In order to figure out turn performance, you need a few numbers. You need an accurate stall speed at a given weight. Eric Brown gives the A4 a clean stall of 127 mph. Weight is probably around 8700 lbs for the version that he flew with the bomb racks removed. Using the lift equation, you can then figure out the maximum lift coefficient (which is used in a max rate turn). The lift equation looks like this
Lift = 1/2 density * cl * V^2 * area
Drag = 1/2 density * cd * V^2 * area
If you know the max cl, just plug in the V, area and density to get the lift in a turn.
Turn radius = V^2 * mass / Force
The turn rate depends on how fast the plane flies the circle. The sustained turning speed is hard to figure out, without knowing the maximum thrust values for any given speed. It's not constant. You can however, determine the induced drag coefficient by the following formula
Cdi = cl^2 / (pi * aspect ratio)
Induced drag will be highest at high angles of attack.
If you know the thrust value at the maximum level speed (where induced drag is minimal), you can figure out the zero-lift drag coefficient (cd0), but this is not an easy process. Putting the 2 drag coefficients together will give you a total drag coefficient. Where max thrust = drag at max angle of attack will be the sustained turning speed.
There's an article in the Jan 99 issue of Sport Aviation that gives the Dora a drag coefficient of 0.0063 for 761.6 sq ft of wetted area (or 0.024 for 197 sq ft of wing area) at cruise lift coefficient.
I've done some work on thrust values but they may not be totally accurate. Go here
http://www.iaw.com/~general6/flightmodels.htm
