I spoke briefly to a sky-diving instructor mate of mine this morning. He mentioned devices called AAD's . Automatic Activation Devices (I think that was what he said). Basically an unconscious sky-diver in free fall passes a threshold altitude without popping his canopy and the AAD pops the reserve automatically. He has seen the video and suggests that the rate of descent would trigger these on the packs of the occupants. This might explain what looks like a candled canopy and the eyewitness reports of the skydivers attempting to get out of the aircraft. I don't know enough about these bits of kit but assume that they can be de-activated or the pilot ensures a reduced decent rate close to the the trigger altitudes to prevent them going off unintentionally when returning to land with pax still on board. In this tragic accident, I doubt anyone on board had chance to deactivate them if that is the case.
Anyone know any more about parachuting safety gadgets?