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Topic: Suddenly occurring ground resonance was probably the cause of the accident committed by the experienced test pilot. The topic of ground resonance has already been discussed by the ProPilots training software via 3D animated educational film, to provide pilots with the information for a right and intuitive reaction to an emergency situation like this.
Are there any other measures for ground resonance for the pilot to prevent a flight accident in the future? Thankfully the accident only resulted in a huge material damage.
The answer is actually very simple: Lift off and convert!
The trigger for ground resonance is the ground itself. Unfiltered oscillation (amplitudes) on the ground of the turning main rotor can be translated and extremely enhanced to the landing gear (chassis). As a consequence the helicopter builds up, dances on the ground and can be dismantled in a couple of seconds or can turn completely.
Therefore the pilot needs to react immediately: A sudden lift off is possible within seconds through pulling the collective pitch lever. With turning off the engines it is differently: Even if you turn off the engines and hit the brakes of the main rotor you loose valuable seconds, which is enough for ground resonance to occur.
