Definition
A small sensor mounted on the exterior of the aircraft that measures the temperature of the ambient air surrounding the airplane and sends that reading to the cockpit display or temperature gauge.
Plain English
A little sensor sticking out of the aircraft that tells the pilot how cold or warm the air outside is right now.
Context Anchor
Seen on aircraft with electronic flight displays, where outside air temperature may be used by the airspeed display and other instrument calculations.
Derivation
Probe comes from an older word meaning “to test.” That helps here because the device is not just a pointer or display; it is the part that samples or tests the outside air for temperature.
Why Pilots Care
Accurate readings are required for correct true airspeed computation and to identify conditions where icing may occur.
Intuition Check
Do not read “outside air temperature” as the temperature in the cockpit or the forecast temperature on the ground. It means the air temperature being sensed outside the aircraft where the probe is mounted.
Example Sentence 1
Before descending into the cloud layer, the pilot checked the outside air temperature probe reading and confirmed conditions were warm enough to avoid structural icing.
Example Sentence 2
With the outside air temperature probe showing minus ten degrees Celsius, the crew turned on the pitot heat.