One bit that puzzles me is the "dastardly" warning that comes from hovering next to a hangar or a cliff. The warning is that the air is recirculated next to the vertical obstruction, and there is thus increased induced flow next to the hazard, less lift means the helicopter will get sucked over to the cliff or hangar and nasty things happen.
Well, if the downwash increases in that sector, the effect should be felt around 90 degrees later, which would pull the aircraft along parallel to the hazard??
And having done quite a bit of hovering next to vertical obstacle walls, I have never felt any problem with it. Any contributions?