RE: Tx X9303 Rx 6200 Rx pwr on Throt not safe
It should go to idle (sensibly) Have you checked any servo reversals or even some ESC's can be reversed. Not sure if you are talking about a nitro or electric.
Have you tried another rx?
Certainly it should stay at idle. Just think of a scenario when an electric model has the rx turned on accidently . Phew. I'd rather not. It simply HAS to go to idle.