Definition
Successive pairs of rotating and stationary blade rows inside an axial flow compressor, where each pair (one rotor row plus one stator row) progressively increases the pressure of air moving straight through the engine along its long axis. Each rotor-and-stator pair is counted as one stage, and a typical turbine engine compressor has many stages arranged in series.
Plain English
The repeating sets of spinning and fixed blades inside a jet engine's compressor. Each set squeezes the air a little more, and the air flows in a straight line along the length of the engine.
Context Anchor
Seen when studying turbine engine layout, especially split-shaft or free turbine engines, where the compressor section prepares air for burning before power is produced.
Derivation
Axial comes from Latin axis, meaning a straight line through the centre. Air flows along the engine's centre line, rather than being thrown outward as in a centrifugal compressor. Stage simply means one step in a series, so each rotor-stator pair is one step in raising the pressure.
Why Pilots Care
Knowing how multiple stages achieve high overall compression helps pilots understand engine thrust, fuel efficiency, and temperature limits during high-power operation.
Analogy
Think of several people in a line passing and squeezing a soft bag of air a little more at each person. One person would not do much, but many steps in a row can build pressure effectively.
Intuition Check
Do not read stage as a phase of flight or a general time period here. In this engine context, a stage is one physical compression step made by a row of moving blades and a row of air-directing vanes.
Example Sentence 1
The compressor section of this turboprop has fourteen axial flow compressor stages, each adding a small increase in pressure before the air reaches the combustion chamber.
Example Sentence 2
Mechanics check the condition of each axial flow compressor stage during borescope inspections to ensure efficient compression.