Definition
The central structural component of a propeller assembly to which the propeller blades are attached and which mounts onto the engine's propeller shaft. The hub transmits engine torque to the blades and holds them in their correct position and pitch.
Plain English
The solid centre piece of a propeller. The blades stick out from it, and it bolts onto the front of the engine so the engine can spin the whole propeller.
Context Anchor
Seen in basic propeller discussions, preflight inspection, and maintenance descriptions of how the propeller is mounted and how the blades are held.
Derivation
‘Hub’ comes from an old English word for the centre of a wheel — the solid middle part that the spokes attach to. A propeller hub does the same job: it’s the centre that the blades (the ‘spokes’) come out from.
Why Pilots Care
The hub must withstand extreme centrifugal and torsional forces; failure can lead to loss of the propeller.
Analogy
Think of a ceiling fan. The motor housing in the middle that the blades bolt into is the hub. The propeller hub does the same thing, just bolted to an engine instead of a ceiling.
Grounding Statement
It is the physical center of rotation for the entire propeller.
Intuition Check
Do not think of the central hub as just the visual middle of the propeller. In this context, it is a structural part that attaches the propeller to the engine and holds the blades securely.
Example Sentence 1
During preflight, the pilot checked the central hub for any signs of cracks or oil seepage before moving on to inspect the blades.
Example Sentence 2
During preflight, check the central hub for cracks that could compromise the entire propeller under rotation.