riff raff: "Unfortunately, the subject of rotorcraft gearbox design is very complex and not easy to summarize in a couple sentences of the typical post."
and that is why the risk assosciated with these gearboxes should be taken into account when the 2 engine solution is considered
it is not correct to say 1x10^-5 squared (1x10^-10) is the risk and it is a completely untrue premise