@blobrana
I see your argument, but it's a fallacy.
When you propose GA flying in a circle, I guess you mean to simulate a 'copter. The ultimate analogy is GA rotating about its centre.
If GA's wings were given 'opposite' pitch akin to helicopter blades and it was made to rotate about the wings' centre point and with a relative wind speed of say 10mph, it wouldn't hover. Hovering requires downthrust, and there is none in the case of aeroplanes. The wings create lift. The equal and opposite force (as required by Newton's first law) is the mass of the craft.
You could think of the 'copter rotor as an air pump, sucking in air from above and compressing it by altering the pitch of the blades. It's not their aerofoil section which creates lift, it's the downward jetstream against which the rotors react and thereby lift the mass.
When planes turn in too tight a circle they become unstable because the relative airspeed across the wings goes down. The airspeed becomes a vector determined by the angle of turn. At a hypothetical 90 degree turn, airpseed is zero and the plane will fall out of the sky. You've probably seen videos of US and Russian fighters getting into such predicaments.
[EDIT: Flying a plane in circles requires more and more power as the radius decreases. In the GA case, I doubt if it could be made to turn in anything but very big circles, maybe a mile across. The peddling man wouldn't have enough extra energy to do otherwise and remain aloft.]
Now it just might be possible to power a helicopter on dung, but never by a man.
Cheers,
JaX
