Being a theorist and not a pilot I open myself to some flack on this but I will repeat what I stated in a post I made a long time ago. This post is in response to the advice given about hovering the helicopter to the edge of the flight deck placing half of the disc in ground effect and the other half out of ground effect.
Many years ago a group of US Marine HRSs (S-55s) did just that only in this case the back ends of the helicopters were hanging over the ocean which was 80 some feet below. When they successively pulled collective they fell backwards one-by-one into the ocean below. A lot of people told me I was full of it and said it was impossible however it did happen and they lost several helicopters in the process. It is similar to hovering above a moving ship and letting the ship move out from under you. When the ground effect of the flight deck was no longer there the helicopter in which I was riding almost fell into the water until the pilot regained positive control.
