I worked as a Commercial Helicopter Pilot for over 20 years, and have 1000 of flight hours in various aircraft. I've flown my Phantom a few times in my backyard, but only at low altitudes. Today, I went to our local Park and flew the Phantom up to about 100 feet. I was hovering there, and yawing/panning the camera. I then decided to descend, straight down, and discovered that the Phantom is effected by the same aerodynamic effects of a real helicopter. That effect is called "Settling With Power", or "Vortex Ring State"(you can google either for a textbook discussion). In a real helicopter-if you descend at a rate of around 300 feet per minute, or more, straight down(assume zero wind), you will enter you own down-wash. This causes the aircraft to start yawing and rolling as it enters this disturbed air. If you add more power, the Helicopter, and the Phantom, will actually descend faster!!! Now I had the blade guards on-and that probably doesn't help. But, what I did was to push forward on the stick and move the Phantom into clean air while it was descending. My post is a warning to all you Drone Drivers-beware!!! Going straight up-not a problem. Coming straight down-big problem. Try going forward/sideward/backward, while descending from higher altitudes to avoid this situation. You will also notice your descent footage is a lot smoother, as you are in clean air. Now if you are flying in wind-note which direction the wind is coming from. It's still possible to enter this Vortex Ring State. For example-you're hovering high up in a head wind, and you decided to descent and go backwards-you could enter your own rotor down wash. This only applies when descending, and only when descending at a speed faster than your down wash is blowing away from your aircraft. If you descend slowly-no problem. Here's a link that will help describe this phenomenon;http://www.copters.com/aero/settling.html And for those that don't think this is possible-it is. I know what it looks like, because I've been in it, many times. And Today, on descent, I was in it.