Definition
The openings in the front of an airplane's engine cowling that allow ram air to enter and flow around the engine cylinders to carry away heat produced during combustion.
Plain English
The air vents at the front of the engine cover that let outside air rush in and cool the engine while it's running.
Context Anchor
Seen during an outside preflight inspection, especially on piston-engine airplanes with openings at the front of the cowling.
Derivation
Cylinder comes from an old Greek word for a roller-shaped object. In an engine, the cylinder is the round chamber where a piston moves. Inlet means a way in, so the term points to the openings that let cooling air in around those round engine parts.
Why Pilots Care
Blocked or inadequate inlets can cause cylinder overheating, leading to detonation, power loss, or engine damage.
Grounding Statement
As the airplane moves forward, outside air enters these openings and helps remove heat from the engine.
Intuition Check
Do not confuse cylinder cooling inlets with the engine air intake. Cylinder cooling inlets bring in air to cool the outside of the engine cylinders, not the air the engine burns with fuel.
Example Sentence 1
During preflight, the pilot checked the cylinder cooling inlets for any debris or obstructions before starting the engine.
Example Sentence 2
In a prolonged climb the cylinder cooling inlets must supply enough air to keep head temperatures within limits.