Here is an interesting video showing a Eurocopter EC135 being used for maintenance operations on giant offshore wind turbines in the UK. Gives a good perspective on the massive size of these turbines. Around here they work on land based turbines by just opening the door at their base and climbing up a bunch of stairs. These guys in the video appear to be part mechanic, part coast guard helicopter rescue diver. Considering how often these things usually need maintenance (at least monthly I believe) this looks like it could get expensive fast and reveals a potential downside to the otherwise excellent idea of offshore turbines which I have always believed in. Enjoy the video, although I recommend muting the poorly chosen soundtrack.