As rotor blades flap up and down during forward flight to compensate for lift asymmetry, their center of gravity shifts inward and outward. To conserve angular momentum, the blades must speed up or slow down in their plane of rotation. Rotor heads use drag hinges or elastomeric bearings to allow this movement and prevent massive stress on the blade root.
The vibration on the test flight suggests we've a worn damper failing to control the lead-lag motion on the red blade.
Also heard as
- hunting
Related terms
Cyclic
A helicopter control stick that changes the pitch of the main rotor blades to direct horizontal movement.
Helicopter
A rotorcraft that generates lift and thrust from engine-driven overhead rotors.
Root
The innermost section of an aircraft wing or rotor blade where it attaches to the fuselage or hub.
Alpha hinge
A mechanical joint in a helicopter rotor hub that allows the blade to move back and forth in the plane of rotation.