1. SAT — Static air temperature (sometimes called true air temperature) is the temperature of undisturbed air; that is, the temperature you would read if you could suspend a thermometer out in the air without having the effects (temperature rise) of an airplane moving through the air nearby. In jets, SAT (aka OAT) is determined by applying the appropriate correction factor to the total air temperature (TAT), or ram air temperature (RAT), probe data. Most large jet aircraft have this function incorporated into the air-data computer. SAT is the actual air temperature, also referred to as true outside temperature or ambient temperature.
Air Temperature Explained
Key Takeaways:
- SAT (Static Air Temperature) or OAT (Outside Air Temperature) is the true, undisturbed ambient air temperature, whereas TAT (Total Air Temperature) or RAT (Ram Air Temperature) is the temperature sensed by the aircraft, which includes a "ram rise."
- Ram rise is a significant temperature increase caused by high-speed flight (e.g., up to 30°C at Mach 0.8), making TAT/RAT considerably higher than SAT/OAT.
- TAT/RAT is crucial for operational decisions like activating engine anti-ice and preventing fuel freezing, as it reflects the actual temperature affecting the aircraft's surfaces and systems.
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