My first CFI told me that magnetos are designed to only produce a charge when turned in one direction. Therefore, when moving a prop by hand (not hand propping) always turn it opposite its normal direction of rotation to help prevent an accidental start. While "teaching" systems to my CFI instructor this came up and he had not heard of it. I realize that I've never seen any mention of this anywhere since and want to make sure I don't go around spreading bad information. I am hoping one of you experts can tell me if this is true or not?