Helicopter Crash in Goshen, Indiana Due to Ground Resonance

[mattpilot]

How did Ground Resonance get its name??
I think I understand the mechanics of it but can't relate the name to the action.

Because you have to be in contact with the ground for it to happen. A corrective action for ground resonance is going into a hover.

Think of it as 4 points on the skids. The front left, front right, rear left, and rear right. The helicopter "bounces" around on those 4 points (due to unequal loading), thus shaking the helicopter pretty badly. To demonstrate, take an object, or your hand, and place it on the desk. Now think of it as a helo with the 4 points mentioned above. Only let 2 points touch the ground at the same time and "move" (wobble) the object (or hand) clockwise (or CCW) over the same spot.