ground resonance
hi all.
Excuse my english. Iīm a spanish helicopter pilot, i was looking for any incident about groun resonance in 412 and find you.
In spain we have four incidents by ground resonance. well no ground resonance, i think there were greats bounces in ground, because when we try to take of whith the helicopter bounce and it separate of the ground it continue flying jumping (or bounce) and the only way to stop bounce was shutdown engines (autorrotacion).
The four helicopters were working in firefighting and all were without persons on board at 100% N/R.
I was flying two of there four (same helicopter)
The first time i complete succesfull the helicopterīs control fighting about one minute with it and maintenance donīt find something inussual. two days later in ground in a sand filed it become to bounce and this time i have to shutdown the engines in flight because it was imposible regain control.
in several flights with anothers 412 we have the same problems,with light and medium bounces and the only way to cut this situation was turnning throtles to idle and try to pass to flight gently aplly a lot of collective.
Excuse my english and thanks to all for your forum