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@turboshaft:
Of those three, only one (N103LN) has an undetermined cause…
True, only one was "officially" undetermined. However, I am very familiar (even peripherally involved) with the accident investigation conducted on the aforementioned N851BP. There were many issues there and the NTSB calling it an encounter with vortex ring with resultant loss of control is a stretch beyond reality.
Read this very detailed Canadian incident:
http://www.tsb.gc.ca/eng/rapports-re...5/a05f0025.pdf (It’s not difficult to find more examples).
I was an Astar instructor for over 15 years. I’m a fan of the Astar, but I am aware of several incident/accidents that in my opinion are not conclusive "pilot error". No conspiracies, just a belief that there is some sort of insidious undetected failure mode involved in some of these incidents/accidents.
BTW, it is impossible to derive stats like you require since the NTSB will ALWAYS determine a "cause" in an accident.
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