I'd have thought the pilot would never risk hitting the line by descending below the top of the tower but instead wait above it for riggers to climb the tower to detach the line. I guess it comes down to what was said and agreed upon in preflight. However the cause is very obvious, the rigger should not have done what he did. Looks like two minds made mistakes of judgement for this to happen, pilot and rigger both made bad calls.
My experience of flying is that regardless of what type of aircraft, from radio controlled hobby gadgets to machines carrying people, one can not be too meticulous about procedures and routines. Because a accident or fatality is just one or two steps away. Good routines are crucial to safe air ops and I think all professionals know that (at least they should! some ppl make you wonder though), on the hobby side it's so-and-so with that and people learn by experience from crashing instead.
