Nick, I was not referring to the sterile laboratory that you fly in. I was referring to a real world comparison between actual zero wind and downwind approaches. In both I assumed starting with the same airspeed, and taking the approach to landing, thus to zero groundspeed.
I know that slowing from one airspeed to another does not depend on the wind.
The power needs don't "know" what the groundspeed is, but they are based on decelerating the helicopter and controlling it's descent. To fly the same approach path with a tailwind requires more decelerating. QED
As far as this not being "a place I don't often go", wrong. I don't fly comanches backwards at 80kts but I fly a heavy underpowered machine in the rocky mountains, frequently in the worst weather conditions (SAR). Mountain approaches sometimes are dictated by terrain and weather rather than winds. Considering downwind safety and power requirements is a place I frequently go.
Matthew.
[ 06 September 2001: Message edited by: heedm ]