Gentlemen
Thank you for the responses.
I am researching co-axial systems within the context of military operations - where the normal operating range may regularly be exceeded, and where high weight, high density operations at the limits of the RRPM envelope may well be exceeded. My current research suggests that low-RRPM conditions well below the placarded stall speed of about 80 per cent RRPM in the Ka-50 are recoverable. I have yet to find a pilot who can actually confirm that, though!
My specific interest is in the Ka-50, but I kept my questions generic since it occurred to me that few (if any) here are likely to have flown it, and that co-axial rotor systems may have specific peculiarities regardless of which type they are installed on.
I understand that the two Ka-50 self-midairs were the result of excessive negative g at high airspeed. I was therefore wondering of there were any other areas of the envelope that would lead to self-midair.