I usually hand launch and I'm always standing still. I make sure it's full throttle and give a gentle(usually very gentle) toss into the wind. I currently fly a plane without a lot of power that is very light in weight and it works well for me. If it is going nose down and won't climb out it could be a center of gravity issue and it's just nose heavy. If you know it's not that I'm not sure what's next. I've always been told to toss it level and never up.I guess your prop could be on backwards or something of that nature but if you've been flying awhile I doubt thats it. Good Luck!