Definition
A single section of a turbine engine compressor in which an impeller spins to fling air outward by centrifugal force, then directs it through a diffuser that slows the airflow and raises its pressure before it enters the next stage or the combustion chamber. One stage consists of one impeller plus its associated diffuser.
Plain English
A spinning disc with vanes throws air outward at high speed, and a surrounding ring slows that air down so its pressure rises. That single throw-and-slow step is one stage. Engines may have one or two of these stages stacked together.
Context Anchor
Seen in turbine-engine descriptions, especially when studying split-shaft or free-turbine engines used in some turboprop airplanes.
Derivation
Centrifugal comes from Latin centrum (center) and fugere (to flee), so 'fleeing the center' — which is exactly what the air does as the impeller spins. Stage simply means one step in a multi-step process; each stage adds another increment of pressure.
Why Pilots Care
Centrifugal compressor designs are common in smaller turbine engines because they are rugged and tolerate damage and contamination better than axial designs, but they produce less pressure rise per stage, which is why these engines often sit in the lower thrust ranges.
Analogy
Think of a spinning lawn sprinkler: water enters at the center and is thrown outward by the spinning arms. A centrifugal compressor does the same thing with air, then funnels that fast-moving air into a smaller space to pressurize it.
Intuition Check
Do not read “stage” as a phase of flight or a step in a checklist. Here, a stage is one working section of the engine that performs one part of the compression process.
Example Sentence 1
The PT6 uses a centrifugal compressor stage at the back of its compressor section to deliver high-pressure air to the combustion chamber.
Example Sentence 2
During a power check the pilot confirms that each centrifugal compressor stage is producing the expected pressure rise across the engine.