The video of the Chinook experiencing ground resonance was taken of a ground run test of the aircraft at the Aberdeen Proving Grounds. The aircraft was there to be shot at by various weapons to determine what resistance it had to various size rounds and when hit in various sensitive places.
Unfortunately, the aircraft was chained tightly to the hardstand and during the remote run test the aircraft was unable to move naturally and encountered ground resonance which led to the aircraft shucking the aft rotor, gearbox, and vertical fin area.
Chalk up another success to the Army!