Ok, how about this one. Everyone knows pilots love a tailwind.

You have a giant fan mounted on a truck positioned behind the airplane.
The fan blows air towards the airplane, helping it to accelerate down
the runway (literally blowing it down the runway) while the truck
follows, keeping up with the airplane. Pretty soon the plane will be
thundering down the runway and the pilot pulls back on the yoke.

Does the pilot have to wait until the airplane's speed down the runway
is twice Vr before he can take off?

Jose
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There is not enough beer in the world to fuel such a discussion!!!!

Peter