Here is a first hand story of this incident from the pilot (I copied off another forum). As a former Rotorway owner, sounds like this guy did pretty well in setting the helicopter down. The Rotorway has a pretty light inertia rotor system, but by the sounds of it, it was the fact that he let it rotate slightly when he landed, that the machine rolled. No cause yet to what happened here.
If people aren't allowed to cross-post the story here, i'll ask him if he'll either post it here himself, or send it to me and i'll post it for him.
as the pilot of the Rotorway that made the news I'll share what happened, and hopefully benefits can be drawn.
Before getting to anything else, my THANK YOU to my Rotorway friend Mark Johnston and his friend David that traded a day of flying gliders for helping me recover the ship. When I was about to dismantle the machine they all of the sudden showed up early in the morning in the farm field. Apart from a whack load of work, it was their ingenuity to get some tubing and a bag of hose clamps, with which we braced the broken skid that allowed us to tow the machine to where we could park the trailer. Many more THANK YOUs to all who offered help. Only this morning I saw their emails. Sorry that you didn't hear from me earlier.
Now to what happened. Took off for a circuit with my wife as passenger. On climb-out I saw that I pulled 32"MAP (turbo). The climb rate was not as good as usual, though. Levelled at 600'AGL and turned crosswind. Typically I have to roll off throttle quite bit to avoid the rpm going up. Not this time - the opposite. To keep the RPM in the green I needed to add power and the MAP went to 33.5 with 35 available. (Turbo set up a la Arthur Gemperle which worked really well - Thanks Arthur). This was unusual and I kept the circuit tight over farm land. Abeam mid field I decided to cut it short to get back to the field. When a couple of seconds later I saw the Rotor RPM leaving the green towards lower I decided to auto rotate. Touched down gently. Maybe 5 feet of sliding forward and almost at stand still a left yaw and the machine rolled to the right and the blades assumed a short life as plows. Got out, helped my wife out and BIG THANK YOU (eyes pointing upward), no injuries. The sirens of fire, ambulance, and police filled the air for a long time, as the entrance to the farm field wasn't obvious. On the phone with emergency dispatch it took a while for me to get to the main road to be able to give directions. And what nice and helpful people they were, police, fire and ambulance! Super nice! Felt really good!
As to the machine: A 1998 Exec 90, which I acquired about 5 years back, took apart and rebuilt with a lot of new parts, such as Talon landing gear and almost all of the improvements that Al B offers, plus exhaust valves from Peter Kooiman, except that I left the electric clutch. It was -and still is- my goal to contribute to improve the reliability of this machine, which I enjoyed very much flying. Al Yard, helping me out a couple of years back, witnessed that the engine could not be kept running when we had high humidity and low but above 0 C temperatures, with the original carb heat system. Carburetor ice happened for sure. That problem I solved by improved heating of the carburetor body. Looked at the water jacket issue and decided to develop aluminum liners with Nikasil coating, inserted with a slip fit and bonded to the water jackets to avoid excessive stress. The current set went into service about 18 months ago and has worked without problems for around 50 hours now. I never posted anything about this as I wanted first to have proof that this is a workable solution. The rockers of the valve train I changed out with the Pauter roller rockers, also as Arthur pioneered, simply as a precaution, not aiming at getting more power. Added an oil supply line with spray nozzles to ensure lubrication of the top rocker at each cylinder head.
Back at the hangar yesterday wanted to see weather anything obvious would show the cause. Two highly experienced flying friends and mechanics looked with me and we have not found anything. Coolant is there at fill level. Fuel and oil were there, rotor turns freely (shaft bent, of course), flywheel can be turned and valve rockers move. Belts are in tact. This was not a thorough examination, just a look for the obvious.
What can be salvaged of the airframe is questionable due to the stresses imparted. But I agree with the comments above regarding crash worthiness of the airframe, which come from much more experienced pilots than myself, but as far as technology is concerned, where I am not exactly a newbe, there is a lot of good design in the Rotorway helicopter.
It is worth to keep going to make improvements.
Greetings and thanks to all who have contributed and continue to contribute in that regard."