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) and OAT (Outside Air Temperature) represent the actual, undisturbed air temperature, whereas TAT (Total Air Temperature) and RAT (Ram Air Temperature) are higher due to "ram rise."
- Ram rise is a significant temperature increase (15-30°C or more at jet speeds) caused by dynamic heating as air compresses against a high-speed aircraft.
- TAT/RAT is critical for in-flight safety decisions, such as activating engine anti-ice (often below 10°C in visible moisture) and preventing fuel freezing, as it reflects the temperature the aircraft's components experience.
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