The same clip was discussed over on Mike Holt's board. I did some looking, and calculated that the _capactive_ current between the lines and the helicopter would be on the order of 50-60mA at 500KV and 60Hz. This would be continuous current, always flowing between the chopper and the line; you would see the arc whenever the two are not bonded but close enough for 500KV to arc over. (This by calculating the capacitance of a sphere somewhere between the size of the helicopter body and the rotor disk.)
On top of this you would have the 'static' current developed by the blades moving through the air. This would only be 1-2mA in the worst possible static charging conditions. (This from DOD studies of discharge devices to eliminate the static build up.)
Finally, I guess that there would be a certain amount of corona discharge from the sharp bits of the helicopter. I've no idea how to calculate the magnitude of this current, but it would again be continuous whenever the helicopter is electrically connected to the line, so you would see it both at approach and departure.
-Jon
