The temperature is an important parameter to be measured in an aircraft as it influences the altitude, speed, performance, etc. The Outside Air Temperature (OAT), also called Static Air Temperature (SAT), is simply the temperature you will find at a given altitude without any motion or other factors impacting the temperature. The Total Air Temperature (TAT) is the OAT plus the kinetic heating (ram rise) due to compressibility resulting from the aircraft’s motion through the air. Therefore, the TAT can only be higher or equal to the SAT.
Relationship between the TAT and SAT using the Mach number:

• TAT = SAT (1 + 0.2M²)
• SAT = TAT ÷ (1 + K x 0.2 x M²)

Relationship between the TAT and SAT using the TAS:

• TAT = SAT + (TAS ÷ 100)²
• SAT = TAT – K (TAS ÷ 100)²

Where K is the recovery factor (the percentage of the measured ram rise). The recovery factor (K) represents the percentage of the kinetic energy of the relative airflow that the temperature probe recovers in reducing the velocity of the airstream. Therefore, for a recovery factor of 0.85, the sensing element will measure the ambient air temperature (SAT) plus 85% of the ram rise.