The up-down motion of the rotor blade on its center hinge. Without at least a small amount of flapping, an autogyro would roll over on its side during flight due to unequal lift between the advancing and retreating rotor blades.
A type of rotor head where the two rotor blades are not connected directly through the feathering shaft (a thick wire), each blade can move somewhat independently of the other resulting in smoother control of the helicopter and the to some degree the feel of a .60 size heli. more.
the motion made by flapping up and down