In this lesson, let us understand about the Total Air Temperature Probe which is used in a Remote Indicating Thermometer. In our earlier post we had learnt about the Remote Indicating Thermometers.
DESIGN OF TAT PROBE
Total Air Temperature Probe (TAT)is the probe fixed outside the aircraft to detect the Outside Air Temperature. The TAT probe is located in the front fuselage to avoid boundary layer effect. The probe uses platinum sensors due to high conductivity and rapid response of platinum to temperature changes. The probe has an air intake made of Nickel-Plated Beryllium Copper due to its strength and good thermal conductivity.
Air is designed to reach the probe at right angle to the airflow in order to remove solid particles, water drops and high pressure air. A heating element is provided to avoid icing which produces an error. This error is less than one degree centigrade which can be offset during calibration.
ASPIRATED TAT PROBE
In a stationary aircraft on ground, stagnant air accumulates in the housing which could be both pre-heated as well as pre-cooled. This prevents the probe in detection of accurate temperature on ground. Therefore TAT probes are equipped with an aspirator to remove the stagnant air by circulating some air from engine bleed valves. Aspirated TAT Probe therefore helps in detecting correct temperature information surrounding an aircraft on ground.
In this lesson, we have understood about the construction of TAT Probe which detects the Total Air Temperature, In our next lessson, let us focus on the Errors in Temperature Measurement and the ways to overcome these errors.