Not sure about the KA-50 midairs being caused by negative G. Could be positive G is an issue.
One of the things that most people don't realize is that the KA-50 is perhaps the loudest helicopter in existance. I was in St. Petersburg many years ago for the European Rotorcraft Forum, and they brought a KA-50 to the Peter and Paul Fortress - you could hear it coming 10 miles away, and it wasn't a cold day.
How you could ever expect to sneak up on someone with the machine is beyond me, but then again, maybe the noise was intended to scare the folks it was being flown against...