Pendular action is simple if you just think of a pendulum. The helicopter swinging from the rotor head is the same thing. To get the swinging under control in a hover, students just need to learn to make very small corrections. It is very common to over correct the helicopter drifting in the hover and this over correcting gets the helicopter swinging like a pendulum from the rotor head.
Pendular Action.... what more can we say?
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