I've had it happen to me. I've parachuted and abseiled and enjoy skiing steep slopes. I have no problem being near an edge as long as I have confidence that what I'm standing on or can grab is secure. On the face of it I should have no problem.
In my case it happened when I was in a glider and joined another in a thermal. A short distance away from me was another glider and underneath, holding it up was............. nothing! My immediate thought was that a few inches under my backside was.......... nothing, and lots of it.
This was many years after I learned to fly so why did it suddenly maniifest itself? I have no idea but you get used to it, it's all a matter of having confidence in what's holding you up, whether it's a climbing rope, a ladder, a karabiner or an airframe. We don't worry about a chair bed or hammock giving way under us do we? Once the confidence is there you stop worrying about it.
I can understand the feeling in an R22, after all what your flying is some distance above you, all you're doing is dangling underneath it!