Definition
A turbine engine compressor that combines two compressor types in series: one or more axial-flow stages followed by a centrifugal-flow stage. Air first passes through the axial section, where it is compressed by alternating rows of rotating and stationary blades that move air parallel to the engine's long axis. It then enters the centrifugal stage, where a spinning impeller throws the air outward, raising its pressure further before it enters the combustion section.
Plain English
A compressor that uses two different methods one after the other. First it squeezes the air by pushing it straight through spinning blades, then it squeezes it again by flinging it outward with a spinning disc. The combination gives good airflow and a strong final pressure rise in a compact package.
Context Anchor
Seen in turbine engine descriptions, especially for small turbine engines and auxiliary power units.
Derivation
Axial means 'along the axis,' from the Latin axis (a central line). Centrifugal comes from the Latin centrum (center) and fugere (to flee), meaning 'fleeing the center.' The name describes exactly what the air does: first it travels along the engine's axis through the axial stages, then it is flung outward away from the center in the centrifugal stage.
Why Pilots Care
This compressor type is common in many training and light transport aircraft engines; knowing its layout helps pilots understand engine response, surge margins, and maintenance requirements that affect flight safety and reliability.
Grounding Statement
Picture air entering the front of a small turbine engine, being pushed straight back, then being spun outward hard before it reaches the burner area.
Intuition Check
Do not read this as two unrelated parts. An axial-centrifugal compressor is one compressor arrangement that combines straight-back airflow with outward-spinning airflow.
Example Sentence 1
The PT6 turboprop uses an axial-centrifugal compressor, with three axial stages feeding a single centrifugal stage.
Example Sentence 2
During climb the axial-centrifugal compressor maintained steady pressure rise even as outside air density dropped.