your right headsethair,
everything is centred around engine failure, so you must have two.
so why not two transmissions, two tailrotor drives, etc.
if helicopters were that unreliable you wouldn't get in one, i wouldn't.
twin engined helicopters with one out just take you a bit further to the crash site.
the two engine argument is a crock.
by the way, in australia at the moment the emergecy helicopters of the gov't emergency services are not being utilised much because the medical unions are arguing about life insurance for the staff.
this organisation has highly trained pilots flying 412's, they have had only one incident (minor) that i can remember but because of the problems (accidents) encountered by other operators , nothing to do with the machines, they are not being tasked for medical retrieval.
even though there has been a series of accidents here over the years it has to be said that the (single engined) helicopters were in perfect working order when they came to grief. a twin would have met the same fate. they don't fly themselves.
the problem here is far from resolved. what a waste of a very expensive but effective resourse.
