maintenance troubleshooting.
Derivation
“Exhaust” comes from a root idea of drawing or carrying out. In this term, it points to gases being carried out of the engine after burning. “Temperature” means the degree of heat, so the term means the heat of the gases leaving the engine.
Why Pilots Care
Abnormal readings can signal mixture problems, cylinder issues, or impending engine damage, guiding in-flight adjustments.
Grounding Statement
Picture a small sensor in the exhaust flow measuring how hot the gases are right after they leave the cylinder.
Intuition Check
Exhaust gas temperature is not the same as overall engine temperature. It is specifically the temperature of the gases leaving the engine after combustion.
Example Sentence 1
After leveling off in cruise, the pilot leaned the mixture until the exhaust gas temperature peaked, then enriched slightly for best economy.
Example Sentence 2
A sudden rise in exhaust gas temperature on one cylinder prompted the mechanic to inspect the spark plugs.