Definition
A system on a reciprocating or turbine engine that measures the temperature of the exhaust gases as they leave the cylinders or turbine section, displaying the result on a cockpit gauge. On piston engines it uses a thermocouple probe in the exhaust stack to help the pilot lean the fuel-air mixture for efficient combustion. On turbine engines it monitors exhaust gas temperature as a primary indication of engine health and operating limits.
Plain English
A gauge system that tells the pilot how hot the engine's exhaust gases are, used to fine-tune the fuel mixture on piston engines or to watch for overheating on turbine engines.
Context Anchor
Seen on engine instruments, especially when adjusting the fuel-air mixture or checking engine condition during flight.
Derivation
A thermocouple is the sensor used in this system. The word comes from 'thermo-' (Greek for heat) and 'couple' (two joined things) — two different metals joined together that produce a small electrical voltage when heated. That voltage is what drives the EGT gauge needle.
Why Pilots Care
On piston engines, the EGT helps you lean the mixture correctly — too rich wastes fuel, too lean can damage the engine. On turbine engines, exceeding EGT limits can mean serious internal damage, so it is one of the most closely watched gauges during start and high-power operation.
Intuition Check
Do not think of the EGT indicating system as only the cockpit gauge. The system includes the sensor in the exhaust, the connections, and the display the pilot reads.
Example Sentence 1
After reaching cruise altitude, the pilot leaned the mixture slowly while watching the EGT indicating system rise toward peak.
Example Sentence 2
A sudden drop on the EGT indicating system prompted the pilot to troubleshoot a possible exhaust leak.