What is total air temperature?

Total air temperature, also known as the True air temperature (TAT), is a measure of the combined effect of temperature and the compression heating caused by the forward motion of an aircraft through the air. It represents the actual temperature experienced by an aircraft and is essential for accurate flight performance calculations and aircraft systems operation.

When an aircraft moves through the air, it compresses the incoming air, increasing its density. As a result, the air gets heated due to the conversion of kinetic energy to thermal energy. The total air temperature refers to the temperature of this heated air.

Total air temperature is generally measured by a probe called a Total Air Temperature (TAT) probe, which is usually located on the aircraft's nose or wing. This probe collects the undisturbed air flow and measures the temperature accurately. It is designed to minimize the effects of airflow distortion and maintain accuracy at high speeds.

TAT is different from the ambient or static air temperature (SAT), which is the actual temperature of the surrounding air. SAT does not consider the impact of aircraft motion and compression heating. In comparison, TAT provides a more accurate representation of the air temperature that affects the aircraft's performance, especially at high speeds.

Accurate measurement of TAT is crucial for various aircraft systems and calculations. It is essential for determining true airspeed (TAS), which is the actual speed of an aircraft through the air, independent of altitude and atmospheric conditions. TAS is used for navigation, flight planning, and aircraft performance analysis.

Additionally, TAT is critical for the operation and control of anti-ice systems on aircraft. As TAT accounts for the heating effect of aircraft motion, it helps to ensure accurate activation and regulation of anti-icing systems, preventing ice formation on critical surfaces like wings and sensors.

In summary, total air temperature is the temperature of the air experienced by an aircraft, considering both the ambient temperature and the compressional heating due to aircraft motion. It plays a vital role in accurate flight performance calculations, true airspeed determination, and proper operation of anti-icing systems.