Thank you - very interesting.
"not risk related ie payload capacity - yes has an effect on risk in number of trips and exposure but no impact on an individual flight. More of a commercial concern."
Yes I was thinking more trips/exposure per payload delivered - a Lynx might take Food or Ammunition a Single Lynx might take both (as might a Gazelle more cost effectively/reliably). So; for example 100Engine.miles against 400Engine.miles (plus all the other doubly exposed failure points)
"assumed worse auto performance design than a single of the same weight?"
I don't think the Single version would be the same weight.... ? Yes - Auto performance generally much better in singles - more rotor energy stored per MAUW?
The floats circular discussion just leads one to conclude that ditching needs to be safer - detachable allweather survival cabins!? *&%£@! perhaps
The other topics make it too big a discussion - but the general theme is the weight justification of where in an airframe design you chose to spend weight on safety - if you spend it on Engines, Gearboxes and Fuel (to supply 2 engines) then for a given weight you have less to spend on critical components (tail rotors, pitch links, tail booms etc)(where the engine may not be one) - Airbags might provide a better yeild? - 2 Pilots might provide a better yeild? etc
OR you just have everything you can think of and make carrying 1 Kilo require 5Kilos of helicopter ?? Not practical?