It seems to be the 'type' of wind that grounds me at our local park. I've been caught out twice now, the trees don't seem to be moving and there certainly is very little wind at ground level but at 50 feet or so....crikey! Each time as soon as I hit that certain level the plane would immediately gain height, loop over and come back down quickly, trying to regain control would see it blown back another 100 yards or so until it reached the tree line. Lost one plane in the woods (never found it again) and the second I retrieved from a tree!