I have had a bit of time to ponder on the accident, done a lot of research, and have also read the insightful posts on this thread. I would like to include some more details on the simulated engine out landing that ended in the hard landing. I believe there may be some useful insight.
I sometimes make very tight turns where I can feel some strong G effect, and I roll out and perform the landing without any problem. The engine is at idle. As brought out by me earlier, there were wind gusts that day. But maybe that had nothing to do with the accident. I did a tight turn during the last practice, but also was not in a hover prior to the rapid sink. I was flaring as I normally do.
There is a thread that was discussed in 2013 regarding Drag Over.
Birdy explains it thus:
"As Leigh n Doug says, its useing the stored excess rotor inertia to hover momentarily.
Obviously, if your useing it 5' off unlandable ground, or over a tree, you need to know just how much hangtime you have built up, and
snap the throttle open before the sink starts.
Light, tip weighted blades are excellant for the job, as is a reliable 912.
The bad bit [ anythn i dont understand is bad] is a short duration phase between the air over [ helicoptering] and air under [
autorotation] phases.
I cant realy explain it, mainly coz iv never been in a situation where iv had the grey cells to spare to think bout it at the time, but dureing
the transition, the stick is non responcive.All iv ever dun dureing this phase is power out. Iv never tryed to command the rotor to do anythn but backstick.
Even so, with the rotors leaning backwards, the machine "wobbles".
Its like the gyroscopic resistance is be'n transfered to the machine, instead of be'n taken up by the air.
CB could explain more wots go'n on, but to be honest, i dont, coz iv never 'studied' it."
Doug Riley explains it best. I quote from his post:
"A gyro can work like a helicopter for short periods of time. If RRPM is increased above cruising level, the stored energy in the rotor
substitutes temporarily for an engine drive. This means that the gyro can stand still in the air, drawing air down through its rotor in a
way that is inconsistent with autorotation.
But this can't last long. As RRPM decays, the gyro will settle. Specifically, it will settle into its own downwash. That is, the rotor settles
into (1) disturbed air that (2) is already travelling downward.
Just like a helicopter in a similar situation, the gyro will descend vertically very fast and can get buffeted on the way down by the
turbulent air of its own downwash.
If you have altitude, you'll recover from this predicament by nosing down and flying out of it.
If you are at, say, 20 feet, though, things will not go well for you. You will pancake in at greater than normal vertical-descent speed.
Splat."
Lots of food for thought here. My take away from the above is that sometimes in trying to perform the force landing, there is a possibility that something as described above can take place if the rotor speeds up.
Perhaps some of the more experienced folks can elucidate on this phenomenon.