Definition
The change in pitch angle of a helicopter's main rotor blades as they rotate around the rotor hub, with each blade's pitch varying once per revolution. Cyclic feathering is controlled by the pilot's cyclic stick and is what tilts the rotor disc, allowing the helicopter to move forward, backward, or sideways.
Plain English
As each rotor blade spins around, its angle keeps changing — twisting up on one side of the circle and down on the other. This uneven twisting tips the whole spinning rotor in the direction the pilot wants to go.
Context Anchor
Encountered in helicopter flight control discussions, especially when learning how the cyclic control changes the rotor disc to move the helicopter.
Derivation
Cyclic' comes from the Greek kyklos, meaning 'circle' — referring to the change happening once per rotation around the circle. 'Feathering' is the rotorcraft term for rotating a blade about its long axis to change its pitch angle, like turning a feather edge-on or flat to the wind. Together: the blade's pitch changes cyclically as it travels around the disc.
Why Pilots Care
Proper understanding ensures correct interpretation of control inputs for safe helicopter maneuvering.
Grounding Statement
As each rotor blade goes around the helicopter, its angle is adjusted at the right part of the circle so the total lift tilts in the direction needed.
Intuition Check
Do not read “cyclic” as just “repeating” in a general sense; here it means the blade pitch changes as each blade travels around the rotor circle. Do not read “feathering” as anything about feathers; here it means changing a blade’s angle to the air.
Example Sentence 1
When the pilot pushed the cyclic forward, cyclic feathering increased the blade pitch at the rear of the disc and decreased it at the front, tilting the rotor forward.
Example Sentence 2
Cyclic feathering allows the advancing blade to have a lower pitch angle than the retreating blade in forward flight.