Thanks for the tips.
Not so sure about me being a "novice", though. My first introduction to simulators was on the RAF's original Jaguar system at RAF Lossiemouth (Oh, and a quick go on, what I guess was, an elderly Hunter cockpit trainer at RAF Chivenor). back in the early/mid '70's.
I will concede that these were just a quick introduction, but I do understand the further effects of flight control (ie using ailerons and rudder to turn). I find it easier to land an RC helicopter than an RC aeroplane. I guess that's because I can get it closer to me to see what's going on.
And I've owned MSs FS software for years.
I don't agree with your comment "A general note - if you observe a certain behavior of the helicopter in DCS BS you can safely assume it is as it is in reality". Put simply, I'm observing, what I believe are inconsistencies between my commands and the X52 Pro.
For instance; if I use Z & X to control the rudder they work fine, and do what I expect - they revolve the ship around it's center.
So, your mention of "axis curvature" is something I'll investigate further, and of course I'll look all the other links too.