Definition
The temperature of the ambient air surrounding the aircraft, measured by a probe or thermometer mounted on the airframe and displayed in the cockpit, typically in degrees Celsius or Fahrenheit.
Plain English
The temperature of the air outside the aircraft right now, shown on a gauge in the cockpit.
Context Anchor
Seen on cockpit temperature displays, airport weather reports, performance planning charts, and checks for possible icing.
Derivation
“Outside” means the air beyond the aircraft or cockpit. “Temperature” comes from older Latin-based words connected with the condition or degree of heat. In aviation, the key idea is the temperature of the air the aircraft is actually moving through.
Why Pilots Care
Used to determine density altitude, true airspeed, and the likelihood of icing.
Grounding Statement
On a hot day, the same airplane may need more runway and climb more slowly because the outside air is warmer.
Intuition Check
Do not treat outside air temperature as cabin temperature or as the temperature of a surface sitting in the sun. It means the temperature of the surrounding air itself.
Example Sentence 1
During cruise, the pilot noted an outside air temperature of -5°C and began watching for signs of carburetor ice.
Example Sentence 2
A sudden drop in outside air temperature warned of possible icing in the clouds ahead.