Definition
A rotating disk fitted with vanes or blades that accelerates a fluid (air, fuel, or liquid) outward by centrifugal force. In aviation, impellers are most commonly found in centrifugal-flow turbine engines, turbochargers, superchargers, and engine-driven fuel and coolant pumps, where they convert mechanical rotation into increased fluid pressure and flow.
Plain English
A spinning wheel with curved blades that throws air or liquid outward, raising its pressure and pushing it through the system.
Context Anchor
Seen in aircraft engine, fuel, oil, cooling, turbocharger, supercharger, and pump discussions.
Derivation
From the Latin impellere, meaning to drive or push forward (im- 'into' + pellere 'to push'). The name fits: an impeller is the part that does the pushing, driving fluid outward as it spins.
Why Pilots Care
Impeller condition directly affects engine power output in forced-induction systems and steady fuel pressure; damage or wear reduces performance and can cause engine roughness or failure.
Analogy
An impeller is like the spinning blades in a household fan, except it is often enclosed inside a housing and may move liquid as well as air.
Intuition Check
Do not think of an impeller as just any spinning part. It specifically has blades or vanes that move air or liquid as it turns.
Example Sentence 1
As the turbocharger spooled up, its impeller compressed the intake air and restored manifold pressure at altitude.
Example Sentence 2
Fuel flow dropped after the impeller in the engine-driven pump began to erode.