What is cyclic feathering?

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Cyclic feathering is the term used to describe the changing of the blade angle separately for individual blades through pilot input via the cyclic.

The pilot changes the angle of the stationary swashplate with movements of the cyclic.  The rotating swashplate imparts this change by moving the attached pitch links up and down as the rotor system turns.  The movement of the pitch links up or down, increases or decreases the angle of an individual blade.  If there is any angle to the swashplate, the blade angles will be changing as the rotor system turns.  However, the total rotor thrust will remain the same.  When one blade angle increases, another decreases.  Although the total rotor thrust remains the same, cyclic feathering creates differential lift across the rotor disc.  The pilot uses this differential lift to control the helicopter’s attitude.  The combination of cyclic feathering and blade flapping compensate for the dissymmetry of lift across the rotor disc due to wind or airspeed.

Reference(s):

FAA-H-8083-21A – Helicopter Flying Handbook pg. 2-12
Principles of Helicopter Flight, 2nd Edition, pg. 89
FM 3-04.203-2007 Fundamentals of Flight pg. 1-41

Other Helicopter Aerodynamic Principles

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