still there and i'm sorry for that but i'm really newbie... My quad rotor won't found so that i made a new one. I use the same receiver and transmitter to control it and same batteries but all the other parts are new, esc, motor, frame, power board, apm board, gps and so on... Now i get the same problem. When i yaw to the left or to the right the motors loss power and the arducopter go down but after that it try to get power quickly, so i get an up-down like yo-yo only when i yaw. If i don't yaw AC fly but yaw to the right and if i try to correct it with transmitter i get the power loss... Could be the battery? or the receiver?