Definition
An enclosed space or housing in which air is held at a pressure higher than the surrounding atmosphere, allowing it to be distributed evenly to one or more outlets. In aircraft engines, a plenum chamber typically receives air from an intake or supercharger and feeds it smoothly to the cylinders or to cooling passages.
Plain English
A sealed box or chamber that holds pressurised air so it can be delivered evenly to where it is needed, instead of arriving in uneven gusts.
Context Anchor
Seen in aircraft engine cooling and intake-air discussions, especially around cowling, seals, and air distribution inside the engine compartment.
Derivation
From the Latin plenum, meaning 'full' or 'filled.' The chamber is called a plenum because it is kept full of air at higher-than-ambient pressure, ready to flow out wherever it is needed.
Why Pilots Care
Ensures even airflow to all cylinders, avoiding rough running or power loss from uneven distribution.
Analogy
Think of it like a small waiting room for air: air enters, pressure evens out, and then the air leaves through the intended openings.
Intuition Check
A plenum chamber is not a combustion chamber where fuel burns. In this term, chamber means an enclosed air space used to collect and distribute air.
Example Sentence 1
Air from the supercharger enters the plenum chamber before being distributed to each cylinder.
Example Sentence 2
Pressurized air from the turbocharger filled the plenum chamber before flowing evenly to each intake port.