Definition
The temperature of the air entering an aircraft engine's induction system, measured at or near the inlet. In turbine engines it is monitored directly by a sensor and displayed on the instrument panel; in piston engines it is relevant when assessing the risk of induction icing, because air entering the inlet can cool further as it passes through the system.
Plain English
How warm or cold the air is as it enters the engine. It matters because cold, moist air at the inlet can form ice that blocks airflow into the engine.
Context Anchor
Seen in discussions of induction icing, especially when judging whether ice could form in the engine air intake during cold, damp, or cloudy conditions.
Derivation
“Inlet” comes from the idea of letting something in. In aviation, an engine inlet is the opening or path where air is let into the engine, so engine inlet temperature means the temperature of that incoming air at the engine.
Why Pilots Care
A change in this temperature signals conditions where ice can form inside the induction system and reduce engine power.
Grounding Statement
On a damp day, the air going into the engine can be cold enough to support ice formation even though the air outside the airplane does not feel dangerously cold.
Intuition Check
Do not assume engine inlet temperature is the same as the outside air temperature. It means the temperature of the air where the engine actually takes it in.
Example Sentence 1
Although the outside air temperature was +5 °C, the pilot applied carburetor heat because engine inlet temperature can drop several degrees lower inside the induction system.
Example Sentence 2
A sudden drop in engine inlet temperature warned the crew that ice might be forming in the induction system.