OK I have my flame suit on.
I have a question for those that say there is no loss of altitude when turning from upwind to downwind.
First look this over
:
http://en.wikipedia.org/wiki/Inertia
You will find momentum defined as P=MV
Where
M= mass
V= Velocity
Lets say out aircraft weighs 4 lbs
If flies 50MPH
The wind is 10MPH
When flying upwind its momentum is 4x(50-10)=160
After it turns downwind its momentum is 4x(50+10)=240.
Its momentum has increased by a factor of 80.
Where dos the energy come from to increase the momentum?