Aerody question for Nick, Shaun or any genius..

[Ascend Charlie]

OK, we all know about phase lag and how a change of lift conditions (more relative airflow, less induced flow etc) to one part of a disc will manifest itself approximately 90 degrees later. Evidenced by flapback, and inflow roll.

However, I am not convinced by Recirculation.

Supposedly, hovering close to a cliff, wall or hangar will recirculate the airflow through the disc closest to the obstacle, and the loss of lift there will cause the helicopter to drift towards that obstacle.

Eh?? If there is less lift at the nearest section of the blade, the loss of lift will manifest itself about 90 degrees later, and the aircraft will move PARALLEL to the obstacle.

Please shoot holes in this if you can, it is a bit of a puzzle. I have spent plenty of time hovering near obstacles and have never felt any tendency to drift towards it.