You will find answers to your question at the AMA's website. I build scale planes; however, I don't compete. It used to be that along with your membership information from the AMA when you joined, you got a Competition Rule Book, this is no longer true. However, the AMA Official Rule Book is available at the AMA's site in PDF format. I do know that Sport Scale Rules allow ARFs. The planes are not statically judged on the ground and only flying points are awarded.