Definition
The temperature of the ambient air surrounding the aircraft, measured by a temperature probe and displayed in the cockpit. OAT is used in performance calculations such as density altitude, true airspeed, and engine power output.
Plain English
Context Anchor
Seen in weather reports, cockpit temperature displays, performance charts, and density altitude calculations.
Derivation
The name describes itself: the temperature of the air outside the aircraft. The point of the word 'outside' is to distinguish it from cabin temperature or engine temperature — it specifically means the free, undisturbed air the aircraft is flying through.
Why Pilots Care
OAT readings determine density altitude, which affects takeoff distance, climb performance, and engine power output.
Grounding Statement
If the ramp, runway, and airplane feel hot in the afternoon sun, the OAT is one of the key numbers that tells you how that heat will affect takeoff and climb.
Intuition Check
OAT does not mean the temperature inside the cockpit. It means the temperature of the air outside the aircraft, used for performance planning.
Example Sentence 1
Before takeoff at the mountain airport, the pilot checked the OAT at 28°C and recalculated density altitude before committing to the runway.
Example Sentence 2
A higher-than-standard OAT reduced air density and lengthened the required takeoff roll.