Originally Posted by
paco
And contrary to popular belief, you can get it in an AS 350
I don't know whose belief that was but a 350/355 can definitely get into ground resonance. There were a number of aircraft years ago that led to a series of close calls and several complete destructions. Can also attest, as mentioned above, that cutting throttles (change RPM) and hitting the rotorbrake will get you out of it but barely. We had no choice as the aircraft was also tied down.
The culprits back then were the forward crosstube shock absorbers and aft skid tube springs being out of spec. Throw in a weak/out of phase frequency adapter and off to the races. Aerospatiale ate a lot of shocks and springs after that episode. Still amazes me how fast it happens and where it can end up. The Lama GR was docile in comparison in my opinion. We had one 355 end up on the pad with the canopy gone, tailboom on the ground, and sheet everywhere in what seemed like mere seconds. Luckily for the pilot the transmission/head assy failed aft and landed in between the engines and he was still in his seat strapped in. Took a few minutes to pry his grip off the cyclic. He wasn't a big fan of the flying tupperware after that.