That is the T12 sensor inside the engine inlet cowl that is protrude out and its purpose is to send engine inlet temperature to the FADEC for fuel calculations and control.
The T stands for temperature and 12 represents the station number of the engine in which the sensor is located.
That’s reason it called T12 sensor.
HOW T12 WORKS?
T12 sensor consists of two platinum sensing elements that receive a constant voltage from the EEC. In the elements, the current temperature resistance is proportional to the air temperature, where after the signal is send back to the EEC. The EEC now measures the difference between the output voltage and input voltage, which in turn is converted into a Fan Inlet Temperature.
The sensing element is a thermo resistive sensor that changes in resistance according to temperature. The forward slot is designed to help deflect any FOD that may damage the sensing element and also help remove/deflect water so that the sensing element receives a better temperature reading. The aft slot is where the sensing element is located and where the air exits.
FUNCTION OF T12 SENSON
The actual function of this sensor is to supply Total Air Temperature data in the Fan Inlet to the EEC which uses this TAT data for
- Fuel requirement (Thrust) calculations
- Positioning the Variable Bleed Valves
- Positioning the Variable Stator Vanes
- Low Pressure Turbine Active Clearance Control
After five minutes in the air the EEC compares four TAT signals:
- T12 from the active EEC channel
- T12 from the standby EEC channel
- Total air temperature from ADIRU 1
- Total air temperature from ADIRU 2
If all four signals are valid and in limits, the total air temperature from the ADIRU’s are used for the previous described operating functions. The EEC uses the ADIRU temperature before it uses the engine T12 sensor temperature so that both engines use the same value for TAT when possible. If both ADIRU temperatures are not valid, the EEC uses the T12 values for TAT input.