Originally Posted by
Mitchaa
Unburnt fuel, oil or water.
The change in direction of the rising puff of smoke from the engine whilst it was being started suggests to me the initial climb was with a tail wind....granted, maybe the wind was swirling inside the stadium but that smoke did catch a bit of tail wind...I don't think it was sucked in to some inflow into the rotor disc as the rotor had only just started to turn.
I'm still suspicious about that smoke...perhaps caused by oil momentarily getting past a labyrinth seal and burning in the hot engine? I'm not familiar with that particular engine, but it does look unusual.