I can second that. Standing next to a 700 size 3d helicopter is one of the most terrifying experiences I have ever ever had.

Imagine a 20 pound, 700mm wide, rabid, angry, highly agitated, alien dragonfly "thing" with carbon samurai swords for wings (that spin at 5,000 rpm) and high voltage electricity for teeth.

The sound these machines make at full, 3d RPM is enough to cause a visceral bodily reaction. As a human being, you know that you are in danger just being around it. It is incredibly dangerous as one broken solder or linkage failure and its light speed path to the ground is impossible to determine (or see).

Additionally, the coordination required to fly these maneuvers is almost superhuman. Pilots make mistakes and can get disorientated. If you are in the way of the rotors under full power they can (and will) cut thru a human very efficiently. I have witnessed several severe crashes (the largest piece was about the size of my forearm) that were fairly close calls to the pilots. Frankly, I find the sport of large scale 3d heli flying to be "a bit reckless."

That the community has not learned from the recent accidents and recommended or required a barrier or net to be used to ensure safety is beyond me. I am surprised that the AMA has not done more.

I fly smaller Heli's now, up to a 450 and that is enjoyable and fun (and slightly safer).

Sorry to hear about your friends accident and be safe!