I was flying 176m away at a height of 106m which is below the 120m limit when a helicopter flew directly overhead my position. It looked low, to me. I was on a hill so I guess not 500 ft ground clearance. Flying low and quickly the chopper arrived out of nowhere! If my drone was overhead at 400ft I would have been worried. Drones do not descend quickly. I guess I could have dodged sideways if I had enough warning. Needless to say I descended and returned to covered flying quickly.
Maybe I under estimated the helicopter's altitude. Nevertheless, manned aircraft need to be responsible and stick to their rules too. I am not sure that a chopper should be over a city at 500 feet. They do not glide well on engine failure.
Re the video, it's a fake. Helicopter blades produce a wake vortex. When moving forward the vortex fans out behind from the tips (above and below). The rotor or disk as it's know by pilots provides lift from forward motion so acts like a wing, not just a downward thrusting fan as one might think. With a chopper of this size there is an enormous amount of air moving around (stand next to one lifting off). The explanation in the video that air only goes down and the drone is outside the disk is simplistic and plain wrong. A small drone would have been thrown all over the sky, possibly destroyed mid air. Very very clever video editing I think. Good video though and good messages. We do have to be careful as demonstrated by my true story.