Definition
A temperature-sensing device, typically a thermocouple, installed in the exhaust manifold or exhaust pipe of a piston engine to measure the temperature of the gases leaving a cylinder. The signal from the probe is sent to a cockpit gauge that the pilot uses to monitor combustion and to lean the fuel/air mixture for efficient operation.
Plain English
A small heat sensor placed in the exhaust pipe that tells the pilot how hot the burned gases coming out of the engine are. The pilot uses that reading to set the fuel-to-air ratio correctly.
Context Anchor
Seen in piston-engine aircraft engine instruments, engine monitoring systems, and exhaust system discussions.
Derivation
Probe comes from the Latin probare, meaning to test or examine. The probe is the sensing element that reaches into the exhaust stream to test its temperature.
Why Pilots Care
Monitoring EGT helps optimize fuel mixture, prevent engine damage from overheating, and diagnose cylinder performance issues.
Intuition Check
An EGT probe does not measure the whole engine’s temperature. It measures the temperature of the gases leaving the engine through the exhaust system.
Example Sentence 1
After reaching cruise altitude, the pilot leaned the mixture slowly while watching the EGT probe reading climb to peak and then settle back to the recommended setting.
Example Sentence 2
A faulty EGT probe can give inaccurate readings, leading to improper engine management.