Destructive vibration that occurs with a helicopter, usually on landing. If the helicopter touches down rough and unevenly, the shock can throw a load into the lead-lag hinges of the rotor blades and cause the blades to oscillate (move back and forth) about this hinge.

If the frequency of this oscillation is the same as the resonant frequency of the fuselage, the energy will cause the helicopter to strike the ground hard with the opposite skid or wheel. This will increase the energy and cause more severe contact with the ground. If corrective action is not taken immediately, either lifting the helicopter or placing it firmly on the ground, ground resonance can destroy it.