nigelh - this wasn't jackstall on the ground, but a hardover, which nobody has yet really come up with an explanation for, as far as I am aware, despite taking a machine into the deepest Arctic to see if cold was affecting the servos. Transport Canada banned all hydraulics-off training for a while, which upset all the type conversions, since it's on the syllabus!
My friend was sitting there at the run up and the cyclic just motored over to the left and he couldn't pull it back, which is why there is now an extra hydraulics off check at low RPM before you wind the machine up. I believe the Canadian Helicopters problem was similar.
I only mentioned it in my previous post because it is a problem with those machines that is hydraulics related and some people might not have heard about it.
Phil