Guys - there is no difference in the acceleration you feel between a turn in calm winds, and a turn in steady winds. That does not mean you do not experience an acceleration. It just means that the acceleration you experience is the same in both cases.
Let's say I am flying north at 100 knots, in calm winds. I am experiencing no forces other than gravity, and other than looking outside, I have no way to tell I am moving relative to the ground.
I now make a 180 degree turn to head south, maintaining 100 knots TAS. Over the course of this turn, I feel an acceleration in the north-south direction that ultimately accelerates me by 200 knots - I was originally traveling 100 knots in the north direction, and I am now traveling 100 knots in the south direction, so my velocity has changed by 200 knots relative to my original reference frame.
Now, let's say I am flying north at 100 knots, in a 100 knot headwind. As before, I am experiencing no forces other than gravity, and other than looking outside, I have no way to tell if I am moving relative to the ground (in fact, I am not!)
I now make a 180 degree turn to head south, maintaing 100 knots TAS. Over the course of this turn, I feel an acceleration in the north-south direction that ultimately accelerates me by 200 knots - I was originally traveling 0 knots in the north direction, and I am now traveling 200 knots in the south direction, so my velocity has changed by 200 knots relative to my original reference frame.
Obviously, both situations are identical. Your velocity relative to the ground changes in magnitude by -200 knots. The only difference between the two situations is what your original groundspeed was, and you obviously have no way of feeling that.
You may wonder how an inertial navigation systems works if these two situations cannot be differentiated from inside the plane. The answer is simple - the INS has to be initialized while you are on the ground, at 0 groundspeed.
