the only heli I've ever seen fly off was a 30 Concept that the guy programmed his PCM failsafe to 'hold' and when it lost TX signal it held exactly where it was and flew off into the horizon. he did find it the next day in a peanut field about two miles from the flying field in reasonably good shape, just needed the regular blades/boom/flybar and was back up and running. he'd always argued with me about setting my failsafe to pull throttle to idle but after that he did the same.

kc