Definition
The central structural component of a helicopter's main or tail rotor assembly to which the rotor blades are attached and through which engine power is transmitted to drive the blades.
Plain English
The strong central piece on top of a helicopter that holds the rotor blades and spins them around.
Context Anchor
Seen in discussions of helicopter and rotorcraft structure, especially when comparing metal parts with composite parts.
Derivation
Rotor comes from the Latin 'rotare,' meaning to turn or rotate. A hub is the central part of a wheel that the spokes attach to. So a rotor hub is literally the spinning center where the blades, like spokes, are mounted.
Why Pilots Care
Composite rotor hubs are lighter and more resistant to fatigue than traditional metal designs, improving performance and reducing maintenance needs.
Analogy
A rotor hub is like the center fitting on a ceiling fan: the blades attach to it, and it is the part that lets the whole blade set turn as one unit. An aircraft rotor hub is much stronger and also carries control movement, but the center-piece idea is similar.
Intuition Check
Do not read rotor hubs as the whole spinning rotor. The rotor hubs are the center assemblies that the blades attach to.
Example Sentence 1
Composite materials are now commonly used in rotor hubs because they are lighter and more durable than metal.
Example Sentence 2
Mechanics checked the rotor hubs for cracks after the long cross-country flight.