Definition
An engine-driven air compressor that uses one impeller to raise the pressure of the air entering the cylinders, allowing the engine to maintain power at altitudes where the surrounding air is too thin to produce rated output.
Plain English
A one-stage air pump, driven by the engine, that squeezes thin high-altitude air before it reaches the cylinders so the engine can keep making normal power.
Context Anchor
Seen in aircraft engine discussions about superchargers, manifold pressure, and how piston engines keep power at higher altitudes.
Derivation
‘Single-stage’ means the air passes through one compression step (one impeller) before entering the engine. A two-stage supercharger would compress the air, then compress it again. ‘Single-stage’ tells you how many times the air gets squeezed on its way in.
Why Pilots Care
Knowing the difference helps pilots anticipate power available at altitude and recognize the simpler maintenance and operating limits of single-stage systems versus multi-stage designs.
Grounding Statement
As the airplane climbs, the single-stage supercharger helps pack more air into the engine than the thin outside air would provide by itself.
Intuition Check
Do not read “stage” as a platform or phase of flight. Here, a stage is one compression step inside the supercharger.
Example Sentence 1
The engine in this trainer has a single-stage supercharger, so it holds rated power up to its critical altitude and then begins to lose performance.
Example Sentence 2
In the preflight checklist the mechanic verified that the single-stage supercharger impeller turned freely with the engine.