I know many of you enjoy discussing resonance. Check this out:
Ground resonance as in “a resonance that took place while the chopper was grounded”? I’d agree with that. But the resonance was not caused by the ground (i.e. an earthquake). My guess would be mechanical failure: a bearing that cracked or fell off in the rotor assembly, or maybe something seized up due to lack of lubrication.
No, it’s real. Lots of videos of the phenomenon on youtube.
The asymmetric force from the landing gear moves the rotor mast sideways, and the rotor blades move so the rotor center of mass is no longer at the mast. Then the other skid imparts the same effect in a positive feedback loop until everything breaks. Solution: get off the ground before everything breaks.
http://www.youtube.com/watch?v=D2tHA7KmRME is an impressive example.
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