I haven't done any sort of research but I've never personally heard of a catastrophic engine failure following a short shaft failure in any Bell. YMMV
Hence the previous derogatory post.
A mechanical failure of a driveshaft would most of the time NOT be related to the amount of torque on the shaft.
It could just as easily fail with little or no torque so the hellfire and brimstone regarding overspeed is meaningless.
The N1 governor should stop the N1 at 105%
Only after the normal N2 governor (
Pr/Pg)has failed and if we are talking about B206 and C-18 and C-20 derivatives there is also the N2 mechanical overspeed governor (Py dump) in addition.
Electrical overspeed governors are a whole different thing and for different reasons and certification requirements.