Sad to watch, given the reported experience of the driver. But verrrrrry eentereshting!
The Rotorway's rotor(way!) turns the same direction as a Squirrel, opposite that of a Bell. So the nose will tend to want to turn to the left, requiring a bootful of right-pedal to keep it straight. In watching the video, you can hear the main rotor rpm clearly decreasing - and with it, the T/R rpm. The pilot appears to be focusing on...something else...and *probably* doesn't realize that he's just about out of right pedal.* The right skid touches and then the yaw rate begins. From our vantage point, it's easy to see what's coming. And it does.
Classic case of DR.
Man, I can so put myself in his shoes. "I know how to hover a friggin' helicopter, I can hover this thing."I can hear myself saying it. And Fate laughs and says, "Oh yeah? I'm gonna re-teach you something you may have forgotten about low tail rotor authority and decreasing t/r rpm, and how easy helicopters are to crash."
Ouch.
*Or, maybe he's just not aggressive enough with the right pedal. Just before it rolls over, you can see a little twitch of the nose to the right. So it mad me wonder: Did he have some pedal available that he wasn't using? In any case, he seems very rough on the cyclic. Or was it just a very gusty day?