Gday Bruce,
The D and E models fling their shafts for two reasons I know of. Firstly, if it is just after maintenance it is because during the balancing the recommended Rpm was exceeded before the recommended Ips were in place. ie You have too high a Rpm with too high vibration . Look in the maintenance manual and you will see the limitations. Secondly, there is a guy in Canada? who sells a copy of the real T/R driveshaft hangar bearing, that big black hangar, and it is not on speck and not of the correct material. We lost two shafts because of this sub standard part. Go buy one from MD and the problem goes away. Enjoy your 500, they are magic machines.