I don't really understand this negative Airspeed business, if you hovering in a 10 knot headwind, you have a IAS of 10 knots, in order to maintain that you need some power, as you turn around you will gradually start moving relative to the ground, but a given power setting will always (all other things being equal) maintain that 10 Knot IAS, what has negative airspeed got to do with anything?
I wonder whether a different scenario entirely will help explain the concept.
Consider a Su-29 in a vertical dive at 250kts IAS which is rotated rapidly in pitch through 180deg to point vertically upwards. Does it retain 250kts IAS? Does it initially have any positive IAS? Nope, it tail slides at negative IAS. A nice airshow party piece!
Conceptually, that scenario is not materially different from a level flight rapid rotation in yaw through 180 degrees, and is independent of wind velocity (as long as it's constant). This is inertia at play (albeit, in the vertical plane, aided by gravity), eventually overcome by thrust.
Any clearer?