Just worth noting that I know someone who was still at the game and has been to several and seen the helicopter take off.
apparently, it was all normal (including that first initial yaw input when it first looks controlled). You cannot make it out too well in the video, but the gear retracts and it begins a rotation - apparently as it always did.. At that point it never seems to recover.
im no expert and could be coincidence - but could that suggest a peddle / input problem. He stated that it actually didn’t sound too out of the ordinary. The strange noise people seem to be referring to from what he saw was the pitch of the blades against the air as it began to rotate seemingly uncontrollably.
just thought I’d share to maybe shed some insight from someone who has some basic understanding of aircraft / rotors rather than just a regular member of the public.
it maybe a result of the cause rather than the cause itself, but thought I’d share it with people much more knowledgeable than myself.