Sorry but I don't understand what you are saying there-kind of confusing the way it is worded. The plane can travel vertically (down) for 500ft and be fine, it is when I suddenly level out (like doing a square loop or "parachute") at the end of the long down line that the rpm drops for only a split second and then return. Someone else said it could be an issue with G force on the meters within the carb which makes sense. I am just looking for possible explanations.