An alpha hinge, more commonly known as a lead-lag hinge, permits a rotor blade to pivot horizontally. This movement compensates for the Coriolis effect as the blade flaps up and down during forward flight, preventing massive bending stresses on the rotor root.
Heard on the job
Check the dampers on the alpha hinge during the preflight to make sure we don't get ground resonance.
Also heard as
- lead-lag hinge
- drag hinge
Do not mix it up with
- Delta hinge: An alpha hinge allows horizontal lead-lag movement, while a delta hinge couples the flapping motion with blade pitch changes.
Related terms
Delta hinge
A mechanical joint in a rotor hub that allows blades to flap up and down.
Helicopter
A rotorcraft that generates lift and thrust from engine-driven overhead rotors.
Lead-lag
The horizontal back-and-forth movement of a helicopter rotor blade as it spins.
Cyclic
A helicopter control stick that changes the pitch of the main rotor blades to direct horizontal movement.