Hi Robborider
It's 44 years since I last flew a Hiller 12E, so I don't remember its transmission system perfectly. However any hard blade strike, whether tail or main, is not good for the transmission train and seizing up is often the result. As this one crashed onto a shingle river bank, the actual cause was not investigated but as the pilot gave exact details over the radio, it was pretty obvious what happened.
Not a good procedure!