Originally Posted by
Brercrow
Clearly when the airspeed Va is greater than the windspeed W (a) when the aircraft makes a 180, the ground-velocity Vg reverses direction and the difference in groundspeed is twice the wind-speed
However, when the airspeed is less than the windspeed (b) after the 180 the groundspeed continues in the same direction and the difference in groundspeed is twice the air-speed
That's utter nonsense.
It would only work if you could mix velocities and speeds in the same calculation, i.e. ignore the direction component of some terms but not of others. You can't do that in any known universe.