AirWon,
Sorry I been away for a while. I thought I would have my tuppence worth and ask a question thats all! Somehow, one of us has confused the issue but I stand by my last reply on vortex ring 100%. I have never have claimed to be an expert but I've managed to get through the last 7000hrs without hurting anybody and about 3/4 of that total is on some pretty sophisticated utillity helicopters. The rest was AH, enjoy.