Highhorse is right, of course, but it's good to be reminded (as in post 42) that an RC pilot standing on the ground may assume from the added ground speed when flying downwind that the plane has enough airspeed to be able to make a sharp turn safely, when it doesn't. Furthermore, when turning onto the base leg and again on final, the urge to make a turn that looks good from the ground combined with the fact that the plane's high downwind ground speed necessitates a sharper-than-normal turn to make that turn look good can lead to a stall. So the "downwind turn" is a myth if you believe wrong things about airspeed changing according to wind direction, but it's real when you take into account the RC pilot's tendency to make mistakes and to take ground speed too seriously. Even full-scale pilots can make mistakes like this, though as they have airspeed indicators they have less excuse than we do.