Years ago when we were operating Puma 330Js to rigs in the South China Sea, one of our pilots would always complain of an unexplained sudden loss of power on approach to a certain helideck. It turned out that when the wind was blowing from a certain direction, the helideck would be smack downwind of 3 big turbine exhausts. We did a plume study and discovered that the exhaust gases caused the temperature above the helideck to be up to 10 degrees hotter when the wind was from a certain sector.
I was just wondering if this may be the case in the GoM incident too.