Tees- Yes its possible....well Incipient VR anyway. I have been there a few times. The air has to be directed up at you from pretty much straight from below. Hovering beside a cliff, machine is twitching and buffeting, trying to lower a load onto a ledge with a longline and anytime I pulled a bit of power to see how it was feeling, the bottom fell out. Nasty. Seeing that the bottom only falls out when you pull power has me leaning in the direction of IVR as the culprit. Other ideas anyone?
Of course generally speaking 99.9% of the time, up flowing air in the mountains is easier than work in than the down flow side. But there are rare exceptions...