Originally Posted by
What-ho Squiffy!
From the CCTV vision, at or shortly after TDP, the helicopter dipped nose down and spun to the right, and entered into a high rate of descent. It's clear what the helicopter did, but there could be a few causes,...
Maybe just my eyes on a grainy CCTV video, but it is not so clear to me that it turned right. Looks to me like it was yawing to the left before impact. Yes, we are speculating, and investigators will do their work.. Since this machine has a CCW main rotor as viewed from above, then tail thrust in hover provides a left yaw input. Most tail rotor are designed and rigged with "neutral bias" that provides some of this anti-torque, that would help in a loss of tail control (not loss of tail thrust), to enable a run-on landing. If control was lost, with drive still intact, then a reduction in main rotor collective would result in excessive "anti-torque", in this case left yaw. Too late to pull back power and collective perhaps. Such a crash would typically result in impact on the blades. In this case the top, blackened tail blade is sheared near the hub, the right one is damaged closer to the tip. Given all the information publicly received, it appears to me (my initial opinion/ speculation only) a Flight Control problem rather than a drive problem. Such issues can take time to sort out, particularly in full AFCS, where the data recorder may yield a related, but indirect, parameter of interest.