Another stupid question from a novice
I thought about it so many times, and I just can't figure it out. How can a heli fly inverted ?!
it is just not possible

With a standard control setup, it is impossible. However, there is a control setup for 3D flying where the throttle increases as you go from zero to positive or negative pitch. Also your collective pitch range for negative pitch is the same size as the range for positive pitch

but how does it work ? do the blades turn arround or something or does the engine make a full stop and then starts turning the other way ? I don't get this. If the blades don't do any of the above, then it is just not possible, I just don't get it

The blades change from a positive pitch to a negative pitch. When you fly up-right the blades have a positive pitch, once the model is flipped inverted you must bring the blades down to a negative pitch or angle of attack. The model stays in the air by accelerating air down towards the earth...no matter what attitude the model is in air has to be accelerated down towards the ground to stay at a given altitude, so when you are inverted the pitch of the blades simply changes so the air can be shot downwards.

Colin

just as I thougth, thanks raptor-dude