". Some like the 92 can not even survive loss of tail rotor drive."
Well Sultan can't say I agree with that statement.
It can if ECL is followed.
I assume you are refering to the NF accident.
Well the "survival" aspect is inherently the same versus other rotorcraft.
A loss of a single gearbox on a conventional helo requires a full auto to ground (if its the TR GB that goes) and possibly even drops like a stone if the MR gearbox croaks and the overrunning clutch seizes. The latter is what is would cause a need for feathering on the tiltrotor.