Concept 30 did the chicken dance!
I don't know for sure the collective came off, but it is my best guess. But now you have me wondering ....
The heli was flying for a while (or it seemed like a while) after the failure, and before it hit the ground. I'll try to relive how it felt in the air.
I brought it around the last turn, and added a little throttle / collective as well as up elevator to keep my altitude and attitude correct. At that moment, I heard the engine sagging horribly, and the heli twitched hard to the left (my right). I managed to snag it and bring the tail back in line, but it seemed I had lost a lot of power. I had to hammer down on the collective to keep it going, and I thought I may be doing my first unplanned auto at that moment.
It did settle back into a hover briefly, however, at around 10 - 15 ft. altitude. This is when I noticed the vibrations and the heli really looked like it was going to shake itself apart. I'm not sure what the engine was doing at this point, as I was focused TOTALLY on trying to set this thing down gently.
I got it to drop 5 feet or so while under control, but then the tail just started going round and round. The heli dove off to my left (towards the trees), and began banking towards the ground. At that point I realized I couldn't do anything with it and yelled a heads up. No one was anywhere near it, but I just wanted to make sure.
So does this sound like a collective failure? I initially thought it was an engine failure where it stuttered long enough to let the head speed drop. But this didn't explain the vibrations I was getting, nor did it make much sense as the engine had been running reliably all morning. As a matter of fact, it was still idling when I reached it afterwards. This is an OS-F 32 btw.
It's possible the link was thrown during impact, and I can't really rule that out. But something happened up there today -- something mechanical. It wasn't radio interference, and I can honestly say it wasn't dumb-thumbs (at least not today, anway).
Hopefully someone can tell me what it may have been based on my description.