his can happen on any multi-blade articulated rotor helicopter but is most likely to occur on 3 blade machines. The blades are free to lead and lag to accomodate the dynamic forces as they go around (there are dampers to restrict this), but on the ground with the rotor unloaded they should normally position themselves equidistant from each other to keep the CG of the rotor on its axis. A sudden jarring action on the ground because of a deflated shock strut can make one of the blades move out of position, shifting the CG of the rotor assembly creating a self-magnifying out of balance condition so the machine literally flings itself to death. Watch the video carefully and you can actually see one of the blades getting closer and closer to its neighbour. All three blade machines have, besides lead/lag dampers for the blades, shock absorbers for the landing gear. It doesn't affect two blade semi rigid rotors like the teetering Bell system. Doesn't seem to affect 4 and 5 blade systems that much either, since the Hughes 500 4 and 5 blade helicopters have rigid skid gear. Any 3 blade light helicopter however, like a Hughes 300, an Enstrom or a Brantley, will have shock struts for it's skid gear to fend off ground resonance. If ground resonance starts the only way to save the machine is to lift into a hover. 2 blade Bell setups are free of this problem, but suffer from a different phenomemon called "mast bumping" which if encountered in flight is fatal (you have to push over to zero G for it to happen). A number of Hueys were lost in the 60s doing "nap of the earth" flight training before it was understood.