The inertia issue is quite interesting as well as the "flowing river" discussions I've heard. You know, the one about a fast powerboat doing a 360 turns on a fast flowing river.
Anyway, if an airplane at a true airspeed of 100 knots is flying with a tailwind of 20 knots, it has a groundspeed (inertia) of 120 knots. After a tight 180 degree turn, it will be traveling in the opposite direction at a groundspeed of 80. The total change in groundspeed (inertia) from 120 knots in one direction to 80 knots in the other is 200 knots, right?
It would be the same in still air: 100 knots groundspeed in one direction to 100 knots groundspeed in the other equals 200 knots change.
It would be the same if the airplane started with the 30 knot headwind: 70 knots groundspeed in one direction to 130 knots groundspeed in the other equals 200 knots change.
Now, can someone please explain to me again about this inertia difference turning downwind?
...and above all,
FLY SAFE!
WileyP