juanswan1900

On Apr 24, 6:41 pm, tman <inv@lid> wrote:
> Here's why I wonder about that. Let's suppose 65 KAS before and after a
> 180 turn from a 10 KT headwind. OK, before the turn, your groundspeed
> is 55KTS and after the turn your groundspeed is 75KTS. Your intertial
> frame of reference is tied to the g/speed, not the a/speed. So -- the
> kinetic energy of the aircraft and contents is about 33% higher
> (75/55)^2. That energy is only going to come from one place with no
> power -- trading in altitude (potential energy) for kinetic energy.

In your world, it's gonna be pretty hard for a sailplane to circle in
a drifting thermal. In my world, it's not a problem.