FAA Aviation Mechanic Powerplant (AMP)Turbine EnginesEasy
A turbine engine's exhaust gas temperature (EGT) indicating system uses several thermocouple probes mounted around the exhaust duct and wired together in parallel to a single indicator. What is the main purpose of connecting the probes this way?
- ATo reduce the number of wires required for the fuel control system
- BTo increase the voltage signal sent to the cockpit indicator
- CTo provide a single averaged temperature reading representative of the entire exhaust duct
- DTo allow each probe to display an individual reading simultaneously
Show answer & explanationAnswer & explanation
Correct answer: C. To provide a single averaged temperature reading representative of the entire exhaust duct
Multiple thermocouple probes are spaced around the exhaust duct and wired in parallel so their individual millivolt outputs are averaged, giving the cockpit a single representative EGT reading rather than one localized measurement that could be skewed by uneven gas temperature distribution.
Why the other options are wrong
- A. Thermocouple wiring is unrelated to the fuel control system's wiring.
- B. Parallel wiring averages voltage, it does not increase it.
- D. Parallel wiring produces one combined reading, not individual displays.
EGT Thermocouple Averaging
Multiple thermocouple probes around the turbine exhaust are wired in parallel to produce a single averaged temperature reading for the cockpit indicator.
- Uses chromel-alumel thermocouples typically
- Parallel wiring averages millivolt signals
- Prevents a single hot spot from giving a misleading reading
Memory trick: Many probes, one number — parallel wiring blends readings into an average.