Definition
A temperature-sensing device that uses two dissimilar metal wires joined at a measuring junction to generate a small voltage proportional to the temperature difference between that junction and a reference junction. In aircraft, thermocouples are commonly used to measure cylinder head temperature (CHT) and exhaust gas temperature (EGT) on reciprocating engines, and turbine inlet or exhaust gas temperature on turbine engines.
Plain English
A temperature sensor made from two different metals joined at a tip. When that tip gets hot, it produces a tiny electrical signal that the cockpit gauge reads as a temperature.
Context Anchor
You may see thermocouple in aircraft engine temperature instrument discussions, and thermal in weather or soaring discussions.
Derivation
From Greek 'therme' (heat) and 'couple' (a pair joined together) — literally a 'heat pair.' The name describes the device exactly: two different metals paired at a junction that responds to heat.
Why Pilots Care
Ensures reliable exhaust gas temperature readings that directly affect engine performance monitoring and safety decisions.
Intuition Check
Do not treat Thermocouple House Thermal as one standard aviation phrase. Thermal does not just mean warm here; in weather and soaring it can also mean rising warm air.
Example Sentence 1
The CHT gauge reads engine temperature through a thermocouple clamped under the spark plug on the hottest cylinder.
Example Sentence 2
During preflight, the pilot noted the thermocouple house thermal was secure before engine start.