I have to agree with Grainger on this one. Although not yet a rotary wing pilot I have been in and around them for some years as a skydiver. (yes I choose to jump out of them).
Earlier this year at a parachute display the RAF had bought in a Chinook as a static display. This was, of course, very popular with the public who were allowed to climb around it and ask the crew very important questions like 'Why does it have two fans?' (Answer:'we keep one as a spare in case the other breaks').
When it came time to leave the site the crowd was being held back by police officers and marshalls. While the engines were turning and burning the crew were trying to get the crowd moved back. It was like King Canute trying to stop waves coming ashore. I could see what was going to happen and even though I tried to assist to move the audience back, the crowd dynamics took over and in the end I retired to a safe distance behind them. Of course when the collective went up, some of the crowd went down. What can be said afterwards except 'We did try to warn you but you didn't want to listen'.