How ski lifts are installed: Vail's new Chair 5 (2011) [video]
Usually tying an in-flight helicopter to the ground is a huge no-no. E.g. there's a subtle sequence of steps for airlifting a casualty from a steep hillside that prevents the helicopter from ever being connected by a rope to the ground (the reasoning, AFAIK, is that the helocpter migth need to depart or move at a very short notice and the line may hinder it and injure people if it breaks).It seems that there are reasonably long period of time here when the helicopter is still connected to a tower segment when the workers are in the process of screwing bolts in. Why isn't this problematic?