Ok, here is how it happened. About a week ago I was ending a flight with RTH. It was coming a little too close to a tree about 3 meters above the ground. So I switched to ATTI mode that's when it dropped like a rock! I bent an arm and broke a prop. I have since replaced the shell, recalibrated everything and it seems to fly like new. My question, what did I do wrong or what possibly went wrong?