Definition
The actual temperature of the undisturbed air surrounding an aircraft in flight, with the heating effect caused by the aircraft's speed through the air mathematically removed.
Plain English
The real temperature of the air outside the aircraft, after correcting for the warming that happens because the aircraft is pushing through the air at high speed.
Context Anchor
Seen in aircraft performance calculations, weather-related cockpit indications, and air data system discussions.
Derivation
True here means corrected to reflect reality, as opposed to the raw indicated reading. At higher speeds, friction and compression of air against the temperature probe cause the sensed temperature to read warmer than the air actually is. Removing that error gives the true value.
Why Pilots Care
Correct true air temperature values are required for accurate performance calculations and safe flight planning.
Analogy
It is like wanting the actual outdoor temperature, not the warmer reading you might get from a thermometer sitting in direct sun. The correction removes the effect that is not part of the real air temperature.
Grounding Statement
As an aircraft moves faster, its temperature probe can be warmed by the airflow, so the sensed temperature may need correction to show the real outside air temperature.
Intuition Check
True does not just mean “probably correct” here. It means the actual outside-air temperature after correcting for heating caused by the aircraft’s motion.
Example Sentence 1
At cruise, the pilot used true air temperature, not the indicated reading, to compute true airspeed.
Example Sentence 2
At cruise the true air temperature was lower than the indicated value because ram rise had warmed the probe.