"I wonder why he didn't step on the clutch, unless it was HST, even so seems like he could have disengaged. "
I've read several safety articles about rear roll overs. The time noted is between 1 and 1½ seconds. Per those articles, you've got to react within ¾'s of a second, otherwise the tractor has gone past the point of no return. That's about 70° to 80°. After that, the tractor has enough inertia to keep pivoting about the rear axle.
No ROPS, so probably an older tractor...
This kind of roll over has always been the kind that bothered me most (even thoughh my machine has a ROPS). ever since I read about a guy who'd left his tracor in a field over night...when he started it and engaged a forward gear, the tracor rolled over backwards..killed him. Seems his rear tires were frozen to the ground! Heck of a thing!
Well, that's what the draw bar is for...so..use it!
GerardC...that is a great picture on your response!!!!