I know by the tone of that simple question that to answer is to put ones foot in the bear trap... so here goes
The way I see it is if you are doing 60 kias with a 30 knot headwind you are traveling across the ground (or through space) at 30 knots.
If you turn 180 deg (or the wind does) without a change in attitude or power you will still be doing 30 knots across the ground( or through space) but will now have a 30 knot tailwind ie ias = 0
Now I 'm sure you are going to tell me I'm wrong but that is how my helicopter seems to work and I can't remember Newtons laws of motion mentioning anything about wind or height above the ground.
Preparing to duck for cover and burn logbook.