So to resume:
1- The 412 has the possibility of ground resonance as any other helo with lead-lag movement in the blades.In the first post I was looking for a previous incident without luck.
2- The replies derived to the 412 well known Ground Bouncing capability
3- Nick:
2) It takes something mis-adjusted or mis-maintained to get it, because all helos that have lag hinges have systems to quell it. Manufacturers have to prove they are immune to ground resonance to themselves and to the FAA. Those systems (oleos, dampers on skids, dampers on blades, elastomers on all the previous) do not cause ground resonance, they prevent it.
This is something... I was missing, I was thinking that a blade with a bad lead-lag damper will develop the ground resonance, but not, it's there just to preven it, Thanks.
Best regards.
Aser
