Spotted over at Watts Up With That, the following video shows what happens when the brake fails on a large wind turbine during a gale :
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Who said these things were useless? I would class that as quality entertainment with additional marks for the gunshot like sound when the blades finally slap the tower column.

Note also the van parked at the base of the turbine which nearly takes a direct hit as the alternator/gearbox unit smashes into the ground. Not the wisest choice of parking spot when you are dealing with a few tons of unruly machinery.