Definition
The outside air temperature as read directly from the aircraft's temperature gauge, before any correction is applied for the heating effect of compressibility and friction caused by the aircraft moving through the air. At cruise speeds, this reading is warmer than the actual static air temperature surrounding the aircraft, and it must be corrected to obtain true outside air temperature for performance calculations such as true airspeed and density altitude.
Plain English
The air temperature shown on the cockpit gauge. It reads slightly warm because air rushing against the temperature probe heats up from friction and compression, so the number on the gauge is not exactly the real temperature outside.
Context Anchor
Seen in performance and cruise power charts, where the pilot uses the displayed outside air temperature to choose or check a power setting.
Derivation
"Indicated" comes from Latin indicare, meaning "to point out or show" — it refers to what an instrument shows the pilot, which may differ from the true value. The full term simply names what the OAT gauge points to, before correction.
Why Pilots Care
Used to select correct power settings and assess expected aircraft performance.
Intuition Check
Do not assume indicated means exact or corrected. Here, indicated means the value displayed on the aircraft’s outside-temperature instrument.
Example Sentence 1
At cruise altitude, the pilot read an IOAT of +5°C from the gauge and entered that value into the cruise power chart to find the predicted true airspeed.
Example Sentence 2
With a lower IOAT the engine produced more power at the same manifold pressure setting.