Ground resonance is an imbalance in the rotation of a helicopter rotor when the blades become bunched up on one side of their rotational plane & cause an oscillation in phase with the frequency of the rocking of the helicopter on its landing gear [video: https://t.co/LheZvV36gW] pic.twitter.com/X5wrbeWDUs

— Massimo (@Rainmaker1973) September 25, 2022