TEMPERATURE - DESCRIPTION AND OPERATION

** ON A/C NOT FOR ALL

1. General
The measurement channel for the Exhaust Gas Temperature (EGT) is designed as follows:

Four probe assemblies each comprising three thermocouples per channel.
Channel A of four probes (three thermocouples from each probe assembly) are used to form an averaged signal sent to the channel A of the EEC.
Channel B of four probes (three thermocouples from each probe assembly) are used to form an averaged signal sent to the channel B of the EEC.
The EEC uses the EGT in the engine start control logic and also transmits the EGT signal to the ECAM through the ARINC bus.

** ON A/C NOT FOR ALL

2. EGT indication

A. General

Probe Assembly ** ON A/C NOT FOR ALL

EGT Harness ** ON A/C NOT FOR ALL

Junction Box Assembly ** ON A/C NOT FOR ALL

EGT Junction Box ** ON A/C NOT FOR ALL

Wiring Diagram of the EGT Harness ** ON A/C NOT FOR ALL

Four probe assemblies are located at station 4.95 (LP turbine exhaust case strut) at 9.5, 7.5, 4.5 and 2 o'clock viewed from the rear.

B. Description

(1) Probe assembly
The probe assemblies are dual channel output and have heat resistant metal thermocouples.On each probe assembly the electrical connection is made by four terminal posts. Each probe assembly has a flange for the terminal block mounting and for its attachment, with bolts, to the turbine exhaust case.

(2) Harness and junction box
The probe assemblies are connected, in parallel, to the junction box by a flexible harness. The wires in the harness are made of insulated chromel and alumel. Terminal lugs, also of chromel and alumel, are welded to the ends of the harness wires. The harness has a copper internal braid to protect it from electro-magnetic interference. It also has a stainless steel external braid to protect it from heat and friction damage. The harness and the junction box are attached by brackets bolted to the flange of the turbine exhaust case.

C. Operation
The thermocouples supply signals that are in direct proportion to the temperature of the exhaust gases. Thermocouples are made with two wires of different metals, joined at one end to form a junction. As temperature changes, the two dissimilar metals begin to deform, causing a change in resistance.
Two separate electrical signals are transmitted from each probe assembly. The harness and junction box electrically average the signals from each probe. The junction box sends two electrically independent signals to the EEC. Each signal is an average of the signals from all four probes.

** ON A/C NOT FOR ALL

3. Indication

Upper ECAM Display Unit - EGT Indication ** ON A/C NOT FOR ALL

The EGT indication appears on the upper ECAM display unit.
The ECAM provides the EGT indication:

In analog form with a pointer which deflects in front of a dial,
In digital form, in the lower section of the dial.

The indication is normally green.
When : 610 deg.C < EGT < 650 deg.C

The numerical indication remains green and the pointer pulses amber (EIS1)
The numerical indication becomes amber and the pointer becomes amber (EIS2)
The MASTER CAUT light comes on accompanied by the single chime
The following message appears on the ECAM: ENG 1(2) EGT OVER LIMIT.

When : EGT >= 650 deg.C

The numerical indication becomes red and the pointer pulses red (EIS1)
The numerical indication becomes red and the pointer becomes red (EIS2)
The MASTER CAUT light comes on accompanied by the single chime
The following message appears on the ECAM: ENG 1(2) EGT OVER LIMIT
The maximum value reached is memorized
A small red line remains positioned on the analog scale, at that value (max pointer).

[Rev.10 from 2021] 2026.04.01 03:18:09 UTC